Mesenteric Ischemia
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þ Mesenteric Ischemia Predisposing factors:
 - elderly
 - a fib
 - coronary disease
 - renal failure

þ Location of Mesenteric Ischemia:
 - usually superior mesenteric artery

þ Natural History
 - 75% die within 3 days.
 
þ Types of Mesenteric Ischemia:
 - embolism:  associated with a fib, MI, CV disease
 - arterial thrombosis: often presaged intestinal angina
 - AAA or dissection
  + Type B dissection, 16% in AAAs>6cm
  + 5% had mesenteric ischemia
  + Suzuki Circulation 2003
 - venous thrombosis:  associated with malignancy, coagulopathy; sudden onset
 - low flow states/sludging (usually in ICU patients)
 - 15-50% of SBO have some element of mesenteric ischemia

þ Rare Causes of Mesenteric Ischemia
 - sometimes in younger patients:
 - can have venous thrombosis in young women on OCPs.
 - can be caused by arteritis such as polyarteritis nodosa
 - Digoxin can (rarely) cause spasm of mesenteric arteries and accentuate
   existing intestinal angina

þ Classic Descriptions of Mesenteric Ischemia
 - "pain without tenderness"
 - "sudden severe pain"
 - "pain out of proportion to the exam"
 - but 40-65% have peritoneal signs on exam!

þ Diagnosis of Mesenteric Ischemia
 - unstable, suspect ischemia: resuscitate, call surgeon, bedise US: FAST, look 
   at aorta, then CT without contrast (no plain films unless going directly to 
   OR)
 - may be able to inject non-nephrotoxic contrast (bubbles) to look for 
   extravasation with ultrasound
 - eventually, with infarction, bloody currant-jelly stools
 - acidosis and elevated lactate in later stages, otherwise labs unremarkable
 - look for "thumbprinting" on the bowel x-ray (if get one); pneumatosis in 
   bowel wall, may distract by showing SBO.
 - 90% will have ^WBC
 - angiography is gold standard
 - may have elevated phosphate as well as lactate (but both might be a late 
   finding): trend lactate, as first one might miss 1:10 cases.
 - angiogram is study of choice, but up to 80% sensitivity for arterial
   occlusion with spiral CT and large doses of IV contrast.  (Per Kaveh
   Ilkanipour, February 2002)

þ Endolwak
 - Leak outside of cage of endovascular repair into old lumen
 - Type I: leaking from end, doesn't fit right, have to repair
 - Type II: aneurysm sac has accessory vessels, retrograde flow into aneurysm 
   sac, usually seal off on own or fixed by radiological
 - Type III: repair
 - Tye IV: rip of material, radiological may see rip