A 72-year-old man is evaluated in the intensive care unit for sudden, severe abdominal pai… — USMLE Step 2 CK

A $72$ -year-old man is evaluated in the intensive care unit for sudden, severe abdominal pain and bilious vomiting that began $4$ hours ago. He was admitted $2$ days ago for a chronic obstructive pulmonary disease (COPD) exacerbation. His past medical history is significant for COPD, heart failure with preserved ejection fraction, and a laparotomy for a perforated appendix $15$ years ago. Since the pain started, he has not passed flatus or stool. His temperature is $38.9^\circ\text{C}$ ( $102.0^\circ\text{F}$ ), blood pressure is $82/50\text{ mmHg}$ , pulse is $130/\text{min}$ , and respiratory rate is $26/\text{min}$ . The jugular venous pressure is $6\text{ cm H}_2\text{O}$ . Physical examination reveals a markedly distended, rigid abdomen with diffuse tenderness, involuntary guarding, and rebound tenderness. Bowel sounds are absent. Laboratory studies show a leukocyte count of $23,000/\text{mm}^3$ and a serum lactate of $6.8\text{ mmol/L}$ . Arterial blood gas analysis on room air reveals a pH of $7.28$ , $\text{PaCO}_2$ of $30\text{ mmHg}$ , and $\text{HCO}_3^-$ of $14\text{ mEq/L}$ . An upright plain radiograph of the abdomen demonstrates multiple dilated loops of small bowel with air-fluid levels and no free intraperitoneal air. Which of the following is the most appropriate next step in management?

Immediate exploratory laparotomyAnswer
B
Placement of a nasogastric tube and serial abdominal examinations
C
Transport to the radiology suite for an abdominal computed tomography scan
D
Administration of intravenous furosemide and noninvasive positive pressure ventilation
E
Administration of intravenous sodium bicarbonate

Answer

Immediate exploratory laparotomy

The patient has a complete small bowel obstruction, likely secondary to adhesions from his previous appendectomy. While many small bowel obstructions can be managed conservatively with bowel rest and nasogastric decompression, this patient presents with classic signs of bowel strangulation and ischemia. These 'red flag' indicators include fever, severe tachycardia, hypotension, a rigid abdomen with rebound tenderness (peritonitis), marked leukocytosis, and lactic acidosis. When an SBO is complicated by strangulation, the affected bowel segment rapidly becomes necrotic. Therefore, the most appropriate next step is an immediate exploratory laparotomy for bowel resection and source control. Any delay for further imaging or conservative observation significantly increases mortality.

Step-by-Step Solution

Identify the primary diagnosis from the clinical and radiographic presentation.

The combination of severe abdominal pain, bilious vomiting, lack of flatus, previous laparotomy, and dilated small bowel loops with air-fluid levels on radiograph confirms a small bowel obstruction (SBO).

Recognizing the classic triad of SBO symptoms and imaging findings establishes the baseline pathology.

Assess for complications indicating bowel compromise or strangulation.

The patient exhibits fever (

38.9^\circ\text{C}

), shock (blood pressure

82/50\text{ mmHg}

), a rigid abdomen with rebound tenderness, leukocytosis (

23,000/\text{mm}^3

), and lactic acidosis (

6.8\text{ mmol/L}

Differentiating between simple and complicated/strangulated SBO dictates the entire management pathway.

Determine the appropriate intervention based on the severity of the SBO.

The presence of ischemia and peritonitis requires an immediate exploratory laparotomy.

Strangulated SBO is a surgical emergency. Medical management or delayed imaging will increase the risk of bowel perforation, worsening sepsis, and mortality.

Key Concept

Management of complicated (strangulated) small bowel obstruction

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