Stylized diagram showing action of the puborectalis sling, the looping of the puborectalis muscle around the bowel. This pulls the bowel forwards, and forms the anorectal angle, the angle between the anal canal and the rectum. A-puborectalis, B-rectum, C-level of anorectal ring and anorectal angle, D-anal canal, E-anal verge, F-representation of internal and external anal sphincters, G-coccyx & sacrum, H-pubic symphysis, I-Ischium, J-pubic bone. Structure of anal canal The mechanisms and factors contributing to normal continence are multiple and inter-related. The puborectalis sling, forming the anorectal angle (see diagram), is responsible for gross continence of solid stool. The IAS is an involuntary muscle, contributing about 55% of the resting anal pressure. Together with the hemorrhoidal vascular cushions, the IAS maintains continence of flatus and liquid during rest. The EAS is a voluntary muscle, doubling the pressure in the anal canal during contraction, which is possible for a short time. The rectoanal inhibitory reflex (RAIR) is an involuntary IAS relaxation in response to rectal distension, allowing some rectal contents to descend into the anal canal where it is brought into contact with specialized sensory mucosa to detect consistency. The rectoanal excitatory reflex (RAER) is an initial, semi-voluntary contraction of the EAS and puborectalis which in turn prevents incontinence following the RAIR. Other factors include the specialized anti-peristaltic function of the last part of the sigmoid colon, which keeps the rectum empty most of the time, sensation in the lining of the rectum and the anal canal to detect when there is stool present, its consistency and quantity, and the presence of normal rectoanal reflexes and defecation cycle which completely evacuates stool from the rectum and anal canal. Problems affecting any of these mechanisms and factors may be involved in the cause.
Fecal incontinence
Open defecation
Coital incontinence
Urinary incontinence
Rectal pain
Constipation
Steatorrhea
Dysuria