BackgroundAcute acalculous cholecystitis (AAC) tends to have a fulminant course and be associated with critically ill diseases, there have been reports of AAC without any risk factors but good prognosis.GoalsTo assess the risk factors, clinical features and prognosis of AAC.StudyAll patients who had a cholecystectomy due to acute cholecystitis at Pundang Jesaeng General Hospital during a 43-month period were prospectively enrolled. AAC was defined by ultrasonographic, intraoperative and pathologic findings of acute cholecystitis without evidence of gallstones. Clinical features and pathologic findings were analyzed and outcome was assessed.Results156 patients with acute cholecystitis were enrolled and 14% (22 of 156) met the criteria of AAC. Fifteen (68%) of the patients with AAC were male and the average age was 63 year old. Twenty patients were presented with AAC as outpatients of whom seven of them (35%) had atherosclerotic vascular disease. Laparoscopic cholecystectomy was performed in 126 patients (80.8%) with acute cholecystitis but was possible in only 12 patients (54.5%) with AAC. AAC was associated with a high incidence of gangrene (59%) but no patients died of acute cholecystitis.ConclusionsWe conclude that AAC frequently occurs in elderly male outpatients without critical illness and gangrene is common but the prognosis is better than reported previously.