• Clinical forms & notes:
  1. gangrenous (15-20% of cases):
     • findings can sometimes be very subtle
     • sometimes crampy pain, sudden onset, with urgent desire to defecate
     • maybe some blood
     • fever and hypotension and septic signs
     • left-shifted leukocytosis on CBC
     • radiologic findings of free abdominal air, pneumatosis intestinalis, and portal venous air signify infarction
  2. non-gangrenous (80-85% 0f cases):
     • findings can sometimes be very subtle
     • pain
     • blood (gross or heme pos.)
     • obstructive signs, sometimes
• Causes:
  1. post-hypotensive and/or low-flow states (syncopal; intra-operative; acute hypotensive, cardiac failure, hypovolemia, sepsis, post-cardiac-bypass, other)
  2. vascular occlusion
     • atherosclerotic or vasulitic stenosis, diabetic small-vessel vasculopathy, post-radiation vasculopathy
     • spasm: cocaine
     • embolic (athero. plaque; clot; tumor)
     • thrombosis:
       1. arterial:
          • primary
          • secondary:
            1.   vasculitides
       2. venous:
       • primary
       • secondary
         1. idiopathic enterocolic lymphocytic phlebitis (as a stenosing mass)
         2. hypercoagulable states
            • genetic [protein S def. act. LMC-97-6538 27 y/o]
            • acquired
         3. portal hypertension
  3. intinsic/extrinsic obstruction: tumor, adhesions, diverticular disease, prolapse, volvulus, fecal impaction, exacerbation of ischemia by intestinal insufflation for colonoscopy (especially if room air...CO2 better because vasodilator)
  4. medication:
     • alosetron: serotonin antagonist for diarrhea-predom. IBS
     • meloxican: for osteoarthritis
     • digitalis
     • nasal decongestants
     • estrogens
     • danazol
     • NSAIDs
     • catecholamines
     • neuroleptics
  5. after abdominal aortic injury (from elective surgery to trauma)
  6. pseudo-obstruction (Ogilvie's syndrome) 
• Histology:
  1. gangrenous: gangrenous necrosis, varying from focal to large segments and mucosal to transmural
  2. non-gangrenous:
     • superficial crypt and bowel-lumen epithelial injury
     • lamina propria hemorrhage (beware biopsy artifact)
     • eosinophilic staining of superficial lamina propria (fibrosis on trichrome stain)
     • may see acute change with many polys and even pseudomembraneous-colitis-like summit lesion [LMC-01-4278]
     • may biopsy "healed area" and only see minimal atrophy, minimal fibrosis, and hemosiderin macrophages
     • if transmural, can scar and form a stricture

References:

1. Hwang & Schwartz, Ischemic Colitis: A Brief Review, Current Surgery, 58(2):192-194, March/April 2001.