Question: An otherwise well 59-year-old man presented with 24 hours of sudden worsening right upper quadrant pain on a background of 2 weeks of mild, self-limiting right upper quadrant pain. No fevers, jaundice, vomiting, or bowel habit changes were reported. He had no previous surgical or medical history, and no known biliary disease in the past. On presentation, he was mildly tachycardic and hypotensive, which was responsive to fluid resuscitation. The abdomen was moderately distended and focally tender in the right upper quadrant and epigastrium. Blood tests revealed a hemoglobin of 105 g/L, C-reactive protein of 41 mg/L, and elevated white blood cell count of 11 × 109/L. His liver function tests, lipase, troponin, renal function, and electrolyte levels were otherwise unremarkable. A computed tomography (CT) scan of his abdomen revealed a large hematoma in the right upper quadrant and a further hematoma in the pelvis and surrounding the gallbladder suggestive of acute perforation. There were no CT features of acute cholecystitis. A 24-mm calculus was identified in the gallbladder neck with hyperdense intraluminal content within the gallbladder, possibly representing hemorrhage or sludge/debris (Figure A). A decrease in the hemoglobin to 89 g/L resulted in transfusion of 1 U of packed red blood cells. A CT angiogram of the abdomen and pelvis showed no evidence of acute bleeding. Given his stable clinical picture and lack of evidence of active bleeding, the decision was made not to proceed to embolization, and he was closely monitored in a high-acuity unit until the following morning, when he underwent an exploratory laparoscopy. Intraoperatively, 2 L of blood were found in the abdominal cavity with 4 free floating gallstones (Figure B, C). After evacuation of the hemoperitoneum and thorough exploration, no bleeding point was identified within the peritoneal cavity, and a perforation in the gallbladder, on the wall opposite to the Dieulafoy’s lesion (DL), was confirmed (Figure D). The patient underwent laparoscopic cholecystectomy and had an uneventful recovery postoperatively. What was the underlying cause of this patient’s hemoperitoneum? See the Gastroenterology web site () for more information on submitting your favorite image to Clinical Challenges and Images in GI. This unusual case of hemoperitoneum was caused by the presence of a DL within the gallbladder. Specifically, massive hemorrhage of the DL into the gallbladder cavity resulted in perforation of the gallbladder and extrusion of gallstones. A frozen section of the gallbladder at the site of bleeding identified a DL, with a medium sized artery (arrow) present <2 mm from the mucosal surface of the gallbladder (arrow heads) at the site of adherent blood clot (Figure D, E). DL, also known as “caliber persistent artery,” describes a histologically normal arterial vessel that maintains an abnormally large diameter of 1–3 mm as it follows a tortuous course through the submucosa, eventually protruding through a small (2–5 mm) mucosal defect.1Baxter M. Aly E.H. Dieulafoy's lesion: current trends in diagnosis and management.Ann R Coll Surg Engl. 2010; 92: 548-554Crossref PubMed Scopus (140) Google Scholar DLs are relatively rare lesions that are believed to account only for 1%–2% of acute gastrointestinal haemorrhages.1Baxter M. Aly E.H. Dieulafoy's lesion: current trends in diagnosis and management.Ann R Coll Surg Engl. 2010; 92: 548-554Crossref PubMed Scopus (140) Google Scholar The commonest location for DL is the stomach and accounts for more than two-thirds of affected patients.2Wu J.M. Zaitoun A.M. A galling disease? Dieulafoy's lesion of the gallbladder.Int J Surg Case Rep. 2018; 44: 62-65Crossref PubMed Scopus (4) Google Scholar Extragastric DL of the gastrointestinal tract are less common and have been described in the literature; however, DL of the gallbladder is extremely rare and to the best of our knowledge, only 7 cases of histologically proven gallbladder DL have been reported to date.2Wu J.M. Zaitoun A.M. A galling disease? Dieulafoy's lesion of the gallbladder.Int J Surg Case Rep. 2018; 44: 62-65Crossref PubMed Scopus (4) Google Scholar,3Santos T. Serra M. Oliveira A. Fernandes C. Dieulafoy lesion of the gallbladder: a rare cause of hemobilia and acute pancreatitis - case report.Int J Surg Case Rep. 2020; 66: 207-210Crossref PubMed Scopus (3) Google Scholar Although some causal links have been described, the exact a etiology of DL remains unknown.1Baxter M. Aly E.H. Dieulafoy's lesion: current trends in diagnosis and management.Ann R Coll Surg Engl. 2010; 92: 548-554Crossref PubMed Scopus (140) Google Scholar Unlike other DLs in the gastrointestinal tract, owing to the anatomy of the gallbladder and its vascular supply, the treatment of choice is surgical (cholecystectomy).2Wu J.M. Zaitoun A.M. A galling disease? Dieulafoy's lesion of the gallbladder.Int J Surg Case Rep. 2018; 44: 62-65Crossref PubMed Scopus (4) Google Scholar This finding is supported in the literature with the other reported cases of gallbladder DL all undergoing cholecystectomy and having an unremarkable recovery postoperatively.2Wu J.M. Zaitoun A.M. A galling disease? Dieulafoy's lesion of the gallbladder.Int J Surg Case Rep. 2018; 44: 62-65Crossref PubMed Scopus (4) Google Scholar,3Santos T. Serra M. Oliveira A. Fernandes C. Dieulafoy lesion of the gallbladder: a rare cause of hemobilia and acute pancreatitis - case report.Int J Surg Case Rep. 2020; 66: 207-210Crossref PubMed Scopus (3) Google Scholar This case describes another rare case of histologically proven DL in the gallbladder and an unusual cause of hemoperitoneum. Owing to its rarity, it is not regularly considered as a differential in presentations of acute gastrointestinal bleeding. However, in the absence of obvious radiological or endoscopic evidence of bleeding from the gastrointestinal tract, clinicians should be aware of this rare but potentially life-threatening entity. As seen in this case, DL of the gallbladder can present acutely that necessitate prompt intervention. Definitive management remains surgical intervention.