Priapism is a persistent and often painful erection that lasts for several hours.
The erection is not necessarily related to sexual stimulation or excitement, and does not subside after ejaculation (when semen is released from the penis).
The erection lasts longer than four hours. During this time, the shaft of the penis is rigid and inflexible, but the head of the penis (the glans) is usually soft. The penis is also usually painful or tender.
Priapism is a medical emergency – you should seek immediate medical assistance if you think you have it.
If it's not treated within 24 hours, your penis may be permanently damaged and you may have difficulties getting an erection in the future.
Types of priapism
There are three main types of priapism:
- low blood flow (ischaemic) priapism – the most common and serious type of priapism usually caused by lack of blood flow through the penis
- high blood flow (non-ischaemic) priapism – much rarer and usually caused by an injury to the genitals or perineum (the area in between the genitals and anus)
- recurrent or intermittant (stuttering) priapism - similar to ischaemic priapism but characterised by recurrent, long-lasting, painful erections that ease after 2-3 hours.
What causes priapism?
Priapism happens when blood that fills the spongy tissue of the penis during an erection is unable to flow out of the penis.
Anything that affects the nervous system or blood flow (or both) can trigger priapism. It can occur, for example, as a complication of sickle cell anaemia (a genetic blood disorder), or as a rare side effect of several other medications, such as antipsychotic agents or anticoagulants.
Read more about the causes of priapism.
If you have ischaemic (low blood flow) priapism, the sooner you receive treatment, the more effective it is likely to be.
Aspiration, a procedure that uses a needle and syringe to drain the blood out of your penis, is usually recommended.
If this does not work, medication may be injected into your penis which squeezes the blood vessels and helps push the blood out of your penis.
Surgery is only recommended if other treatments have failed. There are a number of different surgical procedures available, depending on the type of priapism you have.
Read more about how priapism is treated.
Discovering the cause
Blood tests may be needed to find out what is causing your priapism. These can help detect underlying problems with your blood, such as anaemia (a lack of red blood cells), or unusually high numbers of white blood cells.
Blood tests can also measure the levels of oxygen and carbon dioxide in your blood. Unusually low levels of oxygen and high levels of carbon dioxide would strongly suggest ischaemic priapism (low blood flow).
If non-ischaemic priapism is suspected due to an injury to your genitals or the surrounding area, you may be referred for a scan, such as an ultrasound scan. This will help identify problems with the blood vessels in your penis.
How common is priapism?
Priapism is rare in the general population, but fairly common in certain high-risk groups, such as males with sickle cell anaemia, and men taking medication for erectile dysfunction.
About one in four boys and nine in 10 men with sickle cell anaemia will experience at least one episode of priapism.
The risk of priapism as a side effect of treatment for erectile dysfunction is low and thought to be around one in 1,000.