Priapism is a disorder in which the penis maintains a prolonged erection in the absence of appropriate stimulation. Three broad categories exist for this disease: ischemic, nonischemic, and recurrent ischemic. Ischemic causes of priapism are a true emergency and require prompt intervention to prevent damage to the penis which can progress to erectile dysfunction and permanent impotence. Emergent management of this disease is directed toward achieving detumescence.
The etiology of priapism can broadly be categorized as low flow (ischemic) and high flow (non-ischemic). The causes of ischemic priapism are numerous and include various hemoglobinopathies including sickle cell disease and thalassemia as well as any hypercoagulable state. Vasoactive medications including erectile dysfunction medications (phosphodiesterase five inhibitors and intracavernous injections) have been blamed for an increased incidence of this disease. Additionally, anti-depressants (trazodone) and illicit drugs including cocaine may also cause priapism. Less common causes include neoplastic processes, neurologic disorders, and infections. Recurrent ischemic causes of priapism share many of the same underlying etiologic factors as ischemic priapism, except for some defective regulatory mechanisms which can result in abnormal signaling and intermittent ischemic episodes. Non-ischemic priapism is less common and usually a result of direct trauma. This disease can also result from iatrogenic injury from surgical interventions, congenital arterial malformations, or cancer. In a small subset of patients, no underlying cause or explanation can be found for the disease.
There are several causes of priapism and it is estimated that in about two-thirds of patients, the cause is the use of intracavernosal drugs that are used to treat erectile dysfunction. Sickle cell disease also accounts for a high number of cases of adult priapism, with rates reported between 40-80%. The majority of sickle cell cases of priapism are seen in African Americans and the disease almost always affects the male. The disorder has a bimodal presentation with peaks at ages 7-10 and 20-50 years. Younger people tend to have priapism due to sickle cell disease and the older population due to use of medications.
Ischemic priapism is a disease process marked by low arterial inflow into the corpora cavernosa and results in a rigid and prolonged erection. This trapped venous blood causes increased pressure resulting in tissue ischemia and is associated with penile pain. Alternatively, nonischemic priapism is caused by unregulated arterial blood flow into the corpora cavernosa without associated venous trapping. Patients usually do not develop tissue ischemia, and thus, this presentation is usually painless.
Upon initial assessment of patients presenting with priapism, a history of an erection lasting an abnormally long period in the absence of stimulation with associated penile pain will be elicited in the majority of cases. The history of the patient’s illness is paramount to determining the underlying etiology, and thus will help to specify the type of priapism patient is experiencing. Important clinical questions include the duration of symptoms, any treatments or injection therapy utilized, erectile function before the priapism episode, current medications, and history of underlying disorders known to precipitate priapism. Additionally, the presence or absence of pain is important in determining ischemic versus non-ischemic causes of this disease as a painless presentation lends itself to non-ischemic pathology. On physical examination, the penis should be palpated to determine the presence of palpable pulsation as this may represent arterial high-flow priapism and is usually absent in ischemic conditions. In ischemic priapism, the corpora cavernosa are usually tender to palpation, and absence of tenderness or partially tumescent cavernosa tends to favor a diagnosis of nonischemic disease. A comprehensive history and physical exam are usually sufficient to determine the underlying etiology and subsequent treatment for this disease.
Evaluation of priapism begins with a thorough and complete history and physical examination. If the etiology of priapism is unable to be determined based on this information, then penile hemodynamics and metabolism of penile blood must be evaluated. Aspiration of the corpora cavernosa can be completed with laboratory evaluation of acquired blood. A cavernous blood gas in ischemic priapism will be low, generally with a pH less than 7.0, representing a metabolic acidosis. Additionally, pO2 should be less than 30 mmHg, and pCO2 should be greater than 60 mmHg. Alternatively, high-flow nonischemic priapism reveals more normal arterial blood on aspiration with a pH near 7.4 and pO2/pCO2 levels closer to 90 mmHg and 40 mmHg, respectively. 
Further laboratory testing should be directed toward the determination of underlying or undiagnosed disease that may be causing the patient’s condition. Lab tests including complete blood count, reticulocyte counts, hemoglobin electrophoresis, serum lactic dehydrogenase, and urine toxicology can all be employed to aid in the diagnostic evaluation of priapism.
Penile imaging can be utilized to aid in the diagnosis of ischemic versus nonischemic causes of priapism. Intracorporeal arterial blood flow can be analyzed using color duplex ultrasound (CDU), with absent blood flow in the cavernosal arteries lending toward an ischemic etiology while normal flow is characteristic of nonischemic priapism. Abnormal anatomy including arterial fistulae or pseudoaneurysm may also be identified on examination. Additionally, magnetic resonance imaging (MRI) or magnetic resonance angiography (MRA) can be utilized to evaluate for malignancy or thrombosis, and can also predict the viability of corpora tissue after prolonged or repeated episodes of priapism.
Ischemic priapism is a true emergency, and any episode lasting longer than 4 hours mandates intervention with earlier intervention resulting in a decreased probability of irreversible damage and erectile dysfunction. Although the treatment of a patient’s underlying disease may result in detumescence, emergency department management should be focused on achieving detumescence. Several medications can be utilized for ischemic priapism, and oral therapies such as pseudoephedrine or terbutaline may be tried while awaiting equipment for more advanced interventions. Failure of oral therapies is common, with some studies reporting failure rates of 75%, resulting in the need to perform corporal aspiration of blood with the concurrent intracavernous injection of a sympathomimetic agent. It is recommended to perform a dorsal penile block before aspiration and injection to decrease patient discomfort. Although there are several sympathomimetic agents available, phenylephrine is frequently utilized as a first-line agent due to its efficacy and safety profile. This treatment may be repeated if the penis remains erect. If completed within 12 hours of priapism onset, some studies have reported a near 100% success rate in achieving tumescence with this therapy. If medical therapy fails, urologic consultation for surgical treatment may be required. Surgical intervention primarily consists of shunt procedures with the underlying goal of reducing corporal pressures and ultimately penile pain.
Non-ischemic priapism is generally managed conservatively due to the low probability of penile damage, and thus the initial intervention should be an observation with treatment utilizing topical ice packs. Although aspiration can be completed for diagnostic purposes, this procedure generally does not result in complete detumescence. Many patients elect to avoid surgery due to the inherent risks of erectile dysfunction, and some patients have been reported to maintain their capacity to obtain and maintain an erection despite years of non-ischemic priapism. Should a surgical procedure be desired, the general approach is selective embolization or direct ligation of the dysfunctional cavernous artery fistula.
Recurrent priapism shares many of the treatment goals as ischemic priapism, with acute therapy focused on achieving detumescence, and chronic therapy focused on preventing recurrence. Emergency management should be focused on the acute phase with the same treatments utilized as ischemic priapism, and ultimate urological consultation to dictate long-term therapy and outpatient monitoring.
Priapism is a challenging disease in the emergency department and requires prompt diagnosis and treatment. The primary goal of ischemic priapism management is achieving detumescence, with several acceptable treatments available. Nonischemic priapism can be safely managed conservatively in the majority of cases. Failure of rapid evaluation and treatment can result in significant morbidity and intervention should not be delayed.
Priapism is not a fatal disorder, but it can lead to erectile failure in the future. The key to prevention is education. At the time of discharge, the nurse should educate the patient on seeking medical help as soon the condition develops. Older adults should be cautioned against the use of oral or injectable agents used to treat erectile failure. All patients with a first episode of priapism should be seen by a mental health counselor as the condition is associated with severe anguish and anxiety. Patients need to be told that the condition can be associated with a poor outcome, despite adequate treatment. (Level V)
The prognosis of patients with priapism depends on age, duration of symptoms and the underlying cause. If the priapism is present for less than 24 hours, then the chances of remaining potent are high, but if the duration is more than 72 hours, the risk of remaining potent are greatly diminished. Erectile dysfunction is a long-term complication in many patients and recurrent episodes are associated with the worst prognosis. The risk for recurrence is also high is one episode has occurred. If the cause is associated with trauma, there is a risk of infection and fibrosis. (Level V)
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