- Penile (or less common clitoral) erection lasting for >4 hours and unrelated to sexual stimulation or arousal
- Ischemic (low flow, veno-occlusive): accounts for 95% of priapism cases; it is associated with ischemia of the corpora cavernosa.
- Nonischemic (high flow, arterial): less common and often painless, and does not require urgent treatment
- Recurrent ischemic (“stuttering”) priapism: episodic, short-lived, and may not require intervention
- Malignant priapism: rare, resulting most commonly from penile metastases related to primary bladder, prostatic, rectosigmoid, and renal tumors
- System(s) affected: reproductive and vascular
- Functional impairment: neurophysiologic, sexual, psychosocial
In children, the most common etiology is sickle cell disease (SCD) (63% of cases). Less common etiologies, occurring more typically in the adolescent years, are leukemia, idiopathic, penile trauma (e.g., post circumcision), and illicit drugs (up to 35% of cases).
- About 5.3 per 100,000 men per year
- Age: There has been an age shift since 2008 toward men in their 40s. The incidence doubles in men aged >40 years (2.9 vs. 1.5/100,000 person-years).
- Race: 61.1% African American (correlated with incidence of SCD), 30% Caucasian, 6.3% Hispanic
Etiology and Pathophysiology
- 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 (a branch of the internal pudendal artery that, in turn, is a branch from the internal iliac artery) supplies blood to 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. Nocturnal penile tumescence and erection are driven by the parasympathetic nervous system through the generation of nitric oxide (NO).
- Smooth muscle relaxation occurs via usage of the phosphodiesterase type 5A (PDE5A) pathway, which generates cyclic guanosine monophosphate (cGMP).
- 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). Penile tissue necrosis and fibrosis may occur if priapism persists >24 hours. Pathophysiology mechanisms thought to contribute to impaired smooth muscle relaxation and decreased venous outflow include dysregulation of the NO/cGMP, RhoA/Rho kinase, and opiorphin signaling pathways as well as excessive adenosine signaling (1).
- In nonischemic priapism, increased arterial flow without decreased venous outflow results in a sustained, nonpainful, partially rigid erection.
- Ischemic priapism (2):
- Idiopathic: about 50% cases
- Hematologic dyscrasias: SCD, thalassemia, leukemia, multiple myeloma, fat emboli during hyperalimentation, hemodialysis, glucose-6-phosphate dehydrogenase (G6PD) deficiency, factor V Leiden mutation
- Infections (toxin mediated): urinary tract infections, scorpion sting, spider bite, rabies, malaria
- Metabolic disorders: nephrolithiasis, amyloidosis, Fabry disease, gout
- Neurogenic disorders: syphilis, spinal cord injury, cauda equina syndrome, autonomic neuropathy, lumbar disc herniation, spinal stenosis, cerebrovascular accident, brain tumor, spinal anesthesia
- Neoplasms: penis, urethra, bladder, prostate, kidney, and rectum
- Vasoactive erectile agents (i.e., papaverine, phentolamine, prostaglandin E1/alprostadil)
- α-Adrenergic receptor antagonists (i.e., prazosin, terazosin, doxazosin, tamsulosin)
- Antidepressants and antipsychotics (i.e., trazodone, bupropion, fluoxetine, sertraline, lithium, clozapine, risperidone, olanzapine, chlorpromazine, thioridazine, phenothiazines)
- Antihypertensives (i.e., hydralazine, guanethidine, propranolol)
- Hormones (i.e., gonadotropin-releasing hormone, testosterone)
- Anxiolytics (hydroxyzine)
- Anticoagulants (heparin, warfarin)
- Recreational drugs (i.e., alcohol, marijuana, cocaine)
- Nonischemic priapism (2),(3):
- Almost universally associated with penile or perineal trauma resulting in a fistula between the cavernous artery and the corpus cavernosum
- Acute spinal cord injury
- Treatment of ischemic priapism
- Ischemic priapism (2):
- SCD has a lifetime risk of ischemic priapism 29–42%.
- Dehydration correlated with SCD or trait
- Prior history of priapismic episodes
- Avoid dehydration (SCD cases).
- Avoid excessive sexual stimulation.
- Avoid or limit causative drugs.
- Avoid trauma to the genital area.
Commonly Associated Conditions
- SCD (42.9%) or sickle cell trait (2.5%)
- Drug abuse (7.9%)
- G6PD deficiency
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