Priapism

Updated: Nov 28, 2016
  • Author: Hosam S Al-Qudah, MD; Chief Editor: Edward David Kim, MD, FACS  more...
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Overview

Practice Essentials

Priapism (see the image below) is an involuntary, prolonged erection unrelated to sexual stimulation and unrelieved by ejaculation. This condition is a true urologic emergency, and early intervention allows the best chance for functional recovery.

Priapism. Corporeal relaxation causes external pre Priapism. Corporeal relaxation causes external pressure on the emissary veins exiting the tunica albuginea, trapping blood in the penis and causing erection.

Signs and symptoms

Low-flow priapism

This condition is generally painful, although the pain may disappear with prolonged priapism. Characteristics of low-flow priapism include the following:

  • Rigid erection
  • Ischemic corpora: As indicated by dark blood upon corporeal aspiration
  • No evidence of trauma

High-flow priapism

This type of priapism is generally not painful and may manifest in an episodic manner. Characteristics of high-flow priapism include the following:

  • Adequate arterial flow
  • Well-oxygenated corpora
  • Evidence of trauma: Blunt or penetrating injury to the penis or perineum (straddle injury is usually the initiating event)

See Clinical Presentation for more detail.

Diagnosis

Lab studies

  • Complete blood count (CBC): To determine if the patient has anemia, leukocytosis, or thrombocytosis
  • Plasma thromboplastin or activated partial thromboplastin time: Priapism may require surgical intervention if medical treatment fails
  • Blood type and hold: Exchange transfusion may be necessary to treat underlying sickle cell disease (SCD), a cause of low-flow priapism
  • Penile blood gas (PBG) measurement: Allows differentiation between high- and low-flow priapism

Imaging studies

  • Penile duplex Doppler ultrasonography: To help identify and locate fistulas in patients with high-flow priapism
  • Pelvic angiography: To help confirm the fistula’s location
  • Chest radiography or computed tomography (CT) scanning: Used if the patient’s history is consistent with a malignant or metastatic condition

Other

Perform an electrocardiogram (ECG) if the patient is older than 55 years, has a history of cardiac disease, or is a possible surgical candidate.

See Workup for more detail.

Management

Low-flow priapism

Treatment should progress in a stepwise fashion, involving supportive care and the identification and treatment of reversible causes. Intracavernosal phenylephrine (Neo-Synephrine) is the drug of choice and first-line treatment for low-flow priapism because it has almost pure alpha-agonist effects and minimal beta activity.

Following pharmacologic therapy, the next step in the treatment of low-flow priapism is aspiration of the corpora cavernosa followed by saline irrigation and, if necessary, injection of an alpha-adrenergic agonist (eg, phenylephrine).

If the aforementioned interventions are unsuccessful, a diluted solution of phenylephrine may be used for irrigation. If medical treatment fails, the condition warrants surgical intervention.

Key steps in the management of low-flow priapism caused by SCD include the following:

  • Oxygenation
  • Analgesics (eg, intravenous morphine)
  • Hydration
  • Alkalization
  • Exchange transfusions
  • Emergent surgical decompression: Advocated by most experts when conservative management fails

High-flow priapism

Once the causative fistula has been located, it can be obliterated by selective arterial embolization, using an autologous blood clot, gelatin sponge, microcoils, or chemicals. [1, 2, 3]

Surgery

A transglanular-to–corpus cavernosal scalpel or needle-core biopsy (Ebbehoj or Winter technique) is the first reasonable approach to refractory cases. A unilateral shunt is often effective. Bilateral shunts are used only if necessary (usually apparent after 10 min).

Prolonged low-flow priapism results in a variable degree of cavernosal fibrosis and a subsequent loss of penile length. Immediate insertion of a penile prosthesis in patients with prolonged low-flow priapism is simple and maintains penile length.

See Treatment and Medication for more detail.

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Background

Priapism is defined as an abnormal persistent erection of the penis. It is usually painful and it is unrelated to sexual stimulation and unrelieved by ejaculation. Priapism is frequently idiopathic in etiology but it is a known complication of a number of important medical conditions and pharmacologic agents (see Etiology). [4]

Priapism must be defined as either low-flow (ischemic) or high-flow (nonischemic), because the causes and treatments for these 2 types are different. Low-flow priapism, which is by far the most common type, results from failure of the detumescence mechanism, whereas high-flow priapism results from uncontrolled arterial inflow, often through fistulas caused by genitourinary trauma.

Treatment of low-flow priapism should progress in a stepwise fashion, starting with therapeutic aspiration, with or without irrigation, or intracavernous injection of a sympathomimetic agent. [5] Treatment of high-flow priapism focuses on identification and obliteration of fistulas.

Priapism is a true urologic emergency that may lead to permanent erectile dysfunction and penile necrosis if left untreated. Early intervention allows the best chance for functional recovery [4] ; as with many medical emergencies, the saying "time is tissue" holds true for priapism.

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Pathophysiology

The penis has 3 corporeal bodies: 2 corpora cavernosa and 1 corpus spongiosum. Erection is the result of smooth-muscle relaxation and increased arterial flow into the corpora cavernosa, causing engorgement and rigidity (see image below). In priapism, the corpus spongiosum and glans penis are typically not engorged.

Priapism. Corporeal relaxation causes external pre Priapism. Corporeal relaxation causes external pressure on the emissary veins exiting the tunica albuginea, trapping blood in the penis and causing erection.

Engorgement of the corpora cavernosa compresses the venous outflow tracts (ie, subtunical venules), trapping blood within the corpora cavernosa. The major neurotransmitter that controls erection is nitric oxide, which is secreted by the endothelium that lines the corpora cavernosa (see image below). These events occur in both normal and pathologic erections.

Priapism. Sexual stimulation causes the release of Priapism. Sexual stimulation causes the release of nitric oxide (NO) via stimulation of nonadrenergic noncholinergic neurons. NO-activated intracellular guanylate cyclase, converting guanosine triphosphate (GTP) to cyclic guanosine monophosphate (cGMP), causes relaxation of cavernosal arteries and increased penile blood flow, resulting in erection.

Pathophysiologically, priapism can be of either a low-flow (ischemic) or a high-flow (nonischemic) type. Low-flow priapism, which is by far the most common type, results from failure of venous outflow, whereas high-flow priapism results from uncontrolled arterial inflow. Clinically, differentiation of low-flow from high-flow priapism is critical, because treatment for each is different.

Low-flow priapism may be due to any of the following:

  • An excessive release of neurotransmitters
  • Blockage of draining venules (eg, mechanical interference in sickle cell crisis, leukemia, or excessive use of intravenous parenteral lipids)
  • Paralysis of the intrinsic detumescence mechanism
  • Prolonged relaxation of the intracavernous smooth muscles (most often caused by the use of exogenous smooth-muscle relaxants such as injectable intracavernosal prostaglandin E1)

Prolonged low-flow priapism leads to a painful ischemic state, which can cause fibrosis of the corporeal smooth muscle and cavernosal artery thrombosis. The degree of ischemia is a function of the number of emissary veins involved and the duration of occlusion. Light-microscopy studies conducted early on demonstrated that corporeal tissue becomes thickened, edematous, and fibrotic after days of priapism.

Further studies with electron microscopy have demonstrated trabecular interstitial edema after 12 hours of priapism and destruction of sinusoidal endothelium, exposure of the basement membrane, and thrombocyte adherence after 24 hours of priapism. At 48 hours, thrombi were evident in the sinusoidal spaces and smooth-muscle cell histopathologic findings varied from necrosis to fibroblast-like cell transformation. Priapism for longer than 24 hours is associated with the likelihood of permanent impotence.

High-flow priapism is the result of uncontrolled arterial inflow from a fistula between the cavernosal artery and the corpus cavernosum. This is generally secondary to blunt or penetrating injury to the penis or perineum causing rupture of a cavernous artery. It is usually not painful.

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Etiology

Priapism can be idiopathic or can be secondary to a variety of diseases, conditions, or medications. In the United States, the most common cause of priapism in the adult population involves agents used to treat erectile dysfunction. Internationally, most cases are idiopathic.

The most common cause of priapism in the pediatric population is sickle cell disease (SCD), which is responsible for 65% of cases. Leukemia, trauma, and idiopathic causes are the causes in 10% of patients. Pharmacologically induced priapism is the etiology in 5% of children. [6] Among the secondary causes of low-flow priapism are the following thromboembolic/hypercoagulable states:

  • Sickle cell anemia - One study found that, in unscreened children with SCD, priapism was the first presentation in 0.5% of cases [2]
  • Dialysis
  • Vasculitis
  • Fat embolism (from multiple long-bone fractures or intravenous infusion of lipids as part of total parenteral nutrition)

Neurologic diseases that can result in low-flow priapism include the following:

  • Spinal cord stenosis (ie, trauma to the medulla)
  • Autonomic neuropathy and cauda equina compression

Neoplastic disease (metastatic to the penis or obstructive to venous outflow) that can result in low-flow priapism include the following [7] :

  • Prostate cancer
  • Bladder cancer (highest risk)
  • Hematologic cancer (leukemia)
  • Melanoma

Pharmacologic causes of low-flow priapism include the following:

  • Intracavernosal agents - Papaverine, phentolamine, prostaglandin E1
  • Intraurethral pellets (ie, medicated urethral system for erection with intracavernosal prostaglandin E1)
  • Antihypertensives - Ganglion-blocking agents (eg, guanethidine), arterial vasodilators (eg, hydralazine), alpha-antagonists (eg, prazosin), calcium channel blockers
  • Psychotropics - Phenothiazine, butyrophenones (eg, haloperidol), perphenazine, trazodone, selective serotonin reuptake inhibitors (eg, fluoxetine, sertraline, citalopram) [3]
  • Anticoagulants - Heparin, warfarin (during rebound hypercoagulable states)
  • Recreational drugs - Cocaine [8]
  • Hormones - Gonadotropin-releasing hormone (GnRH), tamoxifen, testosterone, androstenedione for athletic performance enhancement
  • Herbal medicine - Ginkgo biloba with concurrent use of antipsychotic agents [9]
  • Miscellaneous agents - Metoclopramide, omeprazole, penile injection of cocaine, epidural infusion of morphine and bupivacaine [10]

Only rare case reports have associated phosphodiesterase-5 enzyme inhibitors such as sildenafil with priapism. In fact, several reports suggest sildenafil as a means to treat priapism and as a possible means of preventing full-blown episodes in patients with sickle cell disease. [11]

High-flow priapism may result from the following forms of genitourinary trauma:

  • Straddle injury
  • Intracavernous injections resulting in direct cavernosal artery injury

Rare causes of priapism include the following:

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Epidemiology

The frequency of priapism depends on the population being considered. The combination of intracavernosal agents and other drugs is the cause of approximately 21-80% of all adult priapism in the United States. Agents used to treat erectile dysfunction are common causes of adult priapism in the Western world. The overall rate of priapism in persons using these agents ranges from 0.05-6%. This group tends to be better educated about the risk of priapism; therefore, they seek treatment earlier.

In other population groups, sickle cell disease (SCD) and sickle cell trait predominate as the cause of adult priapism. The rate of priapism in adults with SCD is as high as 89%. In one study, 38-42% of adult patients with SCD reported at least one episode of priapism. Approximately two thirds of all pediatric patients who have priapism also have SCD. The rate of priapism among children with SCD is as high as 27%.

Internationally, the overall incidence of priapism is 1.5 cases per 100,000 person-years. In men older than 40 years, the incidence increases to 2.9 cases per 100,000 person-years. [13, 14]

Racial, sexual, and age-related differences in incidence

No racial predilection toward priapism exists. SCD, which predisposes to the development of priapism, mostly in the African-American population.

Priapism is almost exclusively a disease of males. Priapism of the clitoris has been reported but is extremely rare.

Priapism has been described at nearly all ages, from infancy through old age. A bimodal distribution has been noted, with peaks at 5-10 years and 20-50 years. [13] Cases in younger groups are more often associated with SCD, while those in older groups tend to be secondary to pharmacologic agents.

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Prognosis

Prognosis depends on the duration of symptoms, the patient's age, and the underlying pathology. The duration of symptoms is the single most important factor affecting outcome. A Scandinavian study reported that 92% of patients with priapism for less than 24 hours remained potent, while only 22% of patients with priapism that lasted longer than 7 days remained potent. [1]

All patients with priapism should be warned about the long-term risk of erectile dysfunction. The warning should also be clearly written on the discharge instruction sheet and documented in the chart. In general, vaso-occlusive priapism poses a higher risk of impotence than high-flow arterial priapism. Sickle cell disease appears to particularly increase risk: a study by Anele and Burnett found that patients with sickle cell disease who experience even minor episodes of recurrent ischemic priapism are five times more likely to develop erectile dysfunction compared with non–sickle cell patients. [15]

Patients who have experienced an episode of priapism are at risk for recurrence. A review of 3,372 men who presented to emergency departments with priapism found that within 1 year, 24% of patients were readmitted for recurrent priapism. Of those, 68% were readmitted within 60 days. [16]

Infection can complicate priapism. In cases resulting from trauma, the source of the infection may be the trauma itself, or it may be iatrogenic. Corporeal fibrosis due to persistent priapism can result in deep-tissue infections of the penis.

Deaths have been reported in patients with sickle cell disease presenting with priapism, but the cause of death usually is not related to the priapism per se but to complications from the underlying disease process.

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Patient Education

Education is the best way to avoid undesirable outcomes. Any high-risk patient, especially a man using oral or intracavernosal agents for the treatment of erectile dysfunction, must understand that a persistent erection is a possibility, and that prompt medical attention is critical if it should occur.

Patients presenting with priapism deserve special counseling, beginning with the first episode of priapism. Patients must understand that a poor outcome is possible despite appropriate and timely management.

For patient education resources, see the Men's Health Center, as well as Impotence/Erectile Dysfunction and Erectile Dysfunction FAQs.

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