A 38-year-old woman presents to the emergency department with a 6-hour history of sudden-o… — USMLE Step 2 CK

A $38$ -year-old woman presents to the emergency department with a $6$ -hour history of sudden-onset, severe, colicky periumbilical abdominal pain, accompanied by multiple episodes of bilious vomiting. Two years ago, she underwent an uncomplicated laparoscopic Roux-en-Y gastric bypass for morbid obesity. She takes a daily multivitamin. Temperature is $38.4^\circ\text{C}$ ( $101.1^\circ\text{F}$ ), blood pressure is $88/54\text{ mm Hg}$ , pulse is $124/\text{min}$ , and respirations are $22/\text{min}$ . Physical examination reveals a moderately distended abdomen. There is marked tenderness to palpation in the periumbilical region with involuntary guarding and rebound tenderness. Bowel sounds are hypoactive.

Laboratory studies show:
Leukocyte count: $18,500/\text{mm}^3$
Serum bicarbonate: $16\text{ mEq/L}$
Lactic acid: $3.8\text{ mmol/L}$

An upright abdominal radiograph demonstrates multiple dilated loops of small bowel with air-fluid levels and a paucity of colonic gas.

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

A
Placement of a nasogastric tube and serial abdominal examinations
B
Computed tomography of the abdomen and pelvis with oral and intravenous contrast
C
Intravenous administration of sodium bicarbonate
Urgent surgical explorationAnswer
E
Upper gastrointestinal series with water-soluble contrast

Answer

Urgent surgical exploration

The correct answer is urgent surgical exploration. This patient presents with a small bowel obstruction (SBO) complicated by bowel ischemia and septic shock. Her history of a Roux-en-Y gastric bypass puts her at high risk for an internal hernia, which often results in a closed-loop obstruction and rapid progression to strangulation. The presence of peritonitis (involuntary guarding, rebound tenderness), fever, hemodynamic instability (hypotension, tachycardia), marked leukocytosis, and lactic acidosis are absolute indications for immediate laparotomy or laparoscopy. In such cases, delaying surgery for further imaging or pursuing non-operative management drastically increases mortality.

Step-by-Step Solution

Identify the clinical syndrome and its severity based on the patient's presentation.

The patient has a small bowel obstruction (SBO) with signs of strangulation and hemodynamic instability, evidenced by hypotension, tachycardia, fever, and lactic acidosis.

Recognizing ischemia and shock is the most critical factor in determining the urgency of intervention.

Relate the patient's surgical history to the current presentation.

A history of Roux-en-Y gastric bypass places the patient at high risk for internal hernias (e.g., in Petersen's space), which frequently cause closed-loop SBO and rapid bowel necrosis.

Understanding the anatomical risks of prior surgeries guides the differential diagnosis and highlights the risk for rapid deterioration.

Determine the appropriate management for a strangulated SBO.

Immediate surgical exploration is indicated.

When signs of peritonitis or bowel ischemia are present, surgical source control is mandatory to prevent death; further diagnostic imaging is contraindicated.

Key Concept

Management of strangulated small bowel obstruction and internal hernias

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