A fistula (plural: fistulas or fistulae) is an abnormal passage or opening between body organs or between the body and the outside. In terms of hypospadias or epispadias, it is an opening through which urine flows out at a location other than the urinary meatus (the hole where the urethra opens). Fistulas can appear anywhere along the shaft of the penis, on the lower abdominal wall, or even on the perineum behind the testicles. Fistulas can occur soon after surgery when a wound isn’t completely healed, and these can sometimes heal on their own. Alternatively, they can sometimes occur long after surgery. Persistent fistula usually results from a previous surgical wound breaking down under the force of urine wearing away at the tissue until a channel works its way to the outside of the skin and creates a leak. Besides making urination messy, these leaks also increase the possibility of infection. Some fistulas can remain for years without major complications but may eventually require surgical repair. If the leak is inside the penis and breaks into the spongy bodies involved in erection, that kind of leak is called “extravasation” and is very painful, requiring immediate medical attention.