Ulcerative colitis (UC) is a condition that triggers excessive inflammation in the colon and rectum. It can cause a regular, urgent need to pass stools and diarrhea.

UC is a type of inflammatory bowel disease (IBD). In the United States, around 156–291 people in every 100,000 have UC.

People most commonly receive a diagnosis of UC between 15 and 30 years of age. The symptoms of UC occur in flares, or periods when a person’s symptoms become worse. During these flares, frequent diarrhea can interfere with daily life for some people.

The National Institute of Diabetes and Digestive and Kidney Diseases defines diarrhea as the passing of three or more watery stools a day. UC often causes diarrhea up to six times a day. In people with severe UC, also known as fulminant UC, people may experience up to 10 bloody bowel movements in a day.

This article explains the link between diarrhea and UC.

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UC causes inflammation in the inner lining of the large intestine — the digestive tract in which stools form, ready to pass from the body.

During UC flares, the lining becomes less able to absorb fluids from stools. This means that stools contain more fluids, making them looser.

Looser stools are a characteristic of diarrhea. This means the inflammation that is the result of UC can lead to a person experiencing diarrhea.

According to a 2018 study of 269 people with different digestive conditions, 23% of those with UC experienced diarrhea.

While the study was small, its findings suggested that diarrhea is a less common symptom in people with UC than in Crohn’s disease, another type of IBD, and irritable bowel syndrome (IBS).

UC diarrhea gets worse during flares and recovers during periods of remission.

Researchers are still unsure as to what can act as a trigger for UC flares. A 2016 review suggested a link between stress and UC flares, finding a correlation between the timing of stress events and the worsening of symptoms in people whose UC had otherwise been inactive.

However, the review authors accepted that the available evidence did not make a convincing case for how stress triggered flares. Doctors need more research to understand the triggers of UC flares and their symptoms.

UC diarrhea often accompanies other symptoms, including:

  • belly pain
  • an urgent need to pass stools
  • appetite loss
  • nausea
  • fatigue
  • fever
  • not having enough red blood cells (anemia)
  • nutritional deficiencies due to less absorption

There is no cure for UC. However, a person living with UC may benefit from managing diet and stress levels. This can help them relieve pressure on the gut and stay in remission for as long as possible.

Diet

No single diet or food has a proven link with triggering UC flares. However, some changes to the diet can help the body process foods more easily and reduce discomfort in the gut.

Following a low-residue or low-fiber diet can help people with UC diarrhea reduce how often they pass stool and improve their stools’ consistency.

Low-fiber foods include:

  • white bread
  • non-wholegrain breakfast cereals, such as cornflakes
  • white rice
  • white pasta and noodles
  • cooked, skinned, and de-seeded vegetables
  • lean meat and fish
  • eggs

Other helpful dietary changes may include:

  • eating more frequent but smaller meals throughout the day instead of three larger meals
  • staying hydrated, as chronic diarrhea can increase a person’s risk of dehydration
  • taking supplements to top up levels of nutrients that the gut may not be fully absorbing due to UC

Individuals with UC tolerate some foods well, while other foods may trigger a flare of symptoms. Tracking food intake by keeping a food diary can help people with UC identify and rule out their trigger foods.

However, getting rid of whole food groups, such as dairy, can deprive a person with UC of important nutrients. They should check with a healthcare professional or dietitian to find ways of cutting out trigger foods while maintaining a nutritionally complete diet.

Stress management

More evidence is necessary to support the link between stress and UC flares. However, managing stress may help some people with UC reduce how often they experience symptoms. As a chronic condition, managing stress can also help to improve the quality of life for those with UC.

Stress management techniques include:

Medications and surgical options are available to help people with UC keep the condition in remission, treat complications, and remove damaged parts of the digestive system.

Medications

The medication options aim to reduce inflammation and immune system activity in the colon and rectum. Options include:

Surgery

A healthcare professional may recommend surgery if symptoms do not respond to medications, if complications become life threatening, or if investigations find cancerous cells in the colon and rectum.

Surgical procedures for UC usually involve removing the colon and rectum. This will change how a person passes stool.

The following are some questions people frequently ask about ulcerative colitis and diarrhea.

How long does diarrhea last with colitis?

Flares vary in length depending on the individual. An older study using self-reported surveys found that most UC flares lasted less than a week. However, flares in some people can last for months.

What does colitis diarrhea look like?

People with diarrhea due to UC often find that the stools contain blood, mucus, or pus. It may be runny and contain no solid lumps.

UC symptoms vary between people, but diarrhea is common. Many of those living with UC may experience 6–10 instances of diarrhea a day. This occurs due to poor fluid absorption in the gut.

A low-fiber diet may help to improve stool consistency and reduce the frequency of bowel movements. Healthcare professionals can also prescribe medications to prolong remission and suggest surgery if UC becomes severe.