creation date: 2026-04-04 14:56
tags: Pathologies
Ischemic Colitis
Background
Definitions
Ischemic colitis, also known as colonic ischemia, is a condition characterized by hypoperfusion of the large intestines.
This condition is distinguished from acute mesenteric ischemia as hypoperfusion is often a result of global reduction in blood flow and is generally considered nonocclusive.
Etiology
A number of conditions can result in hypoperfusion of the colon. This can be due to compromised systemic circulation or by changes in the local mesenteric vasculature:
- Low blood flow ischemia affecting watershed areas
- Embolic and thrombotic arterial occlusion (typically results in small bowel as well though)
- Mesenteric vein thrombosis (rare)
Pathophysiology
The colon is supplied by the superior mesenteric artery (SMA), inferior mesenteric artery (IMA), and internal iliac arteries. An extensive collateral circulation system protects the intestines from transient hypoperfusion but watershed sections of the colon, which have limited collateral flow, are at risk of ischemia.
The watershed areas are:
- Left colon (particularly the rectosigmoid junction) - affected in 75% of cases
- Splenic flexure - affected in 25%
Other areas include:
- Rectum - affected in 5%
- Distal ileum and right colon
Clinical Presentation
Signs & Symptoms
Manifestation depends on the extent, onset, and duration of the ischemia.
Acute ischemia
Typical presentation is rapid onset mild cramping abdominal pain with tenderness over affected bowel (often left sided). There may be a desire to defecate.
Acute ischemia can be clinically categorized into three phases:
- Hyperactive phase: severe pain with frequent passage of bloody, loose stool (but blood loss is usually mild without need for transfusion)
- Paralytic phase: pain diminishes, becomes continuous, and diffuses; abdomen becomes tender and distended; bowel sounds may be absent
- Shock phase: massive fluid, protein, and electrolyte leak through damaged, gangrenous mucosa; dehydration with shock and metabolic acidosis may develop
Chronic ischemia
Chronic colitis may present with recurrent abdominal pain, bloody diarrhea, weight loss, recurrent bacteremia, persistent sepsis, or symptomatic colonic strictures.
History & Physical Exam
Risk Factors
Risk factors include:
- Drugs such as constripation-inducing drugs, immunomodulators, misused drugs
- Older age
- Myocardial infarction
- Hemodialysis (underlying diabetes and hemodialysis-induced hypotension)
- Aortoiliac instrumentation/surgery
- Cardiopulmonary bypass
- Extreme exercise
- Mesenteric arteriovenous fistula or malformation
- Acquired or hereditary thrombophilia
- Following colonoscopy
- Severe COVID-19 infection
Diagnosis
Criteria
Diagnosis is confirmed with colonoscopy. However, colonoscopy should be deferred in patients with acute peritonitis or evidence of irreversible ischemic damage on imaging (risk of perforation).
- Mucosal lesions
- Biopsy may have findings of injured mucosa
Imaging may have findings that suggest ischemia but are often nonspecific.
Work-up
Laboratory studies
Work-up includes routinely obtained abdominal pain panel:
- CBC
- Metabolic panel
- Coagulation studies
While not diagnostic, lactate, CPK, and/or amylase may indicate tissue damage.
Fecal testing
Testing for infectious etiology of bloody diarrhea should be performed.
Imaging
Both plain radiograph and CT abdomen with IV contrast are performed for abdominal pain with suspected ischemia.
Plain film findings are only seen in severe ischemia:
- Distension or pneumatosis
CT findings are nonspecific and may be initially normal:
- Edema and thickening of bowel wall
- “Target” or “double-halo” appearance from hyperdensity of mucosa and musclaris
Differential
Alternative diagnoses include:
- Small bowel ischemia (more severe pain, associated with vomiting following pain; hematochezia more associated with colonic ischemia than small bowel ischemia)
- Infectious colitis
- Inflammatory bowel disease
Red Flags / Complications
Management
Supportive Care
If there is no evidence of perforation, necrosis, or gangrene:
- Bowel rest and observation
- IV fluids to ensure perfusion
- NG tube inserted if ileus present
- Monitoring for fever, leukocytosis, peritoneal irritation, protracted diarrhea, or GI bleeding
- Nutrition support if not improved within 1-2 days
Asymptomatic lesions should be documented and monitored for healing as persistent colitis can result in stricture or chronic colitis.
Empiric broad-spectrum antibiotics are typically recommended (except for mild disease with no bleeding) although it should be noted that there is no strong evidence for routine use.
For patients who develop colonic ischemia due to mesenteric venous thrombosis or mesenteric thromboembolism, antithrombotic therapy may be considered.
Exploration and Intervention
In patients with colon infarction and necrosis, as indicated by:
- Pain out of proportion on exam, hemodynamic instability
- Evidence on imaging
urgent surgical intervention is required.
Colonic preparation should not be used as it can increase the risk of perforation or toxic dilation of the colon.