Article: Gastrointestinal Complications


This patient summary on gastrointestinal complications is adapted from a summary written for health professionals by cancer experts. This and other credible information about cancer treatment, screening, prevention, supportive care, and ongoing clinical trials, is available from the National Cancer Institute. Gastrointestinal complications such as constipation, impaction, bowel obstruction, and diarrhea are common problems for cancer patients, with causes that include the cancer itself or treatment of the cancer. This brief summary describes the differences between constipation, impaction, bowel obstruction, and diarrhea; their causes, and treatment. Treatment of children is different from adults. The doctor will prescribe treatments according to the child's age and diagnosis.


Constipation is the slow movement of feces (stool or body wastes) through the large intestine resulting in infrequent bowel movements and the passage of dry, hard stools. The longer it takes for the stool to move through the large intestine, the more fluid is absorbed and the drier and harder the stool becomes.

Inactivity, immobility, or physical and social barriers (for example, bathrooms being unavailable or inconveniently located) can make constipation worse. Depression and anxiety caused by cancer treatment or cancer pain can also lead to constipation. The most common causes of constipation are not drinking enough fluids and taking pain medications.

Constipation is annoying and uncomfortable, but fecal impaction (a collection of dry, hard stool in the colon or rectum) can be life-threatening. Patients with a fecal impaction may not have gastrointestinal symptoms. Instead they may have circulation, heart, or breathing problems. If fecal impaction is not recognized, the signs and symptoms will get worse and the patient could die.

A bowel obstruction is a partial or complete blockage of the small or large intestine by a process other than fecal impaction. Bowel obstructions are classified by the type of obstruction, how the obstruction occurred, and where it is. Tumors growing inside or outside the bowel, and scar tissue that develops after surgery, can affect bowel function and cause a partial or complete obstruction. Patients who have colostomies are especially at risk of developing constipation, which can lead to bowel obstruction.

Diarrhea can occur at any time during cancer treatment. Although diarrhea occurs less often than constipation, it can be physically and emotionally devastating for patients who have cancer. Diarrhea can cause:

  • Changes in eating patterns.
  • A loss of body fluids.
  • Chemical imbalances in the blood.
  • Impairments in physical function.
  • Excessive tiredness.
  • Skin problems.
  • A decrease in physical activity.
  • Problems that can be life-threatening in some patients.

Diarrhea is an abnormal increase in the amount of fluid in the stool that lasts more than 4 days but less than 2 weeks. It may also be described as an abnormal increase in the amount of fluid in the stool and the passage of more than 3 unformed stools during a 24-hour period. Diarrhea is considered a long-term problem when it lasts longer than 2 months.


Description and Causes

Common factors that may cause constipation in healthy people are eating a low-fiber diet, postponing visits to the toilet, using laxatives and enemas excessively, not drinking enough fluids, and exercising too little. In persons with cancer, constipation may be a symptom of cancer, a result of a growing tumor, or a result of cancer treatment. Constipation may also be a side effect of medications for cancer or cancer pain and may be a result of other changes in the body (organ failure, decreased ability to move, and depression). Other causes of constipation include dehydration and not eating enough. Cancer, cancer treatment, aging, and declining health can contribute to causing constipation.

More specific causes of constipation that can result in bowel impaction include:


  • Not including enough high-fiber foods in the diet.
  • Not drinking enough water or other fluids.

Changed Bowel Habits

  • Repeatedly ignoring the urge to pass stool.
  • Using too many laxatives and enemas.

Immobility and Lack of Exercise

  • Spinal cord injury, spinal cord compression, bone fractures, fatigue, weakness, long periods of bedrest.
  • Inability to tolerate movement and exercise due to respiratory or cardiac problems.


  • Chemotherapy treatments.
  • Pain medications.
  • Medications for anxiety and depression.
  • Stomach antacids.
  • Diuretics.
  • Vitamin supplements such as iron and calcium.
  • Sleep medications.
  • General anesthesia.

Bowel Disorders

  • Irritable colon.
  • Diverticulitis.
  • Tumor.

Muscle and Nerve Disorders (nerve damage can lead to loss of muscle tone in the bowel)

  • Brain tumors.
  • Spinal cord compression from a tumor or other spinal cord injury.
  • Stroke or other disorders that cause muscle weakness or movement.
  • Weakness of the diaphragm or abdominal muscles making it difficult to take a deep breath and push to have a bowel movement.

Body Metabolism Disorders

  • Under-secretion of the thyroid gland.
  • Increased level of calcium in the blood.
  • Low levels of potassium or sodium in the blood.
  • Diabetes with nerve dysfunction.

Environmental Factors

  • Needing assistance to go to the bathroom.
  • Being in unfamiliar surroundings or a hurried atmosphere.
  • Living in extreme heat leading to dehydration.
  • Needing to use a bedpan or bedside commode.
  • Lack of privacy.

Assessment of Constipation

A medical history and physical examination can identify the causes of constipation. The examination may include a digital rectal exam (the doctor inserts a gloved, lubricated finger into the rectum to check for stool impaction) or a test for blood in the stool. If cancer is suspected, a thorough examination of the rectum and colon may be done with a lighted tube inserted through the anus and into the colon. The following questions may be asked:

  • What is your normal bowel pattern? How often do you have a bowel movement? When and how much?

  • When was your last bowel movement? What was it like (how much, hard or soft, color)? Was there any blood?

  • Has your stomach hurt or have you had any cramping, nausea, vomiting, pain, gas, or feeling of fullness near the rectum?

  • Do you use laxatives or enemas regularly? What do you normally do to relieve constipation? Does this usually work?

  • What kind of food do you eat? How much and what type of fluids do you drink daily?

  • What medicine are you taking? How much and how often?

  • Is this constipation a recent change in your normal habits?

  • How many times a day do you pass gas?


Treatment of constipation includes prevention (if possible), elimination of possible causes, and limited-use of laxatives. Suggestions for the patient's treatment plan may include the following:

  • Keep a record of all bowel movements.

  • Increase the fluid intake by drinking eight 8-ounce glasses of fluid each day (if not contraindicated by kidney or heart disease).

  • Exercise regularly, including abdominal exercises in bed or moving from the bed to chair if the patient cannot walk.

  • Increase the amount of dietary fiber by eating more fruits (raisins, prunes, peaches, and apples), vegetables (squash, broccoli, carrots, and celery), and whole grain cereals, breads, and bran. Patients must drink more fluids when increasing dietary fiber or they may become constipated. Patients who have had a bowel obstruction or have undergone bowel surgery (for example, a colostomy) should not eat a high-fiber diet.

  • Drink a warm or hot drink about one half-hour before the patient's usual time for a bowel movement.

  • Provide privacy and quiet time when the patient needs to have a bowel movement.

  • Help the patient to the toilet or provide a bedside commode instead of a bedpan.

  • Take only medications prescribed by the doctor.

  • Do not use suppositories or enemas unless ordered by the doctor. In some cancer patients these treatments may lead to bleeding, infection, or other harmful side effects.


Description and Causes

Five major factors can cause impaction:

  1. Opioid pain medications.
  2. Inactivity over a long period.
  3. Changes in diet.
  4. Mental illness.
  5. Long-term use of laxatives.

    Regular use of laxatives for constipation contributes most to the development of constipation and impaction. Repeated use of laxatives in higher and higher doses make the colon less able to signal the need to have a bowel movement. (Refer to the Constipation section for causes of constipation that can result in impaction.)

Patients with impaction may have symptoms similar to patients with constipation, or they may have back pain (the impaction presses on sacral nerves) or bladder problems (the impaction presses on the ureters, bladder, or urethra). The patient's abdomen may become enlarged causing difficulty breathing, rapid heartbeat, dizziness, and low blood pressure. Other symptoms can include explosive diarrhea (as stool moves around the impaction), leaking stool when coughing, nausea, vomiting, abdominal pain, and dehydration. Patients who have an impaction may become very confused and disoriented with rapid heartbeat, sweating, fever, and high or low blood pressure.

Assessment of Impaction

The doctor will ask questions similar to those in the Assessment of Constipation section and do a physical examination to find out if the patient has an impaction. The examination may also include x-rays of the abdomen and/or chest, blood tests, and an electrocardiogram (a test that shows the activity of the heart).

Treatment of Impaction

Impactions are usually treated by moistening and softening the stool with an enema. Enemas must be given very carefully as prescribed by the doctor since too many enemas can damage the bowel. Some patients may need to have stool manually removed from the rectum after it is softened. Glycerin suppositories may also be prescribed. Laxatives that stimulate the bowel and cause cramping must be avoided since they can damage the bowel even more.

Bowel Obstruction

Description and Causes

A bowel obstruction may be caused by a narrowing of the intestine from inflammation or damage to the bowel, tumors, scar tissue, hernias, twisting of the bowel, or pressure on the bowel from outside the intestinal tract. It can also be caused by factors that interfere with the function of muscles, nerves, and blood flow to the bowel. Most bowel obstructions occur in the small intestine and are usually caused by scar tissue or hernias. The rest occur in the colon (large intestine) and are usually caused by tumors, twisting of the bowel, or diverticulitis. Symptoms will vary depending on whether the small or large intestine is involved.

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 abdominal surgery or radiation are at a higher risk of developing a bowel obstruction. Bowel obstructions are most common during the advanced stages of cancer.

Assessment of Bowel Obstruction

The doctor will do a physical examination to find out whether the patient has abdominal pain, vomiting, or any movement of gas or stool in the bowel. Blood and urine tests may be done to detect any fluid and blood chemistry imbalance or infection. Abdominal x-rays and a barium enema may also be done to find the location of the bowel obstruction.

Treatment of Acute Bowel Obstruction

Patients who have abdominal symptoms that continue to become worse must be monitored frequently to prevent or detect early signs and symptoms of shock and constricting obstruction of the bowel. Medical treatment is necessary to prevent fluid and blood chemistry imbalances and shock.

A nasogastric tube may be inserted through the nose and esophagus into the stomach or a colorectal tube may be inserted through the rectum into the colon to relieve pressure from a partial bowel obstruction. The nasogastric tube or colorectal tube may decrease swelling, remove fluid and gas build-up, or decrease the need for multiple surgical procedures; however, surgery may be necessary if the obstruction completely obstructs the bowel.

Treatment of Chronic, Malignant Bowel Obstruction

Patients who have advanced cancer may have chronic, worsening bowel obstruction that cannot be removed with surgery. Sometimes, the doctor may be able to insert an expandable metal tube called a stent into the bowel to open the area that is blocked.

When neither surgery nor a stent is possible, the doctor may insert a gastrostomy tube through the wall of the abdomen directly into the stomach by a very simple procedure. The gastrostomy tube can relieve fluid and air build-up in the stomach and allow medications and liquids to be given directly into the stomach by pouring them down the tube. A drainage bag with a valve may also be attached to the gastrostomy tube. When the valve is open, the patient may be able to eat or drink by mouth without any discomfort because the food drains directly into the bag. This gives the patient the experience of tasting the food and keeping the mouth moist. Solid food should be avoided because it may block the tubing to the drainage bag.

If the patient's comfort is not improved with a stent or gastrostomy tube, and the patient cannot take anything by mouth, the doctor may prescribe injections or infusions of medications for pain and/or nausea and vomiting.


Causes of Diarrhea

In cancer patients, the most common cause of diarrhea is cancer treatment (chemotherapy, radiation therapy, bone marrow transplantation, or surgery). Other causes of diarrhea include antibiotic therapy, stress and anxiety related to being diagnosed with cancer and undergoing cancer treatment; and infection. Infection may be caused by viruses, bacteria, fungi, or other harmful microorganisms. Antibiotic therapy can cause inflammation of the lining of the bowel, resulting in diarrhea that often does not respond to treatment. Other causes of diarrhea in cancer patients include:

  • The cancer itself.
  • Physical reactions to diet.
  • Medical problems and diseases other than cancer.
  • The laxative regimen.
  • Bowel impaction with leakage of stool around the blockage.

Undergoing surgery to the stomach and/or intestines can affect normal bowel function and cause diarrhea. Some chemotherapy drugs cause diarrhea by affecting how nutrients are broken down and absorbed in the small bowel. Radiation therapy to the abdomen and pelvis can cause inflammation of the bowel. Patients may have problems digesting food, and experience gas, bloating, cramping, and diarrhea. These symptoms may last up to 8 to 12 weeks after therapy or may not develop for months or years. Treatment may include diet changes, medications, or surgery. Patients who are undergoing radiation therapy while receiving chemotherapy often experience severe diarrhea. (Refer to the PDQ summary on Radiation Enteritis)

Patients who undergo donor bone marrow transplantation may develop graft-versus-host disease (GVHD). Stomach and intestinal symptoms of GVHD include nausea and vomiting, severe abdominal pain and cramping, and watery, green diarrhea. Symptoms may occur 1 week to 3 months after transplantation. Some patients may require long-term treatment and diet management.


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

  • How often have you had bowel movements in the past 24 hours?
  • When was your last bowel movement? What was it like (how much, how hard or soft, what color)? Was there any blood?
  • Have you been dizzy, extremely drowsy, or had any cramping, abdominal pain, nausea, vomiting, fever, or rectal bleeding?
  • What have you eaten? What and how much have you had to drink in the past 24 hours?
  • Have you lost weight recently? How much?
  • How often have you urinated in the past 24 hours?
  • What medicine are you taking? How much and how often?
  • Have you traveled recently?

The doctor will also do a physical examination that should include checking blood pressure, pulse, and respirations; evaluation of the skin and tissue lining the inside of the mouth to check for blood circulation and amount of fluid in the tissue; examination of the abdomen for pain, tenderness, and bowel sounds; and a rectal exam to check for stool impaction and collect stool to test for blood.

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.
  • Alcohol.
  • 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.

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.

Changes to This Summary (02/14/2003)

The PDQ cancer information summaries are reviewed regularly and updated as new information becomes available. This section describes the latest changes made to this summary as of the date above.

Changes were made to this summary.

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Source: National Cancer Institute
Cache Date: December 10, 2004