Chronic mesenteric ischemia: Clinical sciences

Chronic mesenteric ischemia, or CMI, occurs when there is a decrease of blood flow within the mesenteric vasculature. Mesenteric ischemia can affect either the small or large bowel, depending on the blood vessels involved, and is characterized by narrowing of these blood vessels due to atherosclerotic plaques. The mesenteric vasculature has an extensive network of collateral vessels, which usually helps maintain perfusion in patients with atherosclerotic disease. However, if one of the larger vessels is occluded, particularly the celiac artery and the superior mesenteric artery, or SMA, then patients typically become symptomatic. Therefore, the diagnosis of CMI depends on first identifying the presence of stenosis with a duplex ultrasound, then assessing the severity of the occlusion with a CTA.

Now, if you suspect chronic mesenteric ischemia, you should first perform an ABCDE assessment to determine if the patient is unstable or stable. If the patient is unstable, you should initiate acute management to stabilize their airway, breathing, and circulation. This means you might need to obtain IV access, administer IV fluids, and begin empiric broad-spectrum antibiotics.

Here’s a clinical pearl to keep in mind! If you suspect CMI and your patient is unstable, be sure to evaluate for the possibility of bowel infarction due to acute-on-chronic mesenteric ischemia. These patients often have sudden, severe abdominal pain and may have abdominal distension with guarding and rebound on exam. An abdominal x-ray will show pneumatosis intestinalis, or gas within the intestinal wall, which indicates bowel infarction and necrosis; it may also show pneumoperitoneum, or gas in the abdominal cavity, which means that a perforation occurred. These patients need emergent surgical consultation for exploratory laparotomy, which will be both diagnostic and therapeutic. Remember, the only treatment for a necrotic bowel is surgical resection.

Okay, now that we covered how to approach unstable patients, let’s go back to the ABCDE assessment and discuss how to manage stable patients. If the patient is stable, you should first obtain a focused history and physical exam, as well as labs. Be sure to order lactate levels, which can help you determine whether or not there’s tissue hypoxia.

Patients often report postprandial crampy abdominal pain, since the gut has a higher demand for perfusion after eating. This pain is also known as intestinal angina, and usually starts about 30 minutes after eating and resolves within one to three hours. The abdominal pain can be so profound, it can progress to food “fear”, or aversion, and eventually result in unintentional weight loss!

Keep in mind that your patient may also have nonspecific complaints, such as nausea and vomiting, as well as diarrhea or constipation. Finally, history is often positive for tobacco use, hypertension, and other forms of atherosclerosis, such as peripheral vascular disease or coronary artery disease.

On the other hand, physical exam could reveal diffuse abdominal tenderness, but often this finding can be completely absent. Also, there’s no rebound tenderness or guarding, but there’s typically abdominal distension and epigastric bruit on auscultation. Finally, on labs, lactate levels will usually be elevated.

Here’s another clinical pearl! Because patients with CMI typically present with abdominal pain and weight loss, the work up usually starts with an EGD and colonoscopy to rule out malignancy. Therefore, if your patient is still symptomatic despite inconclusive initial testing, keep a high index of suspicion for CMI to prevent any further delay in diagnosis and treatment.