Can Bowel Endometriosis Cause Blood in Your Stool? A Colorectal Surgeon Explains

By Dr. Vincent J. Obias, MD, MS, FASCRS | Reviewed by Dr. Victoria Vargas, MD, MS, FACOG

There are many causes of rectal bleeding. If a patient has endometriosis, can the rectal bleeding be caused by it? Possibly, but other causes of rectal bleeding are more likely.

The incidence of endometriosis involving the bowel (colon, rectum, or small intestine) is relatively low. Approximately 10% of women have endometriosis, and 10% of these women have deep infiltrating endometriosis. Among patients with deep infiltrating endometriosis, the incidence of bowel endometriosis can run as high as 37% in some series.

Thus, thousands of women can have endometriosis involving the bowel. However, for bowel endometriosis to cause bleeding, the disease generally has to erode through the full thickness of the bowel wall. The incidence of this is much lower, approximately 1% of all cases of bowel endometriosis.

What Does the Color of Blood in Your Stool Tell You?

When assessing rectal bleeding, the main questions your doctor evaluates are:

1. Color: Is the blood bright red or dark?
2. Pain: Is the bleeding associated with pain during bowel movements?
3. Type of pain: If you have pain and bleeding with bowel movements, what does the pain feel like?
4. Timing: When does the bleeding occur?
5. Duration: How long has this been going on?

When blood in the stool looks very dark or tarry, that can be a sign that the blood is coming from a source higher in the gastrointestinal tract.

The most common portion of the gastrointestinal tract involved with endometriosis is the rectum. The rectum is very low in the pelvis, located just before the anus, so bleeding from endometriosis involving the rectum is generally bright red.

Endometriosis can occur higher in the bowel, such as the proximal colon, small bowel, and stomach, but that involvement is rare. If bleeding comes from these more proximal sources, the blood in the patient’s stool may appear darker or tarry.

Concerned that your bowel symptoms may be related to endometriosis? At Washington Endometriosis & Complex Surgery, our endometriosis specialists evaluate patients with suspected bowel endometriosis, including those considering surgical treatment.

What Are the Symptoms of Bowel Endometriosis?

Bowel endometriosis can cause symptoms that overlap with other gastrointestinal conditions. Symptoms may include:

• Painful bowel movements, particularly during menstruation
• Constipation or diarrhea
• Bloating and abdominal discomfort
• Rectal or pelvic pain
• A sensation of incomplete bowel emptying
• Changes in bowel habits that worsen around menstruation
• Rectal bleeding, although this is uncommon

Not everyone with bowel endometriosis experiences these symptoms, and having them does not necessarily mean endometriosis is affecting the bowel.

Because these symptoms can have several causes, evaluation by a physician familiar with bowel endometriosis can help determine the appropriate next steps.

Could Blood in Your Stool Be a Sign of Colon Cancer?

Another cause of blood in the stool is colon cancer.

Patients with a family history of colon cancer should undergo colon cancer screening earlier than normal. Current guidelines recommend colon cancer screening for asymptomatic patients with no family history beginning at age 45. If you have a family history of colon cancer, recommendations may call for screening to begin earlier.

You should discuss this with your physician to determine the correct timing for your screening.

Screening can include colonoscopy as well as noninvasive methods such as Cologuard.

It is important to note that colonoscopy is not an effective way to identify bowel endometriosis. Endometriosis grows from the outside of the bowel and works its way inward. It very rarely grows through the full thickness of the bowel wall, where it could be biopsied and diagnosed during a colonoscopy.

Have you been diagnosed with endometriosis and are considering surgery? Our multidisciplinary surgical team includes specialists in endometriosis excision and colorectal surgery who work together when bowel involvement is suspected.

What Are the Most Common Causes of Rectal Bleeding?

Fortunately, the most common causes of rectal bleeding are benign conditions such as constipation, symptomatic hemorrhoids, and anal fissures.

If a patient is constipated and straining to have a bowel movement, hemorrhoids can increase in size and bleed during defecation. Usually, the patient will have no pain with bowel movements, but the amount of blood can be alarming.

If a patient is constipated and straining to have a bowel movement, hard stool can also cause a superficial tear in the anal canal, known as an anal fissure. The patient will experience sharp pain with bowel movements and may see bright red blood from the rectum.

Both are benign conditions that can generally be treated conservatively, although surgery is sometimes required.

An evaluation by a physician familiar with these conditions can be helpful if this is what you’re experiencing.

The Bottom Line: Don’t Ignore Blood in Your Stool

The causes of rectal bleeding can be varied. If a patient has a history of endometriosis, can rectal bleeding be caused by it? Yes, it can, but it’s rare.

The causes of rectal bleeding are usually benign. Still, blood in your stool can be a sign of another issue, including colon cancer.

Thus, when you see blood in your stool, don’t ignore it. Mention it to your doctor, who can help determine the next appropriate course of action.

Experiencing bowel symptoms alongside endometriosis? Washington Endometriosis & Complex Surgery offers specialized evaluations for patients with suspected or diagnosed endometriosis, including those seeking surgical management of bowel disease.

About Dr. Vincent J. Obias

Dr. Vincent J. Obias, MD, MS, FASCRS, is a fellowship-trained colorectal surgeon specializing in complex colorectal surgery and bowel endometriosis at Washington Endometriosis & Complex Surgery in Washington, DC. Trained in both laparoscopic and robotic surgery, he is a pioneer in minimally invasive colorectal techniques and one of the nation’s most experienced bowel endometriosis surgeons.

Medical Review: Dr. Victoria Vargas, MD, MS, FACOG, is a fellowship-trained minimally invasive gynecologic surgeon and endometriosis excision specialist at Washington Endometriosis & Complex Surgery with more than a decade of experience.