see also:

• the patient with acute abdominal pain in the ED
• colitis

• beware the patient with acute abdominal pain in the ED who also has atrial fibrillation - check their serum lactate level!

• 90% occur in >60 yr olds
• younger pts tend to have either:
  • vascular disease
  • arteriosclerotic heart disease
  • diabetes
  • hypercoagulopathy
  • vasoconstrictive drugs - cocaine, digoxin
• chronic ischaemia may be due to Sx, esp. AAA repair (0.1-10% of AAA repairs)
• most cases due to arteriole shunting, spasm or poor perfusion of mucosal vessels
• some cases are caused by embolus or thrombus of mesenteric artery
• most cases involve the splenic flexure with sparing of rectum as this is less dependent on inf. mesenteric A

• transient, reversible ⇒ mucosal sloughing and then regeneration (most common type)
• stricturing - haemorrhagic infarction of mucosa ⇒ ulceration, healing by fibrosis
• gangrenous - complete bowel wall infarction ⇒ perforation, peritonitis and death

• characteristically, acute onset

• most plain films are normal or show a non-specific ileus pattern!
• thickening of the colonic wall, with luminal narrowing and transverse ridging
  • NB. pseudothickening of the wall is NOT a sign of ischaemia and may be due to:
    • ascites as the loops are floating in fluid and become separated from other loops
    • peritonitis
    • loops containing more fluid than air causing an optical illusion
• “thumbprinting” of the bowel wall due to oedema
• fixed, rigid, tubular, ahaustral bowel loops
• pneumatosis (gas in bowel wall):
  • benign causes of pneumatosis include collagen vascular diseases, steroids, COPD and idiopathic causes.
  • this can be seen in any severe bowel insult resulting in bowel wall necrosis and is a classic feature of necrotizing enterocolitis of the newborn infant.
• free gas in peritoneal cavity (uncommon) or in mesenteric veins and portal vein (these findings are ominous and indicate infarction)