496 CHAPTER 12 Erectile function and ejaculation

Priapism

Priapism is prolonged and often painful erection in the absence of a sexual stimulus, lasting >4–6 hours, which predominantly affects the corpus cavernosa.

Epidemiology

It peaks in incidence at ages 5–10 and 20–50 years.

Classification

Low-flow (ischemic) priapism

This is due to veno-occlusion (intracavernosal pressures of 80–120 mmHg). It is more common than high-flow priapism.

It manifests as a painful, rigid erection, with absent or low cavernosal blood flow. Ischemic priapism beyond 4 hours requires emergency intervention.

Blood gas analysis shows hypoxia and acidosis.

High-flow (nonischemic) priapism

This is usually post-traumatic in nature and does not require emergent intervention. It is due to unregulated arterial blood flow, presenting with a semi-rigid, painless erection.

Blood gas analysis shows similar results to arterial blood.

Etiology

Causes are primary (idiopathic) or secondary (see Tables 12.4 and 12.5):

•Intracavernosal injection therapy—PGE1; papaverine

•Drugs—B-blockers; antidepressants; antipsychotics; psychotropics; tranquilizers; anxiolytics; anticoagulants; recreational drugs; alcohol excess; total parenteral nutrition

•Thromboembolic—sickle cell disease (roughly one-third develop stuttering/recurrent priapism); leukemia; thalassemia; fat emboli

•Malignant infiltration of the corpora cavernosa (e.g., advanced bladder cancer)

•Neurogenic—spinal cord lesion; autonomic neuropathy; anesthesia

•Trauma—penile or perineal injury resulting in cavernosal artery laceration or arteriovenous fistula formation

•Infection—malaria; rabies; scorpion sting

Pathophysiology

Priapism lasting for 12 hours causes trabecular interstitial edema, followed by destruction of sinusoidal endothelium and exposure of the basement membrane at 24 hours, and sinusoidal thrombi, smooth muscle cell necrosis, and fibrosis at 48 hours.

Evaluation

•CBC to exclude sickle cell and leukemia.

•Cavernous arterial blood samples to determine the type of priapism (high or low flow). Ischemic priapism is typically associated with a PO2

PRIAPISM 497

Table 12.4 Causes of lowand high-flow priapism

Table 12.5 Examples of drugs that may cause priapism

of <30 mmHg, PCO2 >60 mmHg, and pH <7.25. Nonischemic priapism commonly shows a PO2 of > 90 mmHg, PCO2 <40 mmHg, and pH 7.4. Normal flaccid penile cavernous blood gas levels are roughly equal to those of normal mixed venous blood (PO2 40 mmHg, PCO2 50 mmHg, pH 7.35).

•Color Doppler ultrasound scan of cavernosal artery and corpora cavernosa. Reduced blood flow in ischemic priapism; ruptured artery with pooling of blood around injured area in nonischemic priapism

Management

Low-flow priapism

Ischemic priapism of >4 hours implies a compartment syndrome and requires decompression of the corpora cavernosa. Aspiration of blood from corpora (50 mL portions using a 18–20 gauge butterfly needle) ± intracavernosal injection of A1-adrenergic selective agonist (phenylephrine 100–200 µg (0.5–1 mL of a 200 µg/mL solution to a maximum of 1 mg) are performed every 5–10 minutes until detumescence occurs.

498 CHAPTER 12 Erectile function and ejaculation

Monitor blood pressure and pulse during drug administration. Oral terbutaline may be effective for intracavernosal injection-related cases.

Sickle cell disease requires, in addition, aggressive rehydration, oxygenation, analgesia, and hematological input (consider exchange transfusion). Repeated aspirations or irrigations and sympathomimetic injections during several hours are often necessary and should be performed before initiation of surgical therapy.

High-flow priapism

Early stages may respond to a cool bath or icepack (causing vasospasm

± arterial thrombosis). Delayed presentations require arteriography and selective embolization of the internal pudendal artery.

Complications

These include fibrosis and impotence.