Approved by the Cancer.Net Editorial Board, 02/2014

Constipation occurs when a person cannot empty his or her bowels or has a feeling of needing to move the bowels but can't. It starts when the body begins absorbing more water or begins signaling food to move through the bowel system more slowly. Constipation is a common symptom in people with cancer.

Relieving side effects, also called symptom management, palliative care, or supportive care, is an important part of cancer care and treatment. Several factors affect a person's normal bowel function, including how much and what kind of food he or she is eating, the health of his or her gastrointestinal (GI) tract, and the medications the person is taking. Talk with your health care team about any constipation symptoms you experience, including any new symptoms or a change in symptoms. These can often be controlled by taking some simple steps, but occasionally these symptoms are a sign of a more serious problem that may require further testing.

Surgery to the abdomen often affects the function of the GI tract and may cause either diarrhea or constipation. Sometimes after abdominal surgery, scar tissue (called adhesions) can cause narrowing or partial blockage of the bowel which, when severe, may require surgery to reverse. Also, cancer deposits may grow in the abdomen, interfering with bowel function. The most serious form of this condition is a bowel obstruction, where the bowel becomes blocked by tumor. A person may require surgery to reverse this problem.


In addition to not being able to empty the bowels, people with constipation may experience the following symptoms:

  • Pain and cramping
  • Swelling in the abdomen
  • Appetite loss
  • Nausea and vomiting
  • Inability to urinate
  • Confusion


Common causes of constipation include not eating enough fiber, not drinking enough water or other fluids, and not exercising. However, for people with cancer, the following cancer-related factors and cancer treatments might also cause constipation:

  • Medications, including antacids; some drugs to treat nausea and vomiting, seizures, depression, diarrhea, or blood pressure; iron supplements; chemotherapy; and especially pain medications which can slow the muscular action of the bowel that helps food move through the system.
  • Eating less food
  • Bowel obstruction from scar tissue or tumors
  • Dehydration (not drinking enough water)
  • Being physically inactive
  • Tumor compression (cancer pressing on the spinal cord)
  • High levels of calcium in the blood
  • Low potassium levels
  • Thyroid problems
  • Diabetes


In planning treatment for constipation, the doctor may do a rectal examination or take an x-ray or other imaging scan of the abdomen. This is to make sure you don't have a tumor obstructing your rectum or at another point in the GI tract and to find out whether there is hard stool in your rectum. The doctor may also ask you about the following:

  • Your bowel habits, before the cancer and now
  • Use of medications that may cause constipation
  • What you've been eating and drinking recently
  • Other diseases or illnesses


It is very important to treat constipation properly. If it is left untreated, constipation may cause internal damage to the intestine or rectum, dehydration, or bowel obstruction. It can also slow the body's absorption of medications taken by mouth. If there is scar tissue or a tumor causing the problem, additional tests may be necessary. Talk with your health care team about the best way to manage constipation. Some of the following suggestions may help.

  • Drink more liquids.
  • With the advice of the health care team, ask about changing the dose or stopping medications that cause constipation.
  • Eat more fiber or take fiber supplements. However, if you have adhesions or tumor deposits that narrow your bowel, your doctor may recommend a low-fiber diet instead, also called a low-residue diet,  because the fiber may back up behind the narrower areas of the bowel.
  • Increase physical activity, if possible.
  • Ask your health care team about treatment, such as laxatives, an enema, or rectal suppository. Some of these may be harmful for some patients.

More Information

The Importance of Hydration

Side Effects

Additional Resource

National Cancer Institute: Gastrointestinal Complications