Mesenteric ischaemia is caused by a lack of blood flow through the mesenteric vessels supplying the intestines, resulting in intestinal ischaemia.
There are three main branches of the abdominal aorta that supply the abdominal organs:
- Coeliac artery
- Superior mesenteric artery
- Inferior mesenteric artery
The foregut includes the stomach and part of the duodenum, biliary system, liver, pancreas and spleen. This is supplied by the coeliac artery.
The midgut is from the distal part of the duodenum to the first half of the transverse colon. This is supplied by the superior mesenteric artery.
The hindgut is from the second half of the transverse colon to the rectum. This is supplied by the inferior mesenteric artery.
Chronic Mesenteric Ischaemia
Chronic mesenteric ischaemia (also known as intestinal angina) is the result of narrowing of the mesenteric blood vessels by atherosclerosis. This results in intermittent abdominal pain, when the blood supply cannot keep up with the demand. It is similar to the pathophysiology of angina, where the blood supply is reduced by coronary artery disease, resulting in intermittent symptoms.
The typical presentation is with a “classic triad” of:
- Central colicky abdominal pain after eating (starting around 30 minutes after eating and lasting 1-2 hours)
- Weight loss (due to food avoidance, as this causes pain)
- Abdominal bruit may be heard on auscultation
Risk factors for chronic mesenteric ischaemia are the same as any other cardiovascular disease:
- Increased age
- Family history
- Raised cholesterol
Diagnosis is by CT angiography.
- Reducing modifiable risk factors (e.g., stop smoking)
- Secondary prevention (e.g., statins and antiplatelet medications)
- Revascularisation to improve the blood flow to the intestines
Revascularisation may be performed by:
- Endovascular procedures first-line (i.e. percutaneous mesenteric artery stenting)
- Open surgery (i.e endarterectomy, re-implantation or bypass grafting)
Acute Mesenteric Ischaemia
Acute mesenteric ischaemia is typically caused by a rapid blockage in blood flow through the superior mesenteric artery. This is usually caused by a thrombus (blood clot) stuck in the artery, blocking blood flow. The blood clot may be a thrombus that has developed inside the artery or an embolus from another site that has got stuck in the artery.
A key risk factor is atrial fibrillation, where a thrombus forms in the left atrium, then mobilises (thromboembolism) down the aorta to the superior mesenteric artery, where it becomes stuck and cuts off the blood supply.
Acute mesenteric ischaemia 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.
Over time, the ischaemia to the bowel will result in necrosis of the bowel tissue and perforation.
Contrast CT is the diagnostic test of choice, allowing the radiologist to assess both the bowel and the blood supply. Patients will have metabolic acidosis and raised lactate level due to ischaemia.
Patients require surgery to achieve two objectives:
- Remove necrotic bowel
- Remove or bypass the thrombus in the blood vessel (open surgery or endovascular procedures may be used)
There is a very high mortality (over 50%) with acute mesenteric ischaemia.
Last updated May 2021