In 1916, Schloffer performed the first splenectomy for idiopathic thrombocytopenic purpura (ITP) after his student Paul Kaznelson hypothesized that platelet destruction in ITP occurred in the spleen. Their first patient treated with splenectomy showed dramatic improvement. Splenectomy is now an established treatment for chronic ITP when patients have relapsed or have severe refractory thrombocytopenia. It results in complete or partial response rates of 66-72% in adults and 72% in children, with relapse rates of 15%. Predictors of response to splenectomy are not well established.