Four days after discharge from the hospital, a patient with a recent diagnosis of advanced lung cancer arrived in the emergency department of a Montreal hospital with abdominal pain, nausea and vomiting, and urinary retention. His large bowel was grossly distended with stool, and he required numerous enemas and manual disimpactions to dislodge the large quantities of hard feces.
The patient presented a classic example of constipation resulting from narcotic analgesic administration, without any concomitant laxative program. An unnecessary hospital admission, a great deal of discomfort for the patient, and an unpleasant task for the nursing staff could all have been avoided.
As a physician working in palliative care, I have been continually confronted with patients’ problems of constipation. No other preventable symptom produces so much distress for the patient and the caring family. It is common for physicians either to omit completely any prescription for laxatives or to write a prescription for laxatives “as needed” or ‘laxative of choice” and to leave further management to nurses. The implication is that laxatives are administered only when constipation is present, as a treatment, rather than on a regular, individually adjusted, dosage schedule to prevent further problems.
Constipation is defined as a decrease in the frequency of bowel movements accompanied by a prolonged and difficult passage of feces, followed by an uncomfortable sensation of incomplete evacuation. Frequency of bowel movements can vary from three weekly to three daily, so what is constipation for one patient can be normal for another. Careful evaluation of constipation will require attention to frequency, consistency of stool, and ease of evacuation. Several symptoms can appear: low back pain, abdominal distress, distension, or flatulence.
Obstinate constipation was described by Bockus as one of the most common conditions that the physician is called upon to treat, and one of the most often mismanaged.
Constipation is a common and distressing symptom in cancer patients. St. Christopher’s Hospice in London, England, reported that 45% of male patients and 43% of female patients on admission complained of constipation. At Sir Michael Sobell House, Oxford, 78% of patients on morphine received a laxative. The incidence of the problem’s occurring at some time during the course of the disease approaches 100%.
Causes in Cancer Patients
Certain contributing factors are particularly common in cancer patients and should be evaluated in any differential diagnosis.
1. Physiologic factors include advanced age, decreased exercise, especially in those who are bedridden, decreased bulk in diet, dehydration, inconvenience (inability to reach the toilet when the urge to defecate is present), depression, diminished awareness of loaded rectum, and poor dentition leading to inadequate nutrition.
2. Structural (anatomical-pathologic) factors include intracolonic (partial bowel obstruction, diverticulosis, tumour, bleeding, irritable or “cathartic colon,” ischemic colitis, and stricture), extracolonic (tumour or ascites), and anal (fissure, hemorrhoids, stricture, and proctitis from radiation).
3. Metabolic factors include hypercalcemia, hypokalemia, and uremia.
4. Neurologic factors include neuropathy (chemotherapy-induced or diabetic), compression of nerve roots or of spinal cord, and cauda equina.
5. Drugs affecting the bowel include opiates, antacids (calcium and aluminum compounds), anticholinergic drugs (belladonna alkaloids), antidepressive agents, phenothiazines, anticonvulsants, and diuretics.
Opiates increase the tone and non-propulsive motility of both ileum and colon. There is ample evidence that the opiates have both local effects on the gut and central nervous effects producing changes in motility of the bowel.
Initially simple measures should be tried, such as increasing dietary fibre and increasing fluid intake. Patients should be encouraged to have a bowel movement when the urge occurs by providing a commode that is easily accessible. Almost always an additional systematic laxative regimen will be needed for cancer patients receiving narcotics.
All laxatives work by increasing motor activity, which promotes peristalsis, or by altering hydration of the stool. Physicians need to be acquainted with only a few agents in order to prescribe appropriately. Most effective is the use of a combination of a stool softener and a stimulant. A stimulant alone can lead to abdominal cramps. If a softener alone is given, the patient can develop a loaded rectum with soft stool.
Laxative drugs can be divided into five groups: bulk agents (regulators), lubricants and stool softeners, small bowel flushers (salts and non-absorb-able sugars, i.e., osmotic drugs,) stimulants, and anthracenes. Their site of action is indicated in Table 1.
|Table 1 Site of Action of Commonly Used Laxatives|
|Drug Group||Site of Action|
|Bulk agents||Small and large bowel|
|Saline cathartics||Small and large bowel|
|Stimulants (bisacodyl and cascara)||Mainly colon|
Bulk Agents. Dietary fibre retains several times its weight in water. Foods containing wheat bran and fibre are particularly useful in chronic constipation, but the anorexia so common in advanced cancer limits dietary intake. Psyllium (Metamucil et al.) will increase the water content of the stool as well as the rate of colonic transit. A high fluid intake is required, a limiting factor in most patients with advanced disease. Dietary fibre and bulk agents are contra-indicated in intestinal obstruction, whether partial or complete.
Lubricants and Stool Softeners. Docusate sodium (Colace, Regulex, et al.) is a detergent that acts by drawing water and sodium into the bowel lumen. The dosage is regulated according to the consistency of stool, usually 100 to 600 mg/ day. (It is one of the most commonly used agents in Britain and in the United States.) Mineral oil, liquid paraffin, and other lubricants are contra-indicated. There is an ever-present risk of aspiration pneumonia, and when used for a longer term, of interference with absorption of fat-soluble vitamins. Mixtures of mineral oils with other cathartics is irrational.
Osmotic Agents. Saline cathartics usually contain magnesium or sodium ions, which retain fluid in the large bowel by osmotic pressure. These ions usually act in one or two hours. The major hazard of saline laxatives is their potential to cause electrolyte disturbances, especially in the elderly, who have a diminished capacity to return to an electrolyte balance. Partial absorption of sodium or magnesium can cause toxic effects in patients with cardiac or renal failure.
These agents are most effective if accompanied by a large oral intake of fluids. Commonly used saline cathartics include sodium sulphate, sodium phosphate, magnesium sulphate (Epsom Salt), magnesium hydroxide, and magnesium citrate. Lactulose (Chronulac, Lactulax, et al.) is a non-absorbable sugar that exerts similar osmotic effect. It is reported to be useful in patients with exacerbated abdominal discomfort. It is tolerated better than other drugs by some patients, but is also more costly.
Stimulants. Surface wetting agents and stimulant laxatives both work chiefly on contact with the intestinal mucosa. Contact laxatives change the absorption of water and electrolytes by the mucosa of the gut and soften the feces. The stimulant laxatives all enhance propulsive peristalsis. Because the effect is delayed for six to nine hours, they are best taken at bedtime. Examples include bisacodyl (Dulcolax et al.) by tablet or suppository.
Included in the anthracenes are cascara and senna, both containing glycosides. Senna, a contact laxative, is activated by bacterial action in the large bowel. It is usually prescribed in tablets or granules but is also available in liquid (X-Prep).
Suppositories. A combination of one glycerine suppository (which attracts water into the rectum) and a bisacodyl suppository (which stimulates the musculature) is often effective. Suppositories should be placed against the mucosal wall rather than pushed into the stool. Suppositories work quite quickly and should be given 30 minutes before breakfast or supper to take advantage of the gastrocolic reflex. Suppositories, when used regularly for several weeks, can cause a mild proctitis.
Enemas. A phosphate enema (Fleet) can help to evacuate the lower rectum. If stool is higher in the colon, a normal saline enema can be tried. If ineffective, an oil enema, delivered high up in the rectum and retained for about two or three hours, if possible, will soften stool; if expelled, it can be followed by a cleansing enema.
ManualDisimpaction. Impaction is the result of incomplete evacuation over time. The most common symptoms are rectal discomfort, rectal fullness, and tenesmus. There can be associated overflow incontinence of small amounts of liquid stool. The fecal impaction can be removed in patients who are not too sick by softening the mass from above using a stool softener. If this is not advisable, a gentle rectal examination is performed, using a single finger lubricated with 5% lidocaine ointment. After a few minutes, another finger can be inserted, which allows for dilatation of the anal sphincter without causing too much pain. The fingers are then used to “slice up” the impacted fecal mass. Several cleansing enemas are administered after removal of the pieces of stool. High fluid intake is mandatory on the day of disimpaction.
Rarely patients will require intravenous diazepam before the procedure to assist relaxation. In some centres a mixture of 50% nitrous oxide and 50% oxygen (Entonox) is used by inhalation for analgesia during the procedure.
Proper assessment is the first step in the management of constipation. The patient should be asked about bowel habits and the use of laxatives.
Regular supervision of the laxative regimen by the physician and the nurse will be assisted by use of a recording form, where bowel movements, laxatives used, and other interventions can be noted daily. If the patient has not had a bowel movement for three days or more, the rectum should be examined for impaction. A plan should be developed by the physician in consultation with the attending nurse (Figure 1).
Constipation can be considered an iatrogenic complication. Indeed, constipation is one of the most frequent and distressing symptoms in cancer patients. Too frequently it becomes a major problem if the constipating potential of other drugs is not recognized. When anticipated, constipation can be easily managed by using a protocol, as suggested above. An appropriate recording form, especially when the patient is at home, will facilitate communication between the patient, nurse, and physician. It will assist in the successful prevention of constipation in