Priapism

What happens in priapism

A normal erection happens when arteries bring extra blood into the spongy erectile chambers (corpora cavernosa) while outflow veins are compressed. Afterward, the arteries narrow and blood drains.

In ischemic priapism, blood cannot drain. It becomes stagnant, loses its oxygen, turns acidic and starts to clot. The erectile tissue begins to suffer damage within about 4 to 6 hours, and muscle cells die over the following day. Scarring then prevents normal erections. In non-ischemic priapism, a torn artery pours blood into the penis continuously, but the blood is well oxygenated, so damage is much less likely.

Types of priapism

Causes

Ischemic priapism

• Injections or other treatments for erectile dysfunction: alprostadil, papaverine and phentolamine injected into the penis are the most common cause in adults. Tablets such as sildenafil and tadalafil rarely cause priapism on their own.
• Sickle cell disease: the leading cause in children; many men with sickle cell disease have priapism at some point.
• Medicines: trazodone, some antipsychotics (such as chlorpromazine, risperidone, quetiapine), some antidepressants, alpha-blockers, and blood thinners in some cases.
• Recreational drugs and alcohol: cocaine, methamphetamine, cannabis and heavy alcohol use.
• Blood disorders and cancers: leukemia, especially with a very high white cell count; thalassemia.
• Nerve conditions: spinal cord injury.
• Testosterone therapy, total parenteral nutrition, and scorpion or spider venom (rare).
• Unknown: in a significant share of adults no cause is found.

Non-ischemic priapism

Usually from a straddle injury (falling onto a bike crossbar), a kick or a blow to the perineum or penis, which tears an artery inside the penis. The erection may appear hours to days after the injury.

Diagnosis

Doctors move quickly. They ask how long the erection has lasted, whether it hurts, recent medicines, injections, drug use, injuries, and whether you have sickle cell disease. Tests include:

• Blood gas from the penis: a small needle sample. Dark, oxygen-poor blood confirms ischemic priapism; bright red, well-oxygenated blood suggests the high-flow type.
• Color Doppler ultrasound, which shows whether blood is flowing and can find a torn artery.
• Blood count and, where relevant, sickle cell testing and a toxicology screen.

Treatment

Ischemic priapism

Treatment should start as soon as possible:

1. Numbing: a local nerve block at the base of the penis.
2. Aspiration: a needle drains the trapped dark blood, often with saline flushing.
3. Phenylephrine injection: a medicine that narrows the blood vessels, given in repeated small doses with blood pressure and heart monitoring.
4. Surgical shunt: if these fail, a surgeon creates a channel to let blood drain from the erectile chambers into the head of the penis or a vein.
5. Early penile implant: for priapism lasting many days, when erectile tissue is already destroyed, an implant may be placed early, before scarring shortens the penis.

For men with sickle cell disease, aspiration and phenylephrine are first-line, the same as for other men. Hydration, oxygen and transfusion may be added but should not delay treatment of the penis.

Non-ischemic priapism

Because the tissue is not starved of oxygen, it often resolves on its own over weeks. Ice and pressure may help. If it persists, a radiologist can block the torn artery from inside (selective embolization).

Stuttering priapism

The goal is preventing episodes. Options include treating the underlying cause, optimizing sickle cell care, and preventive medicines prescribed by a urologist. Some men are taught to inject phenylephrine themselves for episodes that do not settle.

What you can try while getting to the ER

Light exercise such as walking up stairs, urinating, or a cold shower sometimes ends an early episode. Do not let these delay medical care once the erection has lasted 4 hours. Do not apply ice directly to the skin, and do not take extra erectile dysfunction medicine.

Complications and outlook

The main complication of ischemic priapism is permanent erectile dysfunction. The outcome depends heavily on time:

• Treated within a few hours: erections usually recover.
• Lasting beyond about 24 hours: erectile dysfunction is common.
• Lasting 36 hours or more: most men lose natural erections, and penile shortening and scarring are likely.

If erections do not return, a penile prosthesis is an effective treatment. Non-ischemic priapism rarely causes lasting problems.

Prevention

• Use erectile dysfunction injections exactly as taught; start low and do not add extra doses.
• Know the 4-hour rule if you take trazodone, antipsychotics or other medicines linked to priapism.
• Avoid cocaine and other stimulant drugs.
• People with sickle cell disease should discuss a priapism action plan with their hematologist and urologist.

Frequently asked questions

Why is an erection lasting more than 4 hours dangerous?

After about 4 hours, the trapped blood in the penis runs out of oxygen and becomes acidic, which starts to damage the erectile tissue. The longer it lasts, the more likely permanent scarring and erectile dysfunction become. Fast treatment in the ER prevents most of this damage.

Can Viagra cause priapism?

Rarely. Sildenafil and similar tablets very seldom cause priapism when used alone at prescribed doses. The risk is higher when they are combined with injections, recreational drugs or certain medicines, or used by men with sickle cell disease. Seek care for any erection lasting 4 hours.

Can trazodone cause priapism?

Yes. Trazodone, an antidepressant often used for sleep, is one of the best-known medicine causes of priapism. It is uncommon, but anyone taking it should know to seek emergency care for an erection lasting 4 hours or a painful prolonged erection. Do not stop it suddenly without advice.

How do doctors get rid of priapism?

For the common ischemic type, a doctor numbs the penis, drains the trapped blood with a needle and injects a medicine called phenylephrine to tighten the blood vessels. If that does not work, a minor surgical procedure creates a drainage channel. High-flow priapism may be treated by blocking a torn artery.

Does priapism happen in children?

Yes, mostly in children with sickle cell disease, where it can begin before puberty. Leukemia and injury are other causes. Families of boys with sickle cell disease should learn the warning signs and seek urgent care for a painful erection that lasts more than 1 to 2 hours despite simple measures.