Analysis of leukopenia and anemia after gastric bypass surgery

Although anemia is a well-described complication after Roux-en-Y gastric bypass (RYGB) in association with iron deficiency, no studies have been published regarding changes in the white blood cell count.

Mixed longitudinal models were used to follow the changes in white blood cell count, platelet count, and hematocrit over time after RYGB.

A total of 590 patients, who had undergone RYGB from 2006 to 2010, inclusively, had laboratory studies available. The mean follow-up was 398 days (range 30-1484). The incidence of leukopenia (white blood cell count ≤4000 cm(3)) increased significantly from 2.0% (12 of 590) before surgery to 14.6% (86 of 590) afterward (P < .0005). A lower white blood cell count was independently predicted by greater weight loss, longer time after surgery, a lower hematocrit, and a lower platelet count (P < .0005). No patient developed neutropenia. The incidence of pre-existing anemia was ∼17% for both men and women. After surgery, the incidence of anemia substantially increased only in premenopausal women (from 16% to 33%). Anemia occurred independently of the degree of weight loss. The platelet counts decreased by a clinically insubstantial, although statistically significant, amount (281,000-250,000; P < .0005).

RYGB is associated with a generalized decrease in the white blood cell and platelet counts. These decreases do not seem clinically important, unlike the substantial decrease in red blood cell mass in premenopausal women. A generalized suppression of hematopoiesis might occur after RYGB.