Ischemic Colitis

Ischemic colitis Definition: • • A condition characterised by hypoperfusion injury to the large bowel from hypotension, vasoconstriction, thrombosis or other conditions that may reduce blood flow. Mostly transient and self-limited (nongangrenous form), but can also lead to severe acute ischemia with bowel infarction (gangrenous form). Epidemiology • • • • Most common form of intestinal ischemia is in the colon. Most commonly affects those aged above 60. 80% of cases are nongangrenous and can resolve without surgery. Isolated right sided colon ischemia: 10-25% of cases. Risk factors. • • • • • • • Hypotension Hypovolemia e.g. due to sepsis, dehydration, haemorrhage. Chronic diseases such as: DM, CVD, renal insufficiency Thrombophilia Surgery e.g. aortic aneurysm repair, abdominal surgery affecting mesenteric arteries, cardiac surgery etc. Medications and recreational drugs e.g. vasoconstrictive drugs, immunomodulators, cocaine. Constipation, irritable bowel syndrome, colonic obstruction. Pathophysiology • • • Intestinal blood flow to the SMA and/or IMA acutely compromised -> intestinal hypoxia -> intestinal wall damage -> mucosal inflammation and possibly bleeding -> possible progression to infarction and necrosis (gangrenous colon ischemia) -> disruption of the mucosal barrier and perforation -> release of bacteria, toxins and vasoactive substances -> life threatening substances. Tissue damage may be exacerbated by reperfusion injury. Sites of compromise: - SMA - IMA - Middle and inferior rectal arteries - Watershed areas in the colon: ✓ Splenic flexure. ✓ Rectosigmoid flexure. ✓ Both are at high risk of ischemia. Clinical features • • • Classic presentation: - Sudden onset of cramping abdominal pain -> usually in the left lower quadrant. - Urgent need to defecate. - Blood diarrhoea or rectal bleeding within 24 hours of symptoms onset. - Symptoms resolve within 2-3 days. Signs of gangrenous colon ischemia: - Progressive abdominal tenderness. - Peritoneal signs. - Fever - Ileus -> absent bowel sounds. Signs of systemic complications: - Acute abdomen guarding and rebound tenderness. - Systemic inflammatory response and/or signs of septic shock. - Hypovolemic shock -> e.g. due to dehydration or haemorrhage. Diagnosis • • There are no specific lab tests for this disease. But can help assess disease severity. • • • • • Findings of a severe on include: - High WBC - Low Hb - Low serum Na+. - Low HCO3-. - High lactate - High amylase - High CK - High LDH Stools are indicated to rule out other causes such as C. difficile associated diarrhoea. CT abdomen with IV and PO contrast: - Indications: required in all patients with suspected colon ischemia. - Findings: ✓ Bowel wall thickening ✓ Bowel edema ✓ Pneumatosis intestinalis ✓ Thumbprint sign: oedematous thickening of the mucosa causing indentation in the large bowel wall. - An additional benefit to this is that it may detect alternative pathology. CTA or MR angiography: - Indicated if there is suspension of IRCI or AMI and in severe colon ischemia. - May be performed during urgent assessment of acute abdomen. - Potential findings are non-specific – e.g. air-filled, distended bowel. Colonoscopy: - Confirms the diagnosis, defines the distribution of the ischemia and excluded other pathology. - Indications: suspected mild colon ischemia or moderate colon ischemia. - Contraindications: signs of peritonitis or gangrenous bowel (e.g. pneumatosis on imaging). - Findings: ✓ Oedematous and fragile mucosa with erosions, ulcerations and haemorrhagic lesions. ✓ Clearly defined segmental distribution of disease. Differential diagnosis • • • • Inflammatory bowel disease Infectious colitis Colorectal carcinoma Other differential diagnoses of acute abdomen Treatment and management • • • Colon ischemia usually resolves spontaneously and requires no specific therapy. Surgical intervention is required in severe cases. For example, for patients with gangrenous bowel. Initial management: - Supportive care: analgesia, fluid therapy and bowel rest -> FOR ALL PATIENTS. - • Usually consult surgery for patients with severe colon ischemia, signs of peritonitis, and/or hemodynamic instability. - Consider antibiotic treatment for patients with moderate or severe colon ischemia. Surgery: - Urgent indications: signs of peritonitis, massive bleeding, portal venous gas or pneumatosis intestinalis and toxic megacolon. - Procedures: ✓ laparotomy and possible bowel resection ✓ creation of a temporary or permanent stoma.