A nursing home resident is brought to the surgical evaluation unit due to a sudden decline… — USMLE Step 2 CK

A nursing home resident is brought to the surgical evaluation unit due to a sudden decline in his clinical status. The 76-year-old male has a history of severe dementia, atrial fibrillation, and a remote open appendectomy. According to the accompanying staff, he has not had a bowel movement in three days and began vomiting dark, foul-smelling fluid this morning. Over the last hour, he has become increasingly lethargic. Vital signs show a temperature of 38.6 °C (101.5 °F), pulse of 122/min, respirations of 24/min, and blood pressure of 85/55 mm Hg. Physical examination reveals a rigid, markedly distended abdomen with diffuse rebound tenderness. Laboratory studies demonstrate a leukocyte count of $18,500/\text{mm}^3$ and a serum lactate level of $4.2 \text{ mmol/L}$ . An upright chest radiograph shows no free air under the diaphragm. A supine abdominal radiograph demonstrates significantly dilated loops of small bowel with prominent valvulae conniventes and an absence 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 nonoperative observation
B
Computed tomography angiography of the abdomen and pelvis
C
Colonoscopic decompression and placement of a rectal tube
Immediate exploratory laparotomyAnswer
E
Initiation of a therapeutic intravenous heparin infusion

Answer

Immediate exploratory laparotomy is the most appropriate next step because the patient has an acute abdomen with hemodynamic instability, peritonitis, and signs of bowel ischemia, requiring emergent surgical source control.

Immediate exploratory laparotomy is the correct management. This patient presents with a classic mechanical small bowel obstruction (SBO), likely secondary to adhesions from a prior appendectomy, as evidenced by obstipation, emesis, and dilated small bowel loops on radiography. Crucially, the obstruction is complicated by signs of strangulation and bowel necrosis. This is indicated by his systemic toxicity (fever, tachycardia, hypotension), rigid abdomen with rebound tenderness (peritonitis), and elevated serum lactate. In the setting of an acute abdomen with hemodynamic instability and generalized peritonitis, further diagnostic testing (e.g., CT scan) is unsafe and contraindicated. Emergent surgical exploration is required to perform source control, evaluate bowel viability, and resect necrotic segments.

Step-by-Step Solution

Analyze the patient's clinical presentation, vital signs, and physical examination findings.

The patient exhibits obstipation, feculent emesis, and abdominal distension indicating a bowel obstruction. Furthermore, he is in shock (BP 85/55 mm Hg, HR 122/min) with a systemic inflammatory response (fever) and has a rigid abdomen with rebound tenderness (peritonitis).

Identifying hemodynamic instability and peritonitis is critical as it immediately triages the patient away from conservative management or time-consuming diagnostic pathways.

Evaluate the provided laboratory and radiographic data.

The leukocytosis and elevated serum lactate (

4.2 \text{ mmol/L}

) point strongly toward bowel ischemia or necrosis. The abdominal radiograph confirms a small bowel obstruction (dilated small bowel loops, visible valvulae conniventes, absent colonic gas), likely due to adhesions from his prior appendectomy.

Correlating the diagnostic data confirms the transition from a simple mechanical obstruction to a complicated, strangulated obstruction.

Determine the definitive management for a complicated, strangulated small bowel obstruction in an unstable patient.

The standard of care is to bypass further diagnostic imaging (like CT scans) and proceed directly to the operating room for an immediate exploratory laparotomy.

Any delay in surgical resection of necrotic bowel in a hemodynamically unstable patient significantly increases mortality.

Key Concept

Patients with a mechanical small bowel obstruction who develop clinical signs of strangulation or ischemia (e.g., hemodynamic instability, peritonitis, fever, lactic acidosis) require immediate exploratory laparotomy rather than further imaging or conservative observation.

Estimated Time:1m 30s

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