Colon ischemia

• Acute or chronic hypoperfusion of the colon; typically transient and self-limited (nongangrenous form), but can also result in severe acute ischemia with bowel infarction (gangrenous form)

• Often used interchangeably with the term ischemic colitis.

• Most common type of intestinal ischemia

• Most commonly affects individuals > 60 years of age

• ∼ 80% of cases are nongangrenous, resolving without surgery

• Isolated right-sided colon ischemia (IRCI): 10–25% of case

• Causes

  • Most commonly (∼ 95%) caused by transient hypoperfusion due to nonocclusive disease

  • Less commonly caused by occlusive disease (arterial thromboembolism or mesenteric venous thrombosis)

• Risk factors

  • Hypotension, hypovolemia: e.g., due to sepsis, dehydration, hemorrhage

  • Chronic disease: e.g., diabetes mellitus, cardiovascular disease, renal insufficiency

  • Thrombophilia: e.g., in antiphospholipid syndrome

  • Surgery: e.g., aortic aneurysm repair, abdominal surgery affecting mesenteric arteries, cardiac surgery [7]

  • Medications and recreational drug use: e.g., vasoconstrictive drugs, immunomodulators, cocaine

  • Constipation, irritable bowel syndrome, colonic obstruction

Older patients with risk factors for atherosclerosis are at especially high risk for developing colon ischemia. [8]

Severe abdominal pain and bloody diarrhea after an abdominal aortic aneurysm repair is a classic manifestation of colon ischemia.

• Intestinal blood flow of the superior mesenteric artery (SMA) and/or inferior mesenteric artery (IMA) is 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 sepsis

• Tissue damage depends on the severity and duration of perfusion disruption.

  • Nongangrenous colon ischemia (mucosal or submucosal ischemia): 80–85% of cases; typically reversible

  • Gangrenous colon ischemia (transmural ischemia): 15–20% of cases; typically irreversible

• Tissue damage may be exacerbated by reperfusion injury. [9]

• Sites of compromise

  • Superior mesenteric artery

  • Inferior mesenteric artery

  • Middle and inferior rectal arteries

  • Watershed areas in the colon (i.e., the splenic flexure and the rectosigmoid junction) are at high risk for ischemia. [2][10]

Injury to the intestinal mucosa can occur after just 20 minutes of ischemia; transmural infarction and gangrene occur after 8–16 hours of ischemia.

• Classic presentation of colon ischemia

  • Sudden onset of cramping abdominal pain (usually in the left lower quadrant)

  • Urgent need to defecate

  • Bloody diarrhea or rectal bleeding within 24 hours of symptom 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 with abdominal guarding and rebound tenderness

  • Systemic inflammatory response and/or signs of septic shock

  • Hypovolemic shock (e.g, due to dehydration or hemorrhage)

Consider colon ischemia in any patient with abdominal pain and/or bloody diarrhea without a clear infectious etiology, as many do not have the classic presentation of colon ischemia. [3]

In colon ischemia, pain is typically milder and more laterally located than in small intestinal ischemia. [3]

• There are no specific diagnostic laboratory studies for colon ischemia.

• Blood tests help assess the severity of colon ischemia; findings in severe colon ischemia include:

  • CBC: ↑ WBC and ↓ Hb

  • BMP: ↓ Serum Na+ and ↓ HCO3-

  • Other: ↑ Lactate, ↑ amylase, ↑ creatinine kinase, ↑ LDH

• Stool studies are indicated to rule out differential diagnoses (e.g., C. difficile-associated diarrhea).

Hallmark findings of severe colon ischemia include leukocytosis, metabolic acidosis, ↑ lactate, ↑ LDH, and ↑ CPK.

• CT abdomen with IV and PO contrast

  • Indication: required in all patients with suspected colon ischemia

  • Findings

    • Bowel wall thickening

    • Bowel edema

    • Pneumatosis intestinalis

    • Thumbprint sign: edematous thickening of the mucosa causing indentations in the large bowel wall

  • Additional benefit: may detect an alternative pathology

• Other imaging studies

  • CTA or MR angiography: indicated if there is suspicion of IRCI or AMI and in severe colon ischemia [2]

  • Plain abdominal radiograph

    • May be performed during urgent assessment of acute abdomen

    • Potential findings are nonspecific (e.g., air-filled, distended bowel).

Colonoscopy confirms the diagnosis, defines the distribution of the ischemia, and excludes other pathology.

• Indication: suspected mild colon ischemia or moderate colon ischemia

• Contraindications: signs of peritonitis or gangrenous bowel (e.g., pneumatosis on imaging)

• Findings

  • Edematous and fragile mucosa with erosions, ulcerations, and hemorrhagic lesions

  • Clearly defined segmental distribution of disease

Colonoscopy should be performed within 48 hours in patients with suspected colon ischemia.

• Inflammatory bowel disease

• Infectious colitis

• Colorectal carcinoma

• Other differential diagnoses of acute abdomen

• Colon ischemia usually resolves spontaneously and requires no specific therapy.

• Surgical intervention is required in severe cases (e.g., patients with gangrenous bowel).

Initial management

• Initiate supportive care (e.g., analgesia, fluid therapy, and bowel rest) for all patients.

• Urgently 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

  • Toxic megacolon

• Procedures

  • Laparotomy and possible bowel resection

  • Creation of a temporary or permanent stoma