Acalculous Hemorrhagic Cholecystitis Presenting as Probable Hemobilia: The Diagnostic Role of Susceptibility-Weighted Magnetic Resonance Imaging

Hemobilia from acalculous hemorrhagic cholecystitis (AHC) is exceptionally rare and easily missed when gallstones, antithrombotic exposure, and an angiographic source are all absent. A 61-year-old man with no gallstones or antithrombotic use presented with recurrent melena and right upper-quadrant pain. Laboratory testing showed anemia, hyperbilirubinemia, and elevated transaminases. Upper endoscopy showed blood clots but no source. Ultrasonography revealed an avascular, septate intraluminal gallbladder mass without stones; contrast-enhanced computed tomography showed a hyperdense, non-enhancing lesion without extravasation; and selective hepatic arteriography was negative. T2-weighted and susceptibility-weighted magnetic resonance imaging (MRI) demonstrated marked signal loss within an organized hematoma extending into the cystic duct. Because bleeding persisted despite supportive care with no embolization target, laparoscopic cholecystectomy was performed and bleeding resolved; histopathology confirmed chronic hemorrhagic cholecystitis. AHC should be considered in unexplained hemobilia, where susceptibility-sensitive MRI can characterize intraluminal blood and support the diagnosis when initial studies are suggestive but not definitive.