Fistulas can be caused by several disease conditions or may be surgically created for therapeutic reasons in some cases. Some of the main conditions that can cause fistulas include:
Diseases of the bowel such as Crohn's disease can cause fistulas that may occur between the stomach and the intestines (entero-enteral fistula), between the intestines and the skin (enterocutaneous fistula), and anorectal fistulas, for example.
A person with severe hidradenitis suppurativa is likely to develop fistulas.
After gallbladder surgery, a biliary fistula may form between the biliary tract and the intestines or liver.
Radiation therapy applied to the genital area may lead to a fistula forming between the vagina and the bladder (vesicovaginal fistula). Obstructed and complicated labour may also give rise to a vesicovaginal or rectovaginal (between the rectum and vagina) fistula.
Head injuries may lead to a perilymph fistula or tear in the thin membranes of the middle and inner ear, creating an abnormal passage between the middle and inner ear. Injuries may also cause an arteriovenous fistula or fistula between an artery and a vein.
A lacrimal fistula affects the lacrimal ducts between the eyes and the nose.
A mastoid fistula forms over the side of the head behind the ear and can occur as a complication of otitis media.
A pulmonary arteriovenous fistula refers to a fistula that forms between an artery and a lung vein. Tracheoesophageal fistulas can also form between the wind pipe and the food pipe.
A salivary fistula describes an abnormal connection between a salivary gland duct and an opening in the mouth through which saliva is discharged.
Gastrojejunal fistulas can form between the stomach and the jejunum or middle part of the small intestine as a result of gastric ulcer.
Examples of congenital fistulas include fistula of the salivary gland, portal vein-hepatic artery fistula and fistula of the rectum and anus.
Reviewed by Sally Robertson, BSc