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home - Colon - Colonic Vascular Disorders - Colonic Ischaemia Overview Written by Dr Sebastian Zeki

Colonic Ischaemia Overview

Causes of Colonic Ischaemia:Aortoiliac surgery(5%)— Transmural and distal L.colon.Tx: resection.Mortality of 50%.Cardiopulmonary bypass — Colonic ischemia in< 0.2 % - mortality of 85 %.Risk factors: Older age;End-stage renal disease;Valve operation;Emergent bypass surgery;Severe postoperative low cardiac output.Tx: Prompt resection.Pathogenesis: Low flow state of bypass perfusion.Foreign surfaces may cause hypercoagulability, microemboli, alterations in cells and proteins, release of vasoactive substances, and activation of the complement cascade.Myocardial infarction (up to 15% post MI); Drugs; Exercise and intestinal ischemia —Usually because of dehydation.Haemodialysis — Usually NOMI due to underlying atherosclerosis, diabetes, and hemodialysis-induced hypotension. Nonocclusive ischemiaPatients need supportive care : iv fluids/ NG if ileus/ antibiotics.Relevant meds should be stopped.Optimize cardiac function.Papaverine benefit is unproven.It usually resolves in 2wks.Surgery indicated if deterioration. Nonocclusive colonic ischemia It affects the watershed colonic areas.The left colon is involved in 75 % of patients.25% are at the splenic flexure.5% are in the rectum. Cardiac embolism 30% of colon ischae-mia due to this. Mesenteric vein thrombosis It usually occurs in the distal small intestine (inferior mesenteric vein); rarely colon.Phlebosclerotic colitis is a venous obstruc-tion due to mesenteric vein wall fibrotic sclerosis and linear calcification).Phlebosclerotic colitis is usually in right colon and symptoms usually resolve spontaneously. Angiography This is not useful as throm-boembolic disease is never the cause.In most cases, colonic blood flow has already returned to normal by the time of symp-tom onset, and therefore angiography will be normal.Ischaemic colon vessels are mostly involved at the arteriolar level, whereas mesenteric vessels and arcades are usually patent. Histological Features:For acute and chronic ischaemia patients develop Crohn’s associ-ated change(but no granulomas).Chronic ischaemia can show mucosal atrophy and granulation.Post-ischemic stricture demon-strate xtensive transmural fibrosis and mucosal atrophy. -Pale mucosa +petechial bleeding.-Occasionally pseudo-domembranes. -Bluish hemorrhagic nodules (submucosal bleeding) = "thumbprints" on AXR -More severe disease is marked by cyanotic mucosa and hemorrhagic ulcerations. -Segmental distribution, abrupt transition between injured and non-injured mucosa, rectal sparing, and rapid resolution on serial endoscopy or CT favor ischemia rather than IBD. -A single longitudi-nal linear ulcer ("single-stripe sign") SurgeryThe bowel should not be cleansed pre-op.R-sided colonic ischaemia and necrosis require a R hemicolectomy and primary anastomosis.L-sided colonic involvement requires a proximal stoma and distal mucous fistula/ Hartmann's.Delay ostomy closure for 4-6mnth.May need a "second look" operation within 12 to 24 hours to document bowel viability. Complications Perforation Stricturing Segmental colitis Colonic ischaemia (non-gangrenous) Colonic infarction (gangrenous/ transmural infarction) 85%- resolve and don’t progress 15% Mortality of 75 % with surgical resec-tion, 100% without Minority Hyperactive phaseConsists of eft sided pain (less severe than small bowel infarction) with mild to moderate hematoche-zia 24 hours later.80% have mucosal and submucosal injury only with syptoms that settle with conservative measures. The Paralytic phase: Diffuse continuous pain.Distention.Absent bowel sounds. Shock phaseThis occurs in 20%.Severe dehydration occurs from leakage from gangrenous bowel.Shock and metabolic acidosis may develop, requiring rapid surgical intervention. Indications for surgery:Recurrent bacteremia.Persistent sepsis(from colitis).Symptomatic strictures.Perforation. Endoscopy: Colonic Ischaemia PresentationClinical DiagnosisInvasive studies are hardly ever needed unless diag-nosis is unclear. Asymptomatic strictures can resolve in 12-24 hours.Endoscopic dilatation or stenting may be alterna-tives, albeit unproven ones. Written by Dr Sebastian Zeki Worse severity associated with:Long bypass times; Use of inotropic agents; Intraaortic balloon pump Due to loss of collaterals, embolic events, traction of the vessels with surgical instruments, haematoma within the mesocolon, and hypotension.

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