Hyposplenism

Congenital absence of the spleen is associated with complex cyanotic heart defects, dextrocardia, bilateral trilobed lungs, and heterotopic abdominal organs (Ivemark syndrome; Chapter 425.11). Splenic function is usually normal in children with congenital polysplenia. Functional hyposplenism may occur in normal neonates, especially premature infants. Children with sickle cell hemoglobinopathies (Chapter 456.1) may have splenic hypofunction as early as 6 mo of age. Initially, this is caused by vascular obstruction, which can be reversed with red blood cell (RBC) transfusion or hydroxyurea. The spleen eventually autoinfarcts and becomes fibrotic and permanently nonfunctioning. Functional hyposplenism may also occur in malaria (Chapter 280), after irradiation to the left upper quadrant, and when the reticuloendothelial function of the spleen is overwhelmed (as in severe hemolytic anemia or metabolic storage disease). Splenic hypofunction has been reported occasionally in patients with vasculitis, nephritis, inflammatory bowel disease, celiac disease, Pearson syndrome, Fanconi anemia, and graft vs host disease.

Splenic hypofunction is characterized by RBC inclusions in peripheral blood smears (Howell-Jolly bodies or Heinz bodies), “pits” on interference microscopy, and poor uptake of technetium on spleen scan. Patients with functional hyposplenism or asplenia are at increased risk for sepsis from encapsulated bacteria.

Trauma

Injury to the spleen may occur with abdominal trauma. Small splenic capsular tears may cause abdominal or referred left shoulder pain as a result of diaphragmatic irritation by blood. Larger tears result in more severe blood loss, with similar pain and signs of hypovolemic shock. Previously enlarged spleens (as in patients with infectious mononucleosis) are more likely to rupture with minor trauma. CT scan with IV contrast is the best imaging modality to assess splenic trauma.

Treatment of a small capsular injury should include careful observation with attention to changes in vital signs or abdominal findings, serial hemoglobin determinations, and the availability of prompt surgical intervention if a patient’s condition deteriorates (Chapter 66). RBC transfusion requirements should be minimal (<25 mL/kg/48 hr). These patients are usually hospitalized for 10-14 days and have their activities restricted for months. Laparotomy, with or without splenectomy, is indicated for more marked abdominal bleeding, in patients who have clinical instability or deterioration, or when other organ damage is suspected. Partial splenectomy and splenic repair should be substituted for total splenectomy when feasible to maintain some splenic immune function.

Splenectomy

Splenectomy should be limited to specific indications where medical therapy is (or has been) ineffective. These include traumatic splenic rupture, anatomic defects, severe transfusion dependent hemolytic anemia, immune cytopenias, metabolic storage diseases, and secondary hypersplenism. The major long-term risk of splenectomy is sudden, overwhelming bacterial infection (sepsis or meningitis). This risk is especially high in children younger than 5 yr at the time of surgery. The risk of sepsis is less when splenectomy is performed for trauma, RBC membrane defects, and immune thrombocytopenia (2-4%) than when there is pre-existing immune deficiency (Wiskott-Aldrich syndrome, Hodgkin disease) or reticuloendothelial blockade (storage disease, severe hemolytic anemia) (8-30%). The use of laparoscopic splenectomy has decreased morbidity and hospitalization time.

Encapsulated bacteria, such as Streptococcus pneumoniae (>60% of cases), Haemophilus influenzae, and Neisseria meningitidis, account for >80% of cases of postsplenectomy sepsis. Because the spleen is responsible for filtering the blood and for early antibody responses, sepsis (with or without meningitis) can progress rapidly, leading to death within 12-24 hr of onset. Febrile splenectomized patients should be treated promptly with antibiotics to cover the organisms previously mentioned. This treatment should be initiated at home if access to definitive medical care will be delayed. A broad-spectrum cephalosporin (cefotaxime or ceftriaxone) together with vancomycin (to cover penicillin-resistant pneumococci) is recommended until specific antibiotic susceptibility and presence or absence of meningitis is known. Splenectomized patients are also at increased risk for contracting protozoal infections, such as malaria and babesiosis.

Preoperative, intraoperative, and postoperative management may decrease the risk of postsplenectomy infection. It is important to be certain of the need for splenectomy and, if possible, to postpone the operation until the patient is 5 yr of age or older. Pneumococcal, meningococcal, and H. influenzae conjugate vaccines given before splenectomy may reduce postsplenectomy sepsis. Of note, the efficacy of plain polysaccharide vaccines is low in children younger than 2 yr of age and in immunosuppressed patients. The 23-valent pneumococcal polysaccharide vaccine (Pneumovax) should be given every 5 yr after the initial vaccine series. In patients with traumatic injury, splenic repair or partial splenectomy should be considered in an attempt to preserve splenic function. Partial splenectomy or partial splenic embolization may be sufficient to ameliorate some forms of hemolytic anemia. Up to 50% of children whose spleen is removed because of trauma have spontaneous splenosis; surgical splenosis (distributing small pieces of spleen throughout the abdomen) may decrease the risk of sepsis in patients whose splenectomy is necessitated by trauma. However, in both of these settings, the splenic tissue that regrows frequently has inadequate function. Prophylaxis with oral penicillin V (125 mg twice daily for children younger than 5 yr; 250 mg twice daily for children 5 yr or older) should be given for at least 2 yr after splenectomy (to at least 6 yr of age). Although the greatest risk is in the immediate postoperative period, reports of deaths occurring years after splenectomy suggest that the risk (and the need for prophylaxis) may be lifelong. Lifelong prophylaxis should be strongly considered in patients who have had an invasive pneumococcal infection or who have an underlying immune deficiency. Penicillin reduces the risk of pneumococcal sepsis in younger patients with hemoglobin SS. In children with sickle cell disease, penicillin prophylaxis should be started as soon as the diagnosis is made. Prophylaxis may be continued into adulthood for higher-risk patients, but effectiveness in this group has not been well documented. Other postoperative measures include patient and family education, use of a medical information bracelet, vigilance with pneumococcal vaccines, and prompt evaluation and treatment of fevers.

In addition to postsplenectomy sepsis, splenectomized patients may be at risk for thromboembolic complications, including arterial and venous thrombosis and pulmonary hypertension. These findings have been regardless of the underlying reason for splenectomy and the postsplenectomy platelet count. Proposed mechanisms include loss of filtering function of spleen, allowing abnormal red blood cells to remain in the circulation and activate the coagulation cascade.