If the erection persists for more than 4 hours, experience pain and not due to continuous sexual stimulation or desire this condition is called priapism. In the normal condition sexual stimulation leads to increase in blood to flow into the penis which results in an erection.
After ejaculation or the stimulation is discontinued, the blood drains and the erection recedes. When priapism occurs, blood that is sent to fill the penis becomes trapped, causing the erection to remain without relief. This condition is painful if left untreated for a long time it can result in scarring inside the penis, and sometimes, permanent erectile dysfunction. Priapism can occur in any male, even newborns, but most commonly develops between the ages of 5 and 10 years and 20 and 50 years. Treatment includes applying ice packs, intracavernosal injections, cavernosal wash, aspirating blood from the penis etc. Occasionally surgery is necessary to restore proper blood flow and drainage.