Gallstone Ileus Mimicking a Colonic Tumor: A Case Report

Gallstone ileus is an uncommon complication of cholelithiasis, accounting to 0.5% of all cases of gallstone disease [1]. This condition occurs when a large gallstone passes into the gastrointestinal tract through a bilioenteric fistula, often becoming lodged in the intestinal tract [2]. Common sites for impaction include the ileum and jejunum, with colonic impaction being a particularly rare occurrence [3‒5].

The colon is an unusual location for gallstone impaction, and such cases are often misdiagnosed as neoplastic processes, leading to unnecessary surgical interventions or delayed appropriate management [6, 7]. Given the rarity of this condition and its ability to mimic more common colonic pathologies, it is crucial for clinicians to maintain a broad differential diagnosis, particularly in patients with a known history of gallstones or prior biliary surgery.

A 42-year-old woman with a past medical history significant to Roux-en-Y bariatric surgery (2006), multiple lower extremity deep vein thrombosis status post inferior vena cava filter on warfarin, multiple episodes of perforated sigmoid diverticulitis requiring diverticulectomy initially (2007) but ultimately requiring a sigmoid colectomy (2016) and decompensated cirrhosis complicated by hepatic encephalopathy (2018) presented to the hospital with altered mental status. In the emergency department, the patient was afebrile, tachycardic to 120 s with a blood pressure of 112/69 mm Hg and was saturating well in room air. On physical examination, she was lethargic and able to speak only a few words. The abdominal examination was unremarkable. Laboratory diagnostics showed an elevated ammonia level of 122 µmol/L (reference range: 11–32 µmol/L). According to the family, she was non-adherent to lactulose and was subsequently admitted for grade three hepatic encephalopathies. They denied alcohol use, tobacco use or a family history of cancer and gallstones.

During the hospitalization, the patient started to notice bright red blood with each bowel movement. Computed tomography scan of the abdomen and pelvis with contrast revealed an inflamed gallbladder with pneumobilia, small bowel dilatation, and a 2.7-cm filling defect in the sigmoid colon concerning a fecalith versus colonic mass versus gallstone ileus (Fig. 1).

The gastroenterology team was consulted, and upon review of prior records, the patient was noted to have a colonoscopy a year ago which was notable for a near circumferential ulcerated and inflammatory mass 20 cm from anal verge with pathology showing cryptitis and granuloma formation, but no tumor cells which was confirmed by pathology at our institute and deemed to be secondary to prior colonic resection and anastomosis given the location. Given concern for malignancy on imaging, a repeat colonoscopy was performed which showed a 3 cm gallstone obstructing the sigmoid colon which was removed completely (Fig. 2a, b). There were no masses, polyps or evidence of diverticulosis. She was restarted on home lactulose and her mentation improved during the course of hospitalization. Diet was advanced and she was subsequently discharged home. She underwent elective cholecystectomy as an outpatient and tolerated the procedure well.

Our case underscores the diagnostic challenges of gallstone ileus, particularly when the presentation involves unusual sites like the sigmoid colon. Gallstone ileus is a rare cause of bowel obstruction, accounting for approximately 4% of cases in the general population and is seen more frequently in elderly patients [7]. However, the presence of a large gallstone in the colon mimicking a malignant mass, as seen in our patient, is an exceptionally rare phenomenon and poses significant diagnostic challenges.

There have been prior reported cases of gallstone ileus caused by cholecystoenteric fistulas leading to large bowel obstruction which were removed surgically and endoscopically based on size of the stone and location [8‒10]. Our case is unique given that our patient did not have a fistula, was younger and had multiple risk factors that could have potentially led to a sigmoid gallstone ileus, specifically in the absence of a fistula.

The patient’s age and sex increase the risk of developing gallstones due to hormonal fluctuations, increased cholesterol levels in bile, and changes in bile composition [11]. The patient’s complex medical history, including Roux-en-Y gastric bypass, multiple episodes of perforated diverticulitis, and decompensated cirrhosis, further complicated the clinical picture. Roux-en-Y gastric bypass is known to increase the risk of gallstone formation due to rapid weight loss and altered enterohepatic circulation [12, 13]. Additionally, the patient’s prior sigmoid colectomy may have led to changes in colonic anatomy, potentially facilitating gallstone impaction in the sigmoid colon.

Initial imaging findings raised substantial concern for malignancy, especially considering the patient's history of an ulcerated and inflammatory mass with granuloma formation on previous colonoscopy, although prior pathology did not indicate malignancy. The CT scan revealed pneumobilia and a filling defect in the colon, which raised the suspicion of a gallstone; however, malignancy could not be definitively ruled out without additional diagnostic procedures, especially given that the incidence of early onset colon cancer is increasing in the USA and globally [14].

The definitive diagnosis of a large gallstone obstructing the sigmoid colon was confirmed via colonoscopy, which also identified active bleeding at the site of impaction. This case highlights the importance of maintaining a broad differential diagnosis when evaluating colonic masses, especially in patients with a prior history of gastrointestinal surgery. Gallstone ileus should be considered in the differential diagnosis of colonic obstruction or masses, even in patients who are not typical candidates for this condition.

The management of gallstone ileus often involves either surgical or non-surgical interventions to relieve obstruction. Non-surgical intervention is indicated in cases involving the colon, whereas enterolithotomy and laparoscopic surgery are indicated when the gall stone is impacted in the small intestine or if the colonoscopy is unsuccessful [15]. In our case, the gall stone was in the sigmoid colon and could be removed successfully via colonoscopy. This case highlights the importance of individualized patient care, especially in scenarios where the management and diagnosis may deviate from conventional protocols.

This case illustrates the unusual presentation of gallstone ileus mimicking a colonic mass in a patient with a complex medical history, including Roux-en-Y gastric bypass and sigmoid colectomy. The diagnostic challenge was compounded by imaging and prior colonoscopy findings. It emphasizes the need for a high index of suspicion of gallstone ileus in patients with gastrointestinal obstruction or masses, especially those with a history of gastrointestinal surgery. Timely and accurate diagnosis, supported by advanced imaging and endoscopic evaluation, is critical in guiding appropriate management. The CARE Checklist has been completed by the authors for this case report, attached as an online supplementary material (for online suppl. material, see https://doi.org/10.1159/000544041).

This study protocol was reviewed by MedStar Health Ethics Committee and approval was not required. Written informed consent was obtained for this case report from the patient for publication of the details of their medical case and accompanying images.

The authors have no conflicts of interest to declare.

This study was not supported by any sponsor or funder.

R.V. and B.M. were involved in review of literature, data interpretation, and manuscript writing. S.S. and J.B.B. were involved with manuscript editing and review. All authors have approved the final version for submission. J.B.B. is the article guarantor.

The data supporting the findings of this case report are available upon reasonable request from the corresponding author. Due to privacy and confidentiality concerns, patient-specific data will not be made publicly available. All identifying information has been anonymized in accordance with ethical guidelines to protect patient confidentiality.