By Craig E. Litz, M.D.
In our consult experience misinterpretation of the blood smear findings in the splenectomized patient is a cause of significant misdiagnosis. The blood changes following splenectomy are relatively predictable and knowing these changes can obviate a wrong diagnosis and therapy in your patient.
The diagnosis of a post-splenectomy/hyposplenic blood picture can be made reliably by identifying Howell Jolly bodies in routine Wright-Giemsa stained blood. These are round basophilic bodies in red blood cells that represent residual nuclear material from marrow nucleated red cell precursors that are usually culled out by the spleen (Fig 1, Table 1). These do not occur in individuals with normally functioning splenic tissue and their presence indicates either 1) an asplenic state or 2) hypofunctioning splenic tissue as might be seen in a patient with late-stage sickle cell anemia. Their presence in an individual with splenomegaly leads to a narrow differential diagnosis (Table 2) and their absence in a splenectomized individual indicates accessory splenic Heinz bodies and poikilocytosis typically increase in a splenectomized individual and care must be taken not to overdiagnose hemolysis in such an individual. Benign poikilocytosis can be quite dramatic in an asplenic individual with renal insufficiency. Mean corpuscular volume (MCV) and hemoglobin levels do not change with splenectomy.
Changes in white blood cells include a mild leukocytosis with an increase in large granular lymphocytes and NK cells. Monocytes are frequently increased occasionally leading to a mistaken diagnosis of chronic myelomonocytic leukemia (CMML).
Virtually all individuals undergoing splenectomy experience a thrombocytosis acutely; some may reach levels of greater than 1,000,000/ul.5 Platelet counts persist above 500,000/ul in up to 40% of splenectomized individuals.6 It is important to exclude asplenia in all individuals in whom a diagnosis of a myeloproliferative disorder, in particular, essential thrombocythemia, is being entertained.
1) Lipson RL, Bayrd ED, Watkins CH: The postsplenectomy blood picture. Am J Clin Pathol 32:526-532, 1959.
2) Personal communication with Dr. R. Brunning of the University of Minnesota Medical School, Minneapolis, MN, regarding the subject presented in an honors thesis by Mary Schmalz.
3) Theodorou GL, Mouzaki A, Tsiftsis D et al: Effect of non-operative management (NOM) of splenic rupture versus splenectomy on the distribution of peripheral blood lymphocyte populations and cytokine production by T-cells. Clin Exp Immunol 150:429-436, 2007.
4) Steinberg MH, Gatling RR, Tavassoli M: Evidence of hyposplenism in the presence of splenomegaly. Scand J Haematol 31:437, 1983.
5) Hirsh J, Dacie JV: Persistent post splenectomy thrombocytosis and thrombo-embolism: a consequence of continuing anaemia. Br J Haematol 12:44, 1966.
6) Slater PP, Sherlock EC: Splenectomy, thrombocytosis, and venous thrombosis. Am Surg 23:549, 1957.