An 81-year-old retired teacher is evaluated in the emergency department due to excruciatin… — USMLE Step 2 CK

An 81-year-old retired teacher is evaluated in the emergency department due to excruciating abdominal pain that began abruptly three hours ago. She describes the pain as constant, diffuse, and a 10 out of 10 in intensity. She has a medical history of type 2 diabetes mellitus, hypertension, and paroxysmal atrial fibrillation. She admits to running out of her prescription for rivaroxaban five days ago.

Upon evaluation, her temperature is $37.0^\circ\text{C}$ ( $98.6^\circ\text{F}$ ), blood pressure is $162/88 \text{ mmHg}$ , heart rate is $118/\text{min}$ and irregularly irregular, and respiratory rate is $18/\text{min}$ . Despite her visible distress and severe complaints of pain, her abdominal examination is remarkably benign; the abdomen is flat and soft, with only mild diffuse tenderness and no rigidity, guarding, or rebound tenderness. Bowel sounds are hypoactive.

Laboratory studies reveal:
Leukocyte count: $17,200/\text{mm}^3$
Hemoglobin: $13.1 \text{ g/dL}$
Platelet count: $210,000/\text{mm}^3$
Serum lactate: $4.1 \text{ mmol/L}$

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

A
Insertion of a nasogastric tube and clinical observation
B
Immediate exploratory laparotomy
Computed tomography angiography of the abdomenAnswer
D
Stool cultures and empiric broad-spectrum antibiotics
E
Intravenous administration of sodium bicarbonate

Answer

Computed tomography angiography of the abdomen

This patient's presentation is highly characteristic of acute mesenteric ischemia (AMI). She has a major risk factor (atrial fibrillation off anticoagulation, predisposing her to thromboembolism) and classic symptoms: sudden, excruciating abdominal pain that is out of proportion to her remarkably benign physical examination. The elevated serum lactate and leukocytosis further support the presence of bowel ischemia. In a hemodynamically stable patient with suspected AMI, computed tomography angiography (CTA) of the abdomen is the preferred initial diagnostic test. It can rapidly and accurately identify the location of the vascular occlusion (typically the superior mesenteric artery), which is essential for planning definitive endovascular or surgical revascularization.

Step-by-Step Solution

Analyze the patient's risk factors and clinical presentation.

The patient has atrial fibrillation, subtherapeutic anticoagulation, and sudden, severe abdominal pain out of proportion to a benign physical examination.

Identifying the classic triad of acute mesenteric ischemia (risk factor, sudden pain, benign exam) is critical for forming the correct differential diagnosis.

Evaluate the laboratory findings.

Elevated leukocyte count and a significantly high serum lactate indicate tissue ischemia and metabolic stress.

Lactate is a key marker of bowel ischemia due to anaerobic metabolism in the hypoperfused tissues, confirming the severity of the condition.

Determine the most appropriate diagnostic or therapeutic intervention.

Computed tomography angiography of the abdomen is selected as the next step.

In a hemodynamically stable patient with suspected mesenteric ischemia, imaging is the gold standard to accurately identify the occlusion and guide surgical or endovascular revascularization before irreversible infarction occurs.

Key Concept

Acute mesenteric ischemia typically presents with sudden, severe abdominal pain out of proportion to physical exam findings, often in patients with cardiovascular risk factors such as atrial fibrillation. Computed tomography angiography is the diagnostic test of choice in stable patients.

Estimated Time:1m 30s

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