Ishcemic Colitis

Ischemic Colitis

Definition

• Ischemic colitis is a condition where the arterial blood supply to the colon is insufficient to meet metabolic demands.
• It is the most common form of gastrointestinal (GI) ischemia, with rates of 7.1 to 22.9 per 100,000 person-years.
• Severity ranges from mild, self-limiting disease to severe, life-threatening colonic ischemia.

Anatomic Considerations

Blood Supply to the Colon

• Arterial blood supply is derived from:
  • Superior Mesenteric Artery (SMA):
    • Ileocolic artery
    • Right colic artery
    • Middle colic artery
  • Inferior Mesenteric Artery (IMA):
    • Left colic artery
    • Sigmoid arteries
    • Ends as the superior rectal (hemorrhoidal) artery

Collateral Circulations

• Marginal Artery of Drummond:
  • Main collateral vessel running parallel to the mesenteric margin from the cecocolic junction to the rectosigmoid junction.
  • Provides backup blood supply when major arteries are obstructed.
• Arc of Riolan (Meandering Mesenteric Artery):
  • An infrequent collateral connecting the SMA or middle colic artery to the IMA or left colic artery.
  • Important in cases of SMA or IMA occlusion.

Watershed Areas

• Regions susceptible to ischemia due to reliance on collateral circulation.
• Splenic Flexure (Griffiths Point):
  • Junction of SMA and IMA territories.
  • Up to 50% lack a marginal artery here.
  • Surgeons often avoid anastomoses in this area due to impaired blood supply.
• Rectosigmoid Junction (Sudeck's Point):
  • Supplied by terminal branches of the IMA (superior hemorrhoidal artery and distal sigmoid branches).
  • Prone to atherosclerotic changes.
• Right Colon:
  • Vulnerable due to the ileocolic artery being a terminal branch of the SMA.
  • Prone to ischemia from embolic occlusion and low-flow conditions (e.g., heart failure, sepsis).
• Rectum:
  • Rarely affected due to dual blood supply from IMA and iliac circulation and strong collateral networks.

Risk Factors

Patient Characteristics

• More common in elderly patients and women.
• Patients with multiple comorbidities.

Medical Conditions

• Low-flow states:
  • Heart failure
  • Sepsis
• Chronic diseases:
  • Diabetes mellitus
  • Hypertension
  • Chronic obstructive pulmonary disease (COPD)
  • Peripheral vascular disease
  • Renal disease

Surgical Factors

• Aortic reconstructive surgery or abdominal surgery involving ligation of the IMA.
• Insufficient collateral circulation can lead to ischemia of the sigmoid and left colon.

Medications and Drugs

• Constipation-inducing drugs (opioids, nonopioids): Reduce blood flow and increase intraluminal pressure.
• Immunomodulators (e.g., anti-TNF-α inhibitors): Affect thrombogenesis.
• Illicit drugs (cocaine, methamphetamines): Cause vasoconstriction, hypercoagulation, and endothelial injury.

Other Associated Conditions (Box 52.2)

• Atherosclerosis: Ischemic heart disease, cerebrovascular disease, peripheral vascular disease.
• Gastrointestinal issues: Constipation, diarrhea, irritable bowel syndrome.
• Cardiovascular/Pulmonary: Atrial fibrillation, hypertension.
• Metabolic/Rheumatoid diseases: Dyslipidemia, systemic lupus erythematosus, rheumatoid arthritis.
• Miscellaneous: Hypercoagulable states, sickle cell disease, long-distance running.
• Drugs: Chemotherapeutic agents (e.g., taxanes), female hormones, decongestants (pseudoephedrine), serotoninergic drugs (e.g., alosetron, sumatriptan).

Presentation and Diagnosis

Clinical Symptoms

• Sudden abdominal pain and cramping
• Tenesmus (urge to defecate)
• Bloody diarrhea or hematochezia
  • Pain usually precedes bleeding.
  • Bleeding is usually minor.

Physical Examination

• Abdominal distension
• Tenderness over the affected area
• Important to obtain a thorough medical history, focusing on associated diseases and medications.

Commonly Affected Regions

• Left colon (including splenic flexure): Most common.
• Sigmoid colon
• Right-sided ischemic colitis (~25% of cases):
  • Presents with abdominal pain without bleeding.
  • Associated with atrial fibrillation, coronary artery disease, chronic renal failure.
  • Higher chance of requiring surgery and poorer prognosis.

Laboratory Tests

• Nonspecific but help predict severity.
• Severe disease indicators:
  • Increased white blood cell count
  • Elevated blood urea nitrogen
  • Increased lactate dehydrogenase
  • Decreased hemoglobin and albumin
  • Acidosis, decreased bicarbonate, increased lactate
• Stool tests:
  • Check for Clostridioides difficile toxin
  • Ova and parasites
  • Cultures to exclude infectious causes

Imaging Studies

• Abdominal Plain Films:
  • May show bowel distension.
  • Thumbprinting: Rounded densities indicating submucosal edema.
• CT Scan (with IV and oral contrast):
  • Identifies location and severity.
  • Excludes other diseases.
  • Findings suggestive of ischemia:
    • Segmental bowel thickening
    • Pericolonic fat stranding
    • Thumbprinting
    • Pneumatosis intestinalis: Indicates severe transmural disease.
    • Portal venous gas
    • Lack of bowel wall enhancement.

Endoscopy

• Gold standard for diagnosis.
• Early colonoscopy recommended within 48 hours (unless peritonitis or severe ischemia is suspected).
• Endoscopic findings:
  • Edematous and friable mucosa
  • Erythema
  • Petechial hemorrhage
  • Mucosal ulceration
  • Single-stripe sign: Specific but rare.
• Segmental distribution with abrupt transition supports ischemia over inflammatory bowel disease (IBD).
• Caution:
  • Avoid overinsufflation.
  • Do not advance beyond diseased area.

Diagnostic Algorithm (Fig. 52.50)

• High index of suspicion is crucial.
• Use combination of clinical, laboratory, imaging, and endoscopic findings.

Treatment

Conservative Management

• Mainstay of treatment for ~80% of patients.
• Interventions:
  • Bowel rest (NPO)
  • Intravenous fluids
  • Broad-spectrum antibiotics covering anaerobic and aerobic coliform bacteria.
  • Nasogastric tube if ileus is present.
• Correct underlying causes:
  • Address low-flow states (e.g., hypotension).
  • Optimize treatment for heart failure, sepsis, etc.
• Avoid:
  • Cathartics: May lead to perforation.
  • Glucocorticoids: Unless treating preexisting conditions like lupus or rheumatoid arthritis.

Monitoring and Follow-up

• Most patients improve within a few days.
• Re-evaluate if no improvement or worsening symptoms:
  • Consider repeat imaging or endoscopy.

Complications

• Chronic colitis:
  • Recurrent symptoms.
  • Higher risk of complications.
  • May require surgical resection.
• Chronic strictures:
  • Symptoms: Constipation, narrowed stools, abdominal pain.
  • Diagnosis: Contrast enema, CT, endoscopy.
  • Elective resection if symptomatic or malignancy cannot be excluded.

Indications for Surgery

• Signs of transmural ischemia and perforation:
  • Peritonitis
  • Hemodynamic instability
  • Free peritoneal air
  • CT findings: Portal venous gas, absent bowel enhancement.
• Emergent surgical exploration required.

Surgical Considerations

• High mortality rates:
  • 25% 30-day postoperative mortality.
  • Up to 47% mortality after acute surgery.
• Risk factors for perioperative mortality:
  • Advanced age
  • Poor functional status
  • Multiple comorbidities
  • Preoperative septic shock
  • Blood transfusions
  • Acute renal failure
  • Delayed surgery.

Intraoperative Management

• Assess entire bowel for ischemia and gangrene.
• Anatomic resection:
  • Remove affected segment.
  • Ensure adequate blood supply to remaining colon.

• Determining extent of resection:

  • Visual examination may be inaccurate.
  • Intraoperative infrared angiography (using indocyanine green) can help assess perfusion (Fig. 52.51).

  

• Anastomosis:

  • Usually not recommended in acute settings.
  • Consider temporary abdominal closure with planned second-look surgery after 24 hours.
• Pancolic ischemia:
  • Requires total colectomy with ileostomy.
• Revascularization:
  • Generally not indicated in primary colonic ischemia.

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Key Points:

• Early recognition and management are critical to prevent severe complications.
• High index of suspicion needed due to nonspecific symptoms.
• Most patients respond to conservative treatment.
• Surgical intervention reserved for severe cases with transmural ischemia or perforation.