Fistulas are abnormal communications between two epithelialized surfaces. The causes of enterocutaneous fistulas can be remembered using the mnemonic FRIEND: Foreign body, Radiation, Inflammation/Infection/Inflammatory bowel disease, Epithelialization, Neoplasm, and Distal obstruction. Fifteen to twenty-five percent of enterocutaneous fistulas arise spontaneously as in, for example, Crohn's disease or cancer.
1998, Scott Fisher, “Enterocutaneous Fistulas”, in Theodore J. Saclarides, Keith W. Millikan, editors, Common Surgical Diseases: An Algorithmic Approach to Problem Solving, page 164