Priapism

Priapism
Fresco in Pompeii depicting Priapus
Pronunciation	/ˈpraɪəpɪzəm/[1][2]
Classification and external resources
Specialty	Urology
ICD-10	N48.3
ICD-9-CM	607.3
DiseasesDB	25148
eMedicine	med/1908
MeSH	D011317

Priapism is a medical condition in which the erect penis does not return to its flaccid state, despite the absence of both physical and psychological stimulation, within four hours. Priapism is potentially painful and is considered a medical emergency, which should receive proper treatment by a qualified medical practitioner. There are two types of priapism: low-flow (ischemic) and high-flow (nonischemic); 80% to 90% of clinically presented priapisms are low-flow disorders.^[3] Low-flow involves the blood not adequately returning to the body from the penis. High-flow involves a short-circuit of the vascular system partway along the penis. Treatment is different for each type. Early treatment can be beneficial for a functional recovery.

Not all sources give four hours as the guideline for priapism occurring: "The duration time 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."^[3]

Causes

The causative mechanisms are poorly understood but involve complex neurological and vascular factors. Priapism may be associated with haematological disorders, especially sickle-cell disease, sickle-cell trait, and other conditions such as leukemia, thalassemia, and Fabry's disease, and neurologic disorders such as spinal cord lesions and spinal cord trauma (priapism has been reported in hanging victims; see death erection).

Priapism may also be associated with glucose-6-phosphate dehydrogenase deficiency, which leads to decreased NADPH levels. NADPH is a co-factor involved in the formation of nitric oxide, which may result in priapism.^[4] Raised levels of adenosine may also contribute to the condition by causing blood vessels to dilate, thus influencing blood flow into the penis.^[5]

Sickle cell disease often presents special treatment obstacles. Hyperbaric oxygen therapy has also been used with success in some patients.^[6] Priapism is also found to occur in extreme cases of rabies. Priapism can also be caused by reactions to medications. The most common medications that cause priapism are intra-cavernous injections for treatment of erectile dysfunction (papaverine, alprostadil). Other groups reported are antihypertensives, antipsychotics (e.g., chlorpromazine, clozapine), antidepressants (most notably trazodone), anti-convulsant and mood stabilizer drugs such as sodium valproate,^[7] anticoagulants, cantharides (Spanish Fly) and recreational drugs (alcohol, heroin and cocaine). Priapism has also been linked to achalasia. Priapism is also known to occur from bites of the Brazilian wandering spider and the black widow spider.^[8] PDE-5 inhibitors have been evaluated as preventive treatment for recurrent priapism.^[9][10]

Complications

Because ischemic priapism causes the blood to remain in the penis for unusually long periods of time, the blood becomes deprived of oxygen and can cause damage to the penile tissue itself. Should the penile tissue become damaged, it can further result in erectile dysfunction or disfigurement of the penis.^[11] In extreme cases, if the penis suffers from severe vascular disease, the priapism can result in penile gangrene.^[12]

Treatment

Medical advice should be sought immediately for cases of erection beyond four hours. Generally, this is done at an emergency department. In sickle-cell anaemia guidelines recommend a conservative treatment approach of prompt initial rehydration.^[13] For others, orally administered pseudoephedrine may be effective, pseudoephedrine being an alpha-agonist agent that exerts a constriction effect on smooth muscle of corpora cavernosum, that in turn facilitates venous outflow. Likewise, other sympathomimetic drugs of the amphetamine class have been observed to induce erectile dysfunction, although in a small number of cases they may have the opposite effect. Otherwise, the therapy at this stage is to aspirate blood from the corpus cavernosum under local anaesthetic. If this is still insufficient, then intracavernosal injections of phenylephrine are administered. This should only be performed by a specialist trained in the procedure, with the patient under constant hemodynamic monitoring, as phenylephrine can cause severe hypertension, bradycardia, tachycardia, and arrhythmia.

Terbutaline being a beta-2 agonist causes smooth muscle relaxation; in priapism it probably acts by relaxation of the stretched corporeal smooth muscles, or increasing permeability of erectile cavernous tissue permitting easy flow of fluid from sinusoids into the venous system. In priapism, it was suggested to be administered orally.^[14]

Methylene blue is used intracavernously to treat priapism, but it should not be used in treatment of recurrent priapism or fibrosis because it can induce penile necrosis. Temporary blue discoloration of the penis is also of concern.^[14]

If aspiration fails and tumescence recurs, surgical shunts are next attempted. These attempt to reverse the priapic state by shunting blood from the rigid corpora cavernosa into the corpus spongiosum (which contains the glans and the urethra). Distal shunts are the first step, followed by more proximal shunts.

Distal shunts, such as the Winter's, involve puncturing the glans (the distal part of the penis) into one of the cavernosa, where the old, stagnant blood is held. This causes the blood to leave the penis and return to the circulation. This procedure can be performed by a urologist at the bedside. Winter's shunts are often the first invasive technique used, especially in hematologic induced priapism, as it is relatively simple and repeatable over time.^[15]

Proximal shunts, such as the Quackel's, are more involved and entail operative dissection in the perineum to where the corpora meet the spongiosum, making an incision in both, and suturing both openings together.^[16]

Shunts created between corpora cavernosa and saphenous vein called Grayhack shunt can be done though rarely.

As the complication of shortened, indurated and non-erectile penis is high in prolonged priapism, early penile prosthesis implantation can be performed. Apart from early resumption of sexual activity, early implantation can avoid the formation of dense fibrosis and hence a shortened penis.

Terminology

The name comes from the Greek god Priapus (Ancient Greek: Πρίαπος), a fertility god often represented with a disproportionately large and permanent erection. Priapism in females (continued, painful erection of the clitoris) is known as clitoral priapism or clitorism. Relentless, persistent or continuous erections that lack any complications are sometimes referred to as a "permaboner" in slang terms.^[17]

References

Further reading

• Guideline on the Management of Priapism (2003) - American Urological Association website - The unabridged 275-page version of this guideline.