Large Animal Surgical Nursing

OVERVIEW

ABDOMINAL SURGERY

Abdominal surgery is a major undertaking and requires a full team to perform it in an effective and efficient manner. Adult horses and foals frequently undergo abdominal surgery for gastrointestinal and urogenital tract disease. Although a flank incision in a standing, sedated horse is sometimes used for horses with colic or other abdominal disease, the most common approach to the abdominal cavity is through a ventral midline incision with the horse under general anesthesia and positioned in dorsal recumbency (Figure 31-1). Because most horses with colic requiring surgery will be operated on with the patient under general anesthesia, the veterinary technician will be involved in the preparation of the horse for surgery. This will include placing a catheter, administering perioperative medications, passing a nasogastric tube, washing out the mouth, clipping the hair, preparing the anesthetics, aseptically preparing the incision site, and opening surgical packs at the time of surgery. Most colic patients can be clipped before anesthesia, but if the horse is in severe pain, it may be done after anesthetic induction for the safety of the horse and personnel. The hair should be clipped from rostral to the xiphoid area to the udder or preputial area and to the flank folds on either side; clipped hair and other debris can be removed with a vacuum before aseptic preparation. The incision is draped with four small drapes or towels, and a large, water-impermeable drape is placed that covers the entire horse. The incision is usually made from the umbilicus rostrally toward the xiphoid until the necessary exposure is achieved, but the incision can be extended caudal to the umbilicus. This is particularly necessary for urogenital tract surgery, such as a cystotomy for removal of cystic calculi. Once the incision is made, a thorough exploration is usually performed depending on the reason for surgery. Once the abnormality is identified, it is corrected. Suction is often necessary to decompress gas from the gastrointestinal tract or aspirate fluid, such as urine from the bladder during a cystotomy.

There are numerous surgical techniques and manipulations that the surgeon may perform with which the OR veterinary technician becomes familiar through experience. Many specialized instruments are required for abdominal surgery (see Chapter 28). One group of instruments that has become increasingly popular with veterinary surgeons for use in equine abdominal surgery is gastrointestinal stapling equipment. The technician must become familiar with the different instruments and cartridges. Intestinal resection and anastomosis often require specialized instruments and supplies.

Once the cause of colic or other abdominal problem has been corrected and the horse has recovered from anesthesia, the veterinary technician becomes even more closely involved with patient management. Horses usually require administration of IV fluids, antibiotics, antiinflammatory drugs, and other medications in the postoperative period. The veterinary technician usually administers or oversees administration of these medications. The technician may also perform nasogastric intubation, blood collection, IV catheterization, and changing bandages.

Fortunately, most horses with colic respond to conservative medical treatment, and only a small percentage require surgical intervention. Surgical treatment of colic is necessary for intestinal volvulus and incarceration, enterolithiasis, fibrous foreign body obstruction, and some intestinal displacements. Refer to Chapter 33 for more information about treating horses with medical colic.

UROGENITAL TRACT SURGERY

ORTHOPEDIC SURGERY

Horses frequently sustain severe musculoskeletal injuries, such as long-bone fractures or disruption of tendons or ligaments. These injuries often require stabilization with the use of bandages, splints, or casts before transport to a referral hospital. Successful stabilization of these injuries and safety of transport are important considerations in the outcome of these cases. Most severe injuries should be bandaged and splinted or casted to a level at least one joint above the injury. A heavy Robert Jones bandage should be applied and rigid splints placed on the lateral and either the dorsal or palmar aspects of the limb to provide appropriate support. Splints can be made out of rigid materials, such as wood, steel, or aluminum. The splints should not be excessively heavy or bulky, but must provide appropriate support. Horses with phalangeal fractures can be casted with their distal limb in flexion or can be placed in a commercially available device, such as a Kimsey splint (Figure 31-4). Horses with limb injuries should be hauled in a trailer with partitions to provide some support for them to balance themselves. The head should be tied loosely enough to enable the horse to use the head and neck for balance. Horses with front limb injuries should be transported with their head toward the rear of the trailer, and those with rear limb injuries should be transported with their head toward the front of the trailer.

Orthopedic surgery has become more common in horses. Athletic horses develop numerous orthopedic conditions that are amenable to surgical correction. Historically, fractures of long bones in adult horses were considered irreparable. However, with advanced techniques and more rigid surgical implants, many of these injuries are potentially correctable.

Major fractures of long bones in horses are best repaired with screws and bone plates to prevent movement at the fracture site while the bone heals under rigid fixation (Figure 31-5). Although aseptic technique is imperative for all surgical procedures, it is especially crucial to the overall success of orthopedic surgery in horses. If bony infection develops, it can lead to instability of the implants and fixation failure, which often necessitates euthanasia. It is the responsibility of all personnel to follow aseptic protocol. The technician should strive to maintain asepsis by monitoring the activities of all personnel involved in surgery. Orthopedic surgery requires the use of several specialized instruments and implants; because many of these surgeries are performed on an emergency basis, it is imperative that the technician make sure that instruments are available and ready for use. Many orthopedic injuries that are surgically repaired require the use of external coaptation (cast) for anesthetic recovery or for longer periods postoperatively (see Chapter 34). Therefore the technician should anticipate this need and have the appropriate materials available at the conclusion of surgery. The technician may also be needed to assist with anesthetic recovery of the orthopedic equine patient.

Postoperative monitoring of the orthopedic patient is vital for early detection of potential problems. It is particularly important to observe how the horse is using the affected limb in the stall; any dramatic change in use of the limb may signal an impending problem (infection or cast sores). The cast should also be monitored for heat, odor, or exudate, which would indicate the development of cast sores. The most common locations for sores to develop in association with a half-limb cast are at the proximal, dorsal aspect of the metacarpus or metatarsus, at the palmar or plantar aspect of the fetlock over the sesamoid bones, and over the heel bulbs. Bandages need to be changed frequently, and the incision sites should be monitored for swelling, erythema, and discharge. Drains are commonly used in orthopedic surgery following repair of a long bone. Drains can be useful in preventing seroma formation, but they can serve as potential routes for inoculation of the surgery site. Therefore it is important to keep these drains sterile by keeping a clean, sterile bandage on the leg. This may require changing the bandage more frequently than once daily.

UPPER RESPIRATORY TRACT SURGERY

Abnormalities of the upper respiratory tract can be performance limiting to athletic horses and, if severe, can also be life threatening. Many obstructive diseases of the upper respiratory tract are amenable to surgical correction. The most common of these are left laryngeal hemiplegia, epiglottic entrapment, dorsal displacement of the soft palate (DDSP), and arytenoid chondritis. Others are subepiglottic cysts, guttural pouch empyema, guttural pouch tympany, and guttural pouch mycosis.

Left laryngeal hemiplegia (“roarer”) is a condition resulting in paralysis of the left arytenoid cartilage, which prevents it from being abducted during inspiration. This results in the arytenoid collapsing and being pulled into the airway secondary to the negative pressure that is generated during inspiration. The cause of this condition is unknown, but it results in a recurrent laryngeal neuropathy. Because this nerve normally provides innervation to the major abductor muscle of the arytenoid cartilage, the cricoarytenoideus dorsalis, a neuropathy results in muscle atrophy and an inability to abduct the arytenoid. As the name implies, this condition occurs almost exclusively on the left side (95%); it is believed that this is related to the longer length of the nerve on the left side and that it may become damaged from the vibrations as it courses around the aortic arch. This condition is diagnosed using endoscopy at rest or during exercise on a high-speed treadmill; the left arytenoid cartilage is not fully abducted during inspiration and in severe cases actually collapses into the airway. Horses with this condition make a characteristic inspiratory noise (roaring) and develop exercise intolerance. Surgical treatment is a prosthetic laryngoplasty, which involves placing a suture between the cricoid cartilage and the muscular process of the arytenoid cartilage to mimic the action of the cricoarytenoideus dorsalis and abduct the arytenoid cartilage (tieback). The laryngeal ventricles (saccules) are also everted and resected (ventriculectomy or sacculectomy) through either a ventral laryngotomy or by use of an endoscopically guided laser. Approximately 70% of horses treated with a prosthetic laryngoplasty and sacculectomy return to athletic function. Most horses will continue to make some noise, and in some, the noise may not improve. The laryngotomy incision is usually left open to heal by second intention. This requires daily cleaning with gauze sponges with saline or water followed by application of petrolatum to the skin around the incision and on the mandible and neck to prevent skin scald from the drainage. It usually takes approximately 3 weeks for the incision to heal. Some clinicians partially close the incision, which reportedly shortens the time required to heal.

Epiglottic entrapment is a condition where the aryepiglottic membrane that extends from the arytenoid cartilage to the ventral surface of the epiglottis hypertrophies and rolls upward to envelope the rostral and abaxial portions of the epiglottis. Normally the epiglottis should have a serrated edge and a distinct vascular pattern present on the dorsal surface. When the epiglottis becomes entrapped, the serrated edge and vascular pattern can no longer be seen. The shape or outline of the epiglottis can still be observed (unlike that seen with a DDSP), but the tip appears more rounded and the abaxial surface is smooth rather than serrated. In more chronic cases, the tip of the epiglottis may become ulcerated. The cause of epiglottic entrapment is unknown, but it is believed that these horses have an instability between the caudal edge of the soft palate and the epiglottis and that the aryepiglottic membrane hypertrophies and makes the epiglottis more rigid. Epiglottic entrapment can be intermittent or permanent. Some horses can continue to perform athletically with an entrapped epiglottis, but it does appear to affect performance in most horses. Treatment of epiglottic entrapment includes transecting the aryepiglottic membrane to release the epiglottis. This can be done using several techniques. First, it can be performed with a hooked bistoury placed through the nasal passages in a standing, sedated horse with or without endoscopic guidance; care must be taken to prevent trauma to other structures and to prevent laceration of the soft palate. Second, it can be performed in an anesthetized horse with a mouth speculum by manually guiding a hooked bistoury and transecting the membrane on midline. Third, it can be performed using an endoscopically guided laser in a standing, sedated horse. Finally, in more severe or chronic recurring cases, the aryepiglottic membrane can be resected through a ventral laryngotomy. The prognosis for return to athletic performance is good, but entrapment can recur. Some of these horses may develop DDSP after the entrapment is released. Horses that have the entrapment released using the hooked bistoury or laser can generally resume training in a few days, whereas those treated via resection through a laryngotomy require approximately 3 weeks before resuming training.

DDSP is generally a dynamic obstructive disease of the upper respiratory tract that occurs during exercise. Normally the soft palate remains ventral to the epiglottis. However, if the epiglottis is small or flaccid or the caudal edge of the soft palate is flaccid, the soft palate can become displaced dorsal to the epiglottis during strenuous exercise. The cause of this condition is unknown, but it is believed that the factors listed previously predispose the palate to become displaced during inspiration when negative pressure is generated in the upper airway. This condition usually is intermittent, occurring during strenuous exercise and dissipating once exercise has stopped and the horse swallows. Because horses are obligate nasal breathers, DDSP interferes with the horse’s breathing. Horses with DDSP usually make a characteristic gurgling or snoring type of noise, which will dissipate as soon as they swallow and replace the palate into its normal position.

Treatment options for a horse with DDSP include placing a cloth or leather tie on the horse’s tongue and pulling the tongue rostrad and tying the tongue to the mandible in the interdental space. The epiglottis, tongue, and sternothyrohyoideus muscles are attached to the hyoid apparatus. Because the tongue is attached at the rostral aspect of the hyoid apparatus and the sternothyrohyoideus muscles are attached at its caudal aspect, a tongue tie prevents caudal retraction of the hyoid apparatus, including the epiglottis. This seems to help approximately 50% of horses with DDSP because it prevents caudal retraction of the epiglottis and maintains normal epiglottic-palate alignment. Because of its noninvasive nature, the tongue tie is generally the first thing attempted in horses with DDSP. If this does not work, a section of the sternothyrohyoideus muscles can be resected in the midcervical region; this also prevents caudal retraction of the hyoid apparatus. This myectomy procedure helps in approximately 50% of horses with DDSP that fail to respond to a tongue tie. If this procedure does not work, the caudal margin of the soft palate can be resected (staphylectomy). There are two theories as to why this may help prevent DDSP. First, it is believed that the caudal edge of the palate becomes more fibrous as it heals with scar tissue; this makes the caudal edge more rigid and therefore more resistant to displacement. The other theory is that, if the palate does displace, it enables the palate to be replaced more easily. Regardless of the mechanism, it seems that it helps prevent DDSP in approximately half of the horses that do not respond to the tongue tie or myectomy. A laryngeal tie forward procedure reportedly has achieved a higher success rate in horses with DDSP and should now be considered the surgery of choice if no other source of inflammation is present in the upper respiratory tract. However, it requires general anesthesia, so some of the alternative procedures may be performed initially in the standing patient.

Arytenoid chondritis is an inflammatory, degenerative condition of the arytenoid cartilagines resulting in a proliferative mass on one or both arytenoids. This usually results in an obstructive disease of the upper airway with signs similar to the conditions described earlier. These cartilagines are usually enlarged and more fibrous than normal, which prevents them from being effectively treated with a tieback. The treatment of choice is to remove the affected arytenoid cartilage through a ventral laryngotomy. Because of the time required for dissection in the laryngeal region during an arytenoidectomy, a tracheotomy is usually performed in the middle or proximal trachea to provide a mechanism for ventilation during anesthesia. The tracheotomy can be performed either before anesthetic induction or once the horse is anesthetized. These horses are prone to upper airway obstruction postoperatively and need to be closely monitored. The tracheotomy tube is usually left in place, at least for a couple of days, until it is believed the horse has an airway of adequate diameter for breathing. It is imperative that these horses be monitored closely while the tracheotomy tube is in place to make sure that it does not become dislodged or obstructed with mucus or other discharge. The laryngotomy and tracheotomy sites require daily cleaning and application of petrolatum on the skin around the incisions. Both these incisions will heal by second intention in approximately 3 weeks.

Bacterial infection of the guttural pouch (empyema) usually is a sequela to strangles or retropharyngeal lymph node abscesses. Clinical signs include swelling in the throat-latch region and a bilateral mucopurulent nasal discharge. Horses with guttural pouch empyema can be treated conservatively with antibiotics and guttural pouch lavage; this may be effective in many horses that are treated early in the course of the disease. However, in more chronic cases, the mucopurulent material becomes inspissated and forms gelatinous concretions (chondroids) that lie in the floor of the guttural pouches. Resolution of empyema requires removal of the chondroids, and long-term effective drainage can usually only be achieved with surgical drainage. Several approaches are reported for surgical drainage of the guttural pouches, but the most common surgical approach for guttural pouch empyema is the modified Whitehouse technique; the incision is made in the skin on the ventrum of the throat region just axial to the linguofacial vein and is followed by blunt dissection into the pouch. The guttural pouch is lavaged intraoperatively. Indwelling catheters can be placed into the guttural pouches in standing, sedated horses under endoscopic guidance; these catheters enable frequent lavage of the pouches. The guttural pouches should not be lavaged with irritating solutions because of the proximity of blood vessels and nerves coursing through the area. The incision is managed similarly to a laryngotomy or tracheotomy incision.

Guttural pouch tympany is an accumulation of air in the guttural pouches; this occurs in foals and weanlings and is usually associated with an abnormality of the opening to the pouches. It can occur on one or both sides and is characterized by a fluctuant, nonpainful swelling in the throat-latch region. If unilateral guttural pouch tympany is present, then it is usually treated by surgically creating an opening in the septum between the left and right pouches; this is usually approached through an incision in Viborg’s triangle on the affected side. If bilateral tympany is present, creating an opening in the septum will not effectively drain the two sides. Therefore the opening to one or both of the guttural pouches is surgically revised through a Viborg’s triangle approach. Surgical revision of the guttural pouch opening may be performed on only one side with creation of an opening in the septum to enable both pouches to evacuate the air through one opening.

Guttural pouch mycosis can be life threatening. Fungal plaques form in the lining of the guttural pouches; if the plaques involve vascular structures, such as the internal carotid artery, severe fatal hemorrhage can occur. Fatal hemorrhage is often preceded by several episodes of substantial epistaxis. However, once the diagnosis is made, surgery should not be delayed. The most accepted method of surgical treatment is vascular occlusion of either the internal carotid artery, external carotid artery, or both, depending on which vessels are affected. This can be done following placement of an intraarterial balloon-tipped catheter or by placement of newer springs or coils that stimulate local occlusion. Both the internal and external carotid arteries can be ligated unilaterally with no untoward effects. The major potential complication of external carotid artery occlusion is blindness. Once the affected vessels are ligated, the fungal infection is treated by lavage of the guttural pouches and instillation of antifungal medication into the pouch via indwelling catheters or via the endoscope.

ORAL LACERATIONS

Cattle, especially calves, are not discriminate eaters and often consume debris, such as hardware, found in the pasture. Lacerations or injuries can occur on the tongue, cheeks, or palate when pieces of wire or other sharp objects are chewed and potentially swallowed. Excess salivation or bloody oral discharge may be seen along with varying degrees of dysphagia and malodorous breath if feed is accumulating within the wound. Diagnosis is usually easy once an oral examination has been performed. With appropriate wound care, many of these will heal without much treatment because of the excellent blood supply to the oral cavity. Flushing with copious amounts of water (usually via a hose) will prevent feedstuff accumulating within the wound. Changing the diet to softer feed rather than course roughage will limit feed buildup within the wound. Severe lacerations or punctures may require surgical débridement and repair, and if the tongue is involved, application of a tourniquet may help limit blood loss during the repair.

MANDIBULAR FRACTURES

Fractures are either traumatic or secondary to other pathologic processes, such as lumpy jaw. Fracture location, type, and the ability of the animal to eat and drink will usually dictate whether surgical repair is necessary. Clinical signs observed include dysphagia, salivation, and often crepitus or palpable instability. Oral examination is also important to identify any communication with the oral cavity because this is a route for secondary bacterial infection, which can complicate the healing process. Radiographs will help confirm the diagnosis and aid identification of the optimal therapy. If there is marked displacement or instability of the mandible and if the animal is having difficulty eating and drinking, some form of stabilization is indicated.

Surgical options include figure-eight wiring with orthopedic cerclage wire, screw fixation, or application of an external fixation device. The choice is made depending upon the location of the fracture, the degree of comminution, involvement of tooth roots, if the fracture is open or closed, and the cost of the procedure. External fixators are inexpensive, effective, and relatively easily applied.

Most fractures will heal with some form of stabilization, and many cows will resume eating immediately following fixation. If the cow remains anorexic, offering different types of feed is recommended because some cows will only eat their usual ration. If necessary, the oral cavity can be bypassed completely by performing a rumenostomy. Potential complications of mandibular fractures include osteomyelitis, sequestrum formation, or abscessation of involved tooth roots. Failure or loosening of the implants is often not a problem because these injuries will heal rapidly. Removal of the implants can be performed using sedation once healing has occurred.

LAPAROTOMIES

Numerous surgical approaches to the bovine abdomen have been described, and all have various pros and cons. The majority of procedures can be performed via a flank laparotomy in the standing patient, but ventral midline or paramedian approaches are necessary in specific situations. Clipping a much larger area than is necessary will prevent any problems if the incision has to be extended and will limit any contamination of tissue if any drapes used should slip. Local anesthetic techniques can be used to facilitate surgery in the standing patient. IV sedation is sometimes required so that the patient tolerates this, but once the area is successfully anesthetized, most patients will settle down, often to the point that some will begin to ruminate.

REGIONAL ANALGESIC TECHNIQUES FOR ABDOMINAL SURGERY

For a flank incision, lidocaine can be injected directly over the line of the incision. Local anesthetic must be placed under the skin, into the muscle, and to the level of the peritoneum if complete analgesia is to be achieved. This is effective and simple, but may lead to an increased risk for incisional complications, such as infection or dehiscence. An alternative that does not involve injection directly into the surgical site is an inverted-L block. Local anesthetic is injected into all of the layers of tissue in an inverted-L pattern, vertically behind the last rib and then horizontally below the transverse processes of the lumbar vertebrae. This blocks the nerve fibers at a site distant to the location of the incision, and for this reason, the block must be continued at least a few centimeters distal to and caudal to the edge of the incision. If these blocks do not provide adequate analgesia, more local anesthetic can be placed easily and quickly, but since a large volume of local anesthetic can be used, care must be taken not to exceed the toxic dose of lidocaine (6 to 8 mg/kg).

Paravertebral analgesia can be performed, which requires the use of less local anesthetic and can provide a larger area of surgical analgesia than the other techniques. Two techniques are described, and the simplest to perform in dairy cattle (tend to be thinner and the landmarks are easily palpable) is the distal paravertebral technique. Here the transverse processes of lumbar vertebrae 1, 2, and 4 are palpated through the skin. An 18-gauge, 1½-inch needle is then inserted completely so that it lies parallel to and just below the palpable tip of the transverse process of L1. About 20 ml of 2% lidocaine is injected in a fan pattern, then the needle is withdrawn so that it can be relocated in the same fashion above the transverse process. Ten to 15 ml of lidocaine can be injected in the same fanlike pattern in the area. This process is repeated over the transverse processes of L2 and L4. This technique anesthetizes the nerves T13, L1, and L2 at a site distal to where they exit the vertebral column.

The proximal paravertebral technique requires a longer needle; an 18-gauge, 5-inch spinal needle passed through a 14-gauge, 1-inch guide needle is used for this technique. The 14-gauge needle is placed 2 cm lateral to midline at the cranial edge of the transverse process of L1. The spinal needle is then inserted through the 14-gauge needle down onto the transverse process. The spinal needle is then walked cranially, off the edge of the process. A “pop” will be felt as the needle penetrates the thick fascial layer, and 15 ml of lidocaine should be injected in this location. Withdrawing the needle roughly 1 to 2 cm will place it above the fascia, and another 15 ml of lidocaine should be injected at this site. The technique should be repeated over the transverse processes of L2 and L3.

Successful placement of either paravertebral block will result in analgesia of the flank, but this can take between 15 to 30 minutes. This can be confirmed by observing scoliosis (the side that is blocked will relax, making the spine bend laterally the other way); vasodilation, which will make the side palpably warmer (particularly in cool weather); and a lack of response to a noxious stimuli. Incomplete analgesia may resolve if more time is allowed for diffusion of the anesthetic to occur.

SURGICAL APPROACHES TO THE ABDOMEN

Most abdominal exploratory laparotomies are performed through the right flank (Figure 31-16). This approach provides access to most of the abdominal viscera, although only certain structures can actually be exteriorized. The proximal extent of the incision is approximately one handbreadth below the transverse processes and one handbreadth behind the caudal edge of the ribs. A 15-cm vertical incision will allow passage of an arm into the abdominal cavity. Keeping the incision located higher in the flank is desirable to limit the ability of intestine to prolapse out of the incision. Procedures commonly performed from the right flank include abdominal exploratories and correction of abomasal displacements and torsions. An approach through the left flank is used for C-sections, rumenotomies, or rumenostomies.

Certain procedures may require a ventral midline or paramedian celiotomy. Sedation is essential for these as is some form of restraining device to maintain the cow’s position. Tilt tables can be used, or the cow can be propped up in dorsal recumbency using bales of straw or ropes. Abomasopexies, C-sections, or umbilical procedures sometimes require this approach. Instead of paravertebral analgesia, local infiltration is often used or lidocaine is infiltrated on either side of the incision with a portion that converges together at the most cranial aspect of the incision.

RUMENOTOMY FOR GRAIN OVERLOAD

A rumenotomy is performed via a left flank laparotomy with the cow standing. A broad area should be clipped and prepped for surgery. The skin incision is oriented vertically and often needs to be bigger than usual flank laparotomy incisions (may need to be 20 cm) so that the rumen can be exteriorized and then secured. The rumenotomy site is the dorsal sac of the rumen. This is secured using one of two recommended rumenotomy procedures: use of a rumen board (Weingarth apparatus) or suturing the rumen wall to the skin. This is important to prevent contamination of either the peritoneal cavity or the skin and muscle layers with rumen contents. Ensuring that enough rumen is exposed beyond the site of fixation will help make closure easier. The contents of the rumen have to be evacuated manually, which is time consuming. Having specially designed feed bins to place the rumen contents into can be helpful. A normal trash can with multiple holes drilled through its bottom and a chicken-wire mesh insert to hold fiber in the can be used to allow fluid to drain out and hold in most of the fibrous portion of the rumen contents. This will make movement and subsequent disposal of the rumen contents easier. Siphoning off the fluid can be performed with a larger-bore tube, such as a Kingman tube, placed into the rumen via the rumenotomy. Once the rumen is emptied, transfaunation of ruminal fluid from a normal cow can be beneficial. This can either be given orally or via the rumenotomy before closure. Removing any gross contamination from the edges of the rumenotomy is important before suturing it closed in two layers. The body wall and skin can then be closed in a routine fashion.

A rumenostomy, or permanent rumen fistula, can be created using a similar technique. Commercial rubber rumen fistulae and plugs are available, and if one of these is to be used, close attention to the size of the surgical incision is necessary. The skin incision needs to be longer and should be about 15 cm. This will allow the fistula to form a tight seal and prevent leakage of rumen contents. The skin incision is continued through the external abdominal oblique muscle; then the deeper muscles are separated in the direction of their fibers. Following opening of the peritoneum, a three-layer closure technique can be used. The peritoneum is sutured to the abdominal muscles using an absorbable suture. Following exteriorization of part of the rumen, the rumen is sutured to the subcutaneous tissue, then the rumen is incised and the mucosa is sutured to the skin. Ensuring that the second layer is tight before incising the rumen will help minimize the risk of contaminating the abdomen with rumen contents. Placement of the rubber fistula and plug will now allow the rumen to be sealed, but accessible when necessary. This is usually used for research purposes, but can be helpful when treating sick cattle because it makes collection of ruminal contents for rumen transfaunation considerably easier.

TRAUMATIC RETICULOPERITONITIS

For the diagnosis and medical treatment for this condition, please see Chapter 22. Surgical intervention may be necessary if traumatic reticuloperitonitis (TRP) fails to respond to conservative treatment, if a foreign body is observed outside the reticulum on radiography, or if an intraabdominal or thoracic abscess is suspected. The approach of choice is a left flank exploratory laparotomy and rumenotomy using transruminal exploration. The technique required for rumenotomy is the same as that described for treating grain overload, with the exception that the incision is located a little more cranially to ensure that the reticulum can be reached by the surgeon. Most abscesses that form secondary to TRP are located on the medial wall of the reticulum and are usually tightly adhered. These abscesses are the most common causes of vagal indigestion associated with TRP. These tightly adhered abscesses can be lanced and drained into the reticulum or omasum and then explored for the presence of a foreign body. Lancing these abscesses can be difficult and requires a blind technique. Providing a scalpel blade on a loop of suture will allow the loop to be placed over the surgeon’s wrist to reduce the risk of dropping it into the rumen.

ABOMASAL DISPLACEMENTS AND VOLVULUS

Abomasal displacement is a common problem of high-producing dairy cows fed high-concentrate, low-roughage diets. Displacements are most likely to occur in the first 6 weeks after calving. Predisposing factors include high-grain diets with an increased amount of volatile fatty acids in the abomasum; hypocalcemia; concurrent diseases, such as mastitis, metritis, and ketosis; and lack of exercise. Increased volatile fatty acids, histamine release with concurrent diseases, and hypocalcemia may lead to abomasal dilation and atony and subsequent displacement of the abomasum from its normal right paramedian position to the left or right paralumbar area. Left displaced abomasum (LDA) is much more common than right displaced abomasum (RDA). Abomasal volvulus (AV) may occur after displacement to the right and carries a poorer prognosis than LDA or RDA because of compromise of the innervation and blood supply that occurs when the abomasum twists. AV can quickly lead to development of shock and toxemia if not diagnosed and treated early.

LDA, RDA, or AV can be diagnosed by auscultation of a distinct “ping” in the left or right paralumbar fossa area since the gas trapped in the abomasum produces a characteristic “metallic pinging” sound when percussing the area over the gas cap while simultaneously auscultating with a stethoscope.

The Liptak test can also be used as an aid in diagnosing LDA. After percussion of the abomasum on the left side under the last few ribs, an area just below the gas ping, which corresponds to the fluid level in the abomasum, is clipped and surgically prepared. Centesis is performed using an 18-gauge, 10- to 12-cm needle. Fluid with a pH less than 4.5 confirms the presence of an LDA. Aspiration of gas with a characteristic “burnt almond” odor is indicative of an LDA.

Surgery is usually necessary to correct abomasal displacements, and AV requires immediate surgical intervention. The choices of surgical approach and technique depend on the direction of the displacement, the presence of volvulus, the condition of the animal, and the surgeon’s preference. Traditionally a right flank laparotomy is performed to correct the displacement. The most helpful piece of equipment is a piece of surgical tubing (must be long enough to reach to the far side of the cow and then extend well clear of the surgical incision) attached to a large needle. This is taken into the abdomen, guarded by the surgeon’s hand, and carried round the caudal edge of the rumen and omentum. This is then tunneled through the abomasal wall to decompress it. Once decompressed, the abomasum can be swept or pulled back to the left side where either an omentopexy or pyloropexy can be performed to the abdominal wall. A right sided displacement or volvulus needs to be decompressed and repositioned before pexying to the body wall. Surgical approaches using a left and right flank laparotomy or laparoscopic approaches have been described and are beyond the scope of this text. If a cow has had a recurrence of an abomasal displacement following a left-sided approach, a paramedian abomasopexy may be indicated. In this situation, the cow is sedated and rolled into dorsal recumbency either on a tilt table or by casting her with ropes. The ventral abdomen is clipped and prepped for a paramedian incision roughly 10 cm behind the xyphoid process and 10 cm to the right of midline. The surgical site is anesthetized using local infiltration of local anesthetic and the site is sterilely prepped. An incision is made into the body wall, and the abomasum is exposed through this incision. An abomasopexy is performed, by suturing the abomasum and the body wall closed simultaneously, resulting in a strong adhesion that will prevent future displacements. Postsurgically the diet should be restricted to roughage only, and grain should be introduced gradually into the diet once recovery is complete.

AFTERCARE FOLLOWING A LAPAROTOMY

Feed can be reintroduced once the cow has recovered from any sedation or general anesthesia. It is usually ideal to withhold feed and water until they are no longer showing any signs of sedation, which with xylazine can be prolonged. The goal is to return them to full feed, but this should be done gradually over a few days. Cows that are relatively healthy will often eat well after surgery and will require little further management. If they have been anorectic for a prolonged period, offering different feed is important to try and tempt the cow to eat something. If necessary, force feeding can be performed via a large-bore stomach tube. Slurries made from alfalfa meal or a pelleted feed can be used, but can be difficult to pump through the tube. Constant stirring or increasing the fluid content of the feed can be helpful to ease its passage through the tube. Rumen fluid transfaunation can also be helpful for these cows, if possible. Keeping the cow in a well-bedded, dry, draft-free environment will ensure that they are comfortable and should help them to recover. The incision will usually need little if any care. An infection of the surgical site can be identified by swelling, discomfort upon palpation of the area, and usually some discharge. Flank incisions can be treated by creating ventral drainage and allowing any purulent material to drain out. This is often all that is needed, and the incision will heal by second intention with routine wound management.

OTHER GASTROINTESTINAL CONDITIONS

The remainder of the gastrointestinal tract can also require surgical therapy. In the small intestine, intussusceptions, volvulus, or hemorrhagic bowel syndrome can occur. Cecal tympany or displacement can sometimes be mistaken for an RDA (ping in this case will be further caudal and dorsal on the flank than for an abomasal problem), or this can even become intussuscepted into itself. Obstructions or intussusceptions of the spiral colon can also occur. These often are evaluated surgically, and an approach through the right flank is most commonly used. Exposure of the entire gastrointestinal tract is not always possible, so if the incision needs to be elongated ventrally, general anesthesia may be indicated to prevent sudden movement or the cow becoming sternal, which could allow (uncontrolled evisceration) parts of the intestines to fall onto nonsterile surfaces.

Adhesion formation can be a sequela of abdominal surgery or following a separate disease process. This will often lead to signs of an abomasal outflow obstruction, general colic, or weight loss. An exploratory laparotomy can be performed to evaluate this, but treatment options are limited. Adhesions can be broken down, but the risk of recurrence is high.

LAMENESS

Lameness is commonly encountered in cattle and is most often (88%) caused by lesions or problems in the foot. The majority of these conditions have been discussed in Chapter 22. Upper leg problems, such as anterior cruciate ligament rupture, coxofemoral (hip) luxation, fractures, and arthritis, account for the remaining 12% of lameness seen. When foot problems occur, they are most often seen in the claws that bear the most weight, front medial and hind lateral claws. It is important to examine all foot problems early since many conditions can progress to osteomyelitis and/or septic arthritis if not properly treated. Regardless of the cause of lameness, it can lead to loss of production as a result of decreased milk production, weight loss, delayed breeding or anestrus, and culling. Intensive housing and feeding of large groups of animals has lead to an increased incidence of lameness.

REGIONAL ANALGESIA AND ANTIBIOTIC PERFUSION TECHNIQUES AND PMMA IMPLANTS

Regional analgesia (IV retrograde analgesia) of the foot and/or distal limb is commonly performed before claw amputation or corn removal, although the regional block can also be used for other surgeries or painful techniques of the foot or distal limb or as a diagnostic aid in lameness examinations. A tourniquet is applied distal to the hock or carpus in the midmetatarsal or midmetacarpal area. A superficial vein is located, either the common dorsal metacarpal (metatarsal) vein or the palmar or plantar metacarpal (metatarsal) vein, and surgically prepared. An IV injection of 15 to 30 ml of 2% lidocaine will provide analgesia in 5 minutes, which will persist until the tourniquet is released (the tourniquet should not be left in place more than an hour) (Figure 31-17). It is ideal to have the cow’s leg secured to prevent extravascular placement of the local anesthetic. Even with restraint, movement is often still possible, so the use of a butterfly catheter with a short extension can be helpful. An alternative to this technique involves placing the tourniquet above the tarsus or carpus to achieve analgesia more proximally. Accordingly, more lidocaine should be used to block this larger area (may need 30 to 60 ml of perfusate). This same technique can be used to perform regional perfusion of antibiotics to the distal limb for the purpose of treating localized infections, such as foot rot with cellulitis. An antibiotic with an IV formulation should be used and can be diluted with sterile saline to produce a perfusate volume of at least 20 to 30 ml. Cephalosporins can be injected through the catheter and allowed to perfuse the limb distal to the tourniquet for approximately 45 minutes. Both of these techniques are primarily used in cattle, but can be applied to all food animal species. The implantation of antibiotic-impregnated polymethylmethacrylate (PMMA) beads subcutaneously near infected joints has shown promise for treatment of septic arthritis in calves. The beads slowly release antibiotics into the joint and appear to be more effective than systemic antibiotic treatment or joint flushing alone. Techniques such as joint flushing, PMMA bead implants, regional perfusion, and systemic antibiotics used in combination work well to resolve septic arthritis. Following resolution of the sepsis, the beads can be removed, but should not cause any problem if left in place.

SURGICAL DISEASES OF THE HOOF AND PHALANGES

ANESTHESIA OF THE UROGENITAL AND REPRODUCTIVE SYSTEM

A caudal or low epidural provides loss of sensation to the anus, vulva, perineum, and caudal aspects of the thighs. It is used for relief of tenesmus and obstetric straining; vaginal, rectal, and uterine prolapse repair; and surgical procedures of the perineal area. Injection is made between the first and second coccygeal (Cy1 to Cy2) vertebrae or in the sacrococcygeal space. The space is located by moving the tail up and down and while palpating for the first obvious articulation caudal to the sacrum. Using aseptic technique, an 18-gauge, 1½-inch needle is inserted through the space on the midline at a 10-degree angle (tip of needle directed cranially) until a drop of lidocaine placed in the hub of the needle is sucked into the space. An alternative approach involves insertion of the needle until it hits the floor of the spinal canal at which time the needle is backed out slightly to enter the epidural space. There should be no resistance to injection. The dose of lidocaine used is 0.5 to 1 ml of 2% lidocaine per 45 kg body weight with which the animal should have adequate analgesia but remain standing. If sedation is helpful or longer duration of action is indicated, xylazine can be given alone (0.05 mg/kg diluted to 5 ml in sterile saline) or in combination (use a lower dose, 0.03 mg/kg) with the lidocaine.

A bilateral, internal pudendal nerve block can be performed to facilitate examination or surgery of a bull’s penis. This nerve can be palpated via a rectal examination, on either side of the pelvic canal, dorsal to the pudendal artery where it is associated with the lesser sciatic foramen. Care must be taken to only inject the area around the nerve, and about 15 ml is injected in the region of the nerve and slightly caudally.

UROLITHIASIS

Urolithiasis is the result of formation of calculi (uroliths) within the urinary tract. The result of these uroliths varies from minor urinary tract irritation to complete obstruction of urine flow. The nonclinical manifestation of this condition is referred to as urolithiasis, whereas the clinical form is termed obstructive urolithiasis. When complete obstruction occurs, there is marked distention of the urinary bladder with eventual rupture of the bladder, the urethra, or both. Depending on the site of rupture, urine accumulates in the ventral subcutaneous tissues (urethra) or in the abdomen (bladder) resulting in swelling commonly referred to as water belly.

Although there is no sex predilection for development of calculi, males are much more likely to become obstructed as a result of the length, shape, and size of their urethra. The most common site of obstruction in cattle is the distal sigmoid flexure of the penis (Figure 31-19). Feedlot animals receiving grain rations with high phosphorus levels are predisposed to developing phosphate calculi.

Clinical signs of acute urethral obstruction are attributable to trauma to the urinary tract epithelium and bladder distention. Early in the course, the animal repeatedly assumes a posture for urination, but little or no urination results from these attempts to void. As bladder distention progresses, the animal may tread, stretch, tail swish, and kick at its abdomen. Blood and/or crystals may be present on the preputial hairs. Nonspecific signs such as anorexia, mild bloat, and lethargy are also common. Owners often misinterpret these signs as evidence of acute gastrointestinal disorders, especially since affected animals may show signs similar to colic. After the bladder or urethra ruptures, straining ceases, and the animal may go through a brief phase of euphoria; however, azotemia (increased blood urea nitrogen [BUN] and creatinine) and dehydration quickly develop. If urethral obstruction is diagnosed early, before azotemia develops or before the bladder or urethra rupture, the animal may be immediately slaughtered. If not, medical and/or surgical treatment should be initiated quickly.

Medical management involves the use of muscle relaxants to facilitate passage of the calculi, antimicrobial therapy for urinary tract infection, and the use of a urinary acidifier, such as ammonium chloride. Medical therapy alone is rarely successful, so it may be necessary to consider surgery in some cases. Perineal urethrostomy may be chosen as a salvage procedure, particularly for feedlot steers or bulls of low economic value (Figure 31-20). This surgical approach allows for relief of obstruction and resolution of the uremia before slaughter. Long-term, urethral stricture has been a problem with this technique. The procedure is performed with the animal standing and analgesia provided by a caudal or low epidural block.

The low approach is often preferred for perineal urethrostomy. This allows the penis to be diverted caudally at such an angle as to prevent urine scald to the hind legs. It also makes it possible to perform repeated procedures higher, if necessary. The skin incision is made beginning at the dorsal aspect of the scrotum or scrotal remnant and extending dorsally on the midline for 10 to 15 cm. The incision is continued until the penis is encountered. The retractor penis muscles may be the first structures seen and are frequently mistaken for the penis. These muscles are superficial to the penis, pink, soft, and easily separated into two structures. The penis is a relatively firm, single structure covered by the white tunica albuginea. Once the penis has been located, it is bluntly dissected from the surrounding tough fascia and pulled caudally out of the incision. The penis is transected at a length adequate to allow the transected end to exit the perineal incision without tension leaving a 2- to 3-cm stump exposed. The stump is sutured to the skin of the lower part of the incision using a mattress suture that surrounds the corpus cavernosum penis (CCP) and passes under the urethra. This suture limits hemorrhage from the CCP. In addition, the urethra can be split for several centimeters and spatulated by suturing the urethral mucosa and tunica albuginea to the skin using 2-0 or 3-0 absorbable suture material. This optional technique is intended to limit stricture of the urethral opening. The remaining skin incision is closed with simple interrupted sutures of nonabsorbable suture material. Urethral obstruction may recur as a result of additional calculi or because of stricture of the urethrostomy site.

An alternative surgical procedure that can be used for valuable breeding bulls or “pets” is the ischial urethrostomy, a temporary urethrostomy with catheter placement. This technique allows for urine egress through a Foley catheter placed in the urethra at the level of the ischium, just below the anus, and antegrade or retrograde flushing of the distal urethra to remove calculi. When the tube is pulled, the urethrostomy usually heals by second intention without stricture formation. This procedure can be useful for preservation of fertility in valuable breeding bulls.

Dietary management is the key to control and prevention of obstructive urolithiasis. The calcium to phosphorus ratio of the overall diet should be in the range of 2:1 to 2.5:1. A continuous supply of fresh, clean water should be available at all times, and salt may be added to the ration up to 4% to promote water intake and diuresis. In addition, vitamin A may be added to the ration to help prevent desquamation of epithelial cells in the bladder. Prophylactic use of urinary acidifiers is advocated; administration of ammonium chloride at 1% to 1.5% of the ration is recommended.

RUPTURED BLADDER

This is seen as a secondary complication of obstructive urolithiasis that is not treated promptly enough. In adults, this complication is diagnosed by the clinical signs of progressive abdominal distention, dehydration, anorexia, and depression. Confirmation often requires abdominocentesis, which produces a clear, yellow fluid with a peritoneal:serum creatinine ratio of 2:1 or greater. Urinary catheterization is reported to be an effective treatment to allow the bladder time to heal if a dorsal tear is present. Ventral tears usually require surgical repair, but gaining access to this region of the bladder can sometimes be challenging via a flank laparotomy, necessitating a ventral approach.

UROVAGINA

Older cows with poor perineal conformation or those in poor condition may be more susceptible to urovagina. Urine accumulates in the vagina, resulting in marked inflammation, which can lead to infertility. Performing a vaginal examination will reveal the presence of urine in the vagina, which is considered to be diagnostic. If the cow is to be treated, surgical correction is necessary, to either elongate the urethra or to elevate the transverse fold to redirect the urine externally. Anesthesia can be provided using a caudal or low epidural or by locally infiltrating lidocaine along the site of the incisions. Restraining the cow in stocks is preferable to limit their movement. Before beginning surgery, the rectum should be emptied, and the tail should be restrained so that it is clear from the surgery site. Self retaining retractors can be helpful for this procedure, or alternatively, stay sutures can be placed to hold the vulva open against the perineum. Adequate lighting is best provided by the surgeon wearing a head lamp. Other forms of lighting are difficult to aim properly, and the surgeon’s head usually obstructs the beam. Urethral extensions can be created by splitting the transverse fold, which is located above the urethral orifice in the vagina, and then creating a new shelf by continuing this incision laterally along the vaginal wall on both sides. Dissection of these shelves distally to allow them to meet in the midline with no tension is performed bluntly, and then the mucosal sheets are sutured in a Y pattern. Leaving a urinary catheter in place for a period postoperatively is helpful to ensure that urination can occur because some postoperative swelling may occur.

SUPERNUMERARY TEAT REMOVAL

Removal of extra teats is of most value in young dairy heifers, but it is also performed in beef heifers intended for show. Often this procedure is performed at the time of brucellosis vaccination. The extra teats are removed flush with the skin and parallel to the normal folds of the udder using curved scissors. In young calves, suturing the skin is not usually necessary. Care must be taken not to remove any of the four normal teats.

OVARIAN DISEASE

Ovarian cysts, abscesses, or neoplasms occur in cattle. Other indications for ovariectomy include preventing pregnancy or to try and improve fattening of feedlot cows. To minimize the risk for hemorrhage, ovariectomy should ideally be performed when the ovary is in the follicular or early luteal phase. A flank approach is often used if a unilateral ovariectomy is performed or in situations where the ovary is enlarged. A colpotomy can be used for a bilateral ovariectomy if both are a normal size, but will require a caudal epidural. Achieving good hemostasis is essential, especially in pathologic ovaries. To minimize discomfort during this process, applying a gauze or lap sponge soaked in lidocaine to the ovarian pedicle may reduce any movement by the patient. This gauze or sponge should be attached to the surgeon to prevent it from being lost inside the abdomen. Holding this sponge over the pedicle for at least a minute may be beneficial. Transfixation sutures, application of a chain écraseur or emasculators can be used if a flank approach is used. Specific instruments, such as a Kimberly-Rupp or a Willis rod, should be reserved for normal ovaries.

Postoperatively, these patients should be monitored for signs of hemorrhage because inadequate hemostasis can be life threatening.

DYSTOCIA

C-section is indicated when there is a chance of delivering a live calf during a dystocia, malposition, or presentation or when the calf is excessively large. Several approaches are available for C-section, including flank approaches (right or left), paramedian approaches (right or left), or the ventral midline approach. The technique used is determined by the size, temperament, and physical condition of the cow and the veterinary surgeon’s preference. Most commonly an approach is made in the standing patient via an incision through the left paralumbar fossa, using the landmarks described earlier in this chapter for a right-sided flank laparotomy. One of the benefits of using a left flank approach is that the rumen will obstruct other viscera, such as small intestine, from eviscerating through the incision. This is of particular concern if the incision has to be extended distally as a result of the size of the fetus (this incision will be considerably larger than that necessary for an abdominal exploratory). The limbs of the fetus are used to maneuver the uterus to the body wall. The limb is then pulled through the incision and used to lock the uterus and calf in place. The uterus is then incised over the metacarpus or metatarsus, and the calf can be exteriorized with minimal abdominal contamination. Closure of the uterus is performed in two layers, with at least one layer in an inverting pattern. The uterus is then lavaged and replaced into the abdomen before routine closure of the laparotomy site. If available, oxytocin can be administered at this stage to aid uterine involution and to minimize hemorrhage. This will also encourage passage of the placenta, assuming that it has not been sutured during the uterine closure. If the calf is not viable or is emphysematous, alternative surgical approaches may be indicated, but are often limited by available facilities, equipment, or personnel.

UTERINE TORSION

This is an infrequent cause of dystocia, but, if present, will prevent parturition from proceeding. It is most commonly seen during early labor and is identified when an animal that is having a prolonged labor is evaluated rectally or rarely during a vaginal examination. The torsion is identified by the location of the broad ligaments because one of these is pulled tight as the uterus rotates away from its origin, whereas the other broad ligament is less taut. This also provides information on the direction of the torsion, either clockwise or counterclockwise (when viewed from behind the cow). If the calf’s limbs can be palpated through the cervix, attempts can be made to swing the calf and uterus to reduce the torsion. This can be difficult when the calf is large or the cow is small. Rolling the cow while placing pressure on the flank (usually with an assistant standing on a plank of wood placed over the flank and paralumbar fossa) to unwind the torsion can be attempted, but only if the direction of the torsion has been correctly identified. For example, to reduce a clockwise torsion, the cow should be placed in right lateral recumbency and then rolled onto her left side while pressure is applied to try and stabilize the calf. The rectal examination should then be repeated to see if the torsion has been reduced. If this is not successful, it can be repeated, but a flank celiotomy and C-section may be necessary.

VAGINAL AND UTERINE PROLAPSE

Vaginal prolapse is a fairly common occurrence in cattle (Figure 31-21). It usually occurs in pluripara cows during the last 2 months of gestation and tends to recur during subsequent pregnancies. Hereford, Santa Gertrudis, and Holstein breeds seem to be more commonly affected. Factors that influence the development of vaginal prolapse include increased estrogen levels in late pregnancy, increased fetal size with increased intraabdominal pressure in late pregnancy, bulky diets causing increased intraabdominal pressure, recumbency that forces the urinary bladder and other organs into the pelvic cavity and places pressure on the constrictor vestibuli muscle, and obesity with proliferation of pelvic fat (vaginal prolapse can occur in overconditioned, nonpregnant heifers). A new population of vaginal prolapse cows is emerging in embryo donor cows that are superovulated. Hormonal extremes are a suggested cause of vaginal prolapse in these cows.

Initially the vaginal prolapse may be intermittent, only protruding when the animal is lying down, but eventually it progresses to the point that it remains prolapsed at all times. Although vaginal prolapse is not an emergency, it should be repaired soon after it is noticed by the owner. The most common method of repair is the Buhner technique (see later). Since this condition usually occurs before calving, the cow will need to be observed closely for signs of impending parturition. Owners should be advised to cull these cows since this is likely to recur with subsequent pregnancies.

Uterine prolapse is common in the cow as a result of the anatomic suspension of the uterus (Figure 31-22). It occurs at parturition or shortly thereafter while the cervix is fully dilated. The uterus invaginates, and the uterine mucosa protrudes through the vulvar lips. Uterine prolapse is more likely to occur in first-calf heifers and is not likely to recur at subsequent calvings. Factors playing a role in the development of uterine prolapse include concurrent hypocalcemia, recumbency, such as that resulting from obturator nerve paralysis, dystocias with excessive straining, excessive force used during fetal extraction, and unnecessary traction on retained placentas.

Uterine prolapse is considered an emergency because of the possibility of shock from exposure of uterine mucosa, fatal hemorrhage from rupture of the middle uterine arteries, and concurrent hypocalcemia. In addition, the urinary bladder and/or intestines may also be involved within the prolapse.

To prevent uterine prolapse, it is wise to force the animal to stand as soon as possible after calving and administer oxytocin to begin uterine involution.

Treatment consists of replacement of the prolapsed portion and application of a retention suture (Buhner) to prevent recurrence. This is best accomplished with the animal in a standing position with the aid of a caudal epidural. If the cow is already down and cannot get up, attempt to elevate the hindquarters or pull the cow’s hind legs straight out behind her as she lies in sternal recumbency; an epidural helps maintain this position. Before replacement of the uterus, the placenta is removed atraumatically, if possible; the uterus is cleansed with warm water and a mild disinfectant; and the uterus is lubricated to facilitate replacement. Elevation of the uterus makes it easier to replace. The uterus is inserted a little at a time, making certain that the apical end of each horn has been completely returned to its normal position. Oxytocin (40 IU), calcium, if necessary, intrauterine antibiotics, and systemic antibiotics should be administered. The vulva is then sutured using the Buhner suture technique.

The Buhner suture technique is useful for retention of both vaginal and uterine prolapse. It is a buried purse-string suture that simulates the action of the constrictor vestibuli muscle. To begin the suture pattern, a 1-cm horizontal skin incision is made midway between the dorsal commissure of the vulva and the anus. Another horizontal incision is made at the ventral commissure of the vulva. The Buhner needle is inserted into the ventral incision, driven deeply (5 to 8 cm) and directed out of the dorsal skin incision. The eye of the needle is threaded with Buhner suture tape, and the needle is pulled out through the ventral incision. The procedure is repeated on the opposite side resulting in two free ends of tape from the ventral incision. The suture is tightened so that only two to three fingers can be inserted into the vagina. This allows for normal urination, but prevents reprolapse of the vagina or uterus. This suture may be completely buried and left in place indefinitely. The Buhner suture tape is particularly strong, will not disintegrate, and is well tolerated by the tissues. The tape may be tied such that it can be untied as the cow begins to calve, as in the case of prepartum vaginal prolapse.

FIBROPAPILLOMAS OF THE PENIS

Fibropapillomas of the penis in bulls are caused by the bovine papillomavirus (Figure 31-23). They tend to occur in young bulls housed together and are contracted from warts on other parts of the body when the bulls display homosexual behavior by “riding” each other. The warts may result in hesitancy or refusal to breed and may become large enough that they prevent extension (phimosis) or retraction (paraphimosis) of the penis. Surgical removal of the wart(s) is one treatment option and may be performed in conjunction with vaccination with either a commercial or autogenous wart vaccine. These can be removed in the standing animal using local anesthetic (either bilateral internal pudendal nerve block or anesthesia of the dorsal penile nerve) and restraint. The fibropapilloma can be excised, and the penile mucosa should be sutured using an absorbable suture. Recurrence is not uncommon.

PREPUTIAL PROLAPSE

Preputial prolapse tends to occur in bulls of Bos indicus influence (i.e., Brahman, zebu) as a result of several predisposing breed-related factors, including a pendulous sheath, long prepuce, large preputial orifice, and the absence of retractor prepuce muscles. The prepuce may become traumatized as a result of environmental exposure because of the inability of the bull to keep the prepuce within the preputial cavity, or trauma may occur as an accident during breeding. Once traumatized, the prepuce begins to swell and prolapses further, making it susceptible to further injury (Figure 31-24). The affected prepuce is treated initially by soaking in warm water with Betadine and Epsom salts to reduce swelling and control infection. The prepuce is returned to the preputial cavity and wrapped with a tube in place to prevent further trauma. Once the inflammation and infection are under control, surgery (reefing) to remove scar tissue and shorten the prepuce may be considered if the bull is valuable. Without surgery, recurrence rate for preputial trauma and reprolapse is high.

OCULAR SQUAMOUS CELL CARCINOMA (CANCER EYE)

Ocular squamous cell carcinoma (OSCC), the most common tumor of cattle, is estimated to cause annual losses of $20 million in beef cattle in the United States. Losses result from condemnation of affected carcasses and loss of prime breeding stock.

The cause is multifactorial; there appears to be a genetic predisposition for development of ocular squamous cell tumors, and exposure to ultraviolet radiation (amount and intensity) and lack of protective pigmentation around the eye play an important role. Tumors occur predominantly in Herefords, but also other breeds with similar patterns of periocular pigmentation, such as Simmentals and Holsteins. It is seldom seen in animals less than 4 years of age, and peak age of occurrence is 8 years. The tumors begin as benign plaques or papillomas that often progress quickly to squamous cell carcinoma. Common sites for development of malignancy in decreasing order of prevalence are the lateral and medial limbus (Figure 31-25), eyelids (especially lower), third eyelid, and medial canthus.

Treatment modalities include cryotherapy, radiofrequency hyperthermia, immunotherapy, chemotherapy, radiation therapy, and surgery (keratectomy, lid resection, or extirpation). Although commonly referred to as enucleation, the term extirpation is more accurate. Extirpation is removal of all the contents of the bony orbit. Since this procedure is commonly performed for advanced cases of OSCC where removal of all ocular tissue is crucial and because cosmetic appearance is not as important in cattle, we are more likely to perform extirpation rather than evisceration or enucleation of the eye.

Extirpation is performed with the aid of a retrobulbar or Peterson eye block. To perform the Peterson block, an 18-gauge, 12-cm needle bent to a slight curve is used to block cranial nerves II, IV, V, and VI as they emerge from the round foramen. The needle enters the skin at the angle produced by the supraorbital process and the zygomatic arch and is directed medially. The concavity of the needle is directed caudally so that the point of the needle will pass around the cranial border of the coronoid process of the mandible and to the pterygopalatine fossa of the skull. A reliable indication of proper position is a severe twitching of the eyelids. Once the proper position is located, 5 ml of local anesthetic is injected. The needle is repositioned slightly two more times with injection of 5 ml of local anesthetic each time. Aspiration is essential before injection to prevent depositing lidocaine in the cerebrospinal fluid (CSF), possibly resulting in sudden death. Before withdrawing the needle completely, it is redirected caudally just beneath the skin along the zygomatic arch to block the auriculopalpebral nerve. The four-point retrobulbar block is performed by injecting through the eyelids, both dorsally and ventrally, and at the medial and lateral canthi using a slightly curved, 18-gauge, 12-cm needle that is directed to the apex of the orbit. Five to 10 ml of local anesthetic are injected at each site. Exophthalmos, corneal anesthesia, and mydriasis indicate a satisfactory retrobulbar block.

The eye is surgically prepared, and the lids are sutured or clamped together. A transpalpebral incision is made approximately 1 cm from the lid margins (unless the disease extends beyond this margin). The skin incision is full thickness, but does not penetrate the palpebral conjunctiva; the conjunctival sac helps contain contaminated ocular structures during surgery. Sharp dissection is continued 360 degrees around the bony orbit. The orbital ligament is incised at the medial canthus, and the muscles, adipose, lacrimal glands, and fascia are removed. The optic artery can be ligated, significantly reducing hemorrhage, or the lids can be tightly closed and a gauze stent placed over the incision to provide pressure and hemostasis. The lids are closed with appositional or everting interrupted sutures using nonabsorbable No. 3 suture material. If excessive skin must be removed such that the incision cannot be closed, the orbit can be packed with gauze that is removed in 48 to 72 hours. The incision is left to heal by second intention. NSAIDs and antibiotics may be administered before surgery.

DEHORNING

If possible, calves should be dehorned within the first month of life (or when the horn buds are first palpable) using a dehorning iron. The electrothermal dehorning technique is easy to perform when the calf is young; produces desirable, cosmetic results; and is much less stressful to the young calf. Dehorning of beef calves is commonly performed at the time of weaning in conjunction with castration, vaccination, and other management procedures. This age group is usually dehorned using a Barnes dehorner or scoop to remove the horn (Figure 31-26). Hemostasis, which is crucial, is provided by pulling or twisting the cornual artery. Calves older than 6 months may have exposed frontal sinuses after dehorning and may be at greater risk for development of sinusitis. Dehorning mature cattle often requires analgesia via a cornual nerve block. The block is performed by injecting 10 ml of 2% lidocaine under the frontal crest halfway between the lateral canthus of the eye and the base of the horn. Large horns are removed with a dehorning saw or Gigli wire. Another method of dehorning cattle is surgical or cosmetic dehorning, which is usually performed on show cattle. This method requires local or regional analgesia. An elliptical incision is made around the base of the horn, the horn is removed, and the skin incision is closed. This surgical technique allows for a more cosmetic appearance to the poll and reduces the chances of postoperative hemorrhage or infection.

CASTRATION

Several techniques are available for castration of calves. As with dehorning, castration is best performed when the calf is young because it is easier and less stressful to the calf at that time. Castration of young calves is often done without analgesia. Small calves can be adequately restrained on the ground, whereas larger calves are restrained in a chute with the tail pushed tightly up over the back. A technique commonly employed is the “open” method in which the bottom one third to one half of the scrotum is excised exposing the testicles. In young calves, the testicles are pulled until the cords break. In older calves, the cord can be sharply transected or an emasculator that crushes and cuts can be used to separate the cord (Figure 31-27). Another less commonly used technique is a “closed” castration using an emasculotome, which crushes the cord within the scrotum without cutting the scrotal skin. This technique is also referred to as bloodless castration or pinching. Castration in young calves has also been performed by application of an elastrator band. It is important to make certain that both testicles are below the band when the procedure is completed. It takes 2 to 3 weeks for the scrotum and testicles to slough. This technique has been associated with development of tetanus; therefore vaccination for tetanus may be advisable.

UMBILICAL HERNIAS AND INFECTIONS

As in other species, the umbilicus consists of paired umbilical arteries, a urachus, and an umbilical vein. The foramen where these exit the body wall is a common site of herniation, and this is considered to be a hereditary defect in some breeds, such as Holsteins. Any increase in size of the umbilical stalk, discharge from it, or swelling associated with the adjacent tissue warrants closer investigation. Simple umbilical hernias do occur and if small can be managed with application of belly wraps, hernia clamps, or elastrator bands. Close examination and palpation of the hernia and its ring is vital to ensure that it is completely reducible, no intestines appear to be in the hernia sac, there is no evidence of infection, and that the hernia is small (less than 5 cm in length). Ultrasonographic examination can be useful to identify structures within the hernia sac. Hernias that are greater than 5 cm in length will often benefit from an umbilical herniorrhaphy.

The majority of hernias or umbilical swellings are associated with infection in one or more of the umbilical remnants. Palpation of the mass is often of limited use diagnostically because it is firm, hot, swollen, and the patient usually resents palpation. Ultrasonographic examination allows the umbilical structures to be visualized and any enlargement or involvement of bladder or liver to be identified before initiating treatment. Medical treatment can be started in an attempt to treat the infection, but surgical resection can be necessary for severely affected patients.

Omphalectomy or umbilical herniorrhaphy can be performed with the calf in dorsal recumbency using sedation and a local block or general anesthesia. Feed does not need to be withheld for as long as for adult patients, but this should be removed approximately 6 to 8 hours before surgery. A large area should be clipped and prepped for surgery as if the umbilical vein or urachus is infected; the surgical incision may have to extend as far cranially as the xiphoid process or caudally to the pelvis. If the vein is infected up to the liver, a marsupialization may need to be performed that will require a second incision lateral to the main site. Attempt to remove the infected tissue intact; this may necessitate resection of the apex of the bladder. Following removal of the infected tissue, the body wall will be repaired. Some defects may be large enough to require a mesh herniorrhaphy, but most can be sutured closed.

Following surgery, the calf must be maintained in a stall for a month. Allowing excessive exercise will often lead to incisional complications, such as edema, seroma formation, or dehiscence. If umbilical vein marsupialization was performed, the stoma must be cleaned daily, and low pressure lavage with sterile fluid can be performed to try and treat the infected structures that could not be removed. This stoma will often need to be repaired in the future because it will often form a small hernia when the infection has resolved.

URINARY SYSTEM

Male small ruminants are at high risk for developing urolithiasis as a result of the feeding of excessive grain in the diet. The cause and clinical presentation is similar to that described in cattle. Goats that are obstructed tend to vocalize because of pain. Small ruminants are small enough that it is possible to palpate and/or ultrasound their urinary bladders, which further aids diagnosis of the condition. Management of this condition is somewhat different in small ruminants. Small ruminants possess a urethral process or vermiform appendage, which is usually the first place obstruction occurs. The second most common site of obstruction is the distal sigmoid flexure. Oftentimes calculi resemble sand, which may block most of the distal portion of the urethra.

The urethral process should be examined in all cases of suspected urolithiasis in small ruminants since this is the most common location for calculi to lodge. The penis and urethral process can be exteriorized by placing the animal in a sitting position on its rump (Figure 31-28). If necessary, a lumbosacral epidural can be performed. Epidural anesthesia provides analgesia and prevents resistance to exteriorization of the penis caused by the retractor penis muscles. Lidocaine (2%, 1 ml/20 lb not to exceed a total dose of 15 ml in any small ruminant) is injected into the epidural space at the lumbosacral junction (Figure 31-29). Loss of motor control to the hind legs lasts from 1 to 3 hours, so the patient should be recovered on a well-bedded surface to prevent trauma to the rear legs. Once the penis is exteriorized, it can be grasped with dry gauze. If the urethral process is obstructed, it can be amputated close to its attachment to the glans. If the urethral process is not present, it may mean that it had already been amputated or it may have necrosed and sloughed by itself during a previous episode of obstruction. Immediate urethral patency may occur after urethral process amputation; however, reobstruction is common. Consequently, it appears that urethral process amputation alone rarely results in a long-term cure.

Urethral catheterization with saline flushing may be attempted to relieve obstruction; however, the bladder is difficult to catheterize because of the presence of the suburethral diverticulum in ruminants, and complications associated with catheterization include urethritis, urethral rupture, and urethral damage leading to stricture.

Perineal urethrostomy may be suitable in cattle as a salvage procedure (Figure 31-30). Urethrostomy frequently results in stricture formation in the urethra and is probably not a good choice for pets because of a shortened life span.

Cystotomy and/or tube cystostomy have become the procedures of choice for treatment of obstructive urolithiasis and often result in prolonged life and preservation of breeding capability in breeding males. Using this procedure, calculi can be removed from the bladder, and normograde and retrograde urethral flushing can be attempted. In addition, a Foley catheter placed in the bladder allows urine egress while the urethra and bladder heal (Figure 31-31). The catheter is then removed when it is determined that the animal can urinate a normal stream consistently from the urethra.

OPHTHALMIC SYSTEM

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