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- Penile erection that lasts for >4 hours and is unrelated to sexual stimulation or excitement
- Classified into ischemic and nonischemic types
- Ischemic (low-flow) priapism is painful and requires urgent clinical intervention
- Stuttering priapism is recurrent episodes of short-lived, self-limiting ischemic priapism over an extended period.
- Nonischemic (high-flow) priapism is painless, could be related to prior trauma, and does not require urgent treatment.
- Malignant priapism is a rare condition resulting most commonly from penile metastases from primary bladder, prostatic, rectosigmoid, and renal tumors.
- System(s) affected: Reproductive
In children, nearly all priapism is caused either by sickle cell anemia or trauma (1).
In the US, 1 study estimates 1,868–2,960 cases of priapism each year. They also noted an increasing incidence from 1998 to 2006, specifically in those from nonhematologic causes (2):
- Mean age: 33.7 years. There has been an age shift in recent years toward men in their 40s.
- Other studies have found the incidence of priapism to double in men aged >40 (2.9 vs. 1.5/100,000 person-years) (3).
- Race: 61.1% black, 30% white, 6.3% Hispanic
- Associations: Sickle cell anemia (41.9%), drug abuse (7.9%), sickle cell trait (2.5%)
- Anatomy and physiology:
- The penis consists of three longitudinally oriented corpora: Two dorsolaterally paired corpora cavernosa that are responsible for penile erection and a single ventral corpus spongiosum that surrounds the glans penis and extends distally to form the glans penis.
- In general, the penile artery (which is a branch of the internal pudendal artery that, in turn, is a branch from the internal iliac artery) supplies the penis. It divides into three branches: Dorsal artery, bulbar artery (supplies the corpus spongiosum), and cavernosal artery (the main blood supply to the erectile tissue).
- During an erection, smooth muscle relaxation of the cavernosal arterioles results in high volume inflow to the sinusoids, resulting in compression of the exiting venules. This leads to significant volume expansion of the corpora cavernosa.
- During the flaccid resting state, the sympathetic nervous system is predominantly in control. Penile tumescence and erection are driven by the parasympathetic nervous system through the generation of nitric oxide (NO).
- Smooth muscle relaxation occurs via utilization of the phosphodiesterase type 5 (PDE-5A) pathway, which generates cyclic guanosine monophosphate (cGMP).
Etiology and Pathophysiology
- In ischemic priapism, decreased venous outflow results in increased intracavernosal pressure. This leads to erection, decreased arterial inflow, blood stasis, local hypoxia, and acidosis (a compartment syndrome). Eventually, penile tissue necrosis and fibrosis may occur. The exact mechanism is unknown and may involve trapping of erythrocytes in the veins draining the erectile bodies.
- In nonischemic priapism, there is increased arterial flow without decreased venous outflow. There is increased inflow and outflow, which results in a sustained, nonpainful, partially rigid erection.
- Aberrations in the PDE-5A pathway have been proven in mice to be one mechanism of priapism (4).
- Ischemic priapism:
- Idiopathic, estimated to about 50% (1)
- Intracavernosal injections of vasoactive drugs for erectile dysfunction
- Oral agents for erectile dysfunction
- Pelvic vascular thrombosis
- Prolonged sexual activity
- Sickle cell disease and trait
- Leukemia from infiltration of the corpora
- Other blood dyscrasias (G6PD deficiency, thrombophilia)
- Pelvic hematoma or neoplasia (penis, urethra, bladder, prostate, kidney, rectal)
- Cerebrospinal tumors
- Fabry disease
- Tertiary syphilis
- Total parenteral nutrition, especially 20% lipid infusion (results in hyperviscosity)
- Bladder calculus
- Trauma to penis
- UTIs, especially prostatitis, urethritis, cystitis
- Several drugs suspected as causing priapism (e.g., chlorpromazine, prazosin, cocaine, trazodone, and some corticosteroids); anticoagulants (heparin and warfarin); phosphodiesterase inhibitors (sildenafil, others); immunosuppressants (tacrolimus); and antihypertensives (hydralazine, propranolol, guanethidine)
- Intracavernous fat emulsion
- Hyperosmolar IV contrast
- Spinal cord injury
- General or spinal anesthesia
- Heavy alcohol intake or cocaine use
- Nonischemic priapism:
- The most common cause is penile or perineal trauma resulting in a fistula between the cavernous artery and the corpora.
- Acute spinal cord injury
- Rarely, iatrogenic causes for the management of ischemic priapism can result in nonischemic priapism.
- Certain urologic surgeries have also resulted in nonischemic priapism.
- Sickle cell anemia, lifetime risk of ischemic priapism 29–42% (1)
- Avoid dehydration
- Avoid excessive sexual stimulation
- Avoid causative drugs (see “Etiology and Pathophysiology”) when possible
- Avoid genital and pelvic trauma
Commonly Associated Conditions
- Sickle cell anemia or sickle cell trait
- Drug abuse
- G6PD deficiency