Approach Considerations
A complete blood cell count (CBC) should be performed to determine whether the patient has anemia, leukocytosis, or thrombocytosis. Rarely, the CBC will identify undiagnosed leukemia as the cause of priapism.
Patients with sickle cell disease should have a CBC and a reticulocyte count. If sickle cell status is unknown, a hemoglobin S determination may be useful. Patients with sickle cell disease may also need a blood type and screen performed in case transfusion or plasma exchange is necessary.
Measurement of plasma thromboplastin or activated partial thromboplastin time to determine coagulation status may be useful, as priapism may require surgical intervention if medical treatment fails.
Penile blood gas (PBG) test results allow differentiation between high- and low-flow priapism. Low-flow PBG findings may include a pH of less than 7.0, a PCO2 of greater than 60 mm Hg, and a PO2 of less than 30 mm Hg. Variation depends on the duration of the episode. In high-flow priapism, PBG findings should reflect normal arterial values.
Urine toxicology and psychoactive medication screening should be considered, in suspected patients, as some of these medications are known to cause priapism in standard doses or overdoses.
Color-flow penile Doppler imaging is currently the study of choice to differentiate high-flow from low-flow priapism. In patients with high-flow priapism, ultrasonography can help identify and locate fistulas. In a study of 52 patients, von Stempel et al found that on Dopper ultrasonography, a peak systolic velocity of less than 50 cm/sec and a mean velocity of less than 6.5 cm/sec were predictive of ischemic priapism. [24]
In patients with high-flow priapism, selective penile angiography may be required in order to identify the site of the fistula, or to confirm the location of a fistula identified by ultrasound. The fistula can then be closed by embolization.
Perform chest radiography or computed tomography (CT) scanning if the history is consistent with a malignant or metastatic condition. Perform an electrocardiogram if the patient is older than 55 years, has a history of cardiac disease, or is a possible surgical candidate.
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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.
