abnormalities of the mesenteric arteries

mesenteric ischemia

stenosis/occlusion of 2 or more of the three major arteries which supply the small bowel and colon with oxygenated blood (CA, SMA, IMA)

exam techniques for mesenteric ischemia:

• pre-prandial eval done of CA, SA, CHA, prox, mid, dist SMA, IMA and aorta

• pt given a high calorie liquid meal to stimulate digestive system

• pt will experience reproducible pain after eating due to bowel ischemia

• post-prandial eval done 20-30 min after meal or when pt has symptoms

intraluminal stenosis can occur due to:

• atherosclerosis

• arteritis

• fibromuscular dysplasia

doppler evaluation of mesenteric ischemia:

• CA, HA and SA waveforms should not demonstrate changes in flow after eating

• SMA and IMA flow post-prandial should not show a change in resistance

• portal venous gas may be seen in severe chronic cases → dirty shadowing from portal structures

collateral pathways that can form with chronic mesenteric ischemia include:

• pancreaticoduodenal arcade (GDA to the pancreaticoduodenal arteries) → most common

• arc if Riolan

• marginal artery of Drummond

if flow in the SMA and IMA is low resistance with increased diastolic flow even in a fasting patient, this indicates:

the capillary beds are constantly vasodilated due to ischemia

compensatory flow will demonstrate what flow characteristics?

increased velocity and spectral window

stenosis will demonstrate what flow characteristics?

increased velocity and post-stenotic turbulence

normal mesenteric PSV/Aortic PSV ratio:

around 1.0

a mesenteric PSV/Aortic PSV ratio of what indicates hemodynamically significant stenosis?

>3.0

abnormal PSV in the SMA:

>2.75 m/s which indicates >70% stenosis

abnormal EDV in the SMA:

>0.45 m/s which indicates >50% stenosis

abnormal PSV in the CA:

>2.0 m/s which indicates >70% stenosis

abnormal EDV in the CA:

>0.55 m/s which indicates >50% stenosis

abnormal PSV in the IMA:

>2.0 m/s which indicates stenosis

abnormal EDV in the IMA:

>0.25 which indicates stenosis

treatments for mesenteric ischemia include:

• angioplasty

• sten placement

• bypass graft from aorta to location dist to stenosis in SMA or CA

after treatment of mesenteric ischemia, what should happen to flow resistance and PSV and EDV?

• flow resistance should increase

• PSV and EDV should decrease

stented visceral arteries will demonstrate:

increased velocity without the presence of stenosis

median arcuate ligament syndrome

• intermittent extrinsic compression of the CA

• caused by diaphragm moving superiorly and the median arcuate ligament pinching the CA

• can be mistaken for celiac stenosis with mesenteric stenosis

• rarely causes symptoms, but may see pain with expiration

sonographic appearance of medial arcuate ligament syndrome:

• intermittent increased PSV in CA with respiration maneuvers

• velocities will increase with expiration and return to normal on inspiration

SMA syndrome/Wilkie syndrome

• acute angulation of SMA that causes compression and obstruction of the third part of the duodenum

• if a pt suffers from severe wt loss, the fatty tissue around the SMA is diminished, causing acute angulation and reduction in the distance between the aorta and the SMA

• an angle <22 degrees indicates compression is likely

• measurement of the aortomesenteric angle can demonstrate the risk of compression syndromes

symptoms of SMA syndrome include:

• early satiety

• recurrent episodes of abdominal pain

• vomiting

conditions related to SMA syndrome include:

• anorexia nervosa

• malabsorption

• malignancy

• increased spinal lordosis

• short ligament of Treitz

• abnormally inferior SMA origin