Indeterminate Colitis Overview

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—indeterminate colitis. The term indeterminate colitis is used when it's presumed that 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% and 15% of people with IBD are thought to have indeterminate colitis. In some situations, a diagnosis of another form of IBD might be made later on when more evidence becomes available or the disease changes.

What Indeterminate Colitis Is

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. It just means that, right now, it's unclear which form of the disease is present.

Disease that has progressed beyond its initial stages and become advanced may be especially difficult to classify because of the nature of the inflammation and how extensive it can be in the colon. On the other hand, it can also be difficult to make a solid diagnosis when the disease is quiescent or in remission.

Early disease is also sometimes difficult to diagnose because the cellular changes that IBD causes and that could be seen when a biopsy is viewed under a microscope may not be present yet.

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 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 ulcers are sometimes described as transmural (meaning they go deep through the intestinal wall) or as being like fissures. In some cases, the fissure-like ulcers are narrow (about 13% of cases); sometimes they are shaped like a V (about 60% of cases).

Rectal Involvement

Another characteristic of indeterminate colitis is that the rectum is often not involved, or at least not fully involved.

In ulcerative colitis, the rectum tends to be inflamed in most cases. 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 areas that are or at least appear to be skipped over (i.e., free of inflammation). There could be several reasons this can happen, which is why this attribute can be another factor that doesn't always help in making a solid diagnosis.

Diagnosis

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.

Change in Diagnosis

In most cases, a diagnosis of either Crohn's disease or ulcerative colitis is eventually reached. When and why this happens is highly variable.

In some cases, if new inflammation crops up in the small intestine when there previously 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.

Being diagnosed with one of these forms of disease is important because it helps shape an effective treatment plan. While many treatments are approved by the Food and Drug Administration (FDA) for both forms of IBD, others 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 the other.

Treatment

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 ulcerative colitis. The difference would be if there is inflammation in the small intestine (such as the first part, which is the ileum); in that case, the approach might be a little different and be similar to the treatment of Crohn's disease.

The treatment plan for indeterminate colitis might include these medications:

• Asacol (mesalamine)
• Azulfidine (sulfasalazine)
• Immunosuppressants: Imuran (azathioprine), Purixan (6-MP, mercaptopurine), Neoral (cyclosporine)
• Rheumatrex (methotrexate)
• Biologic medications: Remicade (infliximab), Humira (adalimumab), Entyvio (vedolizumab), Simponi (golimumab), and Stelara (ustekinumab)
• Small molecules: Xeljanz (tofacitinib)
• Corticosteroids: Entocort EC (budesonide) and prednisone

Surgical procedures for indeterminate colitis are also similar to that of ulcerative colitis and ileal pouch anal anastomosis or IPAA (more commonly called a J-pouch) and ileostomy.

J-Pouch Surgery

In some cases, indeterminate colitis is treated as though it is most likely 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—that is, there's too much variability to study this group of patients as a whole.

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.

A Word From Verywell

Some people may live with a diagnosis of indeterminate colitis for a while before anything changes. This can come with a fair amount of uncertainty, making disease management especially frustrating. It's important for anyone who has IBD to be a fierce advocate for themselves, but it is vital if you have indeterminate colitis.

Finding a healthcare team that is fully supportive, assembling and leaning on a network of family and friends that can offer assistance and understanding, and learning as much as possible about IBD should be at the center of your next steps if you've just been diagnosed.