When a connection forms between organs.

A fistula is when a connection forms between organs. One example is an infected tunnel from the anus to the skin, called an anal fistula. Another is an opening from the vagina into the bladder or another nearby organ, called a vaginal fistula. A fistula also can develop between an artery and a vein or in the intestines.

Symptoms of a fistula depends on the location. Symptoms of anal fistulas may include swelling, bleeding or drainage, and a painful opening in the skin. Symptoms of vaginal fistulas may include having urine, gas or stool pass through the vagina, pain, and frequent urinary tract or vaginal infections.

Most fistulas need surgical repair.