Sigmoid Colon Obstruction due to Gallstone Ileus: Case Report.

Introduction: Gallstone ileus of the colon is a rare cause of large bowel obstruction, usually caused by a gallbladder-to-colon fistula allowing stone entry. The classical presentation is with episodic subacute obstruction. Contrast-enhanced CT is valuable for diagnosis, with surgery being the preferred treatment; however, endoscopic therapy has been described and may also be attempted. Case Presentation: We describe the case of an 81-year-old female with a medical history significant for atrial fibrillation and congestive heart failure. She presented with a 2-week history of constipation, abdominal pain, distention, nausea, and vomiting. Clinically, her abdomen was distended but without signs of peritonitis. A CT scan showed a cholecystoduodenal fistula, along with a 3.3-cm gallstone causing a large bowel obstruction at the sigmoid colon. An attempt at flexible sigmoidoscopy to remove the stone failed due to its size and distal hypertrophy. The patient underwent exploratory laparotomy and Hartmann's procedure to relieve the obstruction and remove the gallstone. Conclusion: Gallstone ileus remains an uncommon but clinically important cause of mechanical bowel obstruction, typically occurring in elderly patients with significant comorbidities. This case underscores an especially rare manifestation - large bowel obstruction secondary to gallstone ileus - which can pose diagnostic and therapeutic challenges and is easily overlooked. By illustrating this atypical presentation, our report highlights the need for heightened clinical suspicion in older patients presenting with bowel obstruction and pneumobilia. Furthermore, it emphasizes the spectrum of available management strategies and the importance of individualized decision-making based on patient frailty, anatomical considerations, and surgical risk.