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.

Radiation enteritis is a condition in which the lining of the bowel becomes swollen and inflamed during or after radiation therapy to the abdomen, pelvis, or rectum. The large and small bowels are very sensitive to radiation. The larger the dose of radiation, the greater the damage to normal bowel tissue. Most tumors in the abdomen and pelvis need large doses, and almost all patients receiving radiation to the abdomen, pelvis, or rectum will show signs of acute enteritis.

Acute symptoms are those that appear during the first course of radiation therapy and up to 8 weeks later. Chronic radiation enteritis may appear months to years after radiation therapy is completed, or it may begin as acute enteritis and continue after treatment stops. Only 5% to 15% of persons treated with radiation to the abdomen will develop chronic problems. Several factors affect how long the enteritis will last and how severe it will be:

• The dose of radiation given.
• The tumor size and how much it has spread.
• The amount of normal bowel treated.
• Whether chemotherapy was given at the same time as the radiation therapy.
• Whether radiation implants were used.
• Whether the patient has high blood pressure, diabetes, pelvic inflammatory disease, or poor nutrition, or has had surgery to the abdomen or pelvis. These conditions can decrease blood flow to the bowel wall and affect bowel movement, increasing the chance of radiation injury.

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