Priapism is an erection of the penis that lasts for more than 4 hours without physical and mental stimulation. It develops when blood becomes trapped in the penis and is unable to drain. It is often painful. Priapism is relatively rare in general (<1 case per 100 000 people each year).
Most people who experience priapism recover completely if treated quickly. Treating priapism quickly reduces the risk of permanent problems getting and keeping erections.