Chapter 126

Priapism is a term used to describe a prolonged erection lasting more than 6 hours, usually not associated with sexual activity, and frequently starting during sleep. This descriptive term is derived from the Greek god of fertility, Priapus, whose statues depict him with an erection. An erection lasting over 6 hours is associated with changes that can prevent normal detumescence.

There are two types of priapism and early classification is essential for appropriate treatment. Low-flow (ischemic) priapism is the more common form. Although frequently idiopathic, there are several specific causes that can require specific therapy. Because progressive tissue damage occurs, success of treatment is dependent upon rapid reversal of the ischemia in these patients, who usually are late in seeking help.1,2 The second type of priapism is high-flow (nonischemic) priapism. This is usually due to blunt trauma of the corpora with an arterial rupture giving rise to an arteriovenous fistula. High-flow priapism is uncommon but important to differentiate from low-flow priapism. Treatment of high-flow priapism is not an emergency but requires immediate follow-up. Although ischemic damage does not occur with high-flow priapism, erectile dysfunction is still reported in about 20 percent of patients after treatment.1

There is a significant potential for disability in low-flow patients because either treatment fails to reduce the erection or erectile dysfunction occurs, even if the reduction is successful. Erectile dysfunction can be as high as 50 percent in low-flow priapism.1,3 For this reason patients should be made to understand that even with treatment, the outcome is uncertain. Legal implications are serious in this group of patients and full discussion with appropriate documentation in the medical record as treatment progresses is warranted.

The need for prompt recognition and treatment of low-flow priapism has been demonstrated in both experimental and clinical series. In animal models, interstitial edema occurs in 12 hours, endothelial damage by 24 hours, and smooth-muscle changes within 48 hours.4 In a series of patients with priapism secondary to self-injection for erectile dysfunction, patients under 36 hours duration were usually successfully treated with aspiration and alpha-adrenergic drugs with no resulting fibrosis. No patients responded to alpha-adrenergic therapy and fibrosis was found in all cases if the priapism was present for over 36 hours, even if reduction of the priapism was successful.5 Others have confirmed histomorphological changes within 6 to 8 hours of ischemia in the corpora cavernosa structures.6

The penis is primarily composed of the paired corpora cavernosa and the corpus spongiosum (Figure 126-1). An incomplete septum between the corpora cavernosa allows flow between them. The corpus spongiosum, which surrounds the urethra, terminates in the glans of the penis. A superficial and deep neurovascular bundle is located on the dorsal surface of the penis.

###### Figure 126-1

Cross-section of the penis demonstrating the ...

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