Priapism

Priapism is defined as a prolonged erection developing in the absence of sexual stimulation and unrelieved by ejaculation. The duration of the erection considered to represent priapism is generally over 4. The condition obtains its name from the Greek god of fertility and lust Priapus.

Priapism can be classified into 2 main types; ischemic (synonymous with venocclusive, low-flow) and non-ischemic(arterial, high-flow). 

Ischemic priapism results from the failure of blood to drain from the erect penis. This can be thought of as a compartment syndrome of the penis. Over time, the lack of oxygenated blood flow to the penis results in irreversible structural changes with in the erectile tissue leading to tissue death and scarring. It is believed that even after 6-8 hours of ischemic priapism irreversible damage begins to occur.

Non-ischemic priapism results form unregulated inflow of blood into the erect penis. This differs form non-ischemic priapism in that the blood is oxygenated and does not get trapped with in the erectile tissue.

Proper categorization is essential, as the management of the two conditions is very different, particularly as ischemic priapism is a urologic emergency while non-ischemic is not.

Risks & Causes

Ischemic priapism (venocclusive, low-flow priapism) results from failure of blood to drain from the erectile bodies due to prolonged blockage of the draining veins. Ischemic priapism may result from prolonged relaxation of the erectile smooth muscle (generally due to drugs or toxins) or from sludging of blood (due to blood disorders) with subsequent prevention of venous drainage.

The potential causes of ischemic priapism include: penile injection therapy (used by men for erectile dysfunction), medications (including drugs for depression, psychiatric conditions, certain blood pressure medications, cocaine), toxins (spider venom, rabies), intravenous nutrition (called TPN) and blood disorders (including sickle cell disease, thallasemia, leukemia and multiple myeloma).  

Erectogenic medications are the most common cause of ischemic priapism in the adult United States population. Sickle cell disease is the commonest cause of priapism in the pediatric and adolescent populations. 40% of all men with Sickle Cell Disease experience at least one episode of ischemic priapism in their lifetime. There are a group of men with ischemic priapism who have no obvious causes and by definition have idiopathic priapism. This latter condition is often a recurrent problem. Stuttering priapism refers to males who have recurrent episodes of ischemic priapism.

Non-ischemic priapism (arterial, high flow) results from unregulated inflow of arterial blood into the erectile bodies (corpora cavernosa) secondary to an abnormal communication (fistula) between the main erection (cavernous) artery and the erectile body itself. This generally results from blunt or penetrating trauma to the perineum or penis. The most common forms of trauma are from bicycling injuries and direct kicks to the area such as those that occur during the practice of martial arts.

Symptoms and Evaluation

Erections lasting longer than 4-6 hours are associated with permanent erection problems. It has been estimated that priapism of 24 hours duration is associated with an approximately 50% incidence of permanent erectile dysfunction. When such a patient presents to their physician's office or the emergency department, a urologist should be notified immediately and urgent steps should be taken to initiate evaluation and treatment. The most important step in evaluating and treating a man with priapism is differentiating between ischemic and non-ischemic priapism.

The patient with ischemic priapism typically complains of a painful erection, which is fully rigid. Men with non-ischemic priapism have an erection that is usually less than fully rigid and painless. The latter patient routinely gives a history of some form of penile or perineal trauma.

A comprehensive history and physical exam should be performed. A history should focus on possible causes including the use of prescription, erectogenic, or recreational drugs. Formal laboratory testing routinely includes peripheral blood tests, urine toxicology screen, and a blood gas analysis of the penile blood (corporal blood). Analysis of penile blood gas is paramount in differentiating between ischemic and non-ischemic priapism. Additionally, if the initial evaluation of a man with ischemic priapism is negative a workup for hematologic malignancies (leukemia, multiple myeloma) or blood dyscrasias (sickle cell disease, thalassemia and glucose-6-phosphate dehydrogenase) may be undertaken. Occasionally, a penile doppler ultrasound may be used to assess for the presence or absence of penile blood flow and to locate the possible location of a fistula.

Treatment Options

Treatment of ischemic vs non-ischemic priapism differs considerably.

In the case of ischemic priapism, time is of the essence. Initial conservative measures of exercise, application of ice packs, ejaculation, or oral medication (ie pseudoephedrine) may be considered but evidence to support their success is limited. 

In the office or emergency room setting, upon identification of ischemic priapism, treatment is aimed at controlling pain and returning the penis to the flaccid state. The longer the duration of ischemic priapism, the more difficult it becomes to treat. Even in cases of significantly prolonged erections management should still proceed in a stepwise manner.

The first step in treating ischemic priapism involves draining the old stagnant blood from the penis and injecting a vasoconstrictive medication directly into the erectile tissue (corpora cavernosum) of the penis. The administration of a vasoconstrictive agent will result in resolution of the priapism in the majority of cases.

Occasionally cases may require a surgical procedure to reverse the prolonged erection. Surgical procedures are aimed at shunting the trapped blood within the corpora cavernosum to other sites including the glans penis (head of the penis), corpora spongiosum (vascular urethral tissue), or dorsal or saphenous veins.

Generally, success rates for shunt procedures range from 50-75% with a 25-50% rate of long-term erectile dysfunction.

In refractory cases where shunting is not successful, implantation of a penile prosthesis is a possibility.  

Non-ischemic priapism is not considered a urologic emergency. 

Because of this some patients may opt for observation and may defer management. If a fistula is present the standard management is arterial embolization. This is done by an Interventional Radiologist. The aim of this procedure is to occlude the arteriovenous fistula and return the penis to its normal state. Erectile dysfunction is a known side effect of this with an estimated post-procedure incidence of 20-25%.

The Sexual Medicine Program in the Department Of Urology of Weill Cornell Medicine at The New York Presbyterian Hospital has extensive experience in the diagnosis and management of this condition.