An 87-year-old woman comes to the emergency department due to severe abdominal pain and vomiting. The pain began suddenly yesterday and waxes and wanes, but it never goes away completely. The patient has also felt nauseated and vomited once today. She has not had hematemesis or melena. The patient has a history of hypertension, atrial fibrillation, insulin-dependent type 2 diabetes mellitus, and colonic diverticulosis. She takes amlodipine, metoprolol, and basal-bolus insulin; anticoagulation therapy was stopped a year ago due to gastrointestinal bleeding. She does not use tobacco, alcohol, or illicit drugs. Temperature is 37.7 C (99.8 F), blood pressure is 102/54 mm Hg, pulse is 104/min and irregularly irregular, and respirations are 20/min. BMI is 29 kg/m². On physical examination, the patient appears anxious. Mucous membranes are moist. Cardiopulmonary examination reveals clear lungs and normal first and second heart sounds. The abdomen is soft with mild midepigastric tenderness and no guarding or rebound tenderness. Laboratory results are as follows: Testing for stool occult blood is positive. Which of the following is most likely to reveal the cause of this patient's abdominal pain?

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11ec25c8_d1a7_e1f5_bc81_5d860939e9d4_MD0003_00 This patient with atrial fibrillation has severe abdominal pain, vomiting, leukocytosis, and anion-gap metabolic acidosis, concerning for acute mesenteric ischemia. Most cases arise when a cardiac thrombus from the atria (eg, atrial fibrillation, particularly if not on anticoagulation), ventricles (eg, recent myocardial infarction), or heart valves (eg, infective endocarditis) embolizes to the superior mesenteric artery, leading to acute small bowel ischemia. Patients generally have acute-onset, severe abdominal pain worse with eating (when increased blood flow to the intestines is required). Nausea and vomiting often occur. Abdominal examination is usually benign compared with the amount of pain the patient describes (pain out of proportion to examination). Laboratory studies typically reveal hemoconcentration, leukocytosis with immature neutrophils, and significant anion-gap metabolic acidosis (lactic acidosis from ischemia). Fecal occult blood testing may be positive due to friability of ischemic intestinal mucosa, but frank hematochezia is rare until later in the disease course. Acute mesenteric ischemia can quickly devolve into sepsis, perforation, and death. Diagnosis is generally made with CT mesenteric angiography (noninvasive), but catheter-based mesenteric angiography (invasive) is sometimes required for equivocal cases. Management includes nasogastric decompression, intravenous fluids, anticoagulation, broad-spectrum antibiotics, and (in some cases) surgery. (Choice A) Abdominal ultrasonography can sometimes diagnose an abdominal aortic aneurysm (AAA). A rapidly expanding or ruptured AAA can sometimes cause severe abdominal pain and anion-gap metabolic acidosis (from tissue ischemia). However, the pain is usually constant (does not wax and wane) and radiates to the flanks or back. (Choice B) Peptic ulcer disease (diagnosed on esophagogastroduodenoscopy) can cause abdominal pain and positive fecal occult blood testing. However, significant acidosis, leukocytosis, and a borderline-high hemoglobin would be atypical. (Choice D) Bowel obstruction (seen on x-ray) often presents with waxing/waning abdominal pain and nausea/vomiting, occasionally with positive fecal occult blood and metabolic acidosis (bowel ischemia); however, it is almost always associated with abdominal distension. (Choice E) Diabetic ketoacidosis often presents with abdominal pain, nausea/vomiting, hemoconcentration, and anion-gap metabolic acidosis. However, most patients have significant evidence of dehydration (not moist mucous membranes), hyponatremia, and more pronounced elevations in glucose levels (often ~400 mg/dL). Positive stool fecal occult blood testing would be unsual. (Choice F) Stool culture can help diagnose Salmonella, which often presents with nausea/vomiting, fever, and gastrointestinal cramps. However, diarrhea is common, and significant metabolic acidosis and severe abdominal pain would be atypical. Educational objective: Sudden-onset, severe abdominal pain and anion-gap metabolic acidosis should raise suspicion for acute mesenteric ischemia. Most cases arise in the setting of thromboembolism (eg, atrial fibrillation). Diagnosis is generally made with CT mesenteric angiography.

An 87-Year-Old Woman Comes to the Emergency Department Due to Severe