FIA full form in medical term is Fistula in Ano, also known as an anal fistula. It is a hole between the internal part of the anus and the outside skin around the anus. Basically, it is the muscular opening at the point of the digestive tract where stool passes out of the body. Anal fistulas result from the onset of infection in the anal gland. And this infection can lead to an abscess that drains on its own and is surgically drained through the skin next to the anus.
Signs and symptoms of FIA can include discharge of stool or blood, pus from the opening of the tunnel, an opening on the skin around the anus, an inflamed, red area around the tunnel opening, ache in the anus & rectus when passing or sitting stool, fever, etc.
If the infection starts in the anal gland, it means that the development of an anal fistula has begun. These glands can become infected, or the glands can become clogged, causing an abscess. Surgery is almost always necessary to repair an anal fistula. The aim of surgery is to get rid of the fistula and protect the anal sphincter muscles, which can lead to incontinence.