The inability to control the passing of faeces may be due to psychological or psychiatric conditions, particularly in the elderly. A loss of inhibitions associated with a dementia (eg. Alzheimer disease) is a common cause, while psychiatric patients may use it as an attention-seeking device.
In children, behavioural disorders or emotional stress may be responsible.
Soiling may be due to damage to the brain (eg. a stroke, cerebral palsy) or the nerves supplying the muscle ring around the anus (eg. paraplegia, fractured pelvis).
In advanced pregnancy the pressure on the lower bowel from the growing baby may make control of faeces difficult. Damage to the anus from a difficult birth may be a temporary, or very rarely a permanent, cause of faecal incontinence. Surgery can be performed to control the problem in these cases.
A greatly dilated lower bowel (megacolon) may cause large amounts of hard faeces to collect just inside the anus, and remain for a long time, while watery faeces flows around the outside of this faecal mass in the bowel, to leak out through the anus.