Hi, this is Tom from Zero2Finals.com. In this video, I'm going to be going through mesenteric ischemia and you can find written notes on this topic at Zero2Finals.com slash mesenteric ischemia or in the general surgery section of the Zero2Finals surgery book. So let's jump straight in. Mesenteric ischemia is caused by a lack of blood flow through the mesenteric vessels supplying the intestines and this results in intestinal ischemia. First let's start by talking about the blood supply.
There are three main branches of the abdominal aorta that supply the abdominal organs. And these branches are the celiac artery, the superior mesenteric artery, and the inferior mesenteric artery. The foregut includes the stomach and part of the duodenum, the biliary system, the liver, the pancreas, and the spleen. And the foregut is supplied by the celiac artery.
The midgut is from the distal part of the duodenum to the first part of the transverse colon and this is supplied by the superior mesenteric artery. And the hindgut is from the second half of the transverse colon to the rectum and this is supplied by the inferior mesenteric artery. Let's talk about chronic. mesenteric ischemia.
Chronic mesenteric ischemia is also known as intestinal angina and it's the result of narrowing of the mesenteric blood vessels by atherosclerosis. This results in intermittent abdominal pain where the blood supply cannot keep up with the demand. It's similar to the pathophysiology of angina where the blood supply is reduced by the coronary artery disease resulting in intermittent symptoms. The typical presentation of chronic mesenteric ischemia is with a classical triad of central colicky abdominal pain after eating, which usually starts around 30 minutes after eating and lasts for one to two hours, weight loss, which is due to food avoidance because food causes pain, and an abdominal bruit, which may be heard on auscultation.
A bruit is a whooshing or a blowing sound that's caused by turbulent... blood flow through the narrow abnormal vessels. The risk factors for chronic mesenteric ischemia are the same as any other cardiovascular disease including increased age, family history, smoking, diabetes, hypertension and raised cholesterol. A diagnosis of chronic mesenteric ischemia is made using a CT angiogram which is where an intravenous contrast is injected which highlights the blood vessels to detect any abnormalities or narrowing.
Management involves reducing the modifiable risk factors for example stopping smoking, secondary prevention of cardiovascular disease with statins and antiplatelet medications and revascularization. to improve the blood flow in the intestines. Revascularization may be performed by endovascular procedures which are usually first line, for example percutaneous mesenteric artery stenting where a stent is inserted into the narrowed vessel or by open surgery which could involve endarterectomy or cleaning out the blood vessel, reimplantation of the blood vessel or bypass surgery. Finally, let's talk about acute mesenteric ischemia as opposed to chronic mesenteric ischemia.
Acute mesenteric ischemia is typically caused by a rapid blockage in blood flow through the superior mesenteric artery. This is usually caused by a thrombus or a blood clot which gets stuck in the artery and blocks the flow of blood. The blood clot may be a thrombus that has developed inside the artery or an embolus that has come from another site that has then got wedged inside the artery.
A key risk factor is atrial fibrillation where a thrombus forms in the left atrium then mobilizes, which we call thromboembolism, down the aorta into the superior mesenteric artery where it gets stuck and cuts off the blood supply. Acute mesenteric ischemia presents with acute, non-specific abdominal pain. The pain is disproportionate to the examination findings. Patients can go on to develop shock, peritonitis and sepsis due to the acute bowel ischemia.
Over time, the ischemia to the bowel wall will result in necrosis of the bowel tissue and perforation of the bowel. A contrast CT is the diagnostic test of choice allowing the radiologist to assess the bowel and the blood supply. When you do an arterial blood gas the patient will have a metabolic acidosis with a raised lactate level and this is due to ischemia in the tissue and ischemia leads to anaerobic respiration and the production of lactate. Patients with acute mesenteric ischemia require surgery to achieve two objectives. The first is to remove any necrotic bowel tissue and the second is to remove or bypass the thrombus in the blood vessel and this can be done by open surgery or endovascular procedures.
There is a very high mortality rate of over 50% in patients with acute mesenteric ischemia. If you like this video, consider joining the Zero to Finals Patreon account, where you get early access to these videos before they appear on YouTube. You also get access to my comprehensive course on how to learn medicine and do well in medical exams, digital flashcards for rapidly testing the key facts you need for medical exams, early access to the Zero to Finals podcast episodes, and question podcasts.
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