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What Is Diarrhea?

Diarrhea is a condition where stools become loose or watery and occur more often. A person may have cramping or lose control of bowel movements. In general, diarrhea may be defined as passing more than 3 loose stools in 24 hours.

Diarrhea is a common side effect during childhood cancer. It can have different causes including chemotherapy, antibiotics, and infection. In some cases, diarrhea can lead to serious health problems such as dehydration, malnutrition, and metabolic imbalances.

Ways to manage diarrhea include anti-diarrhea medicines and changes to diet. It is also important to make sure patients stay hydrated by drinking liquids or receiving IV fluids. If diarrhea is caused by a virus or bacteria, treatment of the infection may be needed. If diarrhea is caused by chemotherapy, the care team may modify the treatment schedule until symptoms improve.

Causes of Diarrhea During Cancer

  • Chemotherapy
  • Radiation therapy
  • Antibiotics and other medicines
  • Infection
  • Bone marrow transplant
  • Surgery
  • Stress and anxiety
  • Effects of the cancer or other medical conditions

Assessment of Diarrhea in Childhood Cancer

Assessment of diarrhea considers:

  • Frequency of stools (number of episodes per day)
  • Appearance of stool (loose, liquid, watery)
  • Incontinence (unable to control passing of stool)
  • Waking during the night or getting in the way of daily activities

The care team will evaluate other signs and symptoms such as:

  • Fever
  • Pain and cramping
  • Weakness or dizziness
  • Rectal bleeding or blood in stools
  • Nausea and vomiting
  • Weight and hydration

Lab tests of blood are performed to check blood counts, electrolyte levels, and kidney function.

Stool may be tested to look for viruses or bacteria. Common sources of infection with diarrhea are rotavirus, adenovirus, norovirus, Salmonella, Campylobacter, Shigella, and Clostridioides difficile. Diarrhea due to infection may need different treatment.

The care team will also evaluate other possible reasons for diarrhea such as medicines, diet, and situational factors.

Less often, assessment of diarrhea may include imaging tests to view organs of the gastrointestinal tract.

Diarrhea and constipation are common problems during cancer treatment. The care team might ask families to describe what stools look like using a chart.

Health Problems from Diarrhea

Diarrhea can be life-threatening. Possible health problems due to diarrhea include:

  • Dehydration
  • Malnutrition
  • Electrolyte imbalances
  • Kidney failure

In some cases, chemotherapy and other cancer treatments may be delayed until symptoms improve.

Causes of Diarrhea in Childhood Cancer

Nutrients and water are absorbed as food moves through the digestive tract. Waste is passed out of the body as stool. The intestines secrete digestive fluids and mucous to help break down and move contents. Bacteria are also found in the digestive tract and help break down food. Sometimes, stools become too watery if fluids are not absorbed or if secretions increase. Medicines can also change the balance of bacteria in the intestines. An increase in movement of the intestines (motility) can also cause stool to pass through more quickly. A change or imbalance in one or more of these digestive processes can trigger diarrhea.

Factors that may lead to diarrhea during cancer treatment include:

Chemotherapy-Induced Diarrhea

Diarrhea is a common side effect of chemotherapy. This is sometimes called chemotherapy-induced diarrhea or CID. Chemotherapy may cause diarrhea in different ways. Chemotherapy can damage the mucous membrane lining the intestines. Certain drugs can also change the fluid balance in the intestines. Fluid may not be absorbed properly, or extra fluid or mucous may be secreted. Chemotherapy can also interfere with absorption of nutrients or change the way digestive enzymes work in the intestines.

For children with cancer, cancer medicines that often cause diarrhea include irinotecan, docetaxel, fluorouracil, dasatinib, imatinib, pazopanib, sorafenib, and sunitinib.

What Cancer Medicines Cause Diarrhea?

Cancer Medicines with High Risk of Diarrhea Cancer Medicines with Moderate Risk of Diarrhea
Busulfan Cyclophosphamide
Capecitabine Daunorubicin
Dasatinib Etoposide
Docetaxel Interferon
Fluorouracil (5-FU) Melphalan
Idarubicin Methotrexate
Imatinib Nivolumab
Irinotecan Paclitaxel
Mycophenolate Topotecan
Pazopanib Vincristine

Diarrhea can be a side effect of other common medicines used in pediatric cancer patients. This may occur for different reasons. Some medicines cause an imbalance of “good” and “bad” bacteria in the stomach and intestines. Other medicines can affect the breakdown of food or how much fluid is absorbed or produced.

Medicines that may cause diarrhea include antibiotics such as ampicillin, amoxicillin, amoxicillin-clavulanate, cefixime, cefpodoxime, clindamycin, and erythromycin. Stool softeners, laxatives, antacids with magnesium, potassium chloride, and proton pump inhibitors may also cause diarrhea.

Radiation Therapy and Diarrhea

Radiation to the abdomen, back, or pelvis can cause diarrhea. Radiation triggers cell death in fast-growing cells, like the cells that line the intestines. This is known as radiation enteritis. Symptoms include nausea, vomiting, cramping, fatigue, and diarrhea. Stools may be watery or contain blood or mucous. Radiation enteritis usually improves 2-3 weeks after treatment ends, but symptoms can last 12 weeks or longer. Some patients may have longer lasting diarrhea or have problems with diarrhea later in life.

Factors that increase risk for diarrhea with radiation therapy include:

  • Higher dose and frequency of radiation treatments
  • Greater treatment area involving the intestines
  • Radiation given along with chemotherapy

Treatment of radiation-induced diarrhea includes using medications such as loperamide and octreotide.

Other Causes of Diarrhea

Managing Diarrhea During Childhood Cancer

Diarrhea can cause serious health problems, especially during cancer. It is important for families to work closely with the care team to make sure that children’s symptoms are managed. Strategies to help treat diarrhea include anti-diarrhea medicines and changes in diet. Adequate fluid intake is needed to avoid dehydration. If diarrhea is severe or the patient cannot take in enough liquids by mouth, IV fluids may be needed.

Anti-Diarrhea Medicines

Medicines for diarrhea are prescribed based on the severity of diarrhea and the suspected or known cause. Possible medicines for diarrhea in children with cancer include loperamide (Imodium®) and antibiotics. In special cases, atropine and octreotide can be used to treat certain types of diarrhea.

Probiotics may be recommended in some cases. However, pediatric cancer patients should only use probiotic supplements under a doctor’s supervision.

Treatment of diarrhea is based on individual patient needs, and the care team will decide the best approach for each patient.

What to Eat When You Have Diarrhea

To help with diarrhea, the care team may suggest changes in diet including smaller meals, bland foods, and caffeine-free liquids. The BRAT (Bananas, Rice, Applesauce, and Toast) diet is sometimes recommended for patients with diarrhea. However, this diet is low in important nutrients, so only follow it for a few days or as recommended by the care team. Other foods that may be recommended include oats, low-sugar cereals, crackers, pasta without sauce, and soft, peeled fruits like peaches or pears. Broth-based soups with cooked vegetables and lean meats can be a good way to restart solid foods and increase fluid intake.

Certain foods can make diarrhea worse. These include spicy or greasy foods, milk and dairy products, raw fruits and vegetables, dried fruits, some fruit juices, foods high in fat or sugar, and caffeine.

If diarrhea is caused by GVHD, a special diet may be prescribed that is more limited.

Nutrition tips to help with diarrhea include:

  • Drink plenty of fluids to help prevent dehydration. Choose water or caffeine-free and low-sugar drinks such as Pedialyte® and lower sugar sports drinks.
  • Eat smaller meals, eat slowly, and chew food well.
  • Choose mild foods that don’t upset the stomach.
  • Avoid alcohol and caffeine.
  • Limit foods high in insoluble fiber such as whole fruits and vegetables with skins or seeds. Soluble fiber found in oatmeal, applesauce, bananas and some fiber supplements may help firm loose stool.
  • Avoid foods that could make gas and cramping worse. These include beans, broccoli, cauliflower, cabbage, and carbonated beverages.
  • Offer foods high in potassium like bananas, potatoes, apricots, and peaches.


  • Bananas
  • Rice
  • Applesauce
  • Toast, white bread
  • Oatmeal
  • Cream of rice or wheat
  • Noodles
  • Mashed potatoes
  • Crackers
  • Pretzels
  • Fruit without skin
  • Cooked vegetables without skin
  • Cooked eggs
  • Low-sugar yogurt
  • Ice pops or sherbet
  • Fruit-flavored gelatin


  • Greasy or fried foods
  • Spicy foods
  • Caffeine
  • Milk products (especially if lactose intolerant)
  • Raw fruits and vegetables with skin
  • Popcorn
  • Nuts and seeds
  • Bran
  • Whole grains
  • Alcohol

Find more nutrition tips to help with side effects.

Diarrhea in Children with Cancer: Tips for Families

  • Diarrhea can be serious. Monitor and discuss symptoms with your care team. Watch for signs of dehydration such as thirst, dry mouth, headache, feeling dizzy, muscle cramps, not peeing enough, irritability, and lack of energy.
  • Prepare your child for the possibility of diarrhea and other side effects. Keep communication honest and open. This is especially important for older children and teens who may be embarrassed to talk about toilet habits or want to take care of themselves.
  • Encourage rest to help slow bowel action. If your child is anxious or afraid, try ways to manage anxiety. Physical activity and stress can stimulate movement of the intestines.
  • Frequent stools can irritate the skin. Be sure to clean gently but thoroughly, and keep the area dry. Use a barrier cream or ointment as recommended by the care team. Diaper dermatitis (diaper rash) can occur at any age, causing discomfort and increasing risk for infection. Older children and teens who have pain may not clean as well after going to the bathroom, which will make skin problems worse. For children with weak immune systems, any breakdown of the skin can lead to serious infection. Watch for skin changes, and discuss skin care with your doctor.
  • Carry an extra change of clothes and plastic bags for dirty items. Keep disposable gloves, cleansing wipes, and hand sanitizer on hand for cleanup. A travel-sized air freshener or deodorizer can help lessen odors.
  • Pads and underwear may be needed for accidents or incontinence. Youth and adult size products are available including liners, pull-on briefs, and diaper covers. Talk to your care team about items available from your hospital or home health company. Products can also be ordered online from companies like NorthShore Care Supply.
  • Help your child make a plan for using the bathroom at school or public places. Make sure teachers allow bathroom use at any time. Have a code word or signal to use when your child needs a bathroom immediately but might be too embarrassed to say.

More Resources on Diarrhea in Children with Cancer

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Reviewed: March 2019