Priapism is a persistent and usually painful erection that lasts for several hours.

Priapism is not necessarily related to sexual stimulation or desire, and it does not subside after ejaculation (when semen is released from the penis).

The most common cause of priapism is when blood cannot leave the penis.

Priapism commonly arises as:

• a complication of sickle cell anaemia (a genetic blood disorder where the red blood cells develop abnormally)
• a side-effect of medications such as sildenafil (sold under the brand name Viagra) that are used to treat men who have difficulty obtaining or maintaining an erection (erectile dysfunction)

Priapism should be regarded as a medical emergency. If treatment is not started within 24 hours, the penis may be permanently damaged, which may affect the ability to get an erection in the future.

How common is priapism?

Priapism is rare in the general population but relatively common in certain high-risk groups, i.e. boys or men with sickle cell anaemia, and men who are taking medication to treat erectile dysfunction.

It is estimated that 1 in 4 children with sickle cell anaemia and 9 out of 10 adults 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 thought to be low at around 1 in a 1,000.

Outlook

The outlook for priapism that is treated promptly is good. There are a number of treatment options, such as medication or draining blood out of the penis, which can often manage symptoms successfully.

However, the longer that treatment for priapism is delayed, the worse the outcome usually is, and the greater a person’s chance of developing erectile dysfunction.

The symptoms of priapism include:

• a persistent and unwanted erection that lasts longer than four hours
• the shaft of the penis is fully rigid and inflexible, but the glans (head) of the penis is usually soft
• the penis is usually painful or tender

The persistent erection that is associated with priapism is unrelated to feelings of sexual excitement or stimulation.

When to seek medical advice

If you think that you have priapism, you may require emergency medical treatment. Go immediately to your nearest accident and emergency (A&E) department. 

To better understand the potential causes of priapism, it is useful to understand how erections occur.

Erections

When a man becomes sexually aroused, his nervous system releases a chemical called nitric oxide. Nitric oxide relaxes and widens the walls of the arteries that supply blood to the penis. This increases the flow of blood into the spongy tissue of the penis, causing it to expand and harden into an erection.

Once the feelings of sexual arousal have passed, the arteries in the penis should get smaller, pushing the excess blood out of the penis and returning it to its normal floppy state.

Therefore, anything that affects either the nervous system or blood flow (or both) can trigger the symptoms of priapism.

Common causes

The most common causes of priapism are discussed below.

Sickle cell anaemia

Sickle cell anaemia is a genetic (inherited) blood disorder where red blood cells develop abnormally. Red blood cells carry oxygen from the lungs to the rest of the body. The cells are usually round and flexible, allowing them to move easily around the body.

However, in people with sickle cell anaemia, the shape and texture of red blood cells can change. They become hard and sticky and are shaped like sickles (crescents). Occasionally, the hardened blood cells can become trapped in the blood vessels of the penis, leading to the symptoms of ischaemic priapism.

See the A-Z topic about sickle cell anaemia for more information about the condition.

Medications

A number of medications can occasionally disrupt the normal workings of the nerves that are responsible for helping to trigger an erection by widening the arteries in the penis. The nerves essentially ‘forget’ to narrow the arteries after the feelings of sexual arousal have passed. This leads to the symptoms of ischaemic priapism.

Types of medication that have been associated with ischaemic priapism include:

• oral medications (tablets or capsules) that are used to treat erectile dysfunction, such as sildenafil (Viagra), tadalafil (Cialis) or vardenafil (Levitra)
• medications for erectile dysfunction, which are injected directly into the penis, such as alprostadil
• blood-thinning medication, such as warfarin or heparin
• some types of antidepressants, such as fluoxetine (Prozac) and bupropion
• some medications that are used to treat high blood pressure (hypertension), such as calcium channel blockers

In addition, some recreational drugs have been linked to priapism. They include:

• cocaine
• ecstasy
• methamphetamine (crystal meth)
• cannabis

Less common causes

Less common causes of priapism include:

• thalassaemia – a blood condition that is similar to sickle cell anaemia
• cancers of the blood, such as chronic leukaemia and multiple myeloma
• cancers that have spread from nearby tissue or organs, such as prostate cancer or bladder cancer, and are disrupting the blood flow inside the penis
• spinal cord injury
• blood clots 

Fabry disease – a rare, genetic condition that affects the metabolism (the process that converts food into energy)  

A stepwise approach is usually recommended for the treatment of priapism.

This means that doctors will first try using non-invasive treatments, such as aspiration (see below) and will only ‘step up’ to more invasive treatments, such as surgery, if the initial treatments are unsuccessful.

Aspiration

Aspiration is usually the first treatment option that is recommended for priapism.

First, your penis will be numbed with a local anaesthetic. A small needle and syringe will then be used to drain some blood from your penis.

In some cases, ‘washing out’ the blood vessels with sterile water to clear away any debris may be recommended. This is known as irrigation.

Aspiration and irrigation can usually help to relieve painful symptoms and may result in your erection subsiding. However, you may need a number of treatment sessions before your symptoms start to respond.

Sympathomimetic injections

If your symptoms fail to respond to aspiration, the next step is to inject a type of medication known as a sympathomimetic directly into the tissue of your penis.

Sympathomimetics work by squeezing the blood vessels in your penis, helping to push blood out of your penis while also preventing any more blood from being pumped in.

A type of sympathomimetic called phenylephrine is usually recommended because it has a lower risk of causing side effects compared with other types of sympathomimetics.

Side effects of phenylephrine include:

• an increase in blood pressure, which can make you feel dizzy and lightheaded
• headache
• rapid heartbeat (tachycardia)
• a noticeably irregular heartbeat

If you have a health condition that could be made worse by an increase in blood pressure, such as heart disease, it is likely that you will be given regular blood pressure and electrocardiogram (ECG) checks. An ECG is a test that measures the electrical activity of your heart.

Surgery

Surgery may be recommended if your symptoms fail to respond to either aspiration or sympathomimetic injections.

Surgery for priapism usually involves implanting a small device called a shunt into your penis. The shunt can be used to re-route the blood supply out of your penis.

A small number of people who have surgery for priapism experience erectile dysfunction after surgery. However, it is difficult to estimate the exact risk of this occurring because there are other factors that may be related to erectile dysfunction, such as priapism itself, which confuse the issue.

If you experience erectile dysfunction after having surgery for priapism, you may need to have further surgery to treat your erectile dysfunction, such as having artificial implants placed inside your penis.

See the A-Z page about treating erectile dysfunction for more information.