Acute mesenteric ischemia
USMLE Step 2 CKDifficulty: mediumLast updated:
A 76-year-old woman with atrial fibrillation, who stopped taking her anticoagulant 1 month ago, presents with sudden, severe periumbilical pain that began 3 hours ago, followed by one episode of vomiting and a bowel movement. She is writhing in pain. Temperature is 37.3°C (99.1°F), pulse 118/min and irregularly irregular, and blood pressure 148/86 mm Hg. The abdomen is soft and only mildly tender, without guarding or rebound. Leukocyte count is 16,800/mm3 and serum lactate is 3.9 mmol/L.
Which of the following is the most appropriate next step to establish the diagnosis?
Answer and explanation
Correct answer: B. CT angiography of the abdomen
Sudden severe abdominal pain out of proportion to the physical findings in an older patient with atrial fibrillation who is off anticoagulation strongly suggests acute mesenteric ischemia from an arterial embolus. The source notes that arterial embolus accounts for more than 40% of cases and that pain out of proportion to the examination is characteristic. Mesenteric ischemia must be considered in any patient older than 50 with risk factors who develops sudden, severe abdominal pain. Patients with clear peritoneal signs go directly to the operating room. For others, selective mesenteric angiography or CT angiography is the diagnostic procedure of choice. Because mortality rises significantly once infarction occurs, imaging should not be delayed. Plain radiographs and endoscopy become abnormal only late.
Each option explained
- A. Upper endoscopyIncorrect. Upper endoscopy does not assess mesenteric arterial flow.
- B. CT angiography of the abdomenCorrect. Without peritoneal signs, CT angiography (or selective mesenteric angiography) is the diagnostic procedure of choice.
- C. Plain abdominal radiographyIncorrect. Plain films are often normal early and become abnormal only once infarction has occurred.
- D. ColonoscopyIncorrect. Colonoscopy may show ischemic colitis but does not evaluate the superior mesenteric artery, and it delays diagnosis.
- E. Hepatobiliary iminodiacetic acid (HIDA) scanIncorrect. A HIDA scan evaluates acute cholecystitis and does not fit this presentation.
Key point
Pain out of proportion to the examination in a patient with atrial fibrillation suggests acute mesenteric ischemia; obtain CT angiography unless peritonitis mandates surgery.
From the source
“Patients with clear peritoneal signs should proceed directly to the operating room for both diagnosis and treatment. For others, selective mesenteric angiography or CT angiography is the diagnostic procedure of choice.”