Definition

Ischaemic Colitis

• Definition: Inflammation and injury to the colon due to insufficient blood supply.
• Cause: Reduced blood flow through mesenteric arteries supplying the colon.
• Blood Supply Compromise: Involves marginal branches of middle colic (superior mesenteric) and left colic (inferior mesenteric) arteries.
• At-Risk Areas: Transverse and descending segments of the colon, especially near splenic flexure.
• Additional Vascular Arcade: Aids blood supply to this vulnerable colon segment.
• Possible Causes of Blood Flow Impairment:
  • Colonic distension (e.g., due to obstruction or pseudo-obstruction).
  • Venous occlusion.

Aetiology

Causes of Ischaemic Colitis

• Acute Arterial Occlusion: Sudden blockage of colonic arteries.
• Chronic Mesenteric Ischemia: Gradual reduction in blood flow to colon.
• Vasculitis: Inflammation of blood vessels affecting blood supply.
• Hypoperfusion during Systemic Hypotension: Reduced blood flow due to low blood pressure.
• Vasoconstrictive Medications: Drugs causing constriction of blood vessels.

Risk Factors

Risk Factors for Ischaemic Colitis

• Age: More common in older individuals.
• Cardiovascular Disease: Underlying heart conditions.
• Hypotension: Low blood pressure.
• Vasoconstrictive Medications: Drugs causing blood vessel constriction.
• Smoking: Tobacco use.
• Abdominal Surgery: History of previous surgeries.
• Thrombosis: Blood clot formation.
• Embolism: Movement of clots causing blockages.
• Decreased Cardiac Output or Arrhythmias: Heart function abnormalities.
• Shock: Conditions like sepsis, hemorrhage, or low blood volume.
• Trauma: Physical injuries.
• Strangulated Hernia or Volvulus: Intestinal obstructions.
• Vasculitis: Inflammation of blood vessels – Systemic lupus erythematosus, Polyarteritis nodosa, Sickle cell disease
• Disorders of Coagulation: Blood clotting disorders – Protein C + S deficiency, Activated protein C resistance, Antithrombin III deficiency.
• Long-Distance Running: Intense physical activity.
• Colonoscopy or Barium Enema: Medical procedures.
• Idiopathic: Unknown causes.
• Drugs: Digitalis, Cocaine, Vasopressin, Psychotropic agents, Immunosuppressive agents.
• Surgery: Cardiac bypass, aortic dissection

Pathophysiology

Ischaemic Colitis Mechanism

• Reduced blood flow to the colon causes tissue hypoxia and inflammation.
• Watershed areas of the colon are particularly vulnerable to damage.

Differential Diagnosis

Differential Diagnosis of Ischaemic Colitis

• Dysentery.
• Acute diverticular disease of the colon (diverticulitis).
• Acute inflammatory bowel disease.
• Acute appendicitis
• Perforation of a hollow viscus or pancreatitis causing left-sided peritonitis.

Epidemiology

Epidemiology of Ischaemic Colitis

• Estimated prevalence: 4-44 per 100,000 individuals per year in the UK.
• Incidence increases with age.
• Incidence has risen over time, from 6.1 cases/100,000 person-years in 1976-80 to 22.9/100,000 in 2005-09.
• Mainly affects the elderly population; rare before age 60 (as due to atheroma of the mesenteric vessels)
• Average age for diagnosis: 70.
• Incidence may rise due to increasing age of the population.
• Can occur in younger age groups due to non-cardiovascular causes like cocaine abuse.

Clinical Presentation

Clinical Presentation of Ischaemic Colitis:

• Variable presentation from mild to severe
• Common symptoms:
  • Abdominal pain
  • Rectal bleeding
  • Diarrhea
• Diagnosis may be challenging due to nonspecific symptoms resembling ‘acute abdomen,’ including:
  • Acute-onset abdominal pain, often left iliac fossa
  • Nausea and vomiting
  • Later stages: loose bowel movements with dark blood
• Marked tenderness in the left iliac fossa
• Presence of peritonitis suggests full thickness ischaemia, perforation, or alternative diagnosis
• Distinguishing factor from inflammatory or infective colitis:
  • Rapid onset of symptoms within hours
  • Symptoms worsen with systemic instability
• Consider in patients with unexplained abdominal pain
• Potential associations in younger patients:
  • Contraceptive pill use
  • Cocaine or methamphetamine abuse
  • Pseudoephedrine use
  • Sickle cell disease
  • Inherited coagulopathies

Investigations

Investigations for Ischaemic Colitis:

Blood Tests:

• Assess inflammation
• Rule out other potential causes

Colonoscopy:

• May reveal distinctive findings:
  • Blue, swollen mucosa
  • Lack of contact bleeding
  • Sparing of the rectum

Plain Abdominal X-ray:

• May show an abnormal segment outlined with gas
• Nonspecific findings in the first 12-18 hours after onset

Barium Enema:

• Early phase:
  • “Thumb printing” appearance
  • May persist for several days
• Subsequent changes:
  • Mucosa may return to normal or progress to ulceration
  • Resembles segmental ulcerative colitis or Crohn’s disease
• Potential outcomes:
  • Spontaneous resolution
  • Progression to intestinal narrowing
  • Sacculation of the antimesenteric border

Other Modalities:

• CT Scan
• MRI Scan
• Angiography

Key Points:

• Metabolic acidosis presence may be a diagnostic clue.
• Colonoscopy can reveal specific mucosal changes.
• Plain abdominal X-ray findings may be nonspecific initially.
• Barium enema shows characteristic early-phase “thumb printing.”
• Other modalities like CT scan, MRI scan, and angiography may also be used for assessment.

Management

Ischaemic Colitis Treatment

• Supportive Care:
  • Bowel rest.
  • Intravenous fluids.
  • Pain management.
• Medical Care:
  • Transient cases may resolve with alleviation of hypoperfusion cause.
  • Broad-spectrum antibiotics recommended.
• Surgical Care:
  • If no improvement in 24-48 hours, re-evaluate severity using colonoscopy or CT angiography.
  • Increasing abdominal tenderness, fever, bleeding, and paralytic ileus suggest severe disease.
  • Urgent laparotomy and removal of necrotic colon part if infarction suspected.

Note: Severe cases may require hospitalization and surgical intervention if there is evidence of bowel infarction or perforation.

Prognosis and Complications

Prognosis of Ischaemic Colitis

• Mild Cases:
  • May resolve without complications.
• Severe Cases:
  • Risk of complications: bowel necrosis, perforation, sepsis.
  • Higher risk of mortality.
• Factors Influencing Prognosis:
  • Location and extent of disease.
  • Coexistent conditions.
  • Need for emergency surgery.
• Statistics:
  • Overall mortality: about 22%.