Ischemic colitis: Clinical sciences

Ischemic colitis, or IC for short, is the most common form of intestinal ischemia. It is typically caused by reduced intestinal blood flow, usually due to small vessel occlusion or hypoperfusion of the colon. Hypoperfusion usually follows the blood supply pattern and is most common in the watershed areas, so the splenic flexure and rectosigmoid junction. This occurs because the arteries supplying the watershed areas are the most distal branches, so when blood flow to the intestine decreases, they’re the most likely to suffer from insufficient blood supply. Reduced intestinal perfusion causes injury to the colon mucosa. However, prolonged hypoperfusion can result in transmural ischemia, which can further lead to complications, such as fulminant gangrene, perforation, and peritonitis.

Now, when assessing a patient with suspected IC, start with an ABCDE assessment to determine if your patient is unstable or stable. If the patient is unstable, you should prioritize acute management to stabilize their airway, breathing, and circulation. This means that you might need to intubate the patient, establish IV access, or administer fluids before continuing with your assessment.

Once the patient is stable, determine the cause of their instability, and proceed with a focused history and physical examination. History usually reveals severe abdominal pain, tenesmus, and bloody diarrhea; while a physical exam might reveal signs of shock, such as hypotension and tachycardia. Sometimes, you may also find signs of peritonitis, like rebound pain, rigidity, or guarding.

If you see these signs, start supportive care, which means continuing IV fluids, and administering empiric, broad-spectrum antibiotics. But, here’s the thing. These findings are not specific to ischemic colitis only, so you should order abdominal imaging such as X-ray or CT to look for bowel dilation and signs of complications such as perforation or peritonitis.

Important findings to look for include pneumatosis coli, or the presence of gas within the bowel wall; as well as portal gas, which refers to gas in the portal vein or its branches; and pneumoperitoneum, or free gas in the peritoneal cavity. In this case, call the surgical team for emergent consultation and laparotomy.

Alright, let’s go back all the way to the ABCDE assessment and take a look at how to approach a stable individual with suspected ischemic colitis. Start by obtaining a focused history and physical examination, as well as labs, such as CBC and lactate. Now, history typically reveals crampy abdominal pain that developed rapidly, usually in the left lower quadrant; as well as tenesmus. Additionally, the patient might report mild rectal bleeding or bloody diarrhea, which usually develops within 24 hours of the abdominal pain.

Here’s a high-yield fact! When taking history, be on the lookout for risk factors for colonic ischemia. First, there are factors like hypertension or diabetes melitus that damage small blood vessels and decrease blood flow to the colon. Another risk factor is atrial fibrillation, which can lead to thromboembolic complications involving the small vessels like those of the colon. Finally, an important risk factor is aortic surgery, during which the aorta and its branches might be temporarily clamped, which can cause hypoperfusion of the colon.