Differences in anal sphincter function and clinical presentation in patients with pelvic floor descent.

Perineal descent is found in patients with idiopathic fecal incontinence and patients with the descending perineum syndrome, who have little or no incontinence but present with a symptom pattern that suggests obstructed defecation. To investigate why patients with perineal descent present in different ways, manometric, radiologic, and neurophysiologic studies were performed in 53 patients with radiologically proven perineal descent and 34 control subjects. Thirty-two patients exhibited incontinence to rectally infused saline, while 21 patients presented with obstructed defecation but exhibited no incontinence. Both patient groups exhibited similar degrees of perineal descent on straining and increases in the motor unit potential duration of the external anal sphincter, indicative of neuropathic damage. Both groups had an abnormal rectoanal inhibitory reflex and an abnormal anorectal angle, though the latter was more obtuse in idiopathic fecal incontinence. However, although patients with incontinence had lower maximum basal and maximum squeeze sphincter pressures than normal, these values were normal in patients with obstructed defecation. Our findings suggest that perineal descent and neuropathy are not necessarily associated with incontinence as long as sphincter pressures remain normal.