Cover image used with licensed permission.

by Ken Sinervo, MD FRCSC ACGE Medical Director
© 2008. Last updated 2018.

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Many of the women seen at the Center for Endometriosis Care have been told they have Irritable Bowel Syndrome or a spastic colon. A few of them do. But many of them have endometriosis somewhere in their intestinal tracts.

Endometriosis patients who present with bowel symptoms may experience a long delay in getting a diagnosis or have other medical conditions related to the bowel considered before their physicians consider the possibility of endometriosis.  

Bowel symptoms are extremely common in patients with endometriosis. While the exact percentage of endometriosis patients affected with bowel symptoms is difficult to pin down, information from the database Dr. Albee and I have compiled suggests that as many as 60% or more may have at least one symptom referable to their gastrointestinal tracts. Because of the nature of our practice we tend to have more patients with stage III and IV (moderate to severe) disease than may occur in the general population. Such patients may have more symptoms related to their bowels. Even so, the incidence is still very high.

Based on the pre-operative questionnaires that all of our patients complete, intestinal cramping and painful bowel movements occur in approximately 25% of patients; constipation occurs in 35% of patients and diarrhea occurs in more than 60% of patients. These numbers reflect the patients with severe or crippling symptoms only. When patients with mild or moderate symptoms are included, these symptoms become even more common.

There is a constellation of bowel symptoms that can occur in endometriosis patients. These include: 

Painful bowel movements



Alternating constipation and diarrhea

Intestinal cramping

Nausea and/or vomiting

Abdominal pain

Rectal pain

Rectal bleeding

Some patients will only have one of these symptoms, while others may have all of them. Often these symptoms are more problematic during their periods or pre-menstrually. These women may seek medical help and undergo a series of GI tests, and when no clear answer is found, their frustration grows. However, a negative colonoscopy can actually be somewhat reassuring, because it indicates that endometriosis has not penetrated through the wall of the bowel.

What Causes Bowel Symptoms in Endo Patients?

In the great majority of patients, endometriosis is not found directly on the bowel. In general, fewer than 10-15% of patients actually have endometriosis directly on their bowel. When endo is found on the bowel, approximately 90% have superficial or localized disease. This disease can usually be effectively removed with simple laparoscopic excision, much as it would be removed from any other surface affected with endometriosis. The serosal or outer layer of the bowel can often be “peeled off” leaving the muscularis or muscular portion of the bowel undamaged. Occasionally, a portion of the muscularis must also be excised to ensure complete treatment of the endo. In these cases, the muscularis is oversewn laparoscopically. This just means one or more reinforcing sutures are placed to maintain the integrity of the bowel wall.

 One to two percent of our patients require more significant surgery for their bowel endometriosis. These patients may have large segments of bowel involved with deeper or multi-focal implants (several areas are affected along a portion of the bowel). A segmental bowel resection may be required to completely treat their disease. This means the diseased portion of the bowel is removed entirely, and the healthy ends are reconnected. These procedures are usually performed with the assistance of a general surgeon or colorectal surgeon, and virtually always laparoscopically.

 Even when endometriosis does not occur directly on the bowel, it can cause bowel symptoms. Inflammatory mediators can affect the bowel and contribute to them. Inflammatory mediators are released by tissues in response to inflammation or injury, and include prostaglandins, tumor necrosis factor (TNF), interleukins and cytokines. They create changes within the tissues and can cause new blood vessel growth, attract other things to the area such as white blood cells or contribute to scarring. Prostaglandins, which are released from the endometriosis implants and uterus during menses, can cause smooth muscle contractility. This not only affects the uterus, but can also cause increased contractility of the bowel. In these cases, diarrhea and intestinal cramping can result. There are likely other mediators that are released that can also contribute to bowel symptoms.

Occasionally, deep nodules in adjacent structures such as the uterosacral ligaments or rectovaginal septum can also cause bowel symptoms. Painful bowel movements and occasionally rectal bleeding can result from endometriosis in these locations.

The Dreaded Bowel Prep

In order to have these procedures at the time of surgery, most of our patients undergo a bowel prep. While this is not the most enjoyable way to spend the afternoon before surgery, it is worth enduring to get to the desired result of completely removing all the endometriosis. The prep is usually clear liquids and an agent to thoroughly clean out the bowel. If a prep were not performed, bowel surgery becomes extremely risky, because fecal matter could spill and put the patient at high risk for serious infection. If a prep is not done, and bowel surgery is needed, a second surgical procedure would be required at a later date.

Here are our bowel prep instructions

Other Causes for Bowel Symptoms

While endometriosis can cause or contribute to bowel symptoms, there are other important causes of bowel symptoms. Inflammatory Bowel Disease (IBD), or Crohn’s Disease and Ulcerative Colitis can be seen. As many as 8% of endometriosis patients with bowel symptoms may eventually be diagnosed with inflammatory bowel disease. IBD is usually characterized by abdominal pain, constipation, diarrhea, or alternating bouts of constipation and diarrhea as well as intestinal cramping. Patients with Crohn’s Disease may also have mouth ulcers, fatigue, anemia and hemorrhoids. Rarely, patients can have abscesses or bowel obstruction. A colonoscopy is usually required to confirm the diagnosis. IBD is usually treated with medical therapy that aims to keep the disease in remission or to treat flare ups. Occasionally, surgery is required for complications such as bowel obstruction or abscesses.

Women with symptoms similar to those of IBD but without any abnormalities on colonoscopy are often diagnosed with Irritable Bowel Syndrome (IBS). IBS is usually treated with dietary changes to avoid food triggers, and increasing dietary fiber. In some patients, stress can be a trigger. Avoiding stress or learning to deal more effectively with stress may help reduce the number of episodes. Exercise is beneficial for many patients. Medications are necessary for some patients. These may include anti-depressants, anti-spasmodics and other medications. In addition, medications that work better for patients with predominantly diarrhea or constipation are also available and have been shown to be beneficial for some, but not all patients.

Adhesions can also cause or contribute to bowel symptoms (as well as other symptoms associated with endometriosis). Often the bowel is stuck to other structures such as the ovaries, uterus or pelvic sidewall. This scarring can lead to pain during bowel movements or constipation or diarrhea. Abdominal bloating is also associated with adhesive disease, and carefully treating the adhesions may help reduce many of these symptoms.

What about the Appendix?

The appendix is another gastrointestinal organ that may contribute to bowel symptoms, or abdominal or pelvic pain. Some studies have demonstrated endometriosis in up to 20% of appendices. Although endometriosis may not be present, other conditions such as scarring or fibrosis may be found, as well as acute or chronic appendicitis, and even carcinoid tumors (a form of cancer) have been found in appendices that have been removed. We are more likely to recommend removal of the appendix if the patient has a history of right lower quadrant pain. However, if the appendix appears to have pathology at the time of surgery, it can usually be removed with minimal additional risk of complication and usually only adds a few minutes to the surgery. When required, appendectomy can almost always be performed laparoscopically.

Will My Symptoms Improve?

The incidence of bowel symptoms does improve significantly after excision surgery for endometriosis. Based on the post-operative follow-up questionnaires that our patients complete yearly, there is an 80% reduction in most bowel symptoms. Of the more than 1000 patients in our database, only 3 to 7% continue to have more severe episodes of painful bowel movements, constipation or intestinal cramping. Diarrhea, which was present in 63% of our endometriosis patients, is only significant in 13% following surgery.

While most patients have improvement in their bowel symptoms following excision surgery for their endometriosis, some will have a persistence of these symptoms. This may be due to another underlying medical condition (IBD or IBS). In those patients in whom a work-up has not been performed, it may be indicated at this time. Blood tests that detect antibodies associated with IBD may be helpful. Often a colonoscopy or other studies are required. 

Many gynecologists have little or no experience treating bowel endometriosis. They choose not to treat it. Sometimes they refer these patients to a general surgeon for later treatment. At the CEC, these procedures can almost always be performed laparoscopically. It is worthwhile to ask your doctor how he or she would deal with endometriosis if it were found on your bowel. If you are not satisfied with the answers, keep searching until you find the right person to work with.

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© 2008. Last updated 2018.