Clinical variables were studied in 3129 patients undergoing coronary artery bypass grafting to identify patients at risk of abdominal complications and common etiologic factors in the development of such; complications. Seventy-three gastrointestinal complications occurred (2.3%), with an overall mortality rate of 16.4% compared,vith a mortality rate of 3.4% for all patients undergoing bypass grafting (p < 0.001), Cholecystitis and intestinal ischemia were the most frequently encountered complications. Multivariate analysis demonstrated that preoperative hypertension, New York Heart Association classes III and IV, preoperative left ventricular ejection fraction less than 40%, age greater than 70 years, reoperation, and urgent operation as independently and significantly associated with gastrointestinal complications. In contradiction to previous reports, no significant correlation existed between gastrointestinal complications and cardiopulmonary bypass time, 99.8 +/- 35.8 versus 101.2 +/- 39.8 minutes. Perioperative myocardial infarction and immediate postoperative hypotension with low cardiac output necessitating substantial inotropic pharmacologic support or intraaortic balloon pumping were significantly more prevalent in patients who had gastrointestinal complications (all p < 0.001). Furthermore, multivariate analysis revealed that postoperative low cardiac output was a significant, independent predictor in the development of gastrointestinal complications of any kind after coronary artery bypass grafting. Postoperative splanchnic hypoperfusion could therefore be a common etiologic factor.