OBJECTIVES: The purpose of the study was twofold: (1) to identify the incidence of acute mesenteric ischaemia (A.M.Isc.) following cardiopulmonary bypass and (2) to identify factors associated with its development. METHODS: A retrospective review of all autopsy reports from 1st January 1994 to 31st December 2000 was undertaken. Fifty-two patients were identified with acute mesenteric ischaemia at post-mortem following cardiac surgery. Demographic, pre-, intra- and post-operative variables were collected from their case notes. Four age, sex and period matched controls [n=208 (4 x 52)] were randomly selected for each case. Conditional logistic regression was used to compare the cases and controls. RESULTS: A total of 11,202 patients underwent surgery requiring cardiopulmonary bypass (CPB) during the study period with an overall mortality rate of 3%. The autopsy rate was 95% throughout the study period. From autopsy reports 52 patients (corrected for autopsy rate: 0.49% of group) were identified with A.M.Isc. Comparing controls with A.M.Isc. cases by univariate analysis, significant associations (P</=0.001) with A.M.Isc. were identified. These included: (1) peripheral vascular disease [15 (7%) vs. 14 (27%)]; (2) intraaortic balloon pump (IABP) use [5 (2%) vs. 22 (42%)]; (3) post-operative renal failure [2 (1%) vs. 32 (61%)]; (4) operation type (coronary artery bypass graft (CABG) alone [143 (69%) vs. 25 (48%)], valve alone [35 (17%) vs. 5 (10%)], valve+CABG [23 (11%) vs. 11 (21%)], major cardiac [7 (3%) vs. 11 (21%)]); (5) priority of operation (elective [155 (75%) vs. 27 (52%) emergency 52 (25%) vs. 25 (48%)]; and (6) smoking 12 (7%) vs. 9 (17%). CPB and cross-clamp times (minutes) were also significantly different between the groups [median (inter-quartile range (IQR)); 72 (55,96) vs. 100 (76,128) and 39 (30,54) vs. 56 (37,84), respectively]. Neither diabetes 23 (11%) vs. 6 (12%) nor hypertension 102 (49%) vs. 26 (50%) achieved significance (P<0.001). CONCLUSION: The incidence of acute mesenteric ischaemia is 0.49% of all cases undergoing CPB. A.M.Isc. is a common association with death following CPB (11%). It appears to be significantly associated with the presence of peripheral vascular disease, IABP use, the development of post-operative renal failure, operation type and priority, smoking, duration of CPB and cross-clamp time. Surprisingly, it was not linked to general risk factors for vascular disease.