Gallstone Ileus: A Definitive Guide to Diagnosis and Management of a Rare Cause of Small Bowel Obstruction

Introduction

Gallstone ileus stands as a fascinating yet treacherous entity in general surgery and emergency medicine. While it accounts for a mere 1-4% of all mechanical small bowel obstructions, its prevalence dramatically increases to 25% in the population over 65, making it a critical diagnosis to consider in elderly patients presenting with obstructive symptoms.

This condition is not a true "ileus" in the paralytic sense but rather a mechanical obstruction caused by an ectopic gallstone that has migrated into the bowel lumen through a fistula. The diagnostic journey can be complex, often delayed by nonspecific symptoms, leading to significant morbidity and mortality.

This column provides a world-class, in-depth exploration of gallstone ileus, using a compelling case study to illustrate the clinical presentation, key imaging features, and modern management strategies. We will delve into the pathophysiology, epidemiology, and treatment protocols, offering a definitive resource for medical professionals, surgeons, and students preparing for board examinations.

Case Presentation: An Insidious Obstruction

We present the case of a 64-year-old woman who arrived at the emergency department with a chief complaint of epigastric pain, nausea, and vomiting. Notably, her clinical history revealed a visit just three days prior for similar symptoms, which were attributed to a urinary tract infection (UTI) based on urinalysis, and she was subsequently discharged on antibiotics.

Her symptoms, however, escalated. The pain diffused throughout her abdomen, and she developed obstipation, a key sign of bowel obstruction. The patient had no prior surgical history, a crucial detail that lowers the suspicion for the most common cause of small bowel obstruction—adhesions.

Initial Imaging Findings

An initial scout radiograph from an abdominal and pelvic CT scan was obtained, revealing critical information.

Figure 1: Scout Image from Abdominal/Pelvic CT. The image demonstrates multiple, centrally located, dilated small bowel loops. These are identified as small bowel due to the presence of valvulae conniventes, which are circumferential folds that traverse the entire lumen, as opposed to the haustra of the large bowel. There is a relative paucity of gas in the distal colon, suggesting a transition point and a mechanical small bowel obstruction.

Advanced Imaging: Unraveling the Diagnosis of Gallstone Ileus

Given the findings on the scout film, a contrast-enhanced CT of the abdomen and pelvis was performed. This modality is the gold standard for diagnosing gallstone ileus, offering unparalleled detail of the underlying pathology.

Figure 2: Axial Contrast-Enhanced CT of the Abdomen and Pelvis.

(A) This upper abdominal slice reveals moderate pneumobilia (air within the biliary tree), seen as branching areas of low density in the central liver. Air is also visible within the gallbladder lumen, alongside multiple large, calcified gallstones.
(B) This slice of the pelvis clearly identifies the transition point. There are dilated, fluid-filled small bowel loops proximally and decompressed loops distally. Critically, a large, laminated, calcified ectopic gallstone is seen lodged at this transition point, confirming the cause of the small bowel obstruction.

These CT findings confirmed the diagnosis of gallstone ileus. The classic diagnostic triad, known as Rigler's Triad, was present:

Pneumobilia: Air in the biliary system, resulting from the fistula between the bowel and the gallbladder.
Small Bowel Obstruction: Dilated proximal loops with a clear transition point.
Ectopic Gallstone: Visualization of the stone at the point of obstruction.

Gallstone Ileus: A Comprehensive Review

Pathophysiology

The pathophysiology of gallstone ileus begins with chronic cholecystitis. Persistent inflammation and pressure from a large gallstone (typically >2.5 cm) can cause the gallbladder wall to erode and become ischemic. This inflamed gallbladder then adheres to an adjacent segment of the gastrointestinal tract, most commonly the duodenum (cholecystoduodenal fistula, ~60% of cases), followed by the colon (cholecystocolonic fistula), and rarely the stomach (cholecystogastric fistula).

Over time, a fistula forms, allowing the gallstone to pass directly into the bowel lumen. The stone travels distally until it reaches a segment of the bowel too narrow for its passage. The most common site of impaction is the terminal ileum, the narrowest part of the small intestine, followed by the jejunum and, rarely, the colon (gallstone colitis). The obstruction it causes leads to proximal bowel dilation, fluid and electrolyte sequestration, and the clinical symptoms of intestinal obstruction.

Epidemiology

Gallstone ileus is a condition predominantly affecting the elderly, with a mean patient age of 72 years. There is a significant female predilection, with a female-to-male ratio of approximately 3.5:1. This demographic often presents with multiple medical comorbidities, which complicates management and contributes to higher rates of morbidity and mortality. While it is a rare cause of small bowel obstruction in the general population (1-4%), its significance is pronounced in patients over 65, where it is responsible for up to 25% of non-strangulated small bowel obstructions.

Clinical Presentation

The clinical presentation of gallstone ileus is often insidious and can be misleading. Many patients experience intermittent symptoms for several days before seeking medical attention, as seen in our case patient. This is due to the "tumbling phenomenon," where the stone intermittently obstructs and then advances along the bowel.

Symptoms are typically those of a distal small bowel obstruction:

Nausea and vomiting (often progressing to feculent vomitus)
Generalized, cramping abdominal pain
Abdominal distension
Obstipation (inability to pass stool or gas)

The non-specific nature of these symptoms, especially in elderly patients with other health issues, frequently leads to a delayed diagnosis.

Imaging Features and Differential Diagnosis

As established, contrast-enhanced abdominal CT is the modality of choice, with a diagnostic accuracy exceeding 90%. It can visualize all components of Rigler's Triad.

However, it is crucial to consider a differential diagnosis for the imaging findings. Pneumobilia, for instance, can also be caused by:

Recent Instrumentation: Procedures like an endoscopic retrograde cholangiopancreatography (ERCP) or sphincterotomy can introduce air into the biliary tree. Our patient had no such history.
Emphysematous Cholecystitis: A severe infection of the gallbladder wall by gas-forming organisms. While this can cause gas in the gallbladder, it is a distinct pathology.
Portal Venous Gas: A more ominous finding associated with bowel ischemia, where gas presents more peripherally in the liver, as opposed to the central location of pneumobilia.

The primary differential for the small bowel obstruction itself includes:

Adhesions: The most common cause of SBO, typically related to prior abdominal surgery.
Hernias: Incarcerated inguinal, femoral, or incisional hernias.
Neoplasms: Primary small bowel tumors or metastatic disease.
Strictures: Often from chronic inflammatory conditions like Crohn's disease.

The combination of pneumobilia and a calcified intraluminal stone in an elderly female without prior surgery makes gallstone ileus the leading diagnosis.

Diagnosis and Further Workup

In our case, the patient underwent further treatment and imaging. The gallstone had caused such significant retrograde reflux during vomiting that a second large stone was found in the stomach.

Figure 3: Additional Axial CT Slice. This image clearly demonstrates a large, calcified gallstone located within the lumen of the stomach.

Figure 4: Post-Procedure Photograph. This is the large gallstone that was endoscopically removed from the patient's stomach.

A few days post-operatively, the patient developed leukocytosis, raising concern for a biliary complication like cholangitis. A Magnetic Resonance Cholangiopancreatography (MRCP) was performed.

Figure 5: Coronal MRCP Image. This image provided an excellent view of the cholecystoduodenal fistula (Red circle), seen as a tract with increased signal between the gallbladder fundus and the adjacent duodenum. It thankfully ruled out any concurrent biliary obstruction.

Treatment

The management of gallstone ileus is primarily surgical. The immediate goal is to relieve the small bowel obstruction, which is a surgical emergency. The standard procedure is an enterolithotomy, where a small incision is made in the bowel proximal to the impacted stone, the stone is milked proximally away from the inflamed and potentially friable impaction site, and then extracted. The bowel is then repaired.

A major point of surgical debate is the timing of the fistula repair and cholecystectomy. The options include:

Enterolithotomy alone: A damage-control approach for unstable, high-risk patients. The fistula is left in place, with a plan for a delayed, elective cholecystectomy and fistula repair later.
One-stage procedure: Enterolithotomy combined with cholecystectomy and fistula repair during the same operation. This is typically reserved for younger, more stable patients who can tolerate a longer, more complex surgery.

The decision is often guided by the patient's clinical stability and comorbidities, frequently assessed using the American Society of Anesthesiologists (ASA) score. In our case, the patient underwent an emergency enterolithotomy to resolve the obstruction, followed by a separate endoscopic procedure (EGD) to remove the stone from her stomach.

Prognosis

Despite advances in surgical care and imaging, gallstone ileus continues to have a high mortality rate, reported to be between 12% and 27%. This is largely attributable to the patient population—elderly individuals with significant comorbidities—and the frequent delay in diagnosis, which can lead to complications like bowel ischemia, necrosis, and perforation. Prompt diagnosis and surgical intervention are paramount to improving outcomes.

A Rare Variant: Bouveret Syndrome

A specific and rare variant of gallstone ileus is Bouveret syndrome. This occurs when a large gallstone passes through a cholecystoenteric fistula but becomes impacted in the duodenum or pylorus, causing a gastric outlet obstruction. This proximal obstruction presents with prominent nausea and vomiting of non-bilious fluid. It is named after the French physician Léon Bouveret.

Quiz

Test your knowledge with these five board-style questions based on the case and review.

Question 1: A 78-year-old female with no prior surgical history presents with abdominal distension and vomiting. A CT scan reveals pneumobilia, dilated small bowel, and a 3 cm calcified mass in the right iliac fossa. What is the most common type of fistula associated with this condition?

A) Cholecystocolonic

B) Cholecystogastric

C) Cholecystoduodenal

D) Choledochoduodenal

Question 2: Which of the following is the least common site of impaction for a gallstone causing gallstone ileus?

A) Terminal ileum

B) Sigmoid colon

C) Proximal jejunum

D) Duodenum (pylorus)

Question 3: A surgeon is performing an emergency enterolithotomy on an 85-year-old patient with multiple comorbidities (ASA Class 4) for gallstone ileus. The patient is hemodynamically unstable. What is the most appropriate next step after removing the stone?

A) Proceed with a one-stage cholecystectomy and fistula repair.

B) Close the enterotomy and the abdomen, and plan for elective fistula repair later.

C) Perform a small bowel resection of the impacted segment.

D) Search the entire length of the bowel for additional stones.

Question 4: A CT scan for suspected gallstone ileus fails to demonstrate a clearly calcified ectopic gallstone. Which feature, if present, would still provide the strongest evidence for the diagnosis?

A) The "tumbling phenomenon" reported by the patient.

B) Pneumobilia and a clear transition point in the small bowel.

C) A history of biliary colic.

D) Elevated white blood cell count.

Question 5: The clinical entity characterized by a gallstone causing gastric outlet obstruction is known as:

A) Mirizzi syndrome

B) Lemmel syndrome

C) Chilaiditi syndrome

D) Bouveret syndrome

Answer & Explanation:

1. Answer: C) Cholecystoduodenal. Explanation: While several types of cholecystoenteric fistulas can occur, the vast majority (~60%) of cases of gallstone ileus result from a fistula forming between the gallbladder and the adjacent duodenum. This anatomical proximity facilitates the erosion and passage of the stone.

2. Answer: B) Sigmoid colon. Explanation: The most common site of impaction is the terminal ileum, the narrowest part of the small bowel. Impaction in the duodenum (Bouveret syndrome) or jejunum is less common but well-documented. While a stone can pass into the colon, causing a gallstone colitis, the sigmoid colon is significantly wider than the ileocecal valve and terminal ileum, making it the least likely site of mechanical obstruction by a gallstone that has already passed through the small intestine.

3. Answer: B) Close the enterotomy and the abdomen, and plan for elective fistula repair later. Explanation: In a high-risk, unstable patient, the primary goal is to resolve the immediate life-threatening condition—the small bowel obstruction. Prolonging the surgery to perform a complex fistula repair and cholecystectomy would significantly increase morbidity and mortality. The safest approach is a two-stage procedure: emergency enterolithotomy now, followed by elective definitive biliary surgery once the patient has recovered and is stable.

4. Answer: B) Pneumobilia and a clear transition point in the small bowel. Explanation: Approximately 15-25% of gallstones are not calcified and are therefore difficult to see on CT. In such cases, the combination of air in the biliary tree (indicating a fistula) and a mechanical small bowel obstruction with a distinct transition point is highly suggestive of gallstone ileus, even without direct visualization of the stone. The other options are non-specific.

5. Answer: D) Bouveret syndrome. Explanation: Bouveret syndrome is the specific eponym for the proximal form of gallstone ileus, where the ectopic gallstone impacts in the duodenum or gastric pylorus, leading to gastric outlet obstruction. Lemmel syndrome involves a duodenal diverticulum causing biliary obstruction , Chilaiditi syndrome is the interposition of the colon between the liver and diaphragm, and Mirizzi syndrome is the extrinsic compression of the common hepatic duct by a stone in the cystic duct.

Conclusion

Gallstone ileus remains a significant surgical challenge. Its presentation in an elderly, comorbid population, coupled with its potential for diagnostic delay, demands a high index of suspicion from clinicians. As our case illustrates, a thorough history and the judicious use of contrast-enhanced CT scanning are the cornerstones of an accurate and timely diagnosis. Understanding the pathophysiology, recognizing the classic imaging findings of Rigler's Triad, and appreciating the nuances of surgical management are essential for optimizing patient outcomes and successfully navigating this rare but critical cause of small bowel obstruction.

References

[1] C. F. Ploneda-Valencia, M. Gallo-Morales, C. Rinchon, et al., “Gallstone ileus: An overview of the literature,” Rev Gastroenterol Mex, vol. 82, no. 3, pp. 248-254, 2017.

[2] D. A. Smith, S. Kashyap, and S. M. Nehring, “Bowel Obstruction,” in StatPearls, Treasure Island, FL: StatPearls Publishing, 2020. [Online]. Available: https://www.ncbi.nlm.nih.gov/books/NBK441975/.

[3] F. Gaillard, et al., “Gallstone ileus: Radiology Reference Article,” Radiopaedia.org. [Online]. Available: https://radiopaedia.org/articles/gallstone-ileus.

[4] A. K. Abou-Saif and A. A. Al-Kawas, “Gallstone ileus: a review of 15 cases from a single center,” Saudi J Gastroenterol, vol. 9, no. 2, pp. 79-84, 2003.

[5] M. Inukai, “Gallstone Ileus: A Review,” BMJ Case Rep, 2019.

[6] F. D. Reisner and J. R. Cohen, “Gallstone Ileus: a review of 1001 reported cases,” Am Surg, vol. 60, no. 6, pp. 441-446, 1994.

[7] G. D. Deitz, R. L. Myers, and J. C. Goodyear, “Bouveret’s Syndrome: a rare form of gallstone ileus,” J Am Osteopath Assoc, vol. 94, no. 4, pp. 331-334, 1994.

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