Priapism is a condition in which a human penis remains erection for hours in the absence of stimulation or after stimulation has ended. There are three types: ischemic (low-flow), nonischemic (high-flow), and recurrent ischemic (intermittent). Most cases are ischemic. Ischemic priapism is generally painful while nonischemic priapism is not. In ischemic priapism, most of the penis is hard; however, the glans penis is not. In nonischemic priapism, the entire penis is only somewhat hard. Very rarely, clitoral priapism occurs in women.
Sickle cell disease is the most common cause of ischemic priapism. Other causes include medications such as , SSRIs, anticoagulants and prostaglandin E1, as well as drugs such as cocaine. Ischemic priapism occurs when blood does not adequately drain from the penis. Nonischemic priapism is typically due to a connection forming between an artery and the corpus cavernosum or disruption of the parasympathetic nervous system resulting in increased arterial flow. Nonischemic priapism may occur following trauma to the penis or a spinal cord injury. Diagnosis may be supported by blood gas analysis of blood aspirated from the penis or an ultrasound.
Treatment depends on the type. Ischemic priapism is typically treated with a nerve block of the penis followed by aspiration of blood from the corpora cavernosa. If this is not sufficient, the corpus cavernosum may be irrigated with cold, normal saline or injected with phenylephrine. Nonischemic priapism is often treated with cold packs and compression. Surgery may be done if usual measures are not effective. In ischemic priapism, the risk of permanent scarring of the penis begins to increase after four hours and definitely occurs after 48 hours.
Priapism occurs in about 1 in 20,000 to 1 in 100,000 males per year.
Some sources give a duration of four hours as a definition of priapism, but others give six. Per the University Hospital Schleswig Holstein, "The duration of a normal erection before it is classifiable as priapism is still controversial. Ongoing penile erections for more than 6 hours can be classified as priapism."C. VAN DER HORST, HENRIK STUEBINGER, CHRISTOPH SEIF, DIETHILD MELCHIOR, F.J. MARTÍNEZ-PORTILLO, K.P. JUENEMANN;
Other conditions that can cause priapism include Fabry's disease, as well as neurology such as spinal cord lesions and spinal cord trauma (priapism has been reported in people who have been hanged; see death erection).
Priapism can also be caused by reactions to . The most common medications that cause priapism are intra-cavernous injections for the treatment of erectile dysfunction (papaverine, alprostadil). Other medication groups reported are antihypertensives (e.g. Doxazosin), (e.g., chlorpromazine, clozapine), (most notably trazodone), anti-convulsant and mood stabilizer drugs such as sodium valproate. Anticoagulants, cantharides ( Spanish Fly) and recreational drugs (alcohol, heroin and cocaine) have been associated. Priapism is also known to occur from bites of the Brazilian wandering spider.
Blood gas testing the blood from the cavernosa of the penis can help in the diagnosis. If the low-flow type of priapism is present, the blood typically has a low pH, while if the high-flow type is present, the pH is typically normal. Color Doppler ultrasound may also help differentiate the two. Testing a person to make sure they do not have a hemoglobinopathy may also be reasonable.
In low-flow (ischemic) priapism the flow in the cavernous arteries is reduced or absent. As the condition progresses, there is an increase in echogenicity of the corpora cavernosa, attributed to tissue edema. Eventually, changes in the echotexture of the corpora cavernosa can be observed due to the fibrotic transformation generated by tissue anoxia.
In high-flow priapism normal or increased, turbulent blood flow in the cavernous arteries is seen. The area surrounding the fistula presents a hypoechoic, irregular lesion in the cavernous tissue.
Proximal shunts, such as the Quackel's, are more involved and entail operative dissection in the perineum where the corpora meet the spongiosum while making an incision in both and suturing both openings together. Shunts created between the corpora cavernosa and great saphenous vein called a Grayhack shunt can be done though this technique is rarely used.
As the complication rates with prolonged priapism are high, early Penile implant implantation may be considered. As well as allowing early resumption of sexual activity, early implantation can avoid the formation of dense fibrosis and, hence, a shortened penis.
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