A 78-year-old woman is brought to the emergency department by her daughter due to 3 days o… — USMLE Step 2 CK

A $78$ -year-old woman is brought to the emergency department by her daughter due to $3$ days of worsening, diffuse abdominal pain accompanied by nausea and voluminous bilious vomiting. She has not had a bowel movement or passed flatus for the past $48$ hours. Her medical history is significant for diet-controlled type 2 diabetes mellitus, essential hypertension, and recurrent episodic right upper quadrant abdominal pain for which she has previously declined surgery.

Temperature is $37.8^\circ\text{C}$ ( $100.0^\circ\text{F}$ ), blood pressure is $105/65\text{ mm Hg}$ , pulse is $112/\text{min}$ , respiratory rate is $18/\text{min}$ , and oxygen saturation is $96\%$ on room air. The abdomen is significantly distended and tympanic to percussion. It is diffusely tender to palpation without guarding or rebound tenderness. High-pitched, tinkling bowel sounds are auscultated.

Laboratory studies show:
Leukocyte count: $11,000/\text{mm}^3$
Serum creatinine: $1.6\text{ mg/dL}$ (baseline $0.9\text{ mg/dL}$ )
Aspartate aminotransferase: $35\text{ U/L}$
Alanine aminotransferase: $40\text{ U/L}$
Alkaline phosphatase: $110\text{ U/L}$
Total bilirubin: $1.0\text{ mg/dL}$

A computed tomography (CT) scan of the abdomen without contrast reveals markedly dilated loops of small bowel with a transition point in the distal ileum, where a $3\text{ cm}$ calcified mass is impacted. There are also tubular radiolucencies in the right upper quadrant conforming to the central biliary tree.

Which of the following is the most appropriate next step in the management of this patient?

Exploratory laparotomy and enterolithotomyAnswer
B
Nasogastric tube decompression, intravenous fluids, and serial abdominal examinations
C
Intravenous piperacillin-tazobactam and urgent endoscopic retrograde cholangiopancreatography
D
Initiation of intravenous furosemide and noninvasive positive-pressure ventilation
E
Measurement of arterial blood gas to calculate expected respiratory compensation

Answer

Exploratory laparotomy and enterolithotomy

The correct management for this patient is an exploratory laparotomy and enterolithotomy. The clinical presentation and CT findings describe gallstone ileus, a mechanical small bowel obstruction resulting from a large gallstone that has eroded through the gallbladder wall into the duodenum (cholecystoenteric fistula). The stone travels distally and typically impacts at the narrowest portion of the small bowel, the terminal ileum. The pathognomonic finding on imaging is Rigler's triad: small bowel obstruction, pneumobilia (air in the biliary tree), and an ectopic calcified gallstone. Because the stone is large enough to cause complete obstruction, it rarely passes spontaneously. Therefore, definitive management requires urgent surgical extraction of the stone (enterolithotomy). Cholecystectomy and fistula closure are often deferred in the acute setting, especially in frail or elderly patients, to minimize surgical morbidity.

Step-by-Step Solution

Analyze the clinical presentation.

The patient is an elderly woman presenting with classic signs of mechanical small bowel obstruction (SBO), including abdominal distension, bilious vomiting, obstipation, and high-pitched tinkling bowel sounds.

Identifying the syndromic presentation establishes the need to look for the etiology of the obstruction.

Interpret the diagnostic imaging in the context of her medical history.

The CT scan reveals Rigler's triad: small bowel obstruction, an ectopic calcified mass (gallstone) in the distal ileum, and pneumobilia (air in the biliary tree). Her history of untreated right upper quadrant pain confirms longstanding gallstone disease.

Rigler's triad is pathognomonic for gallstone ileus, which occurs when a large gallstone erodes through the gallbladder wall into the adjacent duodenum, creating a cholecystoenteric fistula.

Determine the definitive management for this specific pathology.

The correct intervention is urgent surgical enterolithotomy to extract the impacted stone and relieve the obstruction.

Unlike some adhesion-related SBOs, gallstone ileus involves a large, rigid stone that typically will not pass spontaneously, making conservative management inappropriate.

Key Concept

Gallstone ileus presents as a mechanical small bowel obstruction caused by a large gallstone entering the bowel via a cholecystoenteric fistula. Diagnosis is confirmed by Rigler's triad (SBO, pneumobilia, and an ectopic gallstone), and management requires surgical enterolithotomy.

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