Ischemic colitis

• Common in elderly
• 90% cases in patients >60 years old
• Sudden onset abdominal pain, rectal bleeding

Etiology

1. Mesenteric occlusion: arterial or venous
2. Mechanical: strangulation or raised intracolonic pressure proximal to an obstruction
3. Low-flow states
4. Young patients: hypercoagulable states, vasculitis, long-distance running, cocaine use

Spectrum

• Splenic flexure most commons site (watershed zone between SMA-IMA)
• Right colon affected in low-flow states
• Mucosa – most susceptible, but can repair
• Submucosa, muscle layer – necrosis leads to fibrosis and stricture formation
• Transmural necrosis / bowel infarction: life threatening, requires immediate surgery

Imaging

• Plain radiograph: narrowing, thumbprinting. Helps to exclude toxic megacolon, free perforation, intramural or portal venous gas
• USG: thickened wall with stratification
• CT: wall thickening worse with venous occlusion. Low-attenuation target sign due to submucosal edema. Pneumatosis or portomesenteric gas suggests transmural necrosis. Look for large vessel occlusion.
• Features not specific for ischemia but overlaps with infection
  • Wall thickness does not correlate with extent of ischemia
  • Mesenteric fat stranding
  • Free fluid

Read more

Berritto, Daniela, et al. “MDCT in ischaemic colitis: how to define the aetiology and acute, subacute and chronic phase of damage in the emergency setting.” The British journal of radiology 89.1061 (2016): 20150821.

Thoeni, Ruedi F., and John P. Cello. “CT imaging of colitis.” Radiology 240.3 (2006): 623-638.