Stool may be tested in the laboratory to check for bacterial, fungal, or viral infections. Blood and urine tests may be done to detect fluid and blood chemistry imbalances or infection.
In some cases, abdominal x-rays may also be done to identify bowel obstruction or other abnormalities. In rare cases, a thorough examination of the rectum and colon may be done with a lighted tube inserted through the anus and into the colon.
Diarrhea is treated by identifying and treating the problems causing diarrhea. For example, diarrhea may be caused by stool impaction and medications to prevent constipation. The doctor may make changes in medications, diet, and fluids. Diet changes that may help decrease diarrhea include eating small frequent meals and avoiding some of the following foods:
- Milk and dairy products.
- Spicy foods.
- Caffeine-containing foods and drinks.
- Some fruit juices.
- Gas-forming foods and drinks.
- High-fiber foods.
- High-fat foods.
For mild diarrhea, a diet of bananas, rice, apples, and toast (the BRAT diet) may decrease the frequency of stools. Patients should be encouraged to drink up to 3 quarts of clear fluids per day including water, sports drinks, broth, weak decaffeinated tea, caffeine-free soft drinks, clear juices, and gelatin. For severe diarrhea, the patient may need intravenous fluids or other forms of intravenous nutrition. (See the Diarrhea section in the PDQ summary on Nutrition in Cancer Care for more information.)
To manage diarrhea caused by graft-versus-host disease (GVHD), the doctor may recommend a special 5-phase diet. During phase 1, the patient receives intravenous fluids and nothing by mouth to rest the bowel until the diarrhea slows down. In phase 2, the patient may begin drinking fluids. If the patient is able to drink fluids and the diarrhea improves, he or she may begin phase 3, eating solid foods that are low-fiber, low-fat, low-acid, and do not irritate the stomach. In phase 4, the patient is gradually allowed to eat regular foods. If the patient is able to eat regular foods without any episodes of diarrhea, he or she may begin phase 5, eating their regular diet. Many patients may continue to have problems digesting milk and dairy products.
Depending on the cause of the diarrhea, the doctor may change the laxative therapy regimen or may prescribe medications that slow down bowel activity, decrease bowel fluid secretions, and allow nutrients to be absorbed by the bowel.
Probiotics are live microorganisms taken as nutritional supplements or added to foods to improve digestion and bowel function. There are many types of probiotics, such asLactobacillus. Probiotics help support the normal balance of bacteria in the colon. They may be used to:
- Prevent diarrhea caused by an infection or by antibiotics.
- Prevent or treat inflammatory bowel disease, irritable bowel syndrome, and gastroenteritis.