INTRODUCTION — The term "priapism" is derived from Priapus, the Greek god of fertility, gardening, and lust who is depicted with a massive phallus . Priapism is defined as a persistent erection of the penis or clitoris that is not associated with sexual stimulation or desire. The focus of this topic will be penile priapism. Studies differ on the length of time of erection used to define priapism, but most describe priapism as an erection lasting at least four hours. Priapism has been found to adversely affect quality of life, sexual function, and physical wellness .
Priapism is relatively rare but can occur in all age groups and is particularly common in patients with sickle cell disease. It is generally classified as ischemic or nonischemic. Ischemic priapism is a urologic emergency, whereas nonischemic priapism is usually self-limited.
The epidemiology, pathophysiology, diagnosis, and management of priapism will be discussed here. Issues related to priapism in sickle cell disease are addressed separately. (See "Priapism and erectile dysfunction in sickle cell disease".)
EPIDEMIOLOGY — In a study of emergency department visits between 2006 and 2009 in the United States, there were 32,462 visits for priapism, which corresponded to an incidence of 0.73 per 100,000 men per year . Clitoral priapism occurs less commonly .
Priapism can be seen in any age group. However, there is a bimodal peak distribution of incidence, occurring between 5 and 10 years in children and 20 to 50 years in adults .
PATHOPHYSIOLOGY — Penile erection begins with the relaxation of the smooth muscle of cavernosal arteries and tissue, leading to increased nonischemic inflow and decreased venous outflow (figure 1). As intracorporal pressure rises to mean arterial pressure, the inflow of blood ceases. Priapism generally involves the corpora cavernosa only, although occasionally affects the corpus spongiosum and the glans penis .
The underlying cause is not identified in most cases (primary or idiopathic priapism), but, in others, certain medications and disease states have been implicated (secondary priapism) (table 1). The most common cause in adults is medication use, especially with intracavernosal injections, accounting for 25 percent of cases . The most commonly associated condition in children is sickle cell disease.
There are two main types of priapism: ischemic and nonischemic. Ischemic priapism is much more common in sickle cell disease than nonischemic priapism, which is only seen in this setting with prior trauma or instrumentation of the penis.
Ischemic priapism — Ischemic priapism (also known as low-flow, anoxic, or veno-occlusive priapism) is the more common form.
Ischemic priapism is prolonged erection with failure of detumescence related to impaired relaxation and paralysis of cavernosal smooth muscle [8-10]. This results in a compartment syndrome, with increasing hypoxia and acidosis in the cavernous tissue .
Nitric oxide has been proposed as an important mediator in the development of priapism. Nitric oxide serves a fundamental role in the erectile response by mediating relaxation of smooth muscle . Understanding of the nitric oxide pathway led to the development and use of phosphodiesterase type 5 (PDE5) inhibitors in the treatment of erectile dysfunction. PDE5 inhibitors inhibit breakdown of cyclic guanosine monophosphate (cGMP) and potentiate nitric oxide-mediated penile smooth muscle relaxation for erectile function. A regulatory defect in the nitric oxide pathway has been proposed to account for some patients with priapism, particularly those with sickle cell disease . (See "Priapism and erectile dysfunction in sickle cell disease", section on 'Pathophysiology and classification'.)
Prolonged erection in ischemic priapism leads to structural damage of erectile tissue, related in part to tissue edema [14,15]. Tissue damage is believed to occur at the microscopic level as early as four to six hours after onset of erection [11,16]. Significant structural changes in the cavernous smooth muscle can be seen after 12 hours’ duration of priapism . Irreversible damage can be identified after 24 to 48 hours of priapism, including necrosis of cavernosal smooth muscle and endothelial cells, fibroblast proliferation, and ultimately fibrosis of corpus cavernosa.
The duration of priapism is strongly associated with incidence of subsequent erectile dysfunction. Ninety percent of men with an ischemic priapism lasting 24 hours do not regain the ability to have sexual intercourse . Early relief of priapism with return of normal flaccidity is not likely to be associated with long-term sequelae.
Recurrent priapism — Recurrent priapism (also known as “stuttering priapism”) is an uncommon condition usually occurring in men with sickle cell disease. Recurrent priapism is a form of ischemic priapism, which starts off with erections of short duration. The onset is usually during sleep with persistence upon waking. These episodes become longer in duration and more frequent, eventually leading to a full-blown ischemic priapism event. (See "Priapism and erectile dysfunction in sickle cell disease".)
The pathophysiology of this type of priapism is not fully understood. A mechanism based on dysregulation of nitric oxide and PDE5 in the corporal smooth muscle has been proposed [13,18-21].
Nonischemic priapism — Nonischemic priapism (also known as high-flow, arterial, or congenital priapism) occurs less commonly than ischemic priapism and is usually the result of a fistula between the cavernosal artery and corpus cavernosum.
Nonischemic priapism is commonly related to penile or perineal trauma, often from needle injury of the cavernosal artery. Blunt trauma, which can occur from bicycling, may also damage the cavernosal artery, leading to increased flow through the corpora cavernosa . The onset of post-traumatic, nonischemic priapism can occur up to 72 hours after injury.
Congenital arterial malformations may also cause of nonischemic priapism.
Nonischemic priapism does not represent an emergency situation, as the cavernous blood is well-oxygenated. Nonischemic priapism will resolve spontaneously in up to 62 percent of untreated cases .
History and physical examination — The following information should be obtained on history from a patient with suspected priapism:
●Duration of erection
●Use of recreational drugs
●History of hematologic disease, especially sickle cell disease
●Penile or perineal trauma
●Presence and severity of pain
In ischemic priapism, the patient typically presents with a painful and rigid erection. A history of sickle cell disease or other hematologic abnormality also suggests an ischemic etiology. In rare cases, ischemic priapism can present with penile gangrene, usually resulting in necrosis of the entire penis .
Nonischemic priapism is associated with a history of trauma (often related to needle injection or urologic procedures) and an erection that is less painful and usually less than fully rigid.
The genitalia, perineum, and abdomen should be carefully examined for penile rigidity and signs of trauma or malignancy. With priapism, penile examination reveals engorged corpora cavernosa, but, in contrast to normal erections, the corpus spongiosum and glans penis can remain flaccid.
Determining whether priapism is ischemic or nonischemic may be possible on the basis of history and physical examination alone, but additional studies are helpful in most patients. Cavernosal blood gas analysis is the most useful means for distinguishing the type of priapism and should be performed when the type of priapism is uncertain.
Cavernosal blood gas analysis — Blood can be aspirated from the corpora cavernosum for a blood gas analysis to differentiate between ischemic and nonischemic priapism. A small caliber needle can be used (ie, 19 to 21 gauge) for easier control and to minimize trauma. Blood is aspirated from one side of the corpus cavernosum, and 3 to 5 mL is typically withdrawn.
The color of the aspirated blood sample is black in patients with ischemic priapism. Corporal blood gas analysis will show hypoxemia, hypercarbia, and acidemia. By contrast, the color of aspirated blood is red in patients with nonischemic priapism. Blood gas analysis will show normal levels of oxygen, carbon dioxide, and pH (table 2).
Other blood studies — Appropriate blood tests should be performed if there is clinical concern for a hemoglobinopathy or other blood dyscrasia. A complete blood count may reveal anemia, leukemia, or platelet abnormalities. Reticulocyte count and hemoglobin analysis are indicated when sickle cell disease or trait, thalassemia major, or leukemia is suspected. In sickle cell disease, the peripheral blood smear may identify sickled red cells or Howell-Jolly bodies, reflecting hyposplenia. (See "Diagnosis of sickle cell disorders".)
Toxicology — Urine toxicology and psychoactive drug testing may be performed if drug use is known or suspected (table 1). Usual doses of several classes of psychoactive drugs including antidepressants may cause priapism.
Doppler ultrasonography — Doppler ultrasonography may be performed as an alternative to cavernosal blood gas to differentiate between ischemic and nonischemic types of priapism. Minimal or absent blood flow with Doppler ultrasonography is observed in the cavernosal arteries in ischemic priapism, whereas normal to high blood flow is observed in nonischemic priapism . Doppler ultrasound can also detect cavernous arterial fistula, pseudoaneurysm, or other anatomic abnormalities.
DIAGNOSIS — The diagnosis of priapism is made on the basis of visual inspection of the penis, which reveals an erection that has been present for more than two to four hours in the absence of sexual excitation . Duration of erection may be shorter for patients with recurrent priapism. (See 'Recurrent priapism' above.)
The type of priapism, ischemic versus nonischemic, may be suspected on the basis of history and physical examination and can be confirmed by cavernous blood gas analysis and/or Doppler ultrasonography. Determining the type is particularly important since delayed diagnosis of ischemic priapism can lead to irreversible damage of the penile tissue and erectile dysfunction. (See 'Pathophysiology' above.)
MANAGEMENT — An algorithm for the management of priapism has been developed by the American Urological Association (AUA) and is shown with modifications (algorithm 1). Urology consultation is recommended. The safety and efficacy of different treatments for are not well established. Most evidence is derived from case reports or case series, as there are no randomized controlled trials and a paucity of evidence-based guidelines. Oral analgesics, including opioids if necessary, should be given to control pain.
Management of priapism in individuals with sickle cell disease is discussed separately. (See "Priapism and erectile dysfunction in sickle cell disease", section on 'Ischemic priapism: Acute management'.)
Ischemic priapism — Ischemic priapism requires rapid detumescence to avoid long-term sequelae, and urgent urologic consultation is recommended. Although primarily managed by urologists, emergency medicine clinicians may be the first-line providers and should be capable of attempting management of straightforward priapism. Those providing emergency medical care in low-resource areas should know how to utilize interdisciplinary collaboration with urologists and be familiar with techniques of aspiration, irrigation, phenylephrine injection, and T shunts .
Medical therapy — We treat patients with ischemic priapism of less than four hours’ duration with an intracavernosal injection of a sympathomimetic drug (eg, phenylephrine). After four hours’ duration, aspiration, with or without irrigation, combined with an intracavernosal injection of a sympathomimetic drug is considered to be the optimal treatment.
Sympathomimetics induce contraction of the cavernous smooth muscle and thus permit venous outflow. In one review, resolution of priapism was reported in 24 to 36 percent in studies treating patients with aspiration alone with or without irrigation and in 43 to 81 percent in studies treating with intracavernosal sympathomimetic medication with or without irrigation . The risk of post-priapism erectile dysfunction was also lower with sympathomimetic use. In another study, 86 percent of patients had successful detumescence with the use of intracavernous high-dose phenylephrine in the treatment of ischemic priapism over a five-year period at a single institution .
Phenylephrine, a pure alpha-adrenergic agonist, is considered the sympathomimetic of choice for ischemic priapism by the AUA . Phenylephrine has minimal risk of cardiovascular side effects compared with other sympathomimetic medications such as epinephrine, norepinephrine, and ephedrine. Although trial data are lacking, several small observational studies demonstrate prompt resolution of priapism with phenylephrine intracavernosal injection [29-32].
The toxicity of sympathomimetics include alpha adrenergic-mediated hypertensive effects and beta adrenergic-mediated inotropic and chronotropic effects. Side effects include acute hypertension, headache, and cardiac arrhythmia. Blood pressure monitoring is advised for all patients, and cardiac monitoring is recommended for patients with a history of cardiovascular disease.
Using a non-heparinized 19 gauge butterfly needle, approximately 5 mL of blood should be aspirated to decompress the corpora. Phenylephrine should then be injected into one side of the corpus cavernosum. In adults, phenylephrine should be diluted with normal saline to provide a final concentration of approximately 100 to 500 mcg per mL. One mL intracavernous injections of the freshly diluted phenylephrine solution are administered every three to five minutes until resolution or up until one hour before deciding whether the treatment will be successful . Lower concentrations and smaller volumes are appropriate for use in children and those with severe cardiovascular disease. It may be necessary to repeat aspiration and phenylephrine injections over several hours to achieve detumescence.
Surgical therapy — If patients do not respond to repeated cavernous aspiration and alpha-agonist therapy, shunt surgery is the next treatment option. A surgical fistula is created between the corpus cavernosum and the corpus spongiosum, glans penis, or one of the penile veins. Several observational studies have shown some efficacy in relieving ischemic priapism, with limited preservation of erectile function [33-36]. Some patients requiring multiple surgical procedures. Implantation of a penile prosthesis at the time of fistula surgery has been suggested for patients with late presentation (≥72 hours) because the prognosis for sexual function is poor [37,38].
Implantation of penile prosthesis in acute priapism — Penile prosthesis implantation in acute priapism has been used as a traditional treatment in patients who have developed erectile dysfunction after prolonged priapism attacks but can also be used as an initial treatment in ischemic priapism . Immediate penile prosthesis insertion is considered to prevent fibrosis of corpora cavernosum smooth muscle, penile shortening, and curvature in cases of prolonged refractory priapism [38-40]. Gadolinium-enhanced high-definition magnetic resonance imaging (MRI) of the penis is highly sensitive in detecting necrosis of the cavernosal smooth muscle and corporal bodies and can be useful in determining whether to utilize acute penile prosthesis implantation [39,40].
Recurrent priapism — Episodes of recurrent priapism should be treated as ischemic priapism events. (See 'Ischemic priapism' above.)
Patients with sickle cell disease or other hematologic disorders may benefit from additional therapies to prevent future episodes; these are discussed separately. (See "Priapism and erectile dysfunction in sickle cell disease".)
Nonischemic priapism — Nonischemic priapism is not an urgent condition and may resolve spontaneously after several hours to a few days. A management algorithm is available (algorithm 1).
Once ischemic priapism has been ruled out, observation alone is appropriate for initial management of nonischemic priapism. Aspiration and injectable sympathomimetic agents have not been shown to be effective. Sympathomimetic agents can also lead to cardiovascular side effects without notable benefit.
Nonischemic priapism can be managed on an outpatient basis. The risk of short-term complications in patients with nonischemic priapism appears to be small, and follow-up with a urologist within approximately one week is appropriate.
If the patient prefers an intervention rather than observation, arteriography with embolization of the fistula may be indicated. Embolization can be done using absorbable gelatin powder, metallic coils, or autologous clot. Several observational studies have shown prompt relief of nonischemic priapism with preservation of erectile function [41-43]. Resolution of nonischemic priapism with arterial embolization can be as high as 89 percent .
If initial embolization fails, repeat angiographic embolization or open surgical ligation of the ruptured artery with the aid of intraoperative ultrasonography may be necessary. Surgical ligation has, in isolated case reports, relieved nonischemic priapism after failed embolization therapy, with partial to full recovery of erectile function [45-47].
SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Male sexual dysfunction".)
INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, “The Basics” and “Beyond the Basics.” The Basics patient education pieces are written in plain language, at the 5th to 6th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10th to 12th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.
Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on “patient info” and the keyword(s) of interest.)
●Basics topics (see "Patient education: Priapism (The Basics)")
SUMMARY AND RECOMMENDATIONS
●Priapism most commonly occurs among young adult men, with an incidence of 1.5 cases per 100,000 person years. Priapism has been associated with several medications and diseases, including sickle cell disease (table 1). (See 'Epidemiology' above and 'Pathophysiology' above.)
●There are two main types of priapism: ischemic and nonischemic. Recurrent priapism, a subtype of ischemic priapism, is characterized by recurrent erections of short duration. Ischemic priapism usually presents with a painful, rigid erection and requires emergent therapy. Untreated, it may cause permanent erectile dysfunction. Nonischemic priapism usually presents after trauma, without a painful or rigid erection, and resolves spontaneously. (See 'Pathophysiology' above.)
●In addition to history and physical examination, cavernous blood gas analysis or Doppler ultrasound can be performed to distinguish between ischemic and nonischemic priapism. Laboratory testing is warranted in patients with suspected hemoglobinopathy or other blood dyscrasia. (See 'Evaluation' above and 'Diagnosis' above.)
●In patients with ischemic priapism, we suggest intracavernosal injection with a sympathomimetic agent (Grade 2C). We prefer phenylephrine (100 to 500 mcg/mL with 1 mL injection) to other agents based on fewer adverse effects. In addition to sympathomimetic injection, we suggest cavernosal blood aspiration (Grade 2C). (See 'Ischemic priapism' above.)
●Patients with recurrent priapism events that persist beyond four hours should be treated similarly to patients with ischemic priapism. (See 'Recurrent priapism' above.)
●In patients with nonischemic priapism, we suggest conservative management rather than a specific intervention (Grade 2C). Nonischemic priapism can last hours to days and resolves spontaneously in the majority of patients. Patients who desire immediate treatment can be managed with arterial embolization (Grade 2C). (See 'Nonischemic priapism' above.)
●The management of acute priapism in sickle cell disease, along with preventive strategies to reduce the risk of recurrent episodes and erectile dysfunction, is addressed separately. (See "Priapism and erectile dysfunction in sickle cell disease".)
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