Also known as: acute mesenteric ischemia, AMI, chronic mesenteric ischemia, intestinal angina, NOMI, mesenteric venous thrombosis
Overview
Inadequate blood flow to the small or large intestine. Acute mesenteric ischemia (AMI) results from sudden interruption of the superior mesenteric artery (SMA) via embolism (~50%), thrombosis (~15-25%), nonocclusive mesenteric ischemia (NOMI, ~20%), or mesenteric venous thrombosis (~5-10%). Chronic mesenteric ischemia (CMI) is gradual atherosclerotic narrowing of the mesenteric arteries (usually two or more vessels) producing postprandial abdominal pain.
Epidemiology
AMI is uncommon (~0.1% of hospital admissions) but carries 60-80% mortality if diagnosis is delayed. CMI is also rare and predominantly affects older women with diffuse atherosclerosis.
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Question 1GastrointestinalMedium
A 74-year-old woman with atrial fibrillation on warfarin and known peripheral arterial disease presents with sudden-onset crampy left lower quadrant pain followed within hours by bloody diarrhea. Vitals show HR 102, BP 138/80, and mild left-sided abdominal tenderness without peritoneal signs. WBC is 14,000, lactate is mildly elevated, and stool studies are pending. CT abdomen with contrast shows segmental wall thickening of the descending and sigmoid colon with pericolonic stranding, sparing the rectum. Which is the most likely diagnosis?
AUlcerative colitis
BAcute mesenteric ischemia
CIschemic colitis
DDiverticulitis
EClostridioides difficile colitis
Reveal answer & full explanation
Correct answer: C — Ischemic colitis
AUlcerative colitis
BAcute mesenteric ischemia
CIschemic colitis✓
DDiverticulitis
EClostridioides difficile colitis
Why Ischemic colitis is correct
Classic presentation is an older patient with cardiovascular disease who develops sudden crampy abdominal pain followed by hematochezia
CT shows segmental colonic wall thickening in a watershed distribution (splenic flexure or rectosigmoid) with rectal sparing
Diagnosis is confirmed by colonoscopy showing pale mucosa with petechial hemorrhages or segmental ulceration
Treatment is bowel rest, IV fluids, and broad-spectrum antibiotics, with surgery reserved for gangrene or perforation
Why the others are wrong
Acute mesenteric ischemia — typically involves the small bowel, causes pain out of proportion to exam, and produces profound metabolic acidosis rather than colonic wall thickening with hematochezia
Clostridioides difficile colitis — presents with watery diarrhea after recent antibiotic exposure and shows pancolitis with pseudomembranes, not segmental watershed involvement
Diverticulitis — produces focal left lower quadrant pain with fever and pericolonic inflammation around a diverticulum, and is rarely associated with bright red bleeding plus ischemic CT patterns
Ulcerative colitis — bloody diarrhea with left-sided colonic wall thickening suggests ulcerative colitis, but ulcerative colitis almost always involves the rectum and extends proximally in continuity, and it usually begins insidiously with weeks of bloody diarrhea rather than sudden crampy pain followed within hours by bleeding in a patient with vascular disease
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The intestinal mucosa is highly sensitive to ischemia; within 1-3 hours of arterial occlusion mucosal sloughing occurs, and full-thickness necrosis follows within 6-12 hours. Reperfusion produces oxidative injury and bacterial translocation, leading to systemic inflammatory response and multiorgan failure. In CMI, postprandial demand exceeds chronically reduced supply, causing 'intestinal angina' and food fear.
Clinical presentation
Symptoms
AMI: sudden, severe abdominal pain out of proportion to physical findings; nausea, vomiting, urgent diarrhea; later, distention and bloody stools as bowel infarcts
Mesenteric venous thrombosis: more subacute (days to weeks) of abdominal pain, anorexia, nausea
CMI: postprandial abdominal pain (intestinal angina) 15-60 min after meals, weight loss, food fear (sitophobia), diarrhea
Signs / physical exam
AMI early: minimal exam findings despite severe pain — the cardinal clue
AMI late: peritoneal signs, hypotension, fever, acidosis, altered mentation
Diverticulitis — LLQ pain, fever, diverticula with focal pericolic inflammation on CT; bloody diarrhea uncommon
Ischemic colitis (left colon, watershed) — Most common form of intestinal ischemia: older patient with sudden crampy (often left-sided) pain followed within 24 h by hematochezia and only mild tenderness; watershed segments (splenic flexure, rectosigmoid) with rectal sparing; CT shows segmental wall thickening/thumbprinting; colonoscopy confirms; most resolve with bowel rest and IV fluids (antibiotics if moderate-severe)
Gastric/duodenal ulcer — Epigastric pain, may be relieved or exacerbated by food; EGD
Peptic ulcer disease / dyspepsia (vs CMI) — No weight loss or food fear; EGD diagnostic
Diagnostic workup
Diagnostic criteria
CTA demonstration of SMA/IMA/celiac occlusion, venous thrombosis, or hypoperfusion with characteristic bowel wall findings; CMI requires the appropriate clinical syndrome plus significant mesenteric occlusive disease on imaging, usually ≥2 vessels (isolated severe SMA stenosis can suffice).
Labs
CBC (leukocytosis), BMP, lactate (elevated late, but normal lactate does not rule out AMI early), LDH, amylase/lipase, LFTs
ABG (metabolic acidosis), coagulation studies
Hypercoagulable workup if venous thrombosis suspected
Imaging
CT angiography (CTA) of abdomen — gold standard initial test; identifies arterial occlusion, venous thrombosis, bowel wall thickening, pneumatosis, portal venous gas
Pain out of proportion to exam = mesenteric ischemia until proven otherwise.
Normal lactate does NOT rule out early AMI — clinical suspicion drives early CTA.
Embolic AMI in a-fib classically lodges 3-10 cm distal to the SMA origin, just beyond the middle colic artery, sparing the proximal jejunum and transverse colon while the distal small bowel and right colon are at risk; thrombosis at the SMA origin threatens the entire SMA territory.
Mesenteric venous thrombosis is more subacute and is the variant in younger patients with hypercoagulable disorders.
Triad of postprandial abdominal pain + weight loss + food fear in an older smoker = chronic mesenteric ischemia.
References
WSES 2022 — Acute mesenteric ischemia: updated guidelines of the World Society of Emergency Surgery (Bala M et al., World J Emerg Surg 2022;17:54)
ESVS 2025 — European Society for Vascular Surgery (ESVS) 2025 Clinical Practice Guidelines on the Management of Diseases of the Mesenteric and Renal Arteries and Veins (Koelemay MJ et al., Eur J Vasc Endovasc Surg 2025;70:153-218)
SVS 2021 — Chronic mesenteric ischemia: Clinical practice guidelines from the Society for Vascular Surgery (Huber TS et al., J Vasc Surg 2021;73(1S):87S-115S)
ACG 2015 — ACG clinical guideline: epidemiology, risk factors, patterns of presentation, diagnosis, and management of colon ischemia (Brandt LJ et al., Am J Gastroenterol 2015;110:18-44)
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