Please help! Difference btw Acute vs chronic mesenteric ischemic vs ischemic col

[cooldude89]

Please help! What is the difference between Acute vs chronic Mesenteric ischemia vs ischemic colitis. Is it all the same on the usmle how will we differentiate the three??

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[Phloston]

Please help! What is the difference between Acute vs chronic Mesenteric ischemia vs ischemic colitis. Is it all the same on the usmle how will we differentiate the three??

Going off the top of my head here (based on what I've seen through tons of practice questions):

Acute mesenteric ischaemia will result in severe abdominal pain that is out of proportion to an otherwise relatively normal physical exam. It occurs most often at the splenic flexure (same as with chronic), and the colon grossly demonstrates "patchy areas of necrosis and haemorrhage." Collateral circulation is not well-developed between the middle (SMA) and left (IMA) colic arteries.

For chronic mesenteric ischaemia, I've seen this asked in some tricky ways. They'll tell you the patient has a Hx of cardiovascular disease, but then they'll also tell you that he or she has pain that worsens after meals and weight loss due to food aversion, making you think that it could be a gastric ulcer. In this case, the CVD info is not a distractor, and the answer is actually chronic mesenteric ischaema, not gastric ulcer. Whereas acutely, ischaemia can be due to thrombus/embolus, chronic mesenteric ischaemia is almost always due to atherosclerosis. The USMLE wants you to know that this condition (and its pain) is very similar to angina pectoris. Whereas acutely you have the patchy areas of necrosis, in the chronic state, you have mucosal atrophy and loss of villi in hypoperfused areas.

The other thing: the middle and left colic arteries anastamose via the marginal artery. This anastamosis is better developed in the chronic state. Also, the distal sigmoid is a watershed between the IMA and hypogastric arteries.

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Btw, anything I've bolded has shown up directly through practice questions.

 

[ijn]

Please help! What is the difference between Acute vs chronic Mesenteric ischemia vs ischemic colitis. Is it all the same on the usmle how will we differentiate the three??

Acute vs chronic isn't going to be the differential in the test question. I'd focus on the following scheme for testing purposes...

Pain + blood = acute mesenteric ischemia
Pain + no blood = diverticulitis
No pain + blood = diverticulosis >> angiodysplasia

 

[glykon]

Ischemic colitis= acute/subacute/chronic ischemia.
Occlusion: celiac trunk/SMA/IMA.
Chronic ischemia has a milder course: h/o of chronic abdominal pain which usually begins 15-30min after a meal, lasts for hours and it's due to increased O2 need in the GI tract+/- abdominal distension+/- weight loss. Usually heavy smoker, atherosclerosis or other conditions which decrease mesenteric blood flow.
Make sure u dont confuse this with pain from gastric ulcer, because pain in ischemic colitis can be located in the upper abdomen as well. Diagnose with CT, angiography, angio-MRI to view the stenosis. Treat: supportive+ surgery/ endovascular therapy.
As for acute ischemia, the clinical course is much more dramatic:
sudden onset of midabdominal pain out of proportion to exam+ diarrhea. Exam: hemodynamic instability, irregular HR(particularly in embolic type), abdominal distention, melena or hematochezia Wiki gives a more detailed picture here :
http://en.wikipedia.org/wiki/Mesenteric_ischemia

 

[image187]

acute ischemia is usually a sudden embolic event, caused by cholesterol embolism usually

chronic ischemia is akin to stable angina, where chronic blood supply isn't sufficient for a transient increase in o2 demand during digestion

ischemic colitis is usually caused by hypoperfusion to the gut (e.g. during shock, etc) and is more likely in the SMA/IMA watershed area

 

[glykon]

acute ischemia is usually a sudden embolic event, caused by cholesterol embolism usually

i[I]schemic colitis is usually caused by hypoperfusion to the gut[/I] (e.g. during shock, etc) and is more likely in the SMA/IMA watershed area

I disagree and think you misunderstood the concept of ischemic colitis:
'Ischemic colitis (ischaemic colitis in British English) is a medical condition in which inflammation and injury of the large intestine result from inadequate blood supply. Although uncommon in the general population, ischemic colitis occurs with greater frequency in the elderly, and is the most common form of bowel ischemia.'
Pls see http://en.wikipedia.org/wiki/Ischemic_colitis for more on ischemic colitis.

Acute arterial mesenteric ischemia has 3 causes:
1.embolic-> occlusion SMA, distal to middle colic artery-> spares proximal jejunum and transverse colon. Emboli originate in the left atrium or left ventricle
2. thrombotic-> at origin of SMA, cause by thrombosis on a superimposed area of atherosclerosis-> involes the entire area vasc. by SMA
3. nonocclusive- due to vasoconstriction of mesenteric vessels in low-flow states or admin. of vasopressors

Acute venous occlusion in hypercoagulable states- involves commonly SMV
Source: First Aid for the ABSITE 2012

 

[image187]

I disagree and think you misunderstood the concept of ischemic colitis:
'Ischemic colitis (ischaemic colitis in British English) is a medical condition in which inflammation and injury of the large intestine result from inadequate blood supply. Although uncommon in the general population, ischemic colitis occurs with greater frequency in the elderly, and is the most common form of bowel ischemia.'
Pls see http://en.wikipedia.org/wiki/Ischemic_colitis for more on ischemic colitis.

Acute arterial mesenteric ischemia has 3 causes:
1.embolic-> occlusion SMA, distal to middle colic artery-> spares proximal jejunum and transverse colon. Emboli originate in the left atrium or left ventricle
2. thrombotic-> at origin of SMA, cause by thrombosis on a superimposed area of atherosclerosis-> involes the entire area vasc. by SMA
3. nonocclusive- due to vasoconstriction of mesenteric vessels in low-flow states or admin. of vasopressors

Acute venous occlusion in hypercoagulable states- involves commonly SMV
Source: First Aid for the ABSITE 2012

Hmm... I just read that wikipedia page... please refer on that same page to "non-occlusive ischemia" and "pathophysiology". I don't see where I was wrong so I guess as long as it contributes to helping the OP differentiate between the various pathophysiologies...

I'll add that these questions showed up on my step 1 and my understanding of these concepts proved to be sufficient

 

[glykon]

Hmm... I just read that wikipedia page... please refer on that same page to "non-occlusive ischemia" and "pathophysiology". I don't see where I was wrong so I guess as long as it contributes to helping the OP differentiate between the various pathophysiologies...

I'll add that these questions showed up on my step 1 and my understanding of these concepts proved to be sufficient

Maybe I misunderstood what you were trying to say. I thought you were wrong when you said those 2 things I quoted in my previous reply because:
1. acute ischemia is not caused solely by embolism
2. ischemic colitis is due to mesenteric ischemia (SMA/IMA), which has the 4 causes I wrote in my previous post- not just vasoconstriction, which you said was the only cause of ischemic colitis.
So I had the feeling you mixed these 2 bolded concepts in your reply.

 

[image187]

Maybe I misunderstood what you were trying to say. I thought you were wrong when you said those 2 things I quoted in my previous reply because:
1. acute ischemia is not caused solely by embolism
2. ischemic colitis is due to mesenteric ischemia (SMA/IMA), which has the 4 causes I wrote in my previous post- not just vasoconstriction, which you said was the only cause of ischemic colitis.
So I had the feeling you mixed these 2 bolded concepts in your reply.

I see. I don't remember saying anything about vasoconstriction though, and I never said embolization was the sole cause of acute ischemia. You offered what seem to be more thorough explanations of each individual pathology though, so your answer probably is indeed more helpful here. I was just trying to be as simple and clear cut as possible about differentiating the three because I feel it was all that was required for the step for these specific disorders. Cheers!

 

[glykon]

acute ischemia is usually a sudden embolic event, caused by cholesterol embolism usually

ischemic colitis is usually caused by hypoperfusion to the gut (e.g. during shock, etc) and is more likely in the SMA/IMA watershed area

I was reffering to these 2 paragraphs you wrote in a previous post.
Anyway, I think it's good to have a clear picture of mesenteric ischemia, because it's a high-yield topic and others might not get questions as simple as you say you did. And also, because you see it in the OR if you're lucky and it represents some of the most interesting and challenging cases you can get in General Surgery