An 18-year-old male presented at the casualty department with acute right upper abdominal pain. Laboratory examinations showed no abnormalities apart from a mildly elevated leukocyte count. Ultrasound examination revealed hydrops of the gallbladder, with thickening of the wall, with no indication of gallstones. Laparoscopy revealed a necrotic gallbladder due to torsion. The gallbladder was successfully removed. Torsion of the gallbladder is a rare condition, in which the organ twists on its longitudinal axis. It is found primarily in patients under 18 years or over 65 years of age. Laboratory and radiological investigations usually reveal non-specific abnormalities, which means that a correct diagnosis is made preoperatively in < 10% of patients. Treatment of choice is an emergency cholecystectomy. The prognosis is excellent with adequate treatment.