Narrowing of colon lumen
- Related to scarring from radiation therapy, surgical anastomosis, or compression from growth of extrinsic tumor.
*Frequently seen in oncology patients.
Constipation is frequently the result of autonomic neuropathy caused by the vinca alkaloids, taxanes, and thalidomide. Other drugs such as opioid analgesics or anticholinergics (antidepressants and antihistamines) may lead to constipation by causing decreased sensitivity to the defecation reflexes and decreased gut motility. Since constipation is common with the use of opioids, a bowel regimen will be initiated at the time opioids are prescribed and continued for as long as the patient takes opioids. Opioids produce varying degrees of constipation, suggesting a dose-related phenomenon. One study suggests that clinicians should not base laxative prescribing on the opioid dose, but rather titrate the laxative according to bowel function. Lower doses of opioids or weaker opioids, such as codeine, are just as likely to cause constipation. (Refer to the Side Effects of Opioids section in the PDQ summary on Pain for more information.)
Other diseases, such as diabetes (with autonomic neuropathy) and hypothyroidism, may cause constipation. Metabolic disorders, such as hypokalemia and hypercalcemia, also predispose cancer patients to developing constipation. Once these disorders are corrected, constipation will subside.
Assessment of Constipation
A normal bowel pattern is having at least three stools per week and no more than three per day; however, these criteria may be inappropriate for cancer patients.[1,3] Constipation is viewed as a subjective symptom involving the complaints of decreased frequency with incomplete passage of dry, hard stool. A thorough history of the patient's bowel pattern, dietary changes, and medications, along with a physical examination, can identify possible causes of constipation. The evaluation also includes assessment of associated symptoms such as distention, flatus, cramping, or rectal fullness. A digital rectal examination is done to rule out fecal impaction at the level of the rectum. A test for occult blood will be helpful in determining a possible intraluminal lesion. A thorough examination of the gastrointestinal tract is necessary if cancer is suspected.
The following questions may provide a useful assessment guide:
- What is normal for the patient (frequency, amount, and timing)?
- When was the last bowel movement? What was the amount, consistency, and color? Was blood passed with it?
- Has the patient been having any abdominal discomfort, cramping, nausea or vomiting, pain, excessive gas, or rectal fullness?
- Does the patient regularly use laxatives or enemas? What does the patient usually do to relieve constipation? Does it usually work?
- What type of diet does the patient follow? How much and what type of fluids are taken on a regular basis?
- What medication (dose and frequency) is the patient taking?
- Is this symptom a recent change?
- How many times a day is flatus passed?