Gallbladder volvulus diagnosed by MRCP and diffusion-weighted imaging in an elderly woman.

Gallbladder (GB) volvulus is a rare cause of acute abdominal pain and is frequently misdiagnosed as acute cholecystitis due to its nonspecific presentation. We report an elderly woman in whom magnetic resonance cholangiopancreatography (MRCP) with diffusion-weighted imaging (DWI) enabled a timely, accurate preoperative diagnosis. An 84-year-old woman presented with acute right upper quadrant pain; inflammatory markers were normal. Ultrasound (US) and contrast-enhanced computed tomography (CT) suggested acalculous cholecystitis; CT showed a "whirl sign" but no V-shaped distortion of the extrahepatic ducts. MRCP confirmed a "whirl sign" involving the cystic duct and artery, and DWI demonstrated diffusion restriction in the GB wall, consistent with acute ischemia secondary to torsion. Laparoscopic cholecystectomy confirmed a 360° torsion with ischemic changes. This case highlights the limitations of US and the variable sensitivity of CT for GB volvulus, especially in atypical presentations. MRCP with DWI provides complementary anatomic and functional information, supporting a confident preoperative diagnosis and prompt surgical intervention.