Internal or external biliary drainage

A fistula (plural: fistulas or fistulae ; from Latin fistula, "tube, pipe") is an abnormal connection between two hollow spaces (technically, two epithelialized surfaces), such as blood vessels, intestines, or other hollow organs.Types of fistula can be described by their location. Anal fistulas connect between the anal canal and the perianal skin. [Source: Wikipedia ]