Problem 4.1

Consider the variable significance of using bowel movement frequency as an objective measurement of constipation in the examples below.

Example 1: A 40-year-old man with a high traumatic spinal cord transection passed loose stool several times each day, leading to continual fecal incontinence. Rectal examination revealed a hard mass of impacted stool with leakage of liquid feces past a lax anal sphincter.

Example 2: A 68-year-old woman complained of constipation associated with her opioid analgesic therapy. However, she opened her bowels at least once, often two or three times, each day. Further questioning elicited that her bowel movements consisted of small fecal pellets "like rabbit droppings", and that she rarely achieved the sense of a complete evacuation.

Example 3: 73% of a sample of hospice patients reported a bowel movement in the last 48 hours. But in this group the bowel movement had been associated with rectal intervention, i.e. the administration of either an enema or a suppository, in almost 40% of cases.

Question 4.1.1

What do you conclude about the significance of bowel movement frequency as an objective measurement of constipation?

When making a diagnosis of constipation, simply counting the number of occasions that stool is passed is the most objective and accurate measure.

When making a diagnosis of constipation, it is appropriate to count stool passed after the use of an enema or suppository.

When making a diagnosis of constipation, uncritically counting bowel movement frequency may be misleading.

An accurate measure of bowel movement frequency depends not just on how it is defined, but on how the information is collected. Asking patients at clinic appointments to recall their recent stool history is significantly less accurate than either in-patient observation or the provision of a diary to be contemporaneously filled in by the patient while at home (Manning et al., 1976).

An alternative to the simple calculation of bowel movement frequency is the concept of stool free interval (Agra et al., 1998). This is defined as the number of 72-hour periods during which defecation does not occur, based on an assessment that this is a length of time beyond which it is both abnormal and undesirable for a patient to go without a bowel action. It was used in a comparative trial of two laxatives to provide an indication of "laxative failure", and may indeed be a more clinically relevant measure than bowel frequency per se.

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