mesenteric ischemia

Question 1

arterial systems from the aorta to splanchnic organs

Answer 1

celiac, superior mesenteric, inferior mesenteric

Question 2

celiac axis

Answer 2

supplies left gastric, splenic artery (includes circulation to pancreas), common hepatic artery
supplies stomach, duodenum, pancreas, liver

Question 3

SMA axis

Answer 3

pancreas, small and large bowel

Question 4

IMA axis

Answer 4

distal transverse colon/rectum

Question 5

Important bowel area without good collaterals? Areas of bowel with good collateral circ?

Answer 5

near splenic flexure and sigmoid colon- most frequent sites of ischemia.
most collateralization in stomach, duodenum, and rectum: very rare ischemic events.

Question 6

Overview of facts about mesenteric ischemia

Answer 6

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.

Question 7

Classifications of mesenteric intestinal ischemia

Answer 7

acute or chronic; arterial or venous.
acute: often SMA embolis, non-occlusive mesenteric ischemia, SMA thrombus, focal segmental ischemia, acute mesenteric venous thrombosis

Question 8

acute mesenteric ischemia summary

Answer 8

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

Question 9

Pts at risk for acute mesenteric ischemia

Answer 9

over 50, with CV disease, recent MI or hypotension, CHF, atrial fib, cardiac valvular disease, hypercoagulability

Question 10

clinical presentation of acute mesenteric ischemia

Answer 10

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

Question 11

diagnostic aids for acute mesenteric ischemia

Answer 11

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

Question 12

Dx of acute mesenteric ischemia

Answer 12

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

Question 13

Pre-surgical tx of acute mesenteric ischemia

Answer 13

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

Question 14

specific causes of acute mesenteric ischemia

Answer 14

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

Question 15

what is chronic mesenteric ischemia?

Answer 15

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

Question 16

chronic mesenteric ischemia: clinical manifestations

Answer 16

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.

Question 17

Dx of chronic mesenteric ischemia

Answer 17

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

Question 18

Tx of chronic mesenteric ischemia

Answer 18

1. surgery: surgical revascularization
2. 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

Question 19

ischemic colitis: definition and epi

Answer 19

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.

Question 20

clinical presentation of ischemic colitis

Answer 20

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.

Question 21

ischemic colitis: clinical course

Answer 21

mucosal and submucosal hypoxia with hemorrhage and edema
chronic ulcerations with crypt abscesses and pseudomembranes
transmural infarction if untreated
stricturing can occur

Question 22

Ischemic colitis: Dx

Answer 22

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

Question 23

ischemic colitis

Answer 23

hemodynamic stabilization, including rehydration and blood
elminate offending meds
consider abx for fever and leukocytosis
resection of necrotic colon

Question 24

compare and contrast acute colonic ischemia with acute mesenteric ischemia: age, cause, how ill, where is the pain and how bad, bleeding, dx procedure

Answer 24

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