What Is Indeterminate Colitis?

This Classification is Neither Crohn's Disease Nor Ulcerative Colitis

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When discussing inflammatory bowel disease (IBD), the two forms that are most often talked about are ulcerative colitis and Crohn's disease, but there is a third diagnosis that's called indeterminate colitis. Indeterminate colitis is used when it's presumed that some form of IBD is present, but it's not yet understood which form of the disease it is. This is a confusing and controversial topic in IBD, with broad implications for patients and physicians.

It's estimated that anywhere between 10 percent and 15 percent of people with IBD are thought to have indeterminate colitis. In some situations, a diagnosis of another form of IBD might be made later, when more evidence becomes available or the disease changes.

What Is Indeterminate Colitis?

IBD is often positioned as being an umbrella term, under which Crohn's disease and ulcerative colitis fall. However, there are some situations where a person has a type of IBD that can't currently be classified into either one of those buckets. This doesn't mean that a diagnosis of Crohn's disease or ulcerative colitis won't be made in the future, but what it means is that for right now, it's unclear which form of the disease is present.

Disease that has progressed beyond its initial stages and become advanced, especially, may be difficult to classify because of the nature of the inflammation and how extensive it can be in the colon.

On the other hand, when disease is quiescent or in remission, and there is little in the way of inflammation, it may also be difficult to make a solid diagnosis. Early disease is also sometimes difficult to diagnose because the changes that IBD causes in cells and that might be seen in a biopsy under a microscope may not be present yet.

Indeterminate colitis continues to be a controversial subject in some circles and might even be considered subjective. Some researchers have made a case for indeterminate colitis to be considered a third form of IBD, while others maintain that it is a holding place until another diagnosis can be made. A physician or a pathologist less experienced with diagnosing IBD might classify what they're seeing in a patient to be indeterminate colitis, but a more experienced diagnostician may be able to determine that it is either Crohn's disease or ulcerative colitis.

Signs and Symptoms of Indeterminate Colitis

Rather than being a mash up of various characteristics of both ulcerative colitis and Crohn's disease, indeterminate colitis is associated with a set of signs that was originally described in 1978, although they are not hard and fast rules. Indeterminate colitis could have all or some of the attributes below:

  • Type of ulcers: Indeterminate colitis might be used in cases where there is only inflammation in the large intestine, but the the ulcers don't look like those typically caused by ulcerative colitis. In ulcerative colitis, the ulcers found in the large intestine will only involve the innermost layer of the mucosa, which lines the intestinal wall. If those ulcers are deeper than what would normally be expected with ulcerative colitis, and there's no other indication that the disease is actually Crohn's disease, it might lead a physician down the path to making a preliminary diagnosis of indeterminate colitis. These type of ulcers are sometimes described as transmural ulcers (meaning they go deep through the intestinal wall) or as being like fissures. In some cases the fissure-like ulcers are narrow (in about 13 percent of cases), and sometimes they are shaped like a "V" (in about 60 percent of cases).
  • Rectal involvement: Another characterization of indeterminate colitis is that the rectum is often not involved, or not fully involved. In ulcerative colitis, the rectum tends to be inflamed also, which is why, when that's not the case, it's less specific as a sign that can be used for diagnosis. In Crohn's disease, the rectum may or may not show inflammation.
  • Skip lesions: In Crohn's disease, inflammation may skip areas of the intestine, leaving a patchwork of inflamed areas and more healthy tissue. In ulcerative colitis, the inflammation begins in the rectum and continues up through the colon in a contiguous pattern. With indeterminate colitis, there may be skip areas, or at least, it appears as though there are skip areas between inflamed sections. There could be several reasons why ulcerative colitis can appear to have skip lesions, which is why this attribute can be another factor that doesn't always help in making a solid diagnosis.

    Treatment of Indeterminate Colitis

    Unfortunately, clinical trials on people with indeterminate colitis are lacking, making it challenging to develop treatments. In most cases, indeterminate colitis is treated with the same medications and surgeries as is ulcerative colitis. The difference would be if there is inflammation in the small intestine (such as the first part, which is the ileum), and in that case the treatment plan might be a little different and be similar to that for Crohn's disease.

    The treatment plan for indeterminate colitis might include these medications:

    Surgical procedures for indeterminate colitis are also similar to that of ulcerative colitis, which include ileal pouch anal anastomosis or IPAA (more commonly called a j-pouch) and ileostomy. In an ileostomy, the colon is removed and the end of the small intestine is brought through an incision in the abdomen (which is called a stoma). A person with an ileostomy wears an appliance on the abdomen to catch stool, which now leaves the body through the section of the small intestine that's outside of the body. Stool collects in the appliance and is emptied into the toilet as needed.

    Indeterminate Colitis and J-Pouches

    In some cases, indeterminate colitis is treated as though it is most like ulcerative colitis. Because of that, some people with indeterminate colitis have undergone j-pouch surgery, which is typically reserved for use only in people who have an established diagnosis of ulcerative colitis. In j-pouch surgery, the large intestine is surgically removed and the last part of the small intestine is made into a pouch the shape of a "J" and attached to the anus (or the rectum, if any is left by the surgeon). The j-pouch takes the role of the rectum, and holds stool. This surgery is not typically done in Crohn's disease because there's a small risk that the pouch may become affected by the Crohn's and need to be removed.

    However, studies have shown that people with indeterminate colitis tend to do slightly less well with j-pouches as do people who have ulcerative colitis. However, other researchers have pointed out that the failure rate of a j-pouch in patients with indeterminate colitis could be high because the disease characteristics are not uniform: there's too much variability to study this group of patients as a whole.

    Are All Cases of Indeterminate Colitis the Same?

    Another confounding aspect of indeterminate colitis is that the characteristics can be different between patients. This is a problem with IBD in general: It's a complicated disease that is difficult to classify. The definition of indeterminate colitis doesn't currently have standardization, although there are some broad guidelines.

    There are some cases of indeterminate colitis that are thought of as "probable Crohn's disease" while others are "probable ulcerative colitis," which means there are patients in the indeterminate classification who could be anywhere on the entire spectrum between these two diseases. This makes studying, and therefore understanding, indeterminate colitis a difficult prospect.

    Will the Diagnosis Always Be Indeterminate Colitis?

    In most cases, a diagnosis of either Crohn's disease or ulcerative colitis is eventually reached. When and why this happens is going to be highly variable. In some cases, if new inflammation crops up in the small intestine when previously there was only inflammation in the colon, it might be that a diagnosis of Crohn's disease can now be made. In other situations, a complication may occur that points physicians in the direction of diagnosing one form of IBD over the over. Certain complications, either intestinal or extra-intestinal, are more common with one form of IBD over the other, and their presence can help in making a diagnosis.

    One reason why it is important to get the diagnosis into one of these forms is to create an effective treatment plan. Medications approved by the Food and Drug Administration are for a specific condition, and in this way, Crohn's disease and ulcerative colitis are treated differently. Having a diagnosis of one of the two main forms of IBD means receiving a treatment that's been approved for that disease. Many treatments are approved for both forms of IBD, but there are still some that are only approved for either Crohn's disease or ulcerative colitis. What's more, certain treatments might also be somewhat more effective for one of these diseases than it is for the other. Therefore, it is advantageous to get a definitive diagnosis pinned down.

    A Word From Verywell

    Receiving a diagnosis of indeterminate colitis comes with a fair amount of uncertainty and can be frustrating when considering management of the disease and treatment. It's important for anyone who has IBD to be a fierce advocate on their own behalf, but it is vital for people with indeterminate colitis. Finding a healthcare team that is fully supportive as well as having a network of family and friends that can offer assistance and understanding will help in coping with the disease. Some people may live with a diagnosis of indeterminate colitis for a while, before anything changes, and therefore learning as much as possible about IBD and putting together a support network should be a major focus.

    Sources:

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    Odze R. "Diagnostic problems and advances in inflammatory bowel disease." Mod Pathol. 2003 Apr;16:347-358.

    Pezim ME, Pemberton JH, Beart RW Jr, et al. "Outcome of "indeterminant" colitis following ileal pouch-anal anastomosis." Dis Colon Rectum. 1989 Aug; 32:653-658.

    Price AB. "Overlap in the spectrum of non-specific inflammatory bowel disease--'colitis indeterminate'." J Clin Pathol. 1978 Jun; 31:567-577.

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