A 74-year-old man with atrial fibrillation presents with 6 hours of severe abdominal pain. Pain appears grossly out of proportion to physical findings: the abdomen is soft with minimal tenderness and no peritonism. He has passed one loose stool with altered blood. Arterial blood gas shows pH 7.24 and lactate 4.8 mmol/L. What is the most appropriate next step?
- A CT angiography of the mesenteric vessels ✓
- B Immediate exploratory laparotomy
- C Erect chest radiograph to exclude perforation
- D Colonoscopy to identify the source of bleeding
Explanation
Pain out of proportion to a soft abdomen, atrial fibrillation, acidosis, and bloody stool indicate acute mesenteric ischaemia from superior mesenteric artery embolism. Contrast CT angiography confirms the diagnosis, defines the occlusion site, and detects bowel ischaemia early, guiding whether endovascular or open revascularisation is needed. Laparotomy without imaging risks missing revascularisation options when bowel is still viable. Chest radiograph excludes perforation but cannot explain the lactate rise, and colonoscopy is contraindicated because insufflation may perforate ischaemic bowel.
Reference: Sabiston Textbook of Surgery, 21st ed.
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Written and medically reviewed by the StethoPrep medical team.