Cystic fibrosis is a genetic disease that causes a buildup of mucus in organs throughout your body. Stool may indicate how your gastrointestinal tract is functioning and whether or not treatment is necessary.

Cystic fibrosis (CF) is an inherited disorder where mucus builds up in different parts of your body, like your respiratory and digestive systems. Over time, the thick and sticky mucus can cause cysts and scar tissue in your organs. When this affects your gastrointestinal tract, you can have trouble getting nutrition from foods and may see changes in bowel movements, also called stool or feces.

Here’s more about what your stool may look like if you have CF, what causes these changes, and what treatments may help.

Learn more about cystic fibrosis.

If you have CF, you may experience a range of bowel movement types, from loose stools to constipation and even intestinal blockages.

CF stools may be:

CF is caused by inherited changes to a gene called the CFTR gene. Changes in this gene affect how CFTR protein in your cells works, making it less effective. Usually, this protein moves salt in and out of cells to balance moisture levels. In CF, this process does not work properly. This leads to a lack of moisture which can cause mucus to be thicker and stickier. Thick and sticky mucus can build up in your body.

One organ where mucus can accumulate is your pancreas. When your pancreas isn’t functioning optimally, this can lead to digestive problems. More specifically, your body can’t absorb important nutrients from foods and drinks.

Impaired digestion means that foods move through your gastrointestinal tract without being properly broken down and absorbed. Stools may be bulkier, smellier, or greasier as a result.

Dietary changes may help with nutrient absorption and bowel movements. Experts recommend eating a well-balanced diet that includes fruit and vegetables, whole grains, eggs, seafood, beans, dairy, meats, and nuts and seeds.

Doctors also suggest people with CF eat high energy, high fat, and high protein foods. Supplementation with vitamins is another potential treatment, whether taken orally (by mouth) or enterally (tube feeding).

Aside from lifestyle changes, doctors may prescribe pancreatic enzyme replacement therapy (PERT). Enzymes should be taken with meals and snacks to help with stool symptoms. PERT is also essential to avoid vitamin deficiencies and malnutrition and to promote healthy weight gain.

The stools themselves are not harmful. Instead, stools serve as an indicator of how well the digestive tract and pancreas are functioning.

Gastrointestinal complications of CF may include:

CF-related diabetes is another potential complication related directly to the pancreas. With CF, your pancreas may not produce enough insulin hormone needed to regulate blood sugar. This condition affects between 40 and 50% of adults with CF.

There is no cure for CF, and the condition may worsen over time, leading to more severe digestive problems. Around 50% of people with CF live beyond the age of 40 years. With advancements in treatments, this number is expected to increase.

Regardless, changes in stool are important to note. They may mean the pancreas is not functioning properly or that current treatments are no longer working. Ongoing medical care from a team of doctors is necessary to manage this condition and its potential complications.

At what age may CF stools be noticeable?

Symptoms of CF, including digestive symptoms, typically appear soon after birth into early childhood.

Do all people with CF need PERT?

Between 65–100% of people with CF experience digestive issues. And about 80–90% of people take PERT.

What other gastrointestinal symptoms may a person with CF experience?

Symptoms may include gas, bloating, cramping, and abdominal pain. These symptoms may also be a sign of CF-related complications, like DIOS.

Contact your doctor if you notice changes in your bowel movements. Bulky, foul-smelling, or greasy stools may be a sign of cystic fibrosis or other digestive problems.

If you have already been diagnosed with CF, stool changes may indicate how well your body is processing the foods you eat. Eating a balanced diet and taking PERT and additional supplements may help you reach a healthy weight, maintain adequate nutrition, and avoid other symptoms.