An 82-year-old female resident of a skilled nursing facility is transported to the acute c… — USMLE Step 2 CK

An 82-year-old female resident of a skilled nursing facility is transported to the acute care clinic complaining of severe, crampy abdominal pain accompanied by intractable vomiting for the past 4 days. Her caregivers report that over the last 24 hours, her emesis has become dark brown with a distinct foul, fecal odor. She has not passed flatus or had a bowel movement for 48 hours. Medical history is significant for type 2 diabetes mellitus, coronary artery disease, and heart failure with preserved ejection fraction.

Vital signs include:
- Temperature: $37.9^\circ\text{C}$ ( $100.2^\circ\text{F}$ )
- Heart rate: $118/\text{min}$
- Blood pressure: $92/58\text{ mmHg}$
- Respiratory rate: $22/\text{min}$

Physical examination reveals a markedly distended, tympanic abdomen with high-pitched, tinkling bowel sounds. There is diffuse abdominal tenderness to palpation but no guarding or rigidity.

Laboratory studies demonstrate a leukocyte count of $15,200/\text{mm}^3$ . A basic metabolic panel shows:
- $\text{Na}^+$ : $134\text{ mEq/L}$
- $\text{K}^+$ : $3.1\text{ mEq/L}$
- $\text{Cl}^-$ : $92\text{ mEq/L}$
- $\text{HCO}_3^-$ : $34\text{ mEq/L}$
- $\text{BUN}$ : $48\text{ mg/dL}$
- $\text{Creatinine}$ : $1.8\text{ mg/dL}$

Arterial blood gas on room air shows $\text{pH} = 7.50$ and $\text{pCO}_2 = 45\text{ mmHg}$ .

An upright plain radiograph of the abdomen reveals dilated loops of small intestine with multiple air-fluid levels. Additionally, there are branching radiolucent lines seen over the right upper quadrant (overlying the liver shadow) and a distinct $3.5\text{-cm}$ radiopaque density projected in the right lower quadrant.

After initiating aggressive intravenous fluid resuscitation and placing a nasogastric tube, which of the following is the most appropriate next step in the management of this patient?

Exploratory laparotomy with enterolithotomy aloneAnswer
B
Exploratory laparotomy with enterolithotomy, cholecystectomy, and fistula closure
C
Continued nasogastric decompression and serial abdominal examinations
D
Intravenous broad-spectrum antibiotics and observation for spontaneous passage
E
Administration of normal saline and calculation of expected respiratory compensation

Answer

The most appropriate next step is exploratory laparotomy with enterolithotomy alone.

The correct answer is exploratory laparotomy with enterolithotomy alone. This patient presents with a classic case of gallstone ileus, a mechanical small bowel obstruction caused when a large gallstone erodes through the gallbladder wall into the adjacent duodenum, creating a cholecystoduodenal fistula. The stone travels down the gastrointestinal tract and typically impacts at the narrowest portion, the terminal ileum (accounting for the right lower quadrant radiopacity). The diagnosis is confirmed by Rigler's triad on plain radiography: (1) signs of small bowel obstruction, (2) pneumobilia (air in the biliary tree from the fistula), and (3) an ectopic radiopaque gallstone. Because the patient is elderly, hemodynamically tenuous, and has multiple comorbidities, the surgical approach must be minimized to reduce mortality. The standard of care is an enterotomy proximal to the site of obstruction to extract the stone (enterolithotomy). Addressing the gallbladder and the fistula in the same setting (a one-stage procedure) is generally contraindicated in frail patients due to unacceptably high morbidity and mortality.

Step-by-Step Solution

Interpret the clinical presentation and physical exam.

The patient has signs of a complete small bowel obstruction (SBO), including feculent vomiting, obstipation, severe distension, and high-pitched bowel sounds.

Identifying the clinical syndrome narrows the differential diagnosis to causes of mechanical bowel obstruction.

Analyze the radiographic findings.

The radiograph shows Rigler's triad: small bowel obstruction (air-fluid levels), pneumobilia (branching radiolucencies in the liver shadow), and an ectopic gallstone (radiopaque density in the right lower quadrant).

Rigler's triad is pathognomonic for gallstone ileus, establishing the definitive diagnosis.

Determine the optimal therapeutic intervention.

The patient requires surgical removal of the obstructing stone (enterolithotomy).

3.5\text{-cm}

stone is too large to pass spontaneously, and conservative management will fail, leading to bowel necrosis or perforation.

Select the appropriate surgical approach for the patient's demographic profile.

Enterolithotomy alone is chosen over a complex one-stage procedure (which includes cholecystectomy and fistula repair).

In frail, elderly, or hemodynamically unstable patients, a one-stage repair carries significant mortality. The goal is damage control: relieve the obstruction quickly. The fistula can be left alone unless severe recurrent biliary symptoms develop later.

Key Concept

Gallstone ileus diagnosis (Rigler's triad) and management (enterolithotomy alone in frail patients)

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