Acalculous cholecystitis represents 2% to 14% of cholecystectomies performed for acute cholecystitis. Its main etiology is ischemia of the gallbladder wall, which mainly occurs in critically ill patients, particularly in case of cardiovascular previous disease or diabetes. Acalculous cholecystitis associated with VIH are rare and have a better prognosis. Other etiologies are exceptional. Diagnosis of acalculous cholecystitis is difficult, with a lack of specificity of abdominal ultrasound for the diagnosis of ischemic cholecystitis. In all cases, cholecystectomy is a definitive treatment allowing certain diagnosis. Percutaneous drainage must be reserved to patients whose general condition does not allow general anesthesia. Medical treatment alone is not indicated in acalculous cholecystitis.