Diarrhea is a common side effect of chemotherapy. It can cause dehydration and malnourishment, making a person feel sick and potentially intensifying other chemo-related side effects.
A 2007 Current Oncology paper estimates that as many as 82% of people undergoing chemo experience diarrhea, with one-third developing severe diarrhea.
This article explains how to manage and prevent chemo diarrhea.
Chemo helps kill cancer cells, but it can also target healthy cells. This damage to healthy cells can cause many of chemo’s side effects.
Researchers have proposed several reasons that chemo might cause diarrhea.
For example, certain chemo agents — especially those targeting colorectal cancer and other cancers of the digestive system — may damage the internal surface of the digestive tract, thereby leading to diarrhea.
A 2017 study in rats found that the drugs 5-fluorouracil, oxaliplatin, and irinotecan could damage the digestive tract, potentially explaining why people experience diarrhea when using these drugs.
Chemo may also upset the delicate balance of bacteria and other organisms that help a person digest their food and have normal bowel movements.
One 2019 meta-analysis of 13 randomized controlled trials found a reduction in diarrhea among people undergoing chemo who took probiotics before or during treatment. This suggests that intestinal bacteria damage plays a role in chemo diarrhea.
Sometimes, cancer causes diarrhea by damaging the intestines or digestive system. Some cancer treatments, such as stem cell transplants, may cause graft-versus-host disease, which can cause diarrhea.
Anxiety and stress about cancer or cancer treatment may also contribute to this complaint.
Individual risk factors can also influence the likelihood of experiencing diarrhea during chemo. These factors include:
Some strategies that may help prevent chemo-induced diarrhea include:
Diarrhea is usually a relatively minor chemo side effect, but some people experience severe diarrhea. In some cases, diarrhea can also be life threatening. This is because severe dehydration can cause organ damage and even death.
A doctor will evaluate the diarrhea to determine whether or not it is severe and assess what might be causing it. The right treatment depends on the cause of diarrhea and the specific symptoms it causes.
Some treatment options include:
Very severe diarrhea is diarrhea that:
Very severe diarrhea may require a person to stay in the hospital for treatment and evaluation.
Mild diarrhea may get better with home treatment, such as making dietary changes or using over-the-counter loperamide (Imodium).
However, it is important for people undergoing cancer treatment to discuss all symptoms and side effects with a doctor. People should tell their oncologist about their diarrhea at the next appointment.
A person should contact a doctor right away if they:
People should go to the emergency room if a doctor is not available or it is after office hours.
Chemo can cause a wide range of side effects. The specific effects may change with time, and different drugs are more likely to cause certain side effects. A doctor can help a person anticipate their most likely side effects.
Some common side effects of chemo include:
Diarrhea is a common side effect of chemo, but it can also be serious.
There are many treatment options for dealing with chemo-related diarrhea. A person does not have to resign themselves to endless diarrhea, especially severe diarrhea.
A person should talk with a doctor about their symptoms and keep seeking help until the diarrhea gets better.
Last medically reviewed on June 29, 2021
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