Priapism

Priapism is a potentially harmful and painful medical condition in which the erect penis or clitoris does not return to its flaccid state, despite the absence of both physical and psychological stimulation, within four hours. There are two types of priapism: low-flow and high-flow. Low-flow involves the blood not adequately returning to the body from the organ. High-flow involves a short-circuit of the vascular system partway along the organ. Treatment is different for each type. Priapism is considered a medical emergency, which should receive proper treatment by a qualified medical practitioner. Early treatment can be beneficial for a functional recovery.

The name comes from the Greek god Priapus (Πρίαπος), a fertility god often represented with a disproportionately large and permanent erection.

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. NADPH is a co-factor involved in the formation of nitric oxide, therefore glucose-6-phosphate dehydrogenase deficiency will lower nitric oxide levels, which may result in priapism. Recent breakthroughs in research of the disease have pointed to a raised level of the biochemical adenosine being the cause of the condition. This seems to cause blood vessels to dilate and has the potential to influence blood flow into the penis.

Sickle cell disease often presents special treatment obstacles. Hyperbaric oxygen therapy has also been used with success in some patients. 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), 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. PDE-5 inhibitors have been evaluated as preventive treatment for recurrent priapism.

Complications
Potential complications include ischemia, clotting of the blood retained in the penis (thrombosis), and damage to the blood vessels of the penis which may result in an impaired erectile function or impotence. In serious cases, the ischemia may result in gangrene, which could necessitate penis removal.

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 patients with priapism, the first step in management is a blood exchange transfusion, not a surgical intervention. For other patients, orally administered pseudoephedrine may be effective. 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.

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.

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.

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.

In females
Priapism in females (continued, painful erection of the clitoris) is also known as clitorism.