mesenteric ischemia Flashcards
arterial systems from the aorta to splanchnic organs
celiac, superior mesenteric, inferior mesenteric
celiac axis
supplies left gastric, splenic artery (includes circulation to pancreas), common hepatic artery
supplies stomach, duodenum, pancreas, liver
SMA axis
pancreas, small and large bowel
IMA axis
distal transverse colon/rectum
Important bowel area without good collaterals? Areas of bowel with good collateral circ?
near splenic flexure and sigmoid colon- most frequent sites of ischemia.
most collateralization in stomach, duodenum, and rectum: very rare ischemic events.
Overview of facts about mesenteric ischemia
gut can tolerate up to 75% reduction in blood flow and O2 and be ok for 12 hrs before microscopic damage because collaterals will dilate to compensate for the occluded vessel. Eventually, however, vasoconstriction will occur: further reduction of blood flow to the occluded system. Injury is the combindation of hypoxia and reperfusion injury.
Classifications of mesenteric intestinal ischemia
acute or chronic; arterial or venous.
acute: often SMA embolis, non-occlusive mesenteric ischemia, SMA thrombus, focal segmental ischemia, acute mesenteric venous thrombosis
acute mesenteric ischemia summary
acute interruption and inadequate blood flow to the intestine. may cause a spectrum of damage: from bowel function irregularity to transmural gangrene. Usually caused by SMA embolus. high mortality- must diagnose early
Pts at risk for acute mesenteric ischemia
over 50, with CV disease, recent MI or hypotension, CHF, atrial fib, cardiac valvular disease, hypercoagulability
clinical presentation of acute mesenteric ischemia
sudden abdominal pain in a pt with cardiac disease (periumbilical)
maybe some post-prandial pain in the wks/months prior.
pain accompanied by rapid bowel evacuation.
most pain in the small bowel
most pain in embolic/arterial events, less in non-occlusive disease.
Pain is out of proportion to physical exam
maybe unexplained abdominal distension, which can be first sign of intestinal infarction
diagnostic aids for acute mesenteric ischemia
leukocytosis (high WBCs)
acidemia from high lactic acid
potentially high phosphate, amylase, lactate, Alk Phos
Xray: distended loops and thumbprinting. non-diagnostic but may r/o irreversible causes
Angiography: gold standard for any kind of acute mesenteric ischemia
Dx of acute mesenteric ischemia
resuscitation and stabilization
Work up an ischemic evente whenever a pt has abdominal pain and acidemia
CT and Xray non-diagnostic
Straight to angiography if clinical suspicion is high enough. Give papaverine infusion (vasodilator) before surgery
Pre-surgical tx of acute mesenteric ischemia
goal: restore intestinal blood flow
1. vol. rescucitation and correction of acidemia
2. mirinon/dobutamine/ dopamine: less splanchnic vascoconstriction if hypotension is an issue
3. Anticoagulant if pt isn’t bleeding
4. angiography with vasodilators (papaverine) and/or thrombolytics
specific causes of acute mesenteric ischemia
mesenteric arterial embolism (give embolectomy, local thrombolytic infusion, anticoagulation)
mesenteric arterial thrombus: surgical thrombectomy
3. mesenteric venous thrombosis: anticoagulation/thrombolysis; warfarin
4. nonocclusive mesenteric ischemia: reverse underlying condition (sepsis), antiplatelets
what is chronic mesenteric ischemia?
rare: less than 5% of events.
usually caused by mesenteric atherosclerosis.
seen as blood is shunted away from the small intestine as food enters the stomach
chronic mesenteric ischemia: clinical manifestations
crampy abdominal pain after eating which resolves 1-3 hrs later. worsens over wks/months/yrs.
sometimes see weight loss, nausea/vomiting, food aversion
can progress to acute on chronic mesenteric ischemia.
Dx of chronic mesenteric ischemia
requires high clinical suspicion b/c plain films and endoscopy normal.
MRI and doppler ultrasound give mixed results
Angiography shows occlusion of 2 or more splanchnic arteries and usually involves the SMA
Tx of chronic mesenteric ischemia
- surgery: surgical revascularization
- PTA: percutaneous transluminal angioplasty (easier to tolerate than surgery but less effective)
if vessel is fully occluded, don’t treat unless symptoms/weight loss persists
ischemic colitis: definition and epi
acute or chronic ischemia of the colon
usually in pts over 60; most common colitis in pts of that age. usually non-occlusive causes, though occlusive and obstructive causes possible.
clinical presentation of ischemic colitis
episodic bouts of sudden crampy lower abdominal pain, diarrhea, and bloody stools. Starts as watery, urgent diarrhea but proceeeds to bloody stools as mucosa sloughs off. Most commonly watershed areas: splenic flexure and sigmoid colon. May range from mild submucosal damage to transmural infarction and gangrene.
may be associated with changes in medical status: anti-hyptertensives or post operative period (esp. withinin 1 wk of AAA repair because IMA is often sacrificed during AAA repair.
ischemic colitis: clinical course
mucosal and submucosal hypoxia with hemorrhage and edema
chronic ulcerations with crypt abscesses and pseudomembranes
transmural infarction if untreated
stricturing can occur
Ischemic colitis: Dx
colonoscopy or sigmoidoscopy within 48 hrs to reveal segmental inflammatory changes if no peritonitis is present.
no angiography: blood flow may quickly return to normal.
CT is moderately sensitive
no barium enema
ischemic colitis
hemodynamic stabilization, including rehydration and blood
elminate offending meds
consider abx for fever and leukocytosis
resection of necrotic colon
compare and contrast acute colonic ischemia with acute mesenteric ischemia: age, cause, how ill, where is the pain and how bad, bleeding, dx procedure
colonic ischemia: most pts over 60, acute precipitating cause rare (though may be associated with anti-HTN meds or AAA repair), pts don’t appear ill, mild pain with LLQ tenderness, rectal bleeding and bloody diarrhea common, dx uses colonoscopy
acute mesenteric ischemia:
age is variable, acute precipitating cause is typical, pt is very ill, severe pain w/o prominent tenderness, no bleeding until late, dx is angiography
