CONSTIPATION

Constipation means hard or infrequent feces. Constipation is undoubtedly one of the biggest problems for terminally ill patients. In a study of 200 patients admitted to a hospice 75% needed rectal measures (suppository, enema or manual evacuation) within the first week.

A hospice patient wrote a journal about her experiences in facing up to terminal illness. She wrote:

“If I mention constipation to most people, even friends, who are concerned about the tumor, they grin. . . I understand their amusement but I feel anger, too. For most terminally ill people, constipation is one of the most dreadful aspects of their lives. Analgesics freeze your pain, but they freeze up your bowels, too. I want people and doctors to understand the plight of the terminally ill who have so much to cope with, never mind this most basic of functions. Feeling very, very bunged up is so terrible.”

Causes of constipation:

• Low fiber diet

• Dehydration

• Drugs (opioids, anti-cholinergics, diuretics)

• Reduced defecation (weakness, confusion, pain)

• Depression

• Hypercalcemia

«  The commonest cause of constipation in cancer patients is opioids used without adequate doses of laxatives.

History needs to be detailed:

• Bowels last moved?

• Time before that?

• Motions hard, soft or liquid?

• Normal amount each time?

• Laxatives: how much, how often?

• Suppositories?

• Do you ever have to chip it out with your finger?

An important question is whether laxatives were started at the same time as opioids (or only later once constipation had occurred). Alternating constipation and diarrhea is usually due to the incorrect use of laxatives (intermittently instead of regularly) in a patient on opioid drugs.

On examination the abdomen may appear distended. Fecal masses (which indent on steady pressure) may be palpable in the descending colon (left iliac fossa). The constipated colon is usually moderately tender. In severe constipation the cecum can become distended with pain and tenderness in the right iliac fossa. It is sometimes difficult to decide whether abdominal masses are fecal (which move after treatment to clear the bowel) or neoplastic (which do not). Rectal examination may reveal hard impacted feces, a malignant stenosis, or an empty ballooned rectum (suggesting impaction higher up). Note any painful hemorrhoids or fissures.

X-ray is not usually necessary, but will show the colon loaded with fecal matter with no gaseous distention or fluid levels.

Important points:

1. Opioids constipate from the moment they are started, and high doses of laxatives need to be started simultaneously with any opioid analgesic.

2. Patients can still get severely constipated on inadequate doses of laxatives.

3. Patients who are not eating continue to produce waste in the bowel (gut secretions, desquamation, bacterial matter), continue to need to pass motions, and can still get impacted with feces.

4. It is an important working rule that the bowel should move at least every three days. If a patient goes longer than three days without a bowel movement, he or she should have a rectal examination, and a suppository or microenema should be considered. 

5. An empty ballooned rectum on rectal examination can be a sign of impaction with feces higher up in the colon. If the history is suggestive of constipation, the patient should have high enemas.

6. Constipation can cause anorexia, nausea, vomiting, abdominal pain, rectal pain, confusion, abdominal distention and sometimes even obstruction. Pain tends to be colicky. (“It comes in waves.”) It can radiate to chest, back and upper legs. (see Tenesmus)

7. Severe constipation can present as spurious diarrhea with small amounts of liquid feces leaking past the fecal mass.

8. Prescribe both a fecal softener and a stimulant laxative (Peri-Colace or Senokot-S, for example) whenever starting an opioid analgesic.

9. If maximum doses of laxatives are still ineffective, add oral magnesium sulfate 5mls to 10mls in the morning (taken with plenty of water), which flushes through the small bowel and is a very effective fecal softener.

10. If the patient has fecal masses palpable throughout the colon, he will need either oil retention enemas, or soap and water enemas to soften the feces, followed by phosphate enemas to stimulate the bowel.

11. Constipation often causes painful anal fissures. Bulk-forming agents can be useful and analgesic suppositories can be used before defecation.

12. If rectal examination reveals a large clay-like lump in the rectum that is too big to pass through the anal sphincter, this needs to be removed manually. This is painful, and the patient should be given morphine and diazepam prior to the procedure.

Impacted feces can be suspected from:

• The history (although the patient may be too embarrassed to give the full story)

• Prolonged constipation (5 to 20 days)

• Patient’s chipping out feces with a finger

• Small liquid feces (spurious diarrhea)

• Fecal leak or incontinence

• Pain (colic or tenesmus, or both)

Note on bowel physiology:

The small bowel daily pours out several liters of digestive secretions which are mostly reabsorbed. The ileum probably acts as a reservoir releasing small bowel contents into the colon through the ileo-cecal valve.

The colon absorbs water (about 1.5 liters per day). Semiliquid motions in the cecum gradually become harder as they move round the colon. The hardness of the motions depends upon water content. Feces contain about 50ml to 150ml of water per day. Transit time through the colon normally varies from a few hours to several days.

Both longtitudinal and ring contractions (haustrations) occur, and contents can be propelled in either direction. Opioid drugs increase ring contractions, thus lengthening fecal transit time.

The rectum acts as a reservoir for the storage of feces until evacuation is socially convenient. In fact, sigmoidoscopy shows that the rectum is often empty. The acute angle at the rectosigmoid junction acts as a valve, and the rectum is usually empty until there is active propulsion of feces from the sigmoid colon. The awareness of rectal filling is due to stretch receptors which initiate the emptying reflex.

A bowel movement normally consists of the contents of the rectum only, but, with strong laxatives, can be from the whole descending colon. The evacuation of a large movement requires less effort than a small one. Sitting on a commode requires less effort for an evacuation than sitting on a bedpan.

The internal anal sphincter is responsible for fine control of flatus or liquid feces. Rectal distention causes reflex transient relaxation of the internal anal sphincter. This allows the fecal bolus to contact the sensory area of the anus which distinguishes flatus from feces. (Damage to this region of the anus prevents the distinction between flatus and feces.) Further relaxation of the internal anal sphincter will then allow passage of flatus.

Following internal sphincterotomy continence of solid feces is still possible. The anorectal angle (maintained by the pubo-rectalis muscle) acts as a flap-valve preventing the passage of solid feces. The pubo-rectalis muscle relaxes during defecation.

The external anal sphincter can only contract continuously for about 60 seconds. It serves as an emergency measure to control incontinence. (see Laxatives)

The author and publisher have taken precautions to ensure that the information in this book is error-free. However, readers must be guided by their own personal and professional standards of good practice in evaluating and applying recommendations made herein. The contents of this book represent the views and experience of the author, and not necessarily those of the publisher.