Mesenteric Vasculature

Splanchnic arteries

What is the term used to describe the arteries that supply the bowel

CA (and its branches), SMA, IMA

What are the 3 main arteries that make up the splanchnic arteries which supply the bowel

Common hepatic, splenic, and left gastric

What 3 vessels branch off the celiac axis

Median arcuate ligament of the diaphragm

What is 1

Celiac axis

What is 2

Splenic artery

What is 3

Celiac artery

What is the first branch off of the aorta

IMA (inferior mesenteric artery)

What is 5

Gastroduodenal collaterals

What is 6

Mesenteric collaterals

What is 7

Sigmoidal arteries

What is 8

Hypogastric artery (internal iliac artery)

What is 9

SMA (superior mesenteric artery)

What is 4

Common hepatic artery taking off of the SMA instead of the CA

What is an anatomical variant of the common hepatic artery

15%

What % of people have the common hepatic taking off of the SMA instead of the CA

Low resistance

What resistance should the celiac axis bu

50-160cm/s (about, can range higher and still be normal)

What is the normal PSV of the celiac axis

≤55cm/s

What is the normal EDV of the celiac axis

Stomach, liver, pancreas, duodenum, and spleen

What structures does the celiac axis and its branches supply

Normal waveform of the celiac axis (low resistance and PSV between 50-160cm/s)

What does this image show

1-2cm

How far distal is the SMA from the celiac axis

True

T/F: there is an anatomical variant in which the SMA and the celiac axis occasionally share a common trunk

Aorta

What is 1

CA

What is 2

Branches of the celiac axis

What is 3

SMA

What is 4

Small intestine, cecum, ascending colon, and part of the transverse colon (pretty much small intestine to transverse colon)

What does the SMA supply

Metabolic activity of the gut

What causes the flow to vary within the SMA

High resistance and multiphasic

Describe the waveform seen in the SMA when the patient is in a fasting state

110-175cm/s

What about is the normal PSV of the SMA when the patient is in a fasting state

Low resistance (will probably be monophasic)

Describe the waveform of the SMA when the patient is in a post prandial state

Pre prandial

What is another term for fasting

High velocity then pre-prandial (not really an exact #)

What is the normal PSV seen in the SMA when the patient is in a post-prandial state

Fasting/preprandial (higher resistance, can see dicrotic notch and not a lot of diastolic flow)

Is this image taken form the SMA most likely from a patient who is pre-prandial or post-prandial

Post-prandial

Is this image taken form the SMA most likely from a patient who is pre-prandial or post-prandial

3-4cm superior to the bifurcation of the aorta

Where is the IMA located

Around 1:00 in to the left

Describe the take off of the IMA off the aorta that is usually seen in transverse

IMA may get bigger

How may occlusion of other mesenteric arteries alter the IMA

IMA and SMA often help each other out and compensate/collateral when the other is stenosed

Describe the relationship between the IMA and SMA in the case of stenosis

Left have of the transverse colon, descending colon, sigmoid colon, rectum (so basically the last half of the transverse colon to the end of the system)

What does the IMA supply

False, is usually difficult to image especially in patients with more body fat or gas's

T/F: the IMA is easily and readily visible in most patients

SMA occlusion (helping out the SMA as a collateral)

What may an easy visibility of the IMA possible suggest

Normal take off of the IMA

What does this image show

Asymptomatic

What is the usual presentation of splanchnic arterial occlusion

There are multiple routes for collateralization so when one artery gets stenosed, the section of bowel that it was supplying can usually get its blood supply easily from another artery

Describe why most splanchnic arterial occlusions are often asymptomatic

≥ 70% stenosis in at least 2 out of the 3 arteries that make up the mesenteric arteries before symptoms even occur

Describe the severity of mesenteric arterial disease that is usually present before symptoms occur

Collateral route that links the CA and SMA via arterial branches that surround the duodenum and pancreas

What is the pancreaticoduodenal aracade

Pancreaticoduodenal aracade

Collaterals between the CA and SMA, think:

Pancreaticoduodenal arcade

What is the green circle indicating

Arc of roiled and marginal artery of Drummond

What are two major collateral pathway that form between the SMA and IMA

Links the IMA and SMA via mesenteric arterial branches

What does the arc of riolan and the marginal artery of Drummond do

Left colic-middle artery

What is a common artery that is used as a collateral between the SMA and IMA

Arc of riolan and marginal artery of Drummond (collateral between SMA and IMA)

What is the green circle indicating

Pancreaticoduodenal arcade

What is 1

Marginal artery of Drummond

What is 2

Arc of riolan

What is 3

Chronic mesenteric ischemia

What does CMI stand for

Median arcuate ligament syndrome

What does MALS stand for

suspected CMI, MALS, undergone prior mesenteric intervention

What are the 3 indications for a duplex assessment

Suspected CMI or MALS

What are the 2 main indications for a duplex assessment of the mesenteric arteries

Stents, bypass grafts, etc

What are some examples of prior mesenteric intervention that may need to be evaluated with ultrasound

Aneurysm, atherosclerosis, dissection

What are some other things that may not be the reason the physician ordered the ultrasound assessment, but may be encountered when we are assessing the mesenteric arteries

Bowel is not getting enough blood flow bc too much blockage (would probably be 2/3-3/3 of the splanchnic arteries occluded)

What is mesenteric ischemia

Uncommon

How common is mesenteric ischemia

Due to the multiple potential collaterals, bowel can usually get blood elsewhere when an artery is occluded

Why is mesenteric ischemia uncommon

Acute events

What is usually the cause of mesenteric ischemia

Embolization, thrombosis

What are some examples of acute events that may lead to mesenteric ischemia

Hypotension, small vessel disease, venous obstruction, plaque

What are some other possible, but less common, causes of mesenteric ischemia

Excercise stress test

How do we assess the Mesentery

False! We will NOT get the patient to actually exercise, it will just be assessing them pre and post prandially

T/F: when we assess the Mesentery, we implicate an exercise stress test in which the patient will walk on a treadmill until a THR is reached and then we will assess the affects this has on the bowel. The reasoning behind this is that an increased heart rate will lead to the body not delivering a lot of blood to the bowel

Acute or chronic

What are the two types of mesenteric stenosis or occ lions

Arteriography

What is the gold standard for diagnosis stenoses in the mesenteric artereis

Fasting state

Is mesenteric stenosis or occlusion assessed when the patient is in a fasting or post prandial state

Aorta

What other vessel will be assess in the case of mesenteric stenosis/occluions

The 3 main mesenteric arteries branch directly off of the aorta, so we will be able to see if there is anything from the aorta that is affecting the mesenteric vessels or perhaps there is a thrombus here (since thormbus most commonly occurs at anastomoses)

Why will we look at the aorta before we dive into assessing the mesenteric vessels

Aortic narrowing, aneurysmal, maybe even dissection

What are some aortic pathology that may affect the mesenteric vessels and be causing the problems

Mesenteric vessels pretty hard to see in the average patient due to bowel gas

Why is ultrasound really not the best in assessing mesenteric stenosis or occlusion

≥70%

What is considered a clinically significant stenosis in the mesenteric vesses

≥200cm/s

What PSV of the celiac axis would indicate a stenosis of at least 70%

≥275cm/s

What PSV of the SMA would indicate a stenosis of at least 70%

No PSV parameters (mostly due to it not easily visualized)

What PSV of the IMA would indicate a stenosis of at least 70%

≥3.5

What CA/SMA/IMA PSV: Ao PSV ratio indicate a stenosis of at least 70%

Retrograde common hepatic artery flow

What would be a supporting finding of specially a SEVERE CA stenosis or occluions

CHA will have retrograde flow in order to come back and supply the left gastric and splenic arteries. It is practically acting as the CA when the CA is SEVERLY stenosed (potentially occluded)

Explain why retrograde flow in the common hepatic artery may be seen with severe celiac axis stenosis

SMA stenosis (note that the PSV is 325cm/s which is higher than our PSV of ≥275cm/s that indicates a stenosis)

What does this image show

Post-prandial pain, patient will get so much pain after they eat that they are practically scared to eat

What is a major symptom of chronic mesenteric ischemia seen in patients

Post-prandial pain, weight loss, bloating, diarrhea, anything really that indicates bowel function is thrown off

What are all the possible symptoms of chronic mesenteric ischemia

Smoking

What habit may increase the risk of chronic mesenteric ischemia

Women that are over 60 y/o (females>males)

What patients is chronic mesenteric ischemia seen in at an increased frequency

Angiography

What is the gold standard modality for chronic mesenteric ischemia

True

T/F: although angiography is the gold standard for a diagnosis of CMI, modalities such as MRA, CTA, and duplex ultrasound are becoming better and more popular in the diagnosis

Scanned pre and post=prandially, study is repeated 20-30min after a high caloric liquid meal

Describe the sonographic assessment of chronic mesenteric ischeia

High resistance

What should the resistance be like in a normla fasting state

20-30min OR once pt is symptomatic (ex/starts experiencing pain)

What are the guidlines for when the study is repeated after the pt has a high-caloric liquid meal

Compare them together

How do we use the pre and post prandially study

SMA

Which mesenteric artery will you most likely see the most difference in the waveforms between the pre and post prandial studies

High resistance

Describe the normal waveform during fasting state

Lower resistance, PSV pretty much doubled and ESV pretty much tripled (compared to the pre-prandial waveform)

Describe the normal waveform post-prandial

Low resistance and high velocities (which is the OPPOSITE of what is should be in a fasting patient)

Describe the characteristics of an abnormal SMA waveform in a fasting patient that would already be diagnostic (you wouldn't need to do the post prandial assessment)

Velocities still high

Describe the abnormal post prandial waveform