Priapism

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Basics

Description

  • Penile (or less common clitoral) erection lasting for >4 hours and unrelated to sexual stimulation or arousal
  • Classified into three types: ischemic, nonischemic, and stuttering:
    • Ischemic (low-flow, veno-occlusive) priapism is associated with ischemia of the corpora cavernosa, is prolonged and painful, and requires urgent clinical intervention.
    • Nonischemic (high-flow, arterial) priapism is less common and often painless, may be related to prior trauma, and does not require urgent treatment.
    • Stuttering priapism (recurrent, ischemic) is episodic, short-lived, and may not require intervention.
  • Malignant priapism is a rare condition 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 (quality of life) (1)

Pediatric Considerations

  • 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), or illicit drugs (up to 35% of cases).
  • Neonatal priapism is also rare, occurring in the first few days of life, usually due to perineal trauma during the birthing process (2).

Epidemiology

Incidence
  • The incidence and prevalence of priapism is likely underestimated because medical literature only includes cases in which men sought medical intervention. In a study of emergency department visits in the United States, there is an incidence of 5.3 per 100,000 men per year; accounting for up to 8 out of every 100,000 emergency department visits (3). In the Netherlands, the incidence was 1.5 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: In an American population, 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 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.
    • Smooth muscle relaxation occurs via usage of the phosphodiesterase type 5A (PDE5A) pathway, which generates cyclic guanosine monophosphate (cGMP) (2).
  • In ischemic priapism (accounting for >95% of reported episodes), 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 (4).
  • In nonischemic priapism, increased arterial flow without decreased venous outflow results in a sustained, nonpainful, partially rigid erection.
  • Causes: ischemic priapism (1)
    • Idiopathic, estimated to about 50%
    • Hematologic dyscrasias (SCD, thalassemia, leukemia, multiple myeloma, fat emboli during hyperalimentation, hemodialysis, glucose-6-phosphate dehydrogenase deficiency, factor V Leiden mutation)
    • Infections (toxin mediated) (i.e., urinary tract infections, scorpion sting, spider bite, rabies, malaria; metabolic disorders (i.e., nephrolithiasis, amyloidosis, Fabry disease, gout)
    • Neurogenic disorders (i.e., syphilis, spinal cord injury, cauda equina syndrome, autonomic neuropathy, lumbar disc herniation, spinal stenosis, cerebrovascular accident, brain tumour, spinal anaesthesia)
    • Neoplasms (metastatic or regional infiltration, most commonly: penis, urethra, bladder, prostate, kidney and rectum)
    • Medications associated with priapism include vasoactive erectile agents (i.e., papaverine, phentolamine, prostaglandin E1/alprostadil), α-adrenergic receptor antagonists (i.e., prazosin, terazosin, doxazosin, tamsulosin), anxiolytics (hydroxyzine), anticoagulants (heparin, warfarin), 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), and recreational drugs (i.e., alcohol, marijuana, cocaine [intranasal and topical], crack, cocaine)
  • Causes: nonischemic priapism (1)
    • The most common cause is penile or perineal trauma resulting in a fistula between the cavernous artery and the corpus cavernosum.
    • Acute spinal cord injury
    • Rarely, the management of ischemic priapism can result in iatrogenic nonischemic priapism.
    • Certain urologic surgeries have also resulted in nonischemic priapism.

Risk Factors

  • SCD has a lifetime risk of ischemic priapism 29–42%.
  • Dehydration correlated with SCD or trait
  • Prior history of priapismic episodes (stuttering priapism) (1),(2)

General Prevention

  • Avoid dehydration (SCD cases).
  • Avoid excessive sexual stimulation.
  • Avoid or limit causative drugs (see “Etiology and Pathophysiology”).
  • Avoid physical activity with a high risk of blunt trauma to the genital area (1),(2).

Commonly Associated Conditions

  • SCD (42.9%) or sickle cell trait (2.5%)
  • Drug abuse (7.9%)
  • G6PD deficiency
  • Leukemia
  • Neoplasm

-- To view the remaining sections of this topic, please or --

Basics

Description

  • Penile (or less common clitoral) erection lasting for >4 hours and unrelated to sexual stimulation or arousal
  • Classified into three types: ischemic, nonischemic, and stuttering:
    • Ischemic (low-flow, veno-occlusive) priapism is associated with ischemia of the corpora cavernosa, is prolonged and painful, and requires urgent clinical intervention.
    • Nonischemic (high-flow, arterial) priapism is less common and often painless, may be related to prior trauma, and does not require urgent treatment.
    • Stuttering priapism (recurrent, ischemic) is episodic, short-lived, and may not require intervention.
  • Malignant priapism is a rare condition 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 (quality of life) (1)

Pediatric Considerations

  • 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), or illicit drugs (up to 35% of cases).
  • Neonatal priapism is also rare, occurring in the first few days of life, usually due to perineal trauma during the birthing process (2).

Epidemiology

Incidence
  • The incidence and prevalence of priapism is likely underestimated because medical literature only includes cases in which men sought medical intervention. In a study of emergency department visits in the United States, there is an incidence of 5.3 per 100,000 men per year; accounting for up to 8 out of every 100,000 emergency department visits (3). In the Netherlands, the incidence was 1.5 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: In an American population, 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 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.
    • Smooth muscle relaxation occurs via usage of the phosphodiesterase type 5A (PDE5A) pathway, which generates cyclic guanosine monophosphate (cGMP) (2).
  • In ischemic priapism (accounting for >95% of reported episodes), 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 (4).
  • In nonischemic priapism, increased arterial flow without decreased venous outflow results in a sustained, nonpainful, partially rigid erection.
  • Causes: ischemic priapism (1)
    • Idiopathic, estimated to about 50%
    • Hematologic dyscrasias (SCD, thalassemia, leukemia, multiple myeloma, fat emboli during hyperalimentation, hemodialysis, glucose-6-phosphate dehydrogenase deficiency, factor V Leiden mutation)
    • Infections (toxin mediated) (i.e., urinary tract infections, scorpion sting, spider bite, rabies, malaria; metabolic disorders (i.e., nephrolithiasis, amyloidosis, Fabry disease, gout)
    • Neurogenic disorders (i.e., syphilis, spinal cord injury, cauda equina syndrome, autonomic neuropathy, lumbar disc herniation, spinal stenosis, cerebrovascular accident, brain tumour, spinal anaesthesia)
    • Neoplasms (metastatic or regional infiltration, most commonly: penis, urethra, bladder, prostate, kidney and rectum)
    • Medications associated with priapism include vasoactive erectile agents (i.e., papaverine, phentolamine, prostaglandin E1/alprostadil), α-adrenergic receptor antagonists (i.e., prazosin, terazosin, doxazosin, tamsulosin), anxiolytics (hydroxyzine), anticoagulants (heparin, warfarin), 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), and recreational drugs (i.e., alcohol, marijuana, cocaine [intranasal and topical], crack, cocaine)
  • Causes: nonischemic priapism (1)
    • The most common cause is penile or perineal trauma resulting in a fistula between the cavernous artery and the corpus cavernosum.
    • Acute spinal cord injury
    • Rarely, the management of ischemic priapism can result in iatrogenic nonischemic priapism.
    • Certain urologic surgeries have also resulted in nonischemic priapism.

Risk Factors

  • SCD has a lifetime risk of ischemic priapism 29–42%.
  • Dehydration correlated with SCD or trait
  • Prior history of priapismic episodes (stuttering priapism) (1),(2)

General Prevention

  • Avoid dehydration (SCD cases).
  • Avoid excessive sexual stimulation.
  • Avoid or limit causative drugs (see “Etiology and Pathophysiology”).
  • Avoid physical activity with a high risk of blunt trauma to the genital area (1),(2).

Commonly Associated Conditions

  • SCD (42.9%) or sickle cell trait (2.5%)
  • Drug abuse (7.9%)
  • G6PD deficiency
  • Leukemia
  • Neoplasm

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