Erections can’t happen without proper blood flow. Normally when a man gets aroused, the arteries in his pelvis and penis relax and expand, bringing more blood to spongy tissues in the penis. At the same time, the valves in the veins close, trapping blood in the area and causing an erection. After the excitement ends, the vein valves open, the blood flows out, and the penis returns to its usual state.
Blood flow that’s not normal can cause priapism, an erection that lasts for more than 4 hours, is usually painful, and may happen without sexual arousal.
It can happen to males of all ages, including newborns.
There are two main types:
Low-flow or ischemic priapism: This type happens when blood gets trapped in the erection chambers. Most of the time, there’s no clear cause, but it may affect men with sickle-cell disease, leukemia (cancer of the blood), or malaria. If you don’t get treatment right away, it can lead to scarring and permanent erectile dysfunction (ED).
High-flow or non-ischemic priapism: This type is more rare than low-flow and is usually less painful. It often happens when an injury to the penis or the area between the scrotum and anus, called the perineum, ruptures an artery, which prevents blood in the penis from moving normally.