Fistula. Historical artwork of a patient suffering from a fistula, an abnormal channel connecting parts of the body. In this case, it is an enterocutaneous fistula, connecting an internal organ to the skin. Illustration from a 15th century German edition of the writings of Galen. Galen was an Ancient Greek physician. Although he lived in the 2nd century AD, his teachings were respected in Europe until the 16th century.