Diagnostic Considerations
The diagnosis of priapism may be straightforward, depending on the physical findings. Pathologic states associated with priapism give rise to the differential diagnosis. Some of the major considerations are as follows:
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Intracavernosal agents used to treat erectile dysfunction
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Oral agents used to treat erectile dysfunction
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Genitourinary trauma
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Medications
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Cocaine
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Spinal stenosis
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High spinal cord injury
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Urethral foreign body
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Penile surgical implant
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Erection from sexual arousal
Low-flow versus high-flow priapism
To provide appropriate treatment, physicians must differentiate between low-flow and high-flow priapism. This is accomplished by taking a thorough history, performing a careful physical examination, and measuring the oxygen content of blood within the corpora cavernosa by penile blood gas (PBG) analysis (see Workup).
Low-flow priapism, which constitutes the large majority of cases, is characterized by a rigid, painful erection; ischemic corpora, as indicated by dark blood upon corporeal aspiration; and no evidence of trauma. The history may reveal an underlying cause, such as sickle cell disease or use of intracavernosal or oral agents for treatment of erectile dysfunction, or other medications known to be associated with priapism (see Etiology).
Patients with high-flow priapism typically have a history of blunt or penetrating trauma to the penis or perineum, resulting in a fistula between a cavernosal artery and the corpus cavernosum. Clinically, high-flow priapism is characterized by a painless erection; tumescence is typically less marked than in low-flow priapism.
The presence of bright red blood during aspiration is a helpful but not pathognomonic finding of high-flow priapism. PBG findings approximate normal arterial values. Penile duplex ultrasonography with angiographic confirmation helps to identify and locate these fistulae.
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Priapism. Corporeal relaxation causes external pressure on the emissary veins exiting the tunica albuginea, trapping blood in the penis and causing erection.
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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.
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Priapism. Winter shunt placed by biopsy needle, usually under local anesthetic.
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Priapism. Proximal cavernosal-spongiosum shunt (Quackel shunt) surgically connects the proximal corpora cavernosa to the corpora spongiosum.
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Priapism. Proximal cavernosal-saphenous shunt (Grayhack shunt) surgically connects the proximal corpora cavernosum to the saphenous vein.
