COMMENTARY

Colon Ischemia: Don't Miss This

David A. Johnson, MD

Disclosures

January 10, 2017

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Hello. I am Dr David Johnson, professor of medicine and chief of gastroenterology at Eastern Virginia Medical School.

Ischemic colitis is a very common problem, accounting for 16%-26% of patients presenting with lower gastrointestinal (GI) bleed. Those dealing with patients who come to the emergency department certainly can recognize it. The typical history is quite standard. Patients have abdominal pain with subsequent bloody diarrhea. It is self-limited in the absence of more severe disease.

Dr Larry Brandt is truly one of the masters of gastroenterology, particularly with vascular diseases and ischemic diseases of the GI tract, and he is certainly well recognized for his work in this area. Recently, he had an article, "Beyond Low Flow: How I Manage Ischemic Colitis," in the Red Section of the American Journal of Gastroenterology that caught my eye.[1] I thought there were some very salient points on right colon ischemia.

What Symptoms Does the Patient With Colon Ischemia Have?

The symptoms, as I alluded to, are pretty typical. Abdominal pain is invariably the case.

The patient with transverse and left-sided ischemic disease most frequently has diarrhea, cramping and abdominal pain, and bloody diarrhea. In contradistinction, a patient with symptoms of only right-sided abdominal pain, where bleeding may not even be evident, should be a bell ringer for consideration of isolated right colon ischemia. This is a very important point because [these symptoms are] frequently associated with a higher risk for ischemia in the vasculature of the superior mesenteric artery (SMA), which supplies not only the entire small bowel but also the cecum, the ascending colon, and portions of the transverse colon. This is associated with much more severe disease.

Dr Brandt and his colleague, Dr Feuerstadt, previously published a very interesting retrospective review.[2] If you have not seen this article in Clinical Gastroenterology and Hepatology, please go back and look at it. They reviewed 313 patients and looked at the patients presenting with colon ischemia. Twenty percent of these patients just had isolated right colon ischemia. When they looked at the scans of these patients and identified them by vascular scans, 84% had isolated right colon ischemia, but 15% had involvement of the SMA and acute mesenteric ischemia.

Typically, up to two thirds of these patients have a thrombus; up to about a third of patients have an embolus. These patients present with severe abdominal pain. Rectal bleeding is quite rare—in the range of 12%-16%. This has an incredibly high, if not an absolute, mortality, approaching 100%. These patients clearly have a worse prognosis. They need to be identified early and need to have vascular identification of their SMA. Brandt points this out—not only in the retrospective review but also in this current article, "Beyond Low Flow: How I Manage Ischemic Colitis."

Again, for symptoms, think about isolated right-sided abdominal pain in the absence of bleeding, and high on the list should be isolated right colon ischemia.

What Else Is in the Differential?

The second question he asks is: What else could it be?

Take a good history, including medication use (especially vasoconstrictive agents), and physical examination. Think about infectious colitis, particularly Escherichia coli O157:H7. That would be quite rare but not unusual. Patients may present with colon ischemia but have underlying causality because of an obstructive phenomena such as fecal impaction or even a colonic adenocarcinoma. These could be associated cofactors in the face of colonic ischemia.

Which Diagnostic Testing Should Be Used?

The third question is: What should be done for diagnosis?

A CT) scan with intravenous contrast is clearly the best test to assess the extent and severity. It will certainly limit our workup, particularly if it is just left-sided disease, as opposed to the isolated right colon ischemia. Patients are almost sure to get this in the emergency department when they come in, and it is quite helpful.

If there is any question on the CT scan [whether or not the diagnosis is] isolated right colon ischemia, Dr Brandt recommends these patients be very aggressively evaluated with CT angiography (CTA), MR angiography, or mesenteric angiography to assess for the SMA patency, which would prompt immediate evaluation for intervention and close surgical evaluation.

One caveat raised in the American College of Gastroenterology Guidelines[3] published in 2015, on which Dr Brandt was the senior author, is that when you start your colonoscopy in these patients, use minimal air. If possible, use CO2. It has less barostatic pressure associated with the air distention, which can impede serosal blood flow and may aggravate an underlying ischemia. If you see ischemia when you get to the distal extent, stop and pull out. You do not need to do anything but maybe biopsy to be sure that that is what it is. But pressing on to the cecum in these patients to meet a quality metric may have serious, untoward consequences.

How Severe Are the Symptoms?

How sick is the patient? Are there any discriminants? Certainly, discriminants in patients with acute mesenteric ischemia have more severe symptoms, but not necessarily just symptoms.

In the retrospective review[2] these patients typically had a high white blood cell (WBC) count (= 30 x 109/L) and blood urea nitrogen (BUN) level (> 30 mg/dL). Here, the BUN level is not necessarily reflective of renal insufficiency but of the hypercatabolic state with the colon ischemia. Things you might traditionally be checking for, like lactate dehydrogenase or serum lactate, were not discriminant in patients with isolated right colon ischemia and acute mesenteric ischemia unless there was severe infarction and gangrenous changes.

Again, things you should think about are elevation in WBC and BUN. Also, the other is, in particular, patients with [this were more likely to have had] chronic obstructive pulmonary disease.

If you find an isolated right colon ischemia with these parameters, investigate, and if the patient still does not have evidence of an SMA thrombus or an embolus, the recommendation is to follow them sequentially and extremely carefully. These patients are at risk of developing these things over the sequence of the next 30 days. Watch them closely, even in the absence of an acute mesenteric occlusion that you would identify by interventional angiography, CTA, or MR angiography.

Antibiotics: Yes or No?

Do they need antibiotics? Maybe.

Antibiotics are not recommended for mild disease, but they are for moderate to severe disease. This [recommendation comes not from] clinical trials in humans but from animal studies looking particularly at translocation risks for bacteremia. The recommendation for moderate to severe disease is something to cover gram-negatives (eg, standard third-generation cephalosporin, aminoglycoside, a quinolone) and something to cover anaerobes (eg, metronidazole). These would be heralded by CT findings or the clinical features: WBC, systemic response, BUN, catabolic state.

Is Surgery Indicated?

The final question Dr Brandt raises is: Do they need a surgeon? If the patient has moderate to severe disease, it is certainly good to get a surgeon involved. The recommendations really support this.

In summary, Dr Brandt's article, "Beyond Low Flow: How I Manage Ischemic Colitis," gives us great guidance, new thought, and an opportunity to discuss this topic. Think about isolated right colon ischemia and acute mesenteric ischemia in patients who present with abdominal pain, where bleeding may not be evident. It is not something that can be missed—mortality approaches 100%. CT is the best diagnostic test. Hopefully, these points will be of value to you and your patients.

I am Dr David Johnson. Thanks again for listening.

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