Clinical Aspects of Priapism -[Abnormal Persistent Erection of the Penis]

Introduction

Priapism is defined as an abnormal persistent erection of the penis. It is an involuntary prolonged erection unrelated to sexual stimulation and unrelieved by ejaculation. As with many medical emergencies, the saying "time is tissue" holds true for priapism. This condition is a true urologic emergency, and early intervention allows the best chance for functional recovery.

Pathophysiology

Priapism is the result of persistent engorgement of the corpora cavernosa of the penis, originating from a disturbance in the mechanisms that control normal penile detumescence, depicted in the image below. In most cases, the ventral corpora spongiosum and glans penis remain flaccid.


Two types of priapism are generally described.
           ^Arterial high-flow priapism usually is secondary to a rupture of a cavernous artery and unregulated flow into the lacunar spaces. This rare type of priapism is usually not painful and results from penetrating penile trauma or a blunt perineal injury.
           ^Low-flow priapism is usually due to full and unremitting corporeal veno-occlusion where venous stasis and deoxygenated blood pools within the cavernous tissue. Prolonged veno-occlusive priapism results in fibrosis of the penis and a loss of the ability to achieve an erection. Significant changes at the cellular level are noted within 24 hours in veno-occlusive priapism, whereas arterial priapism is not associated with fibrotic change.

Frequency

United States

In one study, 38-42% of adult patients with sickle cell disease reported at least one episode of priapism.
 International
The overall incidence of priapism is 1.5 cases per 100,000 person-years, which increases to 2.9 cases per 100,000 person-years for men older than 40 years.

Mortality/Morbidity

• Priapism is painful at onset. Corporeal fibrosis due to persistent priapism can result in deep-tissue infections of the penis.
• The major chronic morbidity associated with all types of priapism is persistent erectile dysfunction and impotence.
• The duration of symptoms is the most important factor affecting outcome. A recent 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.

Race

No racial predilection exists. Sickle cell disease, which predisposes to the development of priapism, occurs more frequently in the African American population.

Sex

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

Age

• Priapism has been described at nearly all ages, from infancy through old age. A bimodal distribution between 5 and 10 years in children and 20-50 years in adults is noted. 

• Younger groups are more often associated with sickle cell disease, while older groups tend to be secondary to pharmacologic agents.

Clinical

History

Patients with priapism report a persistent erection. The symptoms depend on the type of priapism and the duration of engorgement.

• Low-flow, ischemic-type priapism is generally painful, although the pain may disappear with prolonged priapism.
• High-flow, nonischemic priapism is generally not painful. This type of priapism is associated with blunt or penetrating injury to the perineum. It may manifest in an episodic manner.
• Aspects of history are as follows:  
  • Erection: Duration of longer than 4 hours is consistent with priapism.
  • Duration of pain
  • Similar prior episodes
  • Genitourinary (GU) trauma
  • Medical history (eg, sickle cell disease [SCD]): Onset occurs during sleep, when relative oxygenation decreases.
  • Medication and/or recreational drug use, especially the antidepressant trazodone, intracavernosal injections of prostaglandin E1 used to treat impotence, and illicit cocaine injection into the penis
  • History of malignancy (prostate cancer)
  • Penile prosthesis: The permanent erection that occurs with some penile prostheses may mimic priapism.
  • Recent urologic surgery
• Aspects of history in high-flow priapism are as follows:
  • Not painful
  • May be sexually active
  • Straddle injury usually the initiating event
  • Chronic recurrent presentation
  • Generally not caused by medication
• Aspects of history of low-flow priapism are as follows:
  • Painful
  • Inactive sexually and without desire
  • No history of trauma
  • Usually presents to emergency department (ED) within hours
  • Associated with substance abuse or vasoactive penile injections
  • Rarely caused by leukemia, fat embolism, acute spinal cord injury, or (extremely rare) cancer metastases to the corporeal bodies
    

Physical

• Presence of priapism should be confirmed by the finding of an erect or semierect penis. The ventral glans and corpus spongiosum are rarely rigid.
• Carefully examine for evidence of trauma or unreported injection sites to the genital region.
• Examine the patient for evidence of an underlying condition that may predispose to priapism.
• Piesis sign - Perineal compression with thumb in young children causes prompt detumescence in high-flow priapism.

Causes

• Medications
  • Only rare case reports of selective cyclic guanosine monophosphate (cGMP) inhibitors such as sildenafil have been associated with priapism. In fact, several case reports suggest sildenafil as a means to treat priapism and may be able to prevent full-blown episodes from occurring in patients with sickle cell disease.
  • Some patients may use injectable medications to induce an erection. In these patients, excessive use may produce priapism. Examples of agents used to induce an erection include papaverine, phentolamine, and prostaglandin E1.
  • Many psychotropic medications such as chlorpromazine, trazodone, quetiapine, and thioridazine have been associated with priapism. The newer agents are not immune to this complication. Priapism has been described with citalopram, a selective serotonin reuptake inhibitor.
  • Rebound hypercoagulable states with anticoagulants such as heparin and warfarin have been associated. Hydralazine, metoclopramide, omeprazole, hydroxyzine, prazosin, tamoxifen, and androstenedione for athletic performance enhancement.
  • Cocaine, marijuana, and ethanol abuse - The complication has been described in patients using ecstasy.
• Thromboembolic
  • Sickle cell disease and thalassemia
  • Leukemia and multiple myeloma
• Trauma (pelvic, genital, or perineal)
• Neoplastic (may be primary or metastatic)
• Neurologic
  • Spinal cord injury and anesthesia
  • Cauda equina compression syndrome
• Infection
  • Recent infection with Mycoplasma pneumoniae (Mechanism is thought to be a hypercoagulable state induced by the infection.)
  • Malaria
• Other causes
  • Fabry disease (rare association, occasionally noted to be priapism of the high-flow type) and amyloidosis
  • Carbon monoxide poisoning, black widow spider bites, and vigorous sexual exercise have been implicated.
  • Rarely, cases of idiopathic priapism have also been reported.

Sources:
http://www.netdoctor.co.uk/sexandrelationships/priapism.htm
http://emedicine.medscape.com/article/777603-overview
http://emedicine.medscape.com/article/437237-overview