(See also Overview of the Spleen.)
Hypersplenism is a secondary process that can arise from splenomegaly of almost any cause (see table Common Causes of Splenomegaly). Splenomegaly increases the spleen’s mechanical filtering and destruction of red blood cells (RBCs) and often of white blood cells (WBCs) and platelets. Compensatory bone marrow hyperplasia occurs in those cell lines that are reduced in the circulation.
Hypersplenism is suspected in patients with splenomegaly and anemia or cytopenias. Evaluation is similar to that of splenomegaly.
Unless other mechanisms coexist to compound their severity, anemia and other cytopenias are modest and asymptomatic (eg, platelet counts, 50 to 100 × 103/mcL [50 to 100 × 109/L]; white blood cell counts, 2500 to 4000/mcL [2.5 to 4 × 109/L] with normal white cell differential count). Red blood cell morphology is generally normal except for teardrop forms and occasional spherocytosis. Reticulocytosis is usual.
Treatment is directed at the underlying disorder. However, if hypersplenism is the only serious manifestation of the disorder (eg, Gaucher disease), splenic ablation by splenectomy or radiation therapy may be indicated. The indications for splenectomy or radiation therapy in hypersplenism are detailed below (see table Indications for Splenectomy or Radiation Therapy in Hypersplenism).
Because the intact spleen protects against serious infections with encapsulated bacteria, splenectomy should be avoided whenever possible, and patients undergoing splenectomy require prior vaccination against infections caused by Streptococcus pneumoniae, Neisseria meningitidis, and Haemophilus influenzae. Patients should also receive the influenza vaccine and may need other vaccinations according to their clinical situation.
After splenectomy, patients are particularly susceptible to severe sepsis with encapsulated microorganisms and are often given daily prophylactic antibiotics such as penicillin, amoxicillin, or erythromycin, particularly when they have regular contact with children. Patients who develop fever should receive empiric antibiotics because rapidly fatal sepsis can sometimes occur.