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Gastrointestinal Complications (PDQ®): Supportive care - Patient Information [NCI]

This information is produced and provided by the National Cancer Institute (NCI). The information in this topic may have changed since it was written. For the most current information, contact the National Cancer Institute via the Internet web site at or call 1-800-4-CANCER.

General Information

The gastrointestinal (GI) tract is part of the digestive system, which processes nutrients (vitamins, minerals, carbohydrates, fats, proteins, and water) in foods that are eaten and helps pass waste material out of the body. The GI tract includes the stomach and intestines (bowels). The stomach is a J-shaped organ in the upper abdomen. Food moves from the throat to the stomach through a hollow, muscular tube called the esophagus. After leaving the stomach, partly-digested food passes into the small intestine and then into the large intestine. The colon (large bowel) is the first part of the large intestine and is about 5 feet long. Together, the rectum and anal canal make up the last part of the large intestine and are 6-8 inches long. The anal canal ends at the anus (the opening of the large intestine to the outside of the body).Gastrointestinal (digestive) system anatomy; drawing shows the esophagus, liver, stomach, colon, small intestine, rectum, and anus.
Anatomy of the lower gastrointestinal (digestive) system showing the colon, rectum, and anus. Other organs that make up the digestive system are also shown.

GI complications are common in cancer patients. Complications are medical problems that occur during a disease, or after a procedure or treatment. They may be caused by the disease, procedure, or treatment, or may have other causes. This summary describes the following GI complications and their causes and treatments:

This summary is about GI complications in adults with cancer. Treatment of GI complications in children is different than treatment for adults.


With constipation, bowel movements are difficult or don't happen as often as usual.

Constipation is the slow movement of stool through the large intestine. The longer it takes for the stool to move through the large intestine, the more it loses fluid and the drier and harder it becomes. The patient may be unable to have a bowel movement, have to push harder to have a bowel movement, or have fewer than their usual number of bowel movements.

Certain medicines, changes in diet, not drinking enough fluids, and being less active are common causes of constipation.

Constipation is a common problem for cancer patients. Cancer patients may become constipated by any of the usual factors that cause constipation in healthy people. These include older age, changes in diet and fluid intake, and not getting enough exercise. In addition to these common causes of constipation, there are other causes in cancer patients.

Other causes of constipation include:

  • Opioids and other pain medicines. This is one of the main causes of constipation in cancer patients.
  • Chemotherapy.
  • Medicines for anxiety and depression.
  • Antacids.
  • Diuretics (drugs that increase the amount of urine made by the body).
  • Supplements such as iron and calcium.
  • Sleep medicines.
  • Drugs used for anesthesia (to cause loss of feeling for surgery or other procedures).
  • Not drinking enough water or other fluids. This is a common problem for cancer patients.
  • Not eating enough food, especially high-fiber food.
Bowel movement habits
  • Not going to the bathroom when the need for a bowel movement is felt.
  • Using laxatives and/or enemas too often.
Conditions that prevent activity and exercise
  • Spinal cord injury or pressure on the spinal cord from a tumor or other cause.
  • Broken bones.
  • Fatigue.
  • Weakness.
  • Long periods of bed rest or not being active.
  • Heart problems.
  • Breathing problems.
  • Anxiety.
  • Depression.
Intestinal disorders
  • Irritable colon.
  • Diverticulitis (inflammation of small pouches in the colon called diverticula).
  • Tumor in the intestine.
Muscle and nerve disorders
  • Brain tumors.
  • Spinal cord injury or pressure on the spinal cord from a tumor or other cause.
  • Paralysis (loss of ability to move) of both legs.
  • Stroke or other disorders that cause paralysis of part of the body.
  • Peripheral neuropathy (pain, numbness, tingling) of feet.
  • Weakness of the diaphragm (the breathing muscle below the lungs) or abdominal muscles. This makes it hard to push to have a bowel movement.
Changes in body metabolism
  • Having a low level of thyroid hormone, potassium, or sodium in the blood.
  • Having too much nitrogen or calcium in the blood.
  • Having to go farther to get to a bathroom.
  • Needing help to go to the bathroom.
  • Being in unfamiliar places.
  • Having little or no privacy.
  • Feeling rushed.
  • Living in extreme heat that causes dehydration.
  • Needing to use a bedpan or bedside commode.
Narrow colon
  • Scars from radiation therapy or surgery.
  • Pressure from a growing tumor.

An assessment is done to help plan treatment.

The assessment includes a physical exam and questions about the patient's usual bowel movements and how they have changed.

The following tests and procedures may be done to help find the cause of the constipation:

There is no "normal" number of bowel movements for a cancer patient. Each person is different. You will be asked about bowel routines, food, and medicines:

For patients who have colostomies, care of the colostomy will be discussed.

Treating constipation is important to make the patient comfortable and to prevent more serious problems.

It's easier to prevent constipation than to relieve it. The health care team will work with the patient to prevent constipation. Patients who take opioids may need to start taking laxatives right away to prevent constipation.

Constipation can be very uncomfortable and cause distress. If left untreated, constipation may lead to fecal impaction. This is a serious condition in which stool will not pass out of the colon or rectum. It's important to treat constipation to prevent fecal impaction.

Prevention and treatment are not the same for every patient. Do the following to prevent and treat constipation:

When constipation is caused by opioids, treatment may be drugs that stop the effects of the opioids or other medicines, stool softeners, enemas, and/or manual removal of stool.

Fecal Impaction

Fecal impaction is a mass of dry, hard stool that will not pass out of the colon or rectum.

Fecal impaction is dry stool that cannot pass out of the body. Patients with fecal impaction may not have gastrointestinal (GI) symptoms. Instead, they may have problems with circulation, the heart, or breathing. If fecal impaction is not treated, it can get worse and cause death.

A common cause of fecal impaction is using laxatives too often.

Repeated use of laxatives in higher and higher doses makes the colon less able to respond naturally to the need to have a bowel movement. This is a common reason for fecal impaction. Other causes include:

Certain types of mental illness may lead to fecal impaction.

Symptoms of fecal impaction include being unable to have a bowel movement and pain in the abdomen or back.

The following may be symptoms of fecal impaction:

These symptoms should be reported to the health care provider.

Assessment includes a physical exam and questions like those asked in the assessment of constipation.

The doctor will ask questions similar to those for the assessment of constipation:

The doctor will do a physical exam to find out if the patient has a fecal impaction. The following tests and procedures may be done:

A fecal impaction is usually treated with an enema.

The main treatment for impaction is to moisten and soften the stool so it can be removed or passed out of the body. This is usually done with an enema. Enemas are given only as prescribed by the doctor since too many enemas can damage the intestine. Stool softeners or glycerin suppositories may be given to make the stool softer and easier to pass. Some patients may need to have stool manually removed from the rectum after it is softened.

Laxatives that cause the stool to move are not used because they can also damage the intestine.

Bowel Obstruction

A bowel obstruction is a blockage of the small or large intestine by something other than fecal impaction.

Bowel obstructions (blockages) keep the stool from moving through the small or large intestines. They may be caused by a physical change or by conditions that stop the intestinal muscles from moving normally. The intestine may be partly or completely blocked. Most obstructions occur in the small intestine.

Physical changes

If the intestine is blocked by physical causes, it may decrease blood flow to blocked parts. Blood flow needs to be corrected or the affected tissue may die.

Conditions that affect the intestinal muscle

The most common cancers that cause bowel obstructions are cancers of the colon, stomach, and ovary.

Other cancers, such as lung and breast cancers and melanoma, can spread to the abdomen and cause bowel obstruction. Patients who have had surgery on the abdomen or radiation therapy to the abdomen have a higher risk of a bowel obstruction. Bowel obstructions are most common during the advanced stages of cancer.

Assessment includes a physical exam and imaging tests.

The following tests and procedures may be done to diagnose a bowel obstruction:

Treatment is different for acute and chronic bowel obstructions.

Acute bowel obstruction

Acute bowel obstructions occur suddenly, may have not occurred before, and are not long-lasting. Treatment may include the following:

Patients with symptoms that keep getting worse will have follow-up exams to check for signs and symptoms of shock and to make sure the obstruction isn't getting worse.

Chronic, malignant bowel obstruction

Chronic bowel obstructions keep getting worse over time. Patients who have advanced cancer may have chronic bowel obstructions that cannot be removed with surgery. The intestine may be blocked or narrowed in more than one place or the tumor may be too large to remove completely. Treatments include the following:


Diarrhea is frequent, loose, and watery bowel movements.

Diarrhea is frequent, loose, and watery bowel movements. Acute diarrhea lasts more than 4 days but less than 2 weeks. Symptoms of acute diarrhea may be loose stools and passing more than 3 unformed stools in one day. Diarrhea is chronic (long-term) when it goes on for longer than 2 months.

Diarrhea can occur at any time during cancer treatment. It can be physically and emotionally stressful for patients who have cancer.

In cancer patients, the most common cause of diarrhea is cancer treatment.

Causes of diarrhea in cancer patients include the following:

Assessment includes a physical exam, lab tests, and questions about diet and bowel movements.

Because diarrhea can be life-threatening, it is important to find out the cause so treatment can begin as soon as possible. The doctor may ask the following questions to help plan treatment:

Tests and procedures may include the following:

Treatment of diarrhea depends on what is causing it.

Treatment depends on the cause of the diarrhea. The doctor may make changes in medicines, diet, and/or fluids.

Radiation Enteritis

Radiation enteritis is inflammation of the intestine caused by radiation therapy.

Radiation enteritis is a condition in which the lining of the intestine becomes swollen and inflamed during or after radiation therapy to the abdomen, pelvis, or rectum. The small and large intestine are very sensitive to radiation. The larger the dose of radiation, the more damage may be done to normal tissue. Most tumors in the abdomen and pelvis need large doses of radiation. Almost all patients receiving radiation to the abdomen, pelvis, or rectum will have enteritis.

Radiation therapy to kill cancer cells in the abdomen and pelvis affects normal cells in the lining of the intestines. Radiation therapy stops the growth of cancer cells and other fast-growing cells. Since normal cells in the lining of the intestines grow quickly, radiation treatment to that area can stop those cells from growing. This makes it hard for tissue to repair itself. As cells die and are not replaced, gastrointestinal problems occur over the next few days and weeks.

Doctors are studying whether the order that radiation therapy, chemotherapy, and surgery are given affects how severe the enteritis will be.

Symptoms may begin during radiation therapy or months to years later.

Radiation enteritis may be acute or chronic:

The total dose of radiation and other factors affect the risk of radiation enteritis.

Only 5% to 15% of patients treated with radiation to the abdomen will have chronic problems. The amount of time the enteritis lasts and how severe it is depend on the following:

Acute and chronic enteritis have symptoms that are a lot alike.

Patients with acute enteritis may have the following symptoms:

Symptoms of acute enteritis usually go away 2 to 3 weeks after treatment ends.

Symptoms of chronic enteritis usually appear 6 to 18 months after radiation therapy ends. It can be hard to diagnose. The doctor will first check to see if the symptoms are being caused by a recurrent tumor in the small intestine. The doctor will also need to know the patient's full history of radiation treatments.

Patients with chronic enteritis may have the following signs and symptoms:

Assessment of radiation enteritis includes a physical exam and questions for the patient.

Patients will be given a physical exam and be asked questions about the following:

Treatment depends on whether the radiation enteritis is acute or chronic.

Acute radiation enteritis

Treatment of acute enteritis includes treating the symptoms. The symptoms usually get better with treatment, but if symptoms get worse, then cancer treatment may have to be stopped for a while.

Treatment of acute radiation enteritis may include the following:

Chronic radiation enteritis

Treatment of chronic radiation enteritis may include the following:

Current Clinical Trials

Use our clinical trial search to find NCI-supported cancer clinical trials that are accepting patients. You can search for trials based on the type of cancer, the age of the patient, and where the trials are being done. General information about clinical trials is also available.

To Learn More About Gastrointestinal Complications

For more information from the National Cancer Institute about constipation or diarrhea, see the following:

About This PDQ Summary

About PDQ

Physician Data Query (PDQ) is the National Cancer Institute's (NCI's) comprehensive cancer information database. The PDQ database contains summaries of the latest published information on cancer prevention, detection, genetics, treatment, supportive care, and complementary and alternative medicine. Most summaries come in two versions. The health professional versions have detailed information written in technical language. The patient versions are written in easy-to-understand, nontechnical language. Both versions have cancer information that is accurate and up to date and most versions are also available in Spanish.

PDQ is a service of the NCI. The NCI is part of the National Institutes of Health (NIH). NIH is the federal government's center of biomedical research. The PDQ summaries are based on an independent review of the medical literature. They are not policy statements of the NCI or the NIH.

Purpose of This Summary

This PDQ cancer information summary has current information about the causes and treatment of gastrointestinal complications, including constipation, impaction, bowel obstruction, diarrhea, and radiation enteritis. It is meant to inform and help patients, families, and caregivers. It does not give formal guidelines or recommendations for making decisions about health care.

Reviewers and Updates

Editorial Boards write the PDQ cancer information summaries and keep them up to date. These Boards are made up of experts in cancer treatment and other specialties related to cancer. The summaries are reviewed regularly and changes are made when there is new information. The date on each summary ("Updated") is the date of the most recent change.

The information in this patient summary was taken from the health professional version, which is reviewed regularly and updated as needed, by the PDQ Supportive and Palliative Care Editorial Board.

Clinical Trial Information

A clinical trial is a study to answer a scientific question, such as whether one treatment is better than another. Trials are based on past studies and what has been learned in the laboratory. Each trial answers certain scientific questions in order to find new and better ways to help cancer patients. During treatment clinical trials, information is collected about the effects of a new treatment and how well it works. If a clinical trial shows that a new treatment is better than one currently being used, the new treatment may become "standard." Patients may want to think about taking part in a clinical trial. Some clinical trials are open only to patients who have not started treatment.

Clinical trials can be found online at NCI's website. For more information, call the Cancer Information Service (CIS), NCI's contact center, at 1-800-4-CANCER (1-800-422-6237).

Permission to Use This Summary

PDQ is a registered trademark. The content of PDQ documents can be used freely as text. It cannot be identified as an NCI PDQ cancer information summary unless the whole summary is shown and it is updated regularly. However, a user would be allowed to write a sentence such as "NCI's PDQ cancer information summary about breast cancer prevention states the risks in the following way: [include excerpt from the summary]."

The best way to cite this PDQ summary is:

PDQ® Supportive and Palliative Care Editorial Board. PDQ Gastrointestinal Complications. Bethesda, MD: National Cancer Institute. Updated <MM/DD/YYYY>. Available at: Accessed <MM/DD/YYYY>. [PMID: 26389438]

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Last Revised: 2020-11-24

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