Priapism symptoms vary depending on the type of priapism. The two main types of priapism are ischemic and nonischemic priapism.
An erection normally occurs in response to physical or psychological stimulation. This stimulation causes certain blood vessels and smooth muscles to relax and/or expand, increasing blood flow to spongy tissues in the penis. Consequently, the blood-filled penis becomes erect. After stimulation ends, the blood flows out and the penis returns to its nonrigid (flaccid) state.
Priapism occurs when some part of this system — the blood, blood vessels, smooth muscles or nerves — changes normal blood flow. Subsequently, the erection persists. While the underlying cause of priapism often can't be determined, several conditions are believed to play a role.
Ischemic priapism can cause serious complications. The blood trapped in the penis is deprived of oxygen. When an erection lasts for too long, this oxygen-poor blood can begin to damage or destroy tissues in the penis. As a result, untreated priapism can cause erectile dysfunction.