Ischemic Colitis

Definition

Early lesions characterized by superficial mucosal hemorrhage, edema and necrosis
- Necrosis usually spares base of crypts and muscularis propria
  - Leaves residual atrophic microcrypts
- Capillary thrombi frequent
- Minimal inflammation in very early lesions
- Submucosal edema may produce discrete blebs
- Sloughed necrotic mucosa may produce a microscopic appearance of a pseudomembrane
Later lesions may exhibit granulation tissue, submucosal fibrosis and atrophy
- Frequent hyalinization of lamina propria
- May mimic chronic architectural changes of inflammatory bowel disease
- Hemosiderin is frequently present in mucosa and submucosa
- Submucosal fibrosis may lead to stricture formation
Occasional findings
- Paneth cell metaplasia
- Endocrine cell hyperplasia
Severe, full thickness lesions lead to gangrene and perforation
Usually sharply defined area of involvement
- Most common location is splenic flexure watershed zone
- All other regions of colorectum can be involved
- May form a polyp or tumor mass
In resection specimens, vascular changes can be seen in about half of cases
- Arterial thrombus or embolus is most common
- Frequently atherosclerotic
- Venous thrombus
- Causes other than primary vascular disease include radiation, uremic colitis and obstructive colitis
- Most cases without vascular cause are due to hypoperfusion
Most cases in patients over age 50

Usually due to cardiovascular disease
Rare cases involving younger patients more often due to non-vascular causes
- Arteritis
- Coagulation disorders
- Drugs, including cocaine and oral contraceptives
- May be seen in long distance runners

Patchy epithelial atrophy may represent the effect of transient ischemic colitis
- Focal hyalinized lamina propria with atrophic microcrypts

Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342

Original posting : November 11, 2009