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Difficulty: Very hardGastroenterology and Hepatology

A 34-year-old woman is evaluated in the emergency department for sudden-onset, severe, and cramping mid-abdominal pain that began 8 hours ago. The pain is continuous but worsens in waves. She has had three episodes of vomiting, which recently became bilious. Her past medical history is significant for a laparoscopic Roux-en-Y gastric bypass performed 2 years ago for class III obesity, resulting in a 45-kg (99-lb) weight loss. Her temperature is 37.8°C (100.0°F), pulse is 115/min, blood pressure is 108/68 mm Hg, and respirations are 18/min. Physical examination reveals an anxious patient in obvious distress. The abdomen is mildly distended with focal tenderness in the mid-abdomen, but there is no rebound tenderness or rigidity. Bowel sounds are high-pitched.

Laboratory results:
Leukocyte count: 14,500/mm³
Hemoglobin: 13.2 g/dL
Serum sodium: 138 mEq/L
Serum potassium: 3.6 mEq/L
Blood urea nitrogen: 24 mg/dL
Serum creatinine: 1.1 mg/dL
Serum lactate: 3.2 mmol/L (Normal: 0.5 - 2.2 mmol/L)

A computed tomography (CT) scan of the abdomen and pelvis with intravenous contrast reveals dilated loops of small bowel with a transition point. The mesenteric vessels appear rotated around a central axis, and there is mild adjacent mesenteric edema. There is no free intraperitoneal air.

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

  1. Urgent operative explorationAnswer
  2. B
    Gastrointestinal decompression with a double-lumen tube and bowel rest
  3. C
    Initiation of empiric broad-spectrum antimicrobial therapy
  4. D
    Diagnostic esophagogastroduodenoscopy
  5. E
    Administration of an oral water-soluble contrast agent

Answer

Urgent operative exploration
The correct answer is urgent operative exploration. This patient presents with acute small bowel obstruction (SBO) symptoms, leukocytosis, and an elevated serum lactate level. She has a history of a Roux-en-Y gastric bypass (RYGB), which places her at high risk for an internal hernia (e.g., through Petersen's space or the mesojejunal defect). The CT finding of mesenteric vessels rotated around a central axis (the 'mesenteric swirl' sign) is highly specific for a volvulus or internal hernia. These conditions create a closed-loop obstruction, where a bowel segment is occluded at two adjacent points. This rapidly compromises vascular supply, leading to ischemia, necrosis, and perforation if not immediately addressed. The presence of tachycardia, leukocytosis, and an elevated lactate (indicating anaerobic metabolism from hypoperfusion) strongly suggests early bowel ischemia. Therefore, urgent surgical intervention is required to reduce the hernia, assess bowel viability, and repair the mesenteric defects.

Step-by-Step Solution

1
Analyze the patient's history and acute presentation.
The patient has acute small bowel obstruction (SBO) symptoms (colicky pain, bilious vomiting, dilated loops with a transition point) and a history of a Roux-en-Y gastric bypass (RYGB).
Identifying prior abdominal surgeries helps determine the specific etiology of the SBO.
2
Interpret the specific imaging and laboratory findings.
CT shows a 'mesenteric swirl' sign, diagnostic of an internal hernia. Laboratories show leukocytosis and an elevated lactate level.
The swirl sign indicates a closed-loop obstruction, while elevated lactate and WBCs suggest impending bowel ischemia.
3
Determine the appropriate management strategy based on the obstruction type.
The patient requires urgent operative exploration.
Unlike simple adhesive SBOs which may be managed conservatively, closed-loop obstructions with signs of ischemia mandate immediate surgical intervention to prevent bowel necrosis and perforation.

Key Concept

Patients with a history of Roux-en-Y gastric bypass who present with signs of a small bowel obstruction and a 'mesenteric swirl' on CT likely have an internal hernia. This creates a closed-loop obstruction with a high risk of rapid bowel ischemia, necessitating urgent operative exploration rather than conservative management.
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Topics

Gastroenterology and Hepatology

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