Priapism: ED Evaluation and Management
By Frederic H. Kauffman, MD, FACEP
Case scenario: A 23-year-old black male with a past medical history significant for sickle cell anemia presented to the ED with a six-hour history of painful penile erection. There was no history of genitourinary trauma, and symptoms were unrelieved by ejaculation. A similar episode had occurred two years ago that resolved spontaneously after two hours. The patient denied other significant medical history, took no prescription or recreational drugs other than folic acid and prn hydromorphone with acetaminophen for painful crises. He denied use of tobacco and alcohol and had no known drug allergies.
What are the physiologic mechanisms by which normal erection and detumescence occur? Erection is mediated by nitric oxide,1 a neurotransmitter secreted by the endothelial lining of the corpora cavernosa, and by nerve endings that supply corporal smooth muscle.2 Smooth muscle relaxation of erectile tissue in the two corpora cavernosa, associated with increased arterial blood flow into this spongy tissue, results in penile engorgement and rigidity. Associated venous compression traps blood in the corpora cavernosa, maintaining erectile function.3
Detumescence is dependent upon corporal body smooth muscle contraction and vasoconstriction, resulting in decreased arterial inflow of blood into the corpora cavernosa. Adrenergic nerves mediate the process, which is counteracted by dopamine, serotonin, and vasoactive polypeptide.3
When does an erection signify priapism? Priapism is defined as an involuntary, painful, persistent erection. It is not related to sexual stimulation or desire, and detumescence fails to return following ejaculation. Engorgement involves the corpora cavernosa; the corpus spongiosum and glans penis are spared.4 Priapism is derived from the name Priapus, the Greek god of fertility. This is ironic in that priapism often results in impotence.
How does sickle cell disease cause priapism? Priapism was first described as a complication of sickle cell disease over 50 years ago.4 There appears to be a bimodal age distribution, with peaks at ages 5-13 and at 21-29 years.4 Overall prevalence ranges from 6%5 to 12%4 of male children with sickle cell disease.
The exact mechanism by which priapism occurs in sickle cell disease has not been conclusively established. It is proposed that sickled erythrocytes cause sludging in the corporeal sinuses.4,6 Such sludging may be accentuated by decreases in oxygen tension and pH, both of which occur during normal erection. Patients may awake from sleep experiencing priapism, perhaps triggered by acidosis resulting from hypoventilation.4
Are there other potential causes of priapism to consider in this case? The most likely etiology of priapism in this case is sickle cell disease. Like nearly all cases in medicine, however, a differential diagnosis does exist and should be considered. Thirty-eight potential etiologies have been described in priapism.7 Table 1 lists pharmacologic and non-pharmacologic factors to consider.
Table 1
Etiologies of Priapism3
Pharmacologic
Intracavernosal agents: papaverine, phentolamine, prostaglandin E1
Antihypertensives: ganglionic blockers, arterial vasodilators, a-antagonists, calcium channel blockers
Psychotropics: phenothiazines, butyrophenones, hypnotics, trazodone, selective serotonin-reuptake inhibitors
Anticoagulants: heparin, warfarin
Recreational drugs: cocaine, marijuana, ethanol
Hormones: GRH, tamoxifen, testosterone
Miscellaneous: metoclopramide, omeprazole, hydroxyzine, TPN
Non-pharmacologic
Hematologic: anemia, leukemia, multiple myeloma, sickle cell disease, thalassemias
Metabolic: amyloidosis, Fabry’s disease, gout
Miscellaneous: carbon monoxide, malaria, black widow spider venom, spinal stenosis, asplenism, idiopathic
Are all cases of priapism caused by similar pathophysiologic mechanisms? Priapism is classified as either high flow, resulting from increased and uncontrolled arterial blood flow into the corpora cavernosa, or low flow, resulting from failure of venous outflow from the corpora cavernosa.3 The low-flow ischemic state is by far the most common. Besides frequency, other differences between the two states exist. High-flow priapism tends to be much less painful and occurs when a fistula develops between the cavernosal artery and the corpus cavernosum, generally a result of either blunt or penetrating trauma. Arterial blood gas analysis of cavernosal blood is normal. Low-flow states tend to be much more painful due to resultant ischemia and may lead to fibrosis of corporal smooth muscle, cavernosal artery thrombosis, and subsequent impotence.3 Intracavernosal blood is dark, poorly oxygenated, and acidic (pH < 7.0). The longer the duration of priapism, the greater the chance of irreversible impotence.
Is priapism a true emergency? Are there long-term consequences of this disorder? Conventional wisdom states that priapism is a urologic emergency, and that a time-dependent relationship exists between the duration of priapism and the ultimate development of impotence. One study found an impotence rate of 35% after five days’ duration of priapism and a rate of 60% after 10 days.7 Within the first five-day period, however, no significant difference was found in potency rates. As such, contrary to other more conventional opinions, the authors did not view the interval between the onset of priapism and the initiation of therapy as critical during this initial five-day span.7 Most authorities, however, view prompt diagnosis and therapy as essential to maintaining potency. Prognosis is more favorable in those patients who are young, have shorter durations of erection, have sickle cell disease, or have high-flow state.3
What is appropriate ED management, and under what circumstances should a urologist consultant be involved? Management is directed by the differentiation between low-flow and high-flow priapism. When a high-flow state is suspected, duplex Doppler ultrasonography is used to confirm the presence of a fistula. Angiography follows, allowing for embolization and return of normal vascular flow.
Low-flow priapism, representing the overwhelming majority of cases, is managed quite differently, with aggressive management including drainage of the corpus cavernosum. If specific pharmacologic agents are identified as potential etiologies, they should be withheld. Patients with sickle cell anemia should receive standard measures, including hydration and oxygenation coupled with analgesia. Exchange transfusion should be undertaken to establish a hematocrit greater than 30%, and to decrease hemoglobin S to less than 30%. Prognostic information can be obtained by the use of Doppler ultrasound, applying the probe to the ventral aspect of the proximal third of the penis to evaluate cavernosal artery flow. The presence of blood flow indicates that some oxygenated blood is reaching the corpora and portends a better chance of retaining potency. The absence of flow implies cavernosal artery thrombosis and dramatically increases the likelihood of subsequent impotence.3
Detumescence is best achieved by intracavernosal injection of a-adrenergic agonists (such as phenylephrine),3,8 coupled with aspiration and saline irrigation of the corpora cavernosa for advanced cases of greater than six hours’ duration.3 Aspiration and irrigation carry the risk of cavernosal artery laceration (albeit rare) and should be performed by a urologist. Injection of adrenergic agonists may result in headache, flushing and hypertension; cardiac disease is a relative contraindication to a-adrenergic agonist injection, and concurrent use of MAO inhibitors is an absolute contraindication in view of the risk of hypertensive crisis. When a-adrenergic agonists are contraindicated, consider the use of ethyl chloride spray, intracorporal methylene blue, IV hydralazine, and IV ketamine.3 When intracavernosal injection of a-adrenergic agonists is indicated, oral pseudoephedrine in doses of 60-120 mg can be administered by the emergency physician pending the arrival of the urologist. Although its use has not been rigorously studied, anecdotal experience indicates successful detumescence in the early phases of priapism.3 For those patients who ultimately fail the above measures, surgical intervention that entails the creation of a corpus cavernosum-corpus spongiosum fistula may be required.3 In view of the specialized nature of treatment and the potential for irreversible impotence, all patients with priapism should be evaluated on an urgent basis in the ED by a urologic consultant.
Summary
Priapism is a urologic emergency with a multitude of possible etiologies. Prompt recognition, differentiation between a low-flow and high-flow state, and early attempts at detumescence all are aimed at maintaining potency. The urologist is a critical consultant with the technical expertise to evaluate and manage these patients after identification, initial management by the emergency physician, and failure to detumesce. Future potential pharmacologic modalities for the treatment of priapism include digoxin (which promotes in vitro corporal smooth muscle contraction) and superoxide radical scavengers (superoxide radicals may play a role in promoting corporal smooth muscle fibrosis.)3
References
1. Melman A, et al. Anatomy and physiology of the penis. In: Bennett AH, ed. Impotence: Diagnosis and Management of Erectile Dysfunction. Philadelphia: W.B. Saunders; 1994:18-30.
2. Kim N, et al. A nitric oxide-like factor mediates non-adrenergic non-cholinergic neurogenic relaxation of penile corpus cavernosum smooth muscle. J Clin Invest 1991;88:112-116.
3. Mulhall JP, Honig SC. Priapism: Etiology and management. Acad Emerg Med 1996;3:810-816.
4. Hamre MR, et al. Priapism as a complication of sickle cell disease. J Urol 1991;145:1-5.
5. Tarry WF, et al. Urological complications of sickle cell disease in a pediatric population. J Urol 1989;138:592.
6. Fowler JE, et al. Priapism associated with the sickle cell hemoglobinopathies: Prevalence, natural history and sequelae. J Urol 1991;145:65-68.
7. Pohl J, et al. Priapism: A three-phase concept of management according to aetiology and prognosis. Br J Urol 1986;58:113-118.
8. Lee M, et al. Chart for preparation of dilutions of a-adrenergic agonists for intracavernous use in treatment of priapism. J Urol 1995;153:1182-1183.
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