Most erection due to sexual stimulation never approach four to six hours. Priapism is not associated with sexual excitement, at least not initially, and the erection does not subside after ejaculation. Priapism can occur in all age groups, including newborns. Most cases of priapism are clustered between two age groups: between the ages of five to ten and twenty to fifty years. Priapism constitutes a true urologic emergency. Men often joke that they wish they could have a permanent erection, but in reality, men are extremely miserable when this actually happens. 

Children with priapism are typically those who have leukemia. In this situation, the white blood cells occlude, or block the outflow of blood from the penis causing priapism.

Children with sickle-cell disease can be afflicted with priapism. In this situation, the penis receives low oxygen, and therefore, the blood sickles and prevents outflow because of sludging.

Other rare causes of priapism in childhood include trauma, either to the penis or to the area underneath the penis known as the perineum. Additionally, spinal cord injuries can cause priapism. Extremely rare causes of priapism include drug side effects, but typically these drugs are not used in children.

In adults, priapism either has a known cause or an unknown cause, in which case it is idiopathic, or has no identifiable cause.

Typical causes in adults include sickle-cell disease, which accounts for almost a third of all cases. It is reported that 42 percent of all sickle-cell adults and 64 percent of all sickle-cell children will eventually develop priapism.

The most common cause of priapism is pharmacological injection therapy, which far out shadows all currently known causes.

Drug-related priapism includes those drug used to treat psychotic type illness, including Thorazine and chlorpromazine. Other more uncommon drugs include those used to treat high-blood pressure such as prazosin.

Rare causes may also be related to cancers that can infiltrate the penis and prevent the outflow of blood.

Once priapism and its source have been identified, it is categorized into two major types:

Low-flow priapism or ischemic, which means that little or no blood flow is getting to the penis and this lack can cause damage

High-flow priapism, which is the result of trauma to the penis. In this case, there is actually a large amount of blood flow to the penis.

The first step after the careful history and physical examination is to obtain a blood-gas measurement of the blood from the penis. This provides a clue as to how long the condition has been present and how much damage has occurred. A small needle is placed in the penis; some of the blood is aspirated and then sent to a lab for determination. This will also help categorize whether the cause of the priapism is low flow or high flow.

It is also important to get an idea of how long the erections normally last and if there has been associated trauma. Following a medical history, a careful physical examination should reveal a hard penis with a soft glans.

It is also important to check the rectum and the abdomen for evidence of unusual cancers and the other causes of priapism.

If a patient gets treatment within four to six hours, the erection can almost always be reduced with medication. The first step for the patient with priapism of less than four hours duration is the use of decongestant medication. These medications include drugs such as pseudoephedrine and terbutaline, which may act to decrease blood flow to the penis and is very successful in early cases.

If the erection does not respond, then aspiration is done. The longer the condition goes without treatment, the worse the prognosis.

Once the blood-gas measurement has been performed and priapism is determined to be ischemic, or that in fact the penis has very poor blood flow, then the old blood is evaluated by aspirating through a small needle placed directly in a corporal body. This is done by first cleansing the area, then infiltrating the local anesthetic over the skin of the penis and placing the needle. 50-to 150cc of old blood is withdrawn. This allows the engorged penis to become flaccid.

which doctor to consult?
You can consult a urologist.