A 74-year-old woman is brought to the emergency department by her daughter due to sudden, … — USMLE Step 2 CK

A $74$ -year-old woman is brought to the emergency department by her daughter due to sudden, severe abdominal pain that started $2$ hours ago. The patient reports the pain is constant, diffuse, and poorly localized. She has a history of type 2 diabetes mellitus, hypertension, and a previous transient ischemic attack. She was diagnosed with atrial fibrillation one year ago but stopped taking her prescribed apixaban three months ago due to financial constraints. Her temperature is $37.2^\circ\text{C}$ ( $99.0^\circ\text{F}$ ), pulse is $112/\text{min}$ and irregularly irregular, blood pressure is $142/88 \text{ mm Hg}$ , and respirations are $20/\text{min}$ . Physical examination shows a patient in significant distress, writhing on the stretcher. However, abdominal palpation elicits only mild, diffuse tenderness without rigidity, guarding, or rebound tenderness. Bowel sounds are hypoactive. Stool is negative for occult blood. Laboratory studies show a leukocyte count of $16,500/\text{mm}^3$ and a serum lactate of $4.2 \text{ mmol/L}$ .

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

A
Emergent exploratory laparotomy
Computed tomography angiography of the abdomenAnswer
C
Colonoscopy
D
Mesenteric duplex ultrasonography
E
Upright abdominal radiography

Answer

Computed tomography angiography of the abdomen

This patient presents with sudden, severe abdominal pain that is out of proportion to her physical examination findings. Combined with her history of atrial fibrillation without current anticoagulation, an elevated leukocyte count, and elevated serum lactate, this presentation is highly suspicious for acute mesenteric ischemia (AMI) due to an arterial embolus. The embolus most commonly lodges in the superior mesenteric artery. The initial management of suspected AMI dictates that patients with unequivocal signs of peritonitis (e.g., rigidity, rebound tenderness) or hemodynamic collapse proceed directly to emergent exploratory laparotomy. However, because this patient has a soft abdomen without peritoneal signs, there is no immediate indication for surgery. Therefore, the most appropriate next step is computed tomography (CT) angiography of the abdomen. This imaging modality rapidly confirms the diagnosis, pinpoints the vascular occlusion, and helps the surgical team decide between open embolectomy versus endovascular revascularization.

Step-by-Step Solution

Analyze the patient's acute clinical presentation and risk factors.

The patient has sudden, severe abdominal pain out of proportion to physical exam findings, an elevated lactate, and untreated atrial fibrillation.

This combination of findings strongly points to acute mesenteric ischemia caused by a thromboembolism to the superior mesenteric artery.

Evaluate the physical examination for acute surgical indications.

The abdomen is soft without rigidity, guarding, or rebound tenderness.

The absence of peritonitis indicates that transmural bowel infarction and perforation have likely not yet occurred, meaning the patient does not require immediate, unguided exploratory surgery.

Determine the optimal diagnostic modality.

Computed tomography angiography of the abdomen should be ordered.

Before exposing a hemodynamically stable patient without peritonitis to the high morbidity of a laparotomy, rapid vascular imaging is required to definitively diagnose the occlusion and guide whether open surgical embolectomy or endovascular revascularization is needed.

Key Concept

The initial management of suspected acute mesenteric ischemia depends on the presence or absence of peritonitis. Patients lacking peritoneal signs require immediate CT angiography to confirm the diagnosis prior to intervention.

Alternative Method

In patients with severe iodine allergy or severe chronic kidney disease who absolutely cannot receive IV contrast for CT angiography, magnetic resonance angiography (MRA) may be considered. However, MRA is generally avoided in the acute setting due to longer acquisition times and inferior resolution of distal mesenteric branches compared to CTA.

Estimated Time:1m 30s

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