The anus is closed by the two sphincters, internal and external. If the muscles are weak and cannot ensure an efficient sealing, this is callied a sphincter atony with different causes: 

-          multiple pregnancy

-          chronic constipation

-          prior surgery

Which are the characteristic symptoms ?

In the less severe cases, difficulties in controlling the flatulence process, but this may reach also the solid stool, up to permanent incontinence.

Treatment

If the sphincter muscle is not completely affected , the daily exercises of contraction the pelvis platform and electro stimulation may help. In severe cases it is necessary the chirurgical intervention.