Constipation

Published on 23/06/2015 by admin

Filed under Emergency Medicine

Last modified 23/06/2015

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7.13 Constipation

Pathophysiology

The rectum and anal canal have two tasks, to store faeces temporarily and to evacuate at a socially convenient time. The distending rectum evokes a wave of contraction with inhibition of the smooth muscle tone of the internal anal sphincter, resulting in a sensation of the urge to defecate. An urgent desire to defecate occurs as the stool stretches the sensitive zone of the upper anal canal. This urge is overcome by the voluntary contraction of the external sphincter and the levator ani muscles. Eventually the rectum habituates to the stimulus of the enlarging faecal mass and the urge to defecate subsides. With time this retentive pattern can become automatic.

It is understandable, therefore, that the child who is afraid to use the non-private, wet, smelly school lavatory, and allows his rectum occasionally to overcome the external sphincter, as he is relieved to arrive home, albeit with ‘poo in the pants’ – is really a normal variant rather than true encopresis.

There is a wide variation of physiology and normal development as can be seen in the age range of successful potty training. To produce a stool at will is one of the child’s first major achievements and most gain satisfaction from framing their success in a pot. If too much persuasion is provided, especially if full control has never been attained, the child’s profound disappointments are compounded by disapproval and hostility from the parents. Like most adults, most children seek solitude to defecate.