What Can Cause Mucus in the Stool?

Mucus In A Bowel Movement Could Be A Sign Of Disease Or Bacterial Infection

Scanning electron micrograph image of Campylocbacter jejuni, an important cause of intestinal enteritis and food poisoning. Commonly transmitted in contaminated milk or by contact with infected pets.. Image © Getty / S. Lowry/Univ Ulster

Mucus in the stool may be considered a common symptom of certain digestive conditions, such as irritable bowel syndrome (IBS) and ulcerative colitis (one form of inflammatory bowel disease, or IBD). Mucus is a stringy, white or yellow substance that is typically found in a healthy stool, but it is normally only present in very small amounts that would not be seen in or on the stool with the naked eye.

Other conditions that can cause visible mucus in the stool include bacterial infections, anal fissures, a bowel obstruction, or Crohn's disease (the second main form of IBD).

What Is Mucus?

Mucus is a clear, white, or yellow substance with the consistency of jelly that is produced by the mucus membrane of the large intestine. Mucus is also produced by other organs in the body, such as the lungs, where it helps to trap any foreign particles that are inhaled. In the intestines, mucus protects the inner lining and because it is slippery, it helps ease along the passage of stool. Passing mucus in the stool is not harmful in and of itself, but it could also be a sign of a disease or condition that may require treatment.

If you have not been diagnosed with a condition where passing mucus could be considered a typical symptom, you should see a physician. This is especially true if the mucus is accompanied by other digestive symptoms such as diarrhea, abdominal pain, constipation, or vomiting.

Ulcerative Colitis

In ulcerative colitis, the mucus membrane of the large intestine (colon) becomes inflamed and develops small sores that are called ulcers. These ulcers bleed and may also produce pus and mucus. The mucus may be voluminous enough that it can be seen as it is passed along with the stool.

Irritable Bowel Syndrome (IBS)

In IBS, there may be increased mucus production by the lining of the intestine. That mucus is then passed in the stool. Mucus is more often associated with diarrhea-predominant IBS than with constipation-predominant IBS or alternating type IBS (IBS-A).

Crohn's Disease

Passing mucus in the stool is a less frequent occurrence in people who have Crohn's disease. If mucus is seen in the stool of a person who has Crohn's disease, it could be associated with developing an anal fissure.


Some people who have had ostomy surgery (either ileostomy or colostomy) surgery may find that they pass mucus from their rectum. Even though stool is leaving the body through the stoma, and not through the rectum and the anus, the rectum is still producing fluids. There could be mucus, which will need to be passed by sitting on the toilet. A build up of mucus could cause discomfort and pressure. 

Bacterial Infections

Bacterial infections, such as those from bacteria such as Campylobacter, Salmonella, Shigella, and Yersinia, may cause mucus to be passed in the stool.

A bacterial infection may also cause symptoms of diarrhea, fever, and abdominal cramps. Some bacterial infections may resolve on their own without treatment, but other cases may be serious and require treatment with antibiotics. If you think you may have contracted a bacterial infection, especially after traveling abroad, contact your physician.

Bowel Obstruction

A bowel obstruction is associated with symptoms of constipation, severe cramps, abdominal distention, and vomiting, as well as the passage of mucus. A bowel obstruction could be caused by one of many conditions such as impacted stool, adhesions (scar tissue), a hernia, gallstones, a tumor, or swallowing a non-food item. Obstructions are typically treated in the hospital, with surgery to remove the blockage being necessary in some cases.

The passage of mucus in the stool in the setting of IBS or ulcerative colitis is not necessarily a cause for alarm because it can be a sign of those conditions. However, passing mucus in the stool, especially if it is a new symptom, should still be mentioned to a physician at the next office visit. Mucus without an underlying cause, such as one of the pre-existing conditions mentioned above, is a change in bowel habits and should be reported to a physician immediately.

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