<prompt> Rectal incontinence is due to involvement ofExternal anal sphincterInternal anal sphincterIschiococcygeusPubococcygeus  <response>: Advanced tumours may cause faecal incontinence by invasion of the sphincters and, in women, anterior extension may result in anovaginal fistulation.Incontinence, especially if there has been inadveent damage to the underlying internal sphincter. Although uncommon, this is obviously a very serious problem that is difficult to treat Ref: Bailey Love;s Sho Practice of Surgery,E25,Page-1258,1269 