It has generally been held that acute cholecystitis and biliary pancreatitis rarely occur concomitantly. The aim of our study was to determine the incidence of concurrent acute cholecystitis and gallstone pancreatitis at our institution. METHODS:The records of all patients undergoing open or laparoscopic cholecystectomy between January 1993 and March 2001 were reviewed retrospectively. ICD-9 codes were cross-referenced to create a database of patients who had biliary pancreatitis and acute or chronic cholecystitis, as determined by pathological examination. Statistical analysis of patient demographics, presenting symptoms and post-operative outcomes were performed using chi-square tests. Student's t tests were used to compare the laboratory data, including leukocyte count, serum bilirubin, aspartate aminotransferase, alkaline phosphatase, glucose, amylase and lipase. RESULTS: 1267 cholecystectomies were performed by 21 operating surgeons during the study period. Seventy-five patients underwent cholecystectomy for biliary pancreatitis. Of these, 30 gallbladders had pathologic evidence of concomitant acute cholecystitis, an incidence of 40%. Age, race and presenting symptoms were not statistically different. Biliary pancreatitis occurred twice as often in women as men, while concomitant acute cholecystitis occurred more commonly in men (p=0.01). Admission laborotory tests were also compared. Among the patients with acute cholecystitis, significantly higher elevations of serum total bilirubin (p=0.05) and lipase (P <0.01) were noted. There were non-significant trends toward open cholecystectomy, common bile duct exploration, ERCP and morbidity in patients with acute cholecystitis. CONCLUSIONS: It is generally accepted that acute cholecystitis and gallstone pancreatitis represent opposite ends of the choledocholithiasis spectrum with cholecystitis arising from stone impaction and pancreatitis from stone passage. This does not appear to be true. 40% of our patients with gallstone pancreatitis also had acute cholecystitis. These findings are similar to data reported in the pathology literature. The clinical ramifications associated with concomitant acute cholecystitis and biliary pancreatitis have not yet been elucidated.