What is soiling?

Causes and Symptoms

Some authors use the term encopresis to mean the passage of an entire bowel movement into the underwear and reserve the term soiling for the seepage of small amounts of semisolid feces. The term encopresis was derived by combining the Greek terms enourein (meaning “to pass urine”) and kopros (meaning “feces”) to form a term that is analogous to enuresis, which describes bed-wetting.

The term functional megacolon is used to describe the rectal dilatation characteristic of this disorder and to distinguish it from congenital aganglionic megacolon, or Hirschsprung disease. In this much rarer and far more serious disorder, the failure of development of part of the autonomic nervous system in the intestines results in a failure of propagation of colonic contractions (peristalsis), which in turn causes distention of the colon. In general, children with Hirschsprung disease rarely, if ever, have fecal soiling.

The term psychogenic megacolon suggests that fecal soiling is part of a constellation of behavioral disorders. Although behavioral abnormalities occur in children with soiling, most recent studies indicate that they are no more common in soiling children than in normal children and that they tend to be a response to the soiling.

Soiling is caused by chronic constipation in school-aged children. About 1.5 percent of second graders experience fecal soiling, which is six times more common in boys than in girls. Constipation and its associated complications are common symptoms in young children, accounting for 25 percent of visits to pediatric gastroenterologists. Constipation becomes less frequent with age and usually resolves as puberty approaches. The basis of constipation is slow motility of the colon, usually present in several family members, which allows excessive water absorption from the stool, causing hard stools that are difficult to expel.

Typically, a child afflicted by fecal soiling will begin having frequent episodes between ages five and seven. Parents may mystified by this symptom and bring the child to the physician because of the impending forced socialization of beginning school. Upon questioning, a history of infrequent, large-caliber bowel movements, sometimes too large to be accommodated by the plumbing, is often obtained. The size of these bowel movements is evidence of distention of the rectum as a result of long-standing constipation, which is the basis of this disorder.

The rectum normally functions as a sensory organ, responding to rectal distention by alerting the brain that a bowel movement is imminent and that appropriate arrangements should be made. Persistent rectal distention (megacolon) as a result of chronic constipation results in decreased sensitivity of the rectum to acute rectal distention. Children in these cases frequently admit that they do not sense an impending bowel movement before or during episodes of soiling, and studies with distention of balloons passed into the rectum bear out this lack of sensitivity to acute rectal distention. Much more air has to be pumped into a rectal balloon before a soiling child can sense it than is the case for a normal child.

In soiling children, the rectum functions as a storage organ, and does so rather poorly. Storage of fecal material in the rectum bypasses the normal mechanisms of continence and leaves the external anal sphincter, a circular muscle holding the anus closed, as the sole mechanism of continence. The external anal sphincter is under voluntary control. To keep it closed, the child must keep all the muscles of the pelvic floor contracted. Any distraction or relaxation of the pelvic floor muscles to urinate can lead to leakage of semisolid stool.

Treatment and Therapy

Since soiling results from rectal distention (megacolon), effective therapy should empty the rectum (catharsis) and keep it empty (maintenance), allowing reversal of the rectal distention and return of normal rectal sensitivity. Several regimens are available, with most using a saline cathartic agent—that is, one that works by pulling water out of the circulation and into the colon, thus flushing out the contents of the colon. Hypertonic sodium phosphate enemas are frequently recommended but carry the risk of dehydration and electrolyte disturbances. In addition, afflicted children are very sensitive to anorectal manipulation. For these reasons, using an oral cathartic is preferable. Such agents include citrate of magnesia, sodium phosphate, and colonic lavage solutions designed for cleaning the colon before an endoscopic examination.

Stool softeners are usually prescribed as maintenance therapy to keep the water content of the stool high. Preparations such as mineral oil, milk of magnesia, lactulose, and sorbitol are generally safe and effective. Stool softeners are safe for long-term use and, unlike stimulant laxatives such as senna and phenolphthalein, do not cause dependence.

The goal of therapy is resolution of the fecal soiling, since this is the only symptom that causes the child to suffer. Constipation is usually benign and self-limiting, and regularity of bowel movements should be seen not as a goal but rather as an indication that the rectal distention is reversing. Even with no treatment, soiling resolves spontaneously around the time of puberty as the underlying constipation resolves.

This therapy is usually very successful if applied consistently, and no child should have to suffer the humiliation of fecal soiling. Many studies indicate that an effort by the child and his or her family to keep track of the episodes of soiling, passage of bowel movements, and dosage of medicine is required for the best outcome. Even if the soiling is resolved, however, the tendency toward constipation remains until puberty, and if the problem falls on the family’s list of priorities as it resolves, the chance of recurrence is high.

Perspective and Prospects

The occurrence of abnormalities of anorectal function has prompted the use of biofeedback training to resolve those abnormalities. Recent studies show comparable results with less expensive and more easily accessible therapy, such as an initial catharsis followed by maintenance with stool softeners, but biofeedback and behavioral therapy can still be beneficial for patients who do not respond to standard first-line treatment.

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