Diarrhea and Cancer Treatment

What is diarrhea?

Diarrhea means having bowel movements (stools) more often than normal. The stool may also be soft, loose, or watery. Diarrhea is a common side effect of many cancer treatments, such as chemotherapy, immunotherapy, and radiation therapy.  
 
When you have severe diarrhea, your body does not absorb enough water and nutrients. This can lead to serious health problems such as dehydration. Dehydration can be life-threatening, so tell your doctor or nurse if you have diarrhea.  
 
Your doctor will find the diarrhea’s cause and recommend ways to feel better, which may include medicines and food that help decrease or stop diarrhea. 

What causes diarrhea in people with cancer?

Frequent diarrhea may be a sign or symptom of cancer or a side effect of cancer treatment. Causes of diarrhea in people with cancer include: 

Causes from cancer and cancer treatments

• Certain types of cancer. Diarrhea can be a symptom of some cancers that form in the abdomen or the digestive tract. Cancers that may cause diarrhea include colon cancer, rectal cancer, neuroendocrine tumors in the digestive tract or thyroid, lymphomas that start in the digestive tract, and pancreatic cancer. 
• Chemotherapy. Many types of chemo can cause diarrhea because they destroy not only cancer cells but also rapidly dividing healthy cells, including those that line your digestive tract.
• Immunotherapy. Some immunotherapy drugs, especially immune checkpoint inhibitors, can cause inflammation. An inflamed colon (colitis) can lead to diarrhea.  
• Radiation therapy. Radiation directed at the abdomen, pelvis, or rectum can cause diarrhea by damaging healthy tissue in the digestive tract. Diarrhea from radiation therapy is a symptom of radiation enteritis.
• Surgery. Having surgery to the esophagus, stomach, gallbladder, or bowel (intestine) can cause diarrhea. 
• Targeted therapy. Diarrhea is a common side effect of many targeted therapy drugs. 
• Bone marrow or stem cell transplant. Medicines and radiation given during these treatments may cause diarrhea. Diarrhea after bone marrow or stem cell transplant may also be a symptom of graft-versus-host disease.

Other causes

• Stress and anxiety. Being diagnosed with cancer and undergoing treatment often leads to stress and anxiety, which are common triggers for diarrhea. Learn about ways to manage stress and anxiety. 
• Medicines. Diarrhea can be a side effect of some medicines, including antibiotics and anti-inflammatory drugs. Drugs used to treat diabetes, depression, mood disorders, and heartburn may also cause diarrhea.  
• Supplements and herbal products. Some supplements can cause diarrhea. Tell your health care team if you are taking any supplements or herbal products or if you start a new supplement.
• Infections. Infections are a common cause of diarrhea. When being treated for cancer, you are more vulnerable to viral and bacterial infections, including foodborne illness, because treatments such as chemo can weaken your immune system.  
• Other conditions. Irritable bowel syndrome, gastroenteritis, fecal impaction, and food allergies can all cause diarrhea.

Symptoms and grades of diarrhea

Signs and symptoms of diarrhea include: 

• having soft, loose, or watery stools 
• having bowel movements more often than normal 
• feeling an urgent need to have a bowel movement that is difficult to control 
• stomach pain or cramps 
• excessive gas 

People with diarrhea may also: 

• have blood or mucus in the stools 
• feel dizzy or lightheaded 
• have a fever 
• experience weight loss 

Your doctor will talk with you about your symptoms to figure out the severity, or grade, of your diarrhea. Grade is based on how many bowel movements you have per day, relative to your normal number of bowel movements. Grades 1 and 2 (having up to six bowel movements above your normal daily number) can usually be managed at home, but grades 3 and 4 (having seven or more bowel movements above your normal daily number) can be life-threatening and may require treatment in a hospital. 

How is diarrhea diagnosed in people with cancer?

Finding the cause of diarrhea is important so you can get relief before it interferes with your cancer treatment or causes life-threatening dehydration. Your doctor may ask questions such as: 

• How many bowel movements have you had in the past day? 
• What was your last bowel movement like (how much, how hard or soft, what color, was there blood or mucus)? 
• Have you had any dizziness, fever, or weight loss? 
• What are you eating and drinking each day? 

Your doctor will do a physical exam and may also use tests and procedures to diagnose the cause of diarrhea and suggest treatment options: 

• Stool tests: Tests that check the stool for blood, viruses, bacteria, and other issues that may cause diarrhea. 
• Blood tests: These include a complete blood count, electrolyte panel, kidney function test, and albumin test that are used to find the cause of diarrhea and determine its severity. 
• Urinalysis: A test to check the color of urine and its contents, such as sugar, protein, red blood cells, and white blood cells. 
• Digital rectal exam: A test in which your doctor or nurse inserts a lubricated, gloved finger into the lower part of the rectum to feel for anything that seems unusual. 

Ways to treat and control diarrhea

Treatment of diarrhea in people with cancer depends on its cause and severity (grade). Your doctor may suggest changes to your diet and prescribe medications. You may also receive intravenous (IV) fluids to help replace the fluids you lost. If chemo is causing severe diarrhea, your doctor may reduce your dose or have you stop taking it until your diarrhea gets better.

Tips for managing diarrhea 

Eating Hints: Before, during, and after Cancer Treatment

Learn about treatment side effects that may affect eating and what to do about them.

• Drink lots of water or other fluids. Ask your doctor or nurse how much fluid you should drink. Drinking clear liquids, such as water, broth, sports drinks, and weak decaffeinated tea, helps replace fluids and electrolytes your body loses when you have diarrhea. Room temperature liquids are easiest on the stomach. 
• Eat small meals. It may help to eat frequent small meals or snacks throughout the day, instead of three larger meals. 
• Eat low-fiber foods. Eating foods that are low in fiber can help to reduce diarrhea. Foods such as white bread, pasta, peeled and boiled vegetables, and canned fruit are good choices. Your doctor may also recommend high-protein, low-fiber foods such as eggs, skinless chicken, and peanut butter.  
• Eat foods that are high in sodium and potassium. You lose these minerals when you have diarrhea, so it’s a good idea to eat foods that help replace them. Peeled and boiled potatoes, soup, bananas, applesauce, and crackers are good options.  
• Avoid foods and drinks that can make diarrhea worse. These include alcohol, milk and dairy products, spicy foods, caffeinated drinks, dried beans, foods high in fat, fruit juices, and sugar-free gum or candies. Learn more about how changing your diet can help you manage side effects of cancer treatment at Nutrition in Cancer Care. 
• Keep your anal area clean and dry. Try using warm water and baby wipes to stay clean. Taking a sitz bath—a warm, shallow bath—can also be soothing to your anal area. 
• Keep a record of your bowel movements. Show this record to your health care team and talk to them about what is normal for you. This can help your doctor treat the diarrhea you are having.

Medicines for diarrhea 

For severe diarrhea that happens while you are getting cancer treatment, your doctor may recommend medication. Your doctor may prescribe loperamide (Imodium) or a combination of diphenoxylate and atropine (Lomotil) to prevent or treat diarrhea. Doctors may also recommend probiotics that help with digestion and bowel function or fiber supplements (e.g., Metamucil). Check with your doctor before taking these or other medicines and supplements.

How a caregiver can help 

• Encourage the person you are caring for to drink water or other fluids their doctor suggests. Make sure they have a water bottle they can carry and refill throughout the day. 
• Keep a record of the person’s bowel movements. Ask the health care team about when you should call them if the diarrhea lasts or becomes more severe. 
• Try to keep the person’s pantry stocked with foods that can help relieve diarrhea. 
• Encourage the person to take warm, shallow baths to relieve pain and irritation from diarrhea.  

Talking with your doctor about diarrhea

Tell your doctor or nurse if you are having diarrhea. They can help you find ways to prevent and control this side effect of cancer and cancer treatment. 

Questions to ask your provider about diarrhea: 

• What symptoms or problems should I call you about? 
• What medicines can I take for diarrhea?  
• What can help decrease rectal pain and irritation? 
• How much and what types of liquid should I drink each day?  
• What foods should I eat while I have diarrhea? What foods should I avoid? 
• Could I meet with a registered dietitian to learn more?

Getting support if you have diarrhea

Side effects like diarrhea can be hard to deal with, both physically and emotionally. It’s important to ask for support from your health care team. They can help you prepare for and make it through difficult times. Learn more about ways to cope with cancer, including ways to adjust to daily life during cancer treatment.  
  
For family members and friends who are caring for someone with cancer, you may find these suggestions for caregivers to be helpful. 

Listen to tips on how to manage diarrhea caused by your cancer treatments such as radiation therapy.
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