A fistula lets the stone escape; the narrow distal bowel makes it stop.
Explain how chronic gallbladder inflammation creates a cholecystoenteric fistula and mechanical obstruction.
Recognize ileocecal impaction, Rigler triad, and the greater diagnostic yield of CT.
Choose enterolithotomy, bowel resection, combined surgery, and recurrence follow-up principles by patient risk.
Biliary obstruction
Localize the obstruction before choosing the test
The figure links the level of obstruction to infection risk, imaging, and intervention.
Quick check
An 82-year-old woman with no prior abdominal surgery has several days of intermittent vomiting and distention. CT shows small bowel obstruction, pneumobilia, and a 3 cm intraluminal stone near the ileocecal valve.
Which diagnosis is most likely?
Reason it through
Which finding identifies a mechanical culprit?The ectopic stone at the transition point.
How did the stone enter bowel?Through a cholecystoenteric fistula.
Why did it stop distally?The terminal ileum and ileocecal valve have a relatively narrow lumen.
Pneumobilia plus obstruction plus an ectopic stone is gallstone ileus until proved otherwise.
The impact site changes the syndrome
Follow the lumen from stomach to ileocecal valve and match symptoms to location.
Most stones enter through a cholecystoduodenal fistula and travel through the small bowel; the ileocecal region is the common final site because of its narrow caliber and less forceful transit.
A stone lodged in the duodenum can cause gastric outlet obstruction, called Bouveret syndrome. Colonic impaction is less common and often requires preexisting narrowing.
Place each manifestation on the gastrointestinal route.
The common fistula origin links chronic cholecystitis to pneumobilia.
Proximal impaction can obstruct gastric emptying and produce early vomiting.
A migrating stone can create intermittent partial obstruction.
The most common impaction region produces distal small bowel obstruction.
Rare impaction usually needs a large stone or a narrowed colonic lumen.
Chronic inflammation opens an escape route
The fistula explains the stone, the air, and the delayed intermittent presentation.
Repeated cholecystitis can make the gallbladder adhere to adjacent bowel, most often the duodenum. Pressure and inflammation then erode the shared wall and form a cholecystoenteric fistula.
A large stone enters the bowel, intestinal air refluxes into the biliary tree, and the stone tumbles distally until the lumen becomes too narrow.
Advance the stone from gallbladder to obstruction.
Choose the first step.
Gallstone ileus is a mechanical obstruction, not a motility ileus
The name is historical; the CT transition point tells the truth.
Gallstone ileus occurs when a gallstone enters the gastrointestinal tract through a biliary-enteric fistula and becomes impacted, most often in the terminal ileum or at the ileocecal valve.
Adhesions and hernias create extrinsic transition points, tumors or strictures narrow the wall, and paralytic ileus produces diffuse dilation without a discrete obstructing stone.
Compare common obstruction patterns.
Older patient, intermittent tumbling symptoms, ectopic stone, pneumobilia, and a mechanical transition point.
Prior surgery is common; a transition point is present but no fistula-mediated ectopic stone is expected.
A bowel loop is trapped at a hernia defect and may become ischemic.
Diffuse small and large bowel dilation occurs without a discrete obstructing lesion.
Gallstone ileus is stone-driven small bowel obstruction.
Rigler triad is memorable but incompletely visible
Do not require all three findings on a plain radiograph before considering the diagnosis.
Rigler triad is mechanical bowel obstruction, pneumobilia, and an ectopic gallstone. The complete triad is often absent on plain films because many stones are not radiopaque and pneumobilia is neither universal nor specific.
CT more reliably identifies the transition point, stone number and location, bowel viability, pneumobilia, and the inflamed or fistulous biliary region, although minimally calcified stones can still be subtle.
Select the complete Rigler triad.
Use the triad as a search pattern, not an all-or-none rule.
Diagnostic certainty rises as the CT pattern assembles
A single sign is weaker than a mapped fistula, transition point, and ectopic stone.
Pneumobilia alone can follow sphincterotomy, surgery, instrumentation, infection, or another fistula. An ectopic stone without a transition point may not be the obstructing lesion.
Recurrence after enterolithotomy is uncommon but real and may occur when another stone remains in bowel or crosses a persistent fistula. Early recurrent symptoms deserve repeat CT rather than reassurance.
Rank the scenarios by support for gallstone ileus.
Pneumobilia after recent ERCP without obstruction
Small bowel obstruction with no visible cause on plain film
Obstruction plus pneumobilia in an older patient without prior surgery
CT transition at an ectopic stone plus pneumobilia
Commit before the explanation appears.
Relieve the obstruction before adding biliary surgery
The safest operation is the one the patient's physiology can tolerate.
Resuscitation, electrolyte correction, nasogastric decompression when indicated, and prompt operative assessment come first. Enterolithotomy removes the stone; nonviable or perforated bowel requires resection, and the bowel should be examined for additional stones.
Enterolithotomy alone is often favored in older or frail patients because it shortens the operation. A one-stage procedure adds cholecystectomy and fistula closure and may be reasonable in carefully selected stable, lower-risk patients with favorable anatomy or active residual biliary disease.
The fistula may close spontaneously, so delayed biliary surgery is not automatic after successful enterolithotomy. Persistent biliary symptoms, residual stones, recurrent infection, or recurrence can justify later intervention after individualized reassessment.
Reveal the operative branch.
Frail patient with viable bowel
Perform enterolithotomy alone and inspect the bowel for additional stones.
Shorter source relief usually matters more than repairing a chronic fistula during the emergency.
Ischemic or perforated segment
Resect the nonviable bowel in addition to removing the obstructing stone.
Bowel viability overrides a minimalist enterotomy.
Stable low-risk patient with favorable anatomy
Consider a one-stage operation after weighing added dissection and operative time.
Combined surgery is selective, not the default for every patient.
Asymptomatic after enterolithotomy
Observe the fistula and residual gallbladder with clinical follow-up rather than mandating interval surgery.
Many fistulas close and many older patients never need another biliary operation.
Recurrent obstruction or persistent biliary disease
Reimage for residual stones and reassess enterolithotomy plus definitive biliary treatment.
Recurrence changes the balance toward addressing the remaining fistula and gallbladder source when feasible.
First free the bowel; repair the fistula only when the patient and anatomy earn the extra operation.
Stage 1 of 3: Overview
Overview
Gallstone Ileus
The fistula explains the stone, the air, and the delayed intermittent presentation.
Step by step
Chronic inflammation opens an escape route
1Adhesion formsAn inflamed gallbladder becomes fixed to adjacent duodenum or another bowel segment.
2Fistula opensPressure necrosis and inflammation create a cholecystoenteric tract.
3Stone and air crossThe stone enters bowel while intestinal gas can enter the biliary tree.
4The stone tumblesTemporary impaction and release can produce waxing and waning symptoms.
5The stone impactsThe terminal ileum or ileocecal valve commonly becomes the final narrow stop.
Clinical takeaway
Why it mattersA large stone enters the bowel, intestinal air refluxes into the biliary tree, and the stone tumbles distally until the lumen becomes too narrow.
RememberPneumobilia plus obstruction plus an ectopic stone is gallstone ileus until proved otherwise.
Obstruction level
Choose the branch that resolves the duct question
Determine the obstruction level and urgency before selecting imaging or intervention.
Which diagnosis is most likely?
Key finding. An 82-year-old woman with no prior abdominal surgery has several days of intermittent vomiting and distention. CT shows small bowel obstruction, pneumobilia, and a 3 cm intraluminal stone near the ileocecal valve.
Answer. Gallstone ileus
Why. An ectopic stone, mechanical obstruction, and pneumobilia form the classic fistula-mediated pattern.
Board rule. Pneumobilia plus obstruction plus an ectopic stone is gallstone ileus until proved otherwise.
Navigate the biliary cases
Five patients test CT recognition, proximal impaction, operative risk, bowel viability, and recurrence.
Cross out the wrong duct location and highlight the obstruction clue. Each case separates diagnosis from urgent decompression.
An 80-year-old woman with no prior surgery has intermittent cramping, vomiting, and distention. Plain radiographs show small bowel obstruction and possible pneumobilia, but no definite ectopic stone.
Which diagnostic study should be obtained next?
Reason it through
Is the plain-film pattern complete?No, the stone is not defined.
Must the full triad be visible on radiograph?No, that requirement would miss cases.
Which study maps stone, transition, and bowel?Abdominal CT.
Do not wait for a perfect plain-film triad; let CT map the obstruction.
Is the plain-film pattern complete?Must the full triad be visible on radiograph?
Is the plain-film pattern complete?No, the stone is not defined.
Must the full triad be visible on radiograph?No, that requirement would miss cases.
Which study maps stone, transition, and bowel?Abdominal CT.
A 76-year-old man has early satiety and persistent nonbilious vomiting. CT shows pneumobilia and a large stone impacted in the duodenum with marked gastric distention but no distal small bowel dilation.
Which named manifestation is present?
Reason it through
Where is the stone?In the duodenum.
Which compartment is dilated?The stomach proximal to the obstruction.
What does that location name?Bouveret syndrome.
A proximal ectopic gallstone can block the stomach before it ever reaches the ileum.
Where is the stone?Which compartment is dilated?
Where is the stone?In the duodenum.
Which compartment is dilated?The stomach proximal to the obstruction.
What does that location name?Bouveret syndrome.
An 86-year-old woman with severe cardiopulmonary disease has CT-confirmed gallstone ileus at the terminal ileum. After resuscitation, she is stable enough for a short operation; bowel is viable and there is no active gallbladder sepsis.
Which operative strategy best balances risk and source relief?
Reason it through
What is the immediate threat?Mechanical bowel obstruction.
Is the bowel nonviable?No.
Which option ends the threat with least added surgery?Enterolithotomy alone.
In a frail patient, remove the stone before trying to repair the entire history.
What is the immediate threat?Is the bowel nonviable?
What is the immediate threat?Mechanical bowel obstruction.
Is the bowel nonviable?No.
Which option ends the threat with least added surgery?Enterolithotomy alone.
A 64-year-old fit patient has gallstone ileus, ongoing acute gallbladder inflammation, multiple residual gallbladder stones, and a clearly accessible cholecystoduodenal fistula. Bowel is viable and the patient remains stable after resuscitation.
Which statement best describes the surgical choice?
Reason it through
Is the patient frail or unstable?No.
Is residual biliary disease active?Yes, with inflammation and additional stones.
What makes combined surgery reasonable rather than mandatory?Favorable physiology and anatomy after individualized review.
One-stage repair is a selected-patient option, not a reflex.
Is the patient frail or unstable?Is residual biliary disease active?
Is the patient frail or unstable?No.
Is residual biliary disease active?Yes, with inflammation and additional stones.
What makes combined surgery reasonable rather than mandatory?Favorable physiology and anatomy after individualized review.
Six weeks after enterolithotomy alone, a patient develops recurrent intermittent obstruction. CT shows a second ectopic stone at a new transition point and a persistent cholecystoenteric fistula.
Which mechanism best explains these findings?
Reason it through
Which finding supports recurrent mechanical obstruction?A new ectopic stone at a transition point.
What route remains open?The cholecystoenteric fistula.
What should now be reconsidered?Stone removal plus definitive biliary and fistula management if risk permits.
Recurrent gallstone ileus means another stone found the old escape route.
Which finding supports recurrent mechanical obstruction?What route remains open?
Which finding supports recurrent mechanical obstruction?A new ectopic stone at a transition point.
What route remains open?The cholecystoenteric fistula.
What should now be reconsidered?Stone removal plus definitive biliary and fistula management if risk permits.
Rapid review
Three questions to check
Which diagnosis is most likely?
Gallstone ileus. An ectopic stone, mechanical obstruction, and pneumobilia form the classic fistula-mediated pattern.
Resident physician and founding medical reviewer at Bone Wizardry, focused on clinical accuracy, clear diagnostic reasoning, and practical board-oriented teaching across the curriculum.
