Anus is the opening of the rectum through which stool passes out of the body. A muscular ring called "Anal Sphincter" keeps the anus closed. This sphincter is controlled subconsciously by the autonomic nervous system. The lower half of the anal canal has sensitive nerve endings. There are blood vessels under the lining, and in its mid portion there are numerous tiny, anal glands. Problems with the anus are common. They include haemorrhoids, abscesses, fissures or cracks and cancer. Treatments vary depending on the particular problem.

Disorders of the anus and rectum include:

•Anal Fissure: Anal fissure is a linear split or tear in the lining of the lower anal canal known as "Anoderm". Most anal fissures happen when a large, hard stool overstretches the anal opening and tears the delicate anoderm. Less often, anal fissures develop because of prolonged diarrhoea, inflammatory bowel disease or sexually transmitted diseases involving the anorectal area.

•Anal Abscess: An anal abscess is a swollen, painful collection of pus near the anus. Most anal abscesses are not related to other health problems and arise spontaneously, for reasons that are uncertain. They originate in a tiny anal gland, which enlarges to create a site of infection under the skin.

•Anal Fistula: Anal fistula is an abnormal narrow tunnel-like passageway, which is the remnant of an old anal abscess after it has drained. It connects the mid portion of the anal canal to the surface of the skin. After an anal abscess has drained, an anal fistula will develop at least half of the time.

•Haemorrhoids: Haemorrhoids do not ordinarily cause pain. Nevertheless, sometime the blood vessels in a small haemorrhoid at the edge of the anal orifice can clot off. This may be triggered by a period of constipation or diarrhoea. When thrombosis occurs, the external hemorrhoid becomes swollen, hard and painful, sometimes with bloody discharge.

•Anal Cancer: Anal cancer occurs in the anus, the end of the gastrointestinal tract. Anal cancer is a lump which is created by the abnormal and uncontrolled growth of cells in the anus. It is a rare disease which is more common in women than in men.

•Rectal Prolapse: Rectal prolapse occurs when part or the entire wall of the rectum slides out of place, sometimes sticking out of the anus. Rectal prolapse is an uncommon disease and primarily affects elderly people. The exact cause of this weakening is unknown; however, rectal prolapse is usually associated with the ageing, chronic constipation or diarrhoea.