Stool Analysis for Cystic Fibrosis

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Stool Analysis for Cystic Fibrosis

Examination Overview

Cystic fibrosis causes mucus to become thick and sticky. The mucus builds up and clogs passages in many of the body's organs, but mostly in the lungs and the pancreas. The thick and sticky mucus can block pancreatic enzymes from reaching the digestive system and prevent fat from being digested and absorbed. If the body is not able to digest fat, the fat comes out in stools that are large, greasy, and smelly.

People who have been diagnosed with cystic fibrosis may have a stool analysis to see how well their pancreas is working and how well their bodies are digesting food. It may also be done when cystic fibrosis is suspected because of the following symptoms:

  • Large, greasy, smelly stools
  • Digestive problems
  • Unexplained weight loss or failure to gain or maintain weight
  • Repeated lung infections

Before having this test, you will eat foods that contain specific amounts of fat. You will keep a record of foods you eat and you will collect samples of your stool. The samples are then sent to a lab where the stools are analyzed for fat content.

Why It Is Done

A stool analysis is done to see how well the pancreas is working and if pancreatic enzymes are reaching the intestine. This test can help determine whether supplemental digestive enzymes are needed. For people who are currently taking digestive enzymes, this test can help determine if they are taking the right amount.


Increased fat in the stool or low enzyme levels can mean that a person has digestive or pancreatic problems.

What To Think About

Other diseases besides cystic fibrosis can cause fatty stools and pancreatic problems. For more information, see the topic Stool Analysis.

Complete the medical test information form (PDF) (What is a PDF document?) to help you prepare for this test.


By Healthwise Staff
Primary Medical Reviewer John Pope, MD - Pediatrics
Primary Medical Reviewer Brian D. O'Brien, MD - Internal Medicine
Specialist Medical Reviewer Susanna McColley, MD - Pediatric Pulmonology
Last Revised August 12, 2011

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