A Rock in a Hard Place: a Unique Case of Colonic Gallstone Ileus

A 64-year-old woman presented to a regional hospital emergency department with abdominal pain, anorexia and obstipation. Her background history included a locally advanced rectal cancer, cholelithiasis, hypertension, and ischaemic heart disease. The rectal cancer was incidentally diagnosed 12 months prior, when the patient presented to hospital in cardiogenic shock following a NSTEMI, and proceeded urgently for single vessel coronary artery bypass graft and tissue mitral valve replacement. A preoperative CT angiogram detected rectal thickening, and subsequent workup confirmed the diagnosis of T4N1 rectal adenocarcinoma thought to involve the cervical os on rectal MRI. The patient had recently completed total neoadjuvant therapy with consolidation chemotherapy, and was planned to undergo a posterior pelvic exenteration. There was no history of right upper quadrant pain or known episodes of cholecystitis. A distended abdomen with mild tenderness was found on physical examination. Laboratory testing revealed a stable chronic anaemia and a mild acute kidney injury. The patient underwent computed tomography of the abdomen and pelvis revealing that a previously visualized large gallstone was no longer in the gallbladder and was instead lodged in the rectosigmoid, proximal to the rectal cancer (Fig. 1) with resultant large bowel obstruction. There was also a fistulous communication between the gallbladder and the hepatic flexure of the colon (Fig. 2). The patient had recently undergone flexible sigmoidoscopy for restaging of her rectal cancer following chemoradiotherapy, and the tumour was unable to be passed with the colonoscope. Given this history it was thought unlikely that the gallstone would pass spontaneously or be amenable to endoscopic removal. The patient was transferred to a tertiary hospital for further management. Upon arrival, the patient was hypotensive and in rapid atrial fibrillation. The patient proceeded to theatre urgently with a specialist colorectal surgeon. Flexible sigmoidoscopy confirmed stone embedded adjacent to tumour, but this was unable to be dislodged endoscopically. At laparotomy, faecal soiling was noted in the peritoneal cavity, with stercoral perforation proximal to the impacted gallstone. The tumour was noted to be mobile, without involvement of the vagina or uterus. An ultralow Hartmann's procedure was performed (Fig. 3). Gallstone ileus is an extremely rare cause of small bowel obstruction, responsible for less than 0.1% of cases.1 Female gender and increasing age are risk factors for the development of gallstone ileus.1 Most commonly gallstone ileus involves a stone which has passed through a cholecysto-duodenal fistula and lodged in the terminal ileum, causing mechanical obstruction.1, 2 Cholecystitis and pressure necrosis due to cholelithiasis is postulated to cause adhesions and fistula formation respectively. Although gallstone ileus is most known as a cause of small bowel obstruction, previous cases of cholecysto-colonic fistula and large bowel obstruction as a result of gallstone ileus have been reported2 but represent only 4% of all cases of gallstone ileus.3 The point at which obstruction occurs is usually a pathological narrowing of the colonic lumen, for example a diverticular stricture, although we are not aware of any previously reported cases of cancer causing this narrowing. Gallstone ileus typically presents with symptoms and signs of bowel obstruction, possibly with a preceding history of right upper quadrant pain. Characteristic CT findings include Rigler's triad of ectopic gallstone, bowel obstruction, and pneumobilia; direct evidence of cholecysto-enteric or cholecysto-colonic fistula may also be evident as in this case. The treatment of gallstone ileus is usually surgical consisting of enterolithotomy by laparotomy or laparoscopy.1, 4 Selected patients may undergo cholecystectomy and fistula repair at the time of enterolithotomy or later although the risks and benefits of this are debated with some authors advocating for no biliary procedures being undertaken.4, 5 Success with colonoscopic treatment in cases of colonic gallstone ileus has been reported.6 This case is unique given the intersection of colonic gallstone ileus and near obstructing rectal cancer. It highlights that, while rare, there is a risk of colonic gallstone obstruction in patients with a known narrowing lesion and known cholelithiasis. Open access publishing facilitated by The University of Adelaide, as part of the Wiley - The University of Adelaide agreement via the Council of Australian University Librarians. Open access funding enabled and organized by Projekt DEAL. Joseph N. Hewitt: Writing – original draft; writing – review and editing; conceptualisation; project administration. Eve Hopping: Writing – original draft; writing – review and editing. Matthew Besley: Writing – original draft; writing – review and editing. Quentin Ralph: Supervision; writing – review and editing. Mark Lewis: Supervision; writing – review and editing. James Moore: Supervision; writing – review and editing. The data that support the findings of this study are available on request from the corresponding author, JNH. Identifiable data are not publicly available due to patient confidentiality.