1. A tract leading from a hollow viscera organ to the external surface: The abdominal fistula that had to be performed on Simon was necessary as a result of an injury he had had.
2. An abnormal passage or tract leading from an abdominal organ to the external surface of the abdomen: In a colostomy, an abdominal fistula extending from the bowel to an opening on the surface of the abdomen is surgically created.

A colostomy is a medical operation in which part of the colon is removed and a hole is made in the stomach through which solid waste can leave the body.

1. An abnormal duct or passage resulting from injury, disease, or a congenital disorder that connects an abscess, cavity, or hollow organ to the body surface or to another hollow organ.
2. An abnormal passage leading from an abscess or hollow organ to the body surface or from one hollow organ to another and permitting passage of fluids or secretions.

Frequently designated according to the organs or parts with which it communicates, as anovaginal, brochocutaneous, hepatopleural, pulmonoperitoneal, rectovaginal, urethrovaginal, etc. Such passages are frequently created experimentally for the purpose of obtaining body secretions for physiological study.

A tube extending from the urinary bladder through the abdominal wall and opening externally onto the skin of the abdomen: The vesicoabdominal fistula is an abnormal duct or passage, caused by an injury, disease, or congenital disorder, and connects an abscess, cavity, or a hollow organ to the body surface or to another hollow organ.