Ischemic Colitis 

Definition

Ischemic colitis (IC) is an acute or subacute inflammatory injury of the colon resulting from transient or sustained reduction in colonic blood flow, leading to mucosal ischemia, ulceration, and in severe cases transmural necrosis and perforation.

It is the most common form of intestinal ischemia, especially in elderly and critically ill patients.

 

Epidemiology

  • Predominantly affects >60 years
  • Slight female predominance
  • Accounts for 50–60% of all intestinal ischemia
  • Increasing incidence due to aging population, vasopressor use, cardiac disease, and ICU survival

Colonic Blood Supply – Why the Colon Is Vulnerable

Major Arteries

  • Superior Mesenteric Artery (SMA) – proximal colon
  • Inferior Mesenteric Artery (IMA) – distal colon
  • Internal iliac arteries – rectum

Watershed (Border-Zone) Areas

These regions have poor collateral flow and are most susceptible:

  1. Splenic flexure (SMA–IMA junction) – most common
  2. Rectosigmoid junction (IMA–hypogastric junction)


Pathophysiology

Primary Mechanisms

  1. Hypoperfusion (most common)
    • ↓ Cardiac output
    • Hypotension / shock
    • Dehydration
    • Sepsis
  1. Vascular obstruction
    • Atherosclerosis
    • Embolism (rare vs small bowel ischemia)
    • Venous thrombosis
  1. Vasoconstriction
    • Vasopressors (noradrenaline)
    • Cocaine, ergot alkaloids, digoxin

Cellular Events

  • Mucosal hypoxia → ATP depletion
  • Increased permeability → bacterial translocation
  • Reperfusion → oxidative stress
  • Progression: mucosal → mural → transmural necrosis


Risk Factors

Cardiovascular

  • Atrial fibrillation
  • Congestive heart failure
  • Recent MI
  • Peripheral vascular disease

Systemic / ICU-Related

  • Septic shock
  • Prolonged hypotension
  • Vasopressor therapy
  • Hemodialysis
  • Major surgery (especially aortic / cardiac)

Drugs

  • NSAIDs
  • Oral contraceptives
  • Vasoconstrictors
  • Chemotherapy agents


Clinical Presentation

Typical Triad

  1. Sudden crampy abdominal pain (often left-sided)
  2. Urgent desire to defecate
  3. Hematochezia or bloody diarrhea (within 24 h)

Other Features

  • Mild–moderate tenderness
  • Low-grade fever
  • Nausea, vomiting
  • Usually not severe peritonitis unless transmural infarction

Key exam point: Pain is out of proportion less dramatic than acute mesenteric ischemia.


Severity Classification

Type

Description

Transient / Reversible

Mucosal ischemia, heals completely

Chronic segmental colitis

Recurrent ischemia → strictures

Gangrenous ischemic colitis

Full-thickness necrosis, perforation


Investigations

Laboratory Findings

  • Leukocytosis
  • Elevated CRP
  • Metabolic acidosis (severe cases)
  • Lactate: normal or mildly elevated (unlike AMI)

Labs are non-specific — diagnosis is imaging + endoscopy based.


Imaging

CT Abdomen with Contrast (Investigation of Choice)

CT Features

  • Segmental colonic wall thickening
  • Thumbprinting (submucosal edema/hemorrhage)
  • Pericolonic fat stranding
  • Reduced mural enhancement
  • Pneumatosis coli (severe)
  • Portal venous gas (ominous)


Colonoscopy (Gold Standard for Diagnosis)

Typical Findings

  • Pale, edematous mucosa
  • Petechial hemorrhages
  • Cyanosis
  • Longitudinal ulcers
  • Sharp demarcation between normal & affected bowel

Avoid colonoscopy if peritonitis or suspected perforation


Histopathology

  • Mucosal & submucosal hemorrhage
  • Withered crypts
  • Lamina propria hyalinization
  • Minimal inflammation (helps differentiate from IBD)


Differential Diagnosis

Condition

Key Difference

Ulcerative colitis

Chronic, continuous, rectal involvement

Crohn’s disease

Skip lesions, transmural

Infectious colitis

Fever, stool cultures positive

Acute mesenteric ischemia

Severe pain, minimal bleeding initially

Radiation colitis

History of radiotherapy


Management

Initial Conservative Management (Most Patients)

  • Bowel rest (NPO)
  • IV fluids (optimize perfusion)
  • Oxygen
  • Broad-spectrum antibiotics
    (Gram-negative + anaerobic coverage)
  • Stop vasoconstrictive drugs if possible

80–85% recover with conservative treatment


Indications for Surgery

  • Peritonitis
  • Bowel perforation
  • Gangrene
  • Persistent bleeding
  • Failure of conservative therapy
  • Toxic megacolon

Surgical Options

  • Segmental colectomy
  • Hartmann’s procedure (critically ill)
  • Damage-control surgery in ICU patients


Prognosis

  • Mild disease: excellent recovery
  • Severe/gangrenous disease: mortality 40–60%
  • Poor prognostic factors:
    • Right-sided involvement
    • Hypotension
    • Renal failure
    • High lactate
    • ICU admission


Special ICU Perspective

  • Often under-diagnosed in septic shock
  • May present with ileus + unexplained metabolic acidosis
  • Vasopressors worsen splanchnic ischemia
  • Early CT and low threshold for surgical consult are critical