A physician evaluates a 78-year-old man in the emergency department for sudden-onset, excr… — USMLE Step 2 CK

A physician evaluates a $78$ -year-old man in the emergency department for sudden-onset, excruciating abdominal pain that began $2$ hours ago. The patient reports one episode of non-bloody emesis. His medical history includes hypertension, diet-controlled type 2 diabetes mellitus, and atrial fibrillation, for which he has been nonadherent to his oral anticoagulant medication for the past several months. Vital signs reveal a temperature of $37.2^\circ\text{C}$ ( $99.0^\circ\text{F}$ ), an irregularly irregular heart rate of $122/\text{min}$ , a respiratory rate of $22/\text{min}$ , and a blood pressure of $105/65\text{ mm Hg}$ . On physical examination, the abdomen is soft and non-distended; there is mild, diffuse tenderness to deep palpation, but no guarding or rebound tenderness is elicited. Bowel sounds are hypoactive. Laboratory studies show a leukocyte count of $17,500/\text{mm}^3$ and a markedly elevated serum lactate level of $5.6\text{ mmol/L}$ . Which of the following is the most appropriate next step in the management of this patient?

A
Placement of a nasogastric tube and initiation of conservative observation
B
Infusion of intravenous sodium bicarbonate to correct the metabolic acidosis
Computed tomography angiography of the abdomenAnswer
D
Initiation of intravenous piperacillin-tazobactam as primary definitive therapy
E
Administration of intravenous furosemide and noninvasive positive pressure ventilation

Answer

Computed tomography angiography of the abdomen

This patient's presentation of sudden-onset, severe abdominal pain that is out of proportion to his benign physical examination findings is highly suspicious for acute mesenteric ischemia. His nonadherence to anticoagulation for atrial fibrillation places him at significant risk for a superior mesenteric artery (SMA) embolism. The elevated serum lactate strongly supports intestinal ischemia. The most appropriate next step in management to confirm the diagnosis and plan potential revascularization is a computed tomography (CT) angiography of the abdomen.

Step-by-Step Solution

Analyze the patient's risk factors.

The patient has a history of atrial fibrillation and nonadherence to anticoagulation, putting him at high risk for thromboembolic events.

Identifying thromboembolic risk helps narrow the differential diagnosis for acute abdominal pain.

Interpret the clinical presentation and physical examination.

The patient has sudden, severe abdominal pain but a relatively benign physical examination (soft abdomen, no peritonitis). This represents 'pain out of proportion to physical findings.'

This is the classic hallmark presentation of acute mesenteric ischemia.

Evaluate the laboratory findings.

There is significant leukocytosis and an elevated serum lactate (

5.6\text{ mmol/L}

Elevated lactate in this context indicates bowel ischemia and anaerobic metabolism, supporting the diagnosis.

Determine the optimal diagnostic modality.

Select computed tomography (CT) angiography of the abdomen.

CT angiography is the rapid, non-invasive gold standard test to visualize mesenteric vessel occlusion and confirm acute mesenteric ischemia.

Key Concept

Diagnosis of acute mesenteric ischemia

Estimated Time:1m 15s

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