Priapism (//) is a potentially painful medical condition, in which the erect penis does not return to its flaccid state, despite the absence of both physical and psychological stimulation, within four hours. There are two types of priapism: low-flow and high-flow; 80% to 90% of clinically presented priapisms are low flow disorders. Low-flow involves the blood not adequately returning to the body from the organ. High-flow involves a short-circuit of the vascular system partway along the organ. Treatment is different for each type. Priapism is considered a medical emergency, which should receive proper treatment by a qualified medical practitioner. Early treatment can be beneficial for a functional recovery.
Not all sources give four hours as the guideline for priapism occurring: "The duration time of a normal erection before it is classifiable as priapism is still controversial. Ongoing penile erections for more than 6 hours can be classified as priapism..."