An abscess is a collection of pus in any localised space in the body. An anal abscess is one that develops in the tissues around the anus. This is sometimes caused by bacteria lodging in small glands in this area which then becomes infected. As the pus and subsequent pressure increases, the pain increases. Small abscesses can be drained by making an opening through the skin under local anaesthetic. Larger abscesses may need to be drained under general anaesthetic. Hospital admission is needed for such a procedure. Antibiotics may be used to control the spread of the infection, but antibiotics alone will not cure an abscess. Drainage of the pus is always necessary.

An anal fistual is an abnormal track (“tunnel”) between the internal lining of the anus and the skin outside the anus and can sometimes excrete pus. Surgery is needed to cure a fistula.