From the Departments of Medicine, Medical Physics, and Haematology, The Royal Infirmary,

SUMMARY Splenic function was assessed in 35 patients with ulcerative colitis and 20 patients with Crohn's disease. Hyposplenism was diagnosed if there were Howell-Jolly bodies in the peripheral blood film or if there was prolongation of clearance from the peripheral blood of injected 5'Cr-labelled heat-damaged red blood cells. Thirteen of the patients with ulcerative colitis had hypo-splenism as compared with only one patient with Crohn's disease. Conversely, heat-damaged red cell clearance values faster than the normal range were found in six out of the 20 patients with Crohn's disease. Four patients with hyposplenism and ulcerative colitis developed life-threatening septicaemia in the early postcolectomy period, two of these being further complicated by disseminated intra-vascular coagulation. Hyposplenism is the functional state that exists after splenectomy in man and it is characterised by the appearance of Howell-Jolly bodies, Pappenheimer bodies, spherocytes, target cells, and bizarre poikilo-cytes in the peripheral blood film. Hyposplenism may occur spontaneously in such conditions as coeliac disease and dermatitis herpetiformis where the causative mechanisms are uncertain (Marsh and Stewart, 1970; Pettit et al., 1972). In a preliminary report (Ryan et al., 1974) we described for the first time the association in three patients of hypo-splenism with ulcerative colitis, an association since confirmed by other authors (Ardeman and Bevan, 1974; Goodyear and Forster, 1974; Wardrop et al., 1975). This paper presents the results of a systematic study into splenic function in inflammatory bowel disease. Methods Thirty-five patients with ulcerative colitis and 20 patients with Crohn's disease were investigated. The diagnosis was based on currently accepted criteria which included clinical features, sigmoidoscopic findings, barium studies, and histology of rectal biopsy material, (Lennard-Jones, 1970; Morson and Dawson, 1972). The diagnosis was confirmed by detailed gross and histological examination of the whole colon in 13 patients with ulcerative colitis and nine patients with Crohn's disease who subsequently came to colectomy. There remains the possibility o