Priapism

Priapism refers to a sustained erection that lasts for more than four hours and is not the result of sexual excitation. Based on etiopathogenesis, priapism may be classified as either low-flow or high-flow. Low-flow priapism, which is caused by inadequate venous outflow from the corpus cavernosum, results in painful penile ischemia. Low-flow priapism in adults most commonly arises as an adverse effect from treating erectile dysfunction (e.g., sildenafil), while sickle cell disease is the most common cause in children. High-flow priapism is less common and usually the result of perineal trauma. High-flow priapism is not associated with penile ischemia and is therefore painless. Penile blood gas analysis and doppler ultrasound of the penis allow high-flow priapism to be distinguished from low-flow priapism. Low-flow priapism is an acute urological emergency that must be treated within 12 hours; treatment involves aspiration of blood from the corpus cavernosum and injection of phenylephrine. If priapism does not subside, surgical therapy to decompress the penis is indicated. When treated within 12 hours, complete restoration of erectile function is possible; delayed treatment leads to cavernous fibrosis and irreparable damage with erectile dysfunction. Non‑ischemic priapism usually does not require treatment.

• A sustained erection that lasts more than 4 hours, is not caused by sexual excitation and is not relieved by ejaculation. ^[1]

• Priapism can affect individuals of all age groups but two peaks are observed at 5–10 years and 20–50 years. ^[2][3]

Epidemiological data refers to the US, unless otherwise specified.

• Occurrence: more common than high-flow priapism
• Etiology ^[4]
  • Idiopathic
  • Drugs
    • Treatment of erectile dysfunction: sildenafil, intracavernosal injection of alprostadil ^[3]
    • Trazodone
    • Prazosin
  • Hypercoagulable states
    • Sickle cell disease: Sickled erythrocytes obstruct venous drainage of corpus cavernosum.
    • Leukostasis reactions associated with leukemia
    • Fabry diseases
    • Thalassemia
  • Autonomic dysfunction: spinal cord stenosis, autonomic neuropathy, cauda equina syndrome
  • Renal pelvic tumors: bladder cancer, prostatic cancer
• Pathophysiology
  • Inadequate venous outflow from corpus cavernosum as a result of:
    • Thrombosis and/or compression of the penile, prostatic, and/or pelvic veins
    • Prolonged tumescence
  • Penile ischemia
• Clinical features ^[1]
  • Early presentation
  • Painful erection (differential diagnosis: Peyronie disease)
  • The corpus cavernosum is completely rigid.
  • No clinical features of perineal trauma are present.
  • Recurrent priapism (stuttering priapism): a form of ischemic priapism that occurs in men with sickle cell disease
• Diagnostics: See “Diagnostics” below.
• Treatment ^[5]
  • First-line therapy
    • Repeating intracavernosal injections of phenylephrine (alpha receptor agonist) up to an hour
    • Aspiration of sludged blood from the corpus cavernosum with/without irrigation with normal saline
  • Second-line therapy (if detumescence does not occur): decompression of the penis by creating a shunt between the corpus cavernosum and either the glans or the corpus spongiosum
• Prognosis
  • Early treatment (within 12 hours) usually allows for complete recovery.
  • Late treatment almost always leads to penile fibrosis and erectile dysfunction. ^[6]

Medication (especially for erectile dysfunction) is the most common cause of low-flow priapism among adults. Among children, sickle cell disease is the most common cause of low-flow priapism.

Low-flow priapism is a urological emergency. Treatment of low-flow priapism within 12 hours is crucial because delayed treatment may result in permanent damage (cavernous body fibrosis with irreversible erectile dysfunction)!

• Occurrence: less common than low-flow priapism ^[7]
• Etiology ^[4]
  • Blunt perineal trauma (e.g., saddle injury) and/or penetrating injury (e.g., local penile injections) → injury to the cavernosal artery → fistula between the cavernosal artery and corpus cavernosum
  • Congenital vascular malformations
• Pathophysiology
  • Excessive arterial influx with sufficient venous outflow
  • No penile ischemia
• Clinical features ^[5]
  • There is up to a 72-hour delay between the initial injury and the onset of priapism.
  • Not painful
  • The corpus cavernosum is not completely rigid.
  • Symptoms of perineal trauma: perineal swelling, hematuria, dysuria
• Diagnostics: See “Diagnostics” below.
• Treatment ^[5]
  • Usually, no treatment is necessary.
  • Persistent high-flow priapism can be treated electively with selective arterial embolization.
• Prognosis: has a good prognosis, with most cases resolving spontaneously.

One or both of the following tests are used to differentiate high-flow from low-flow priapism: ^[5]

• Penile blood gas analysis
  • Low-flow priapism: dark blood with hypoxia, hypercapnia, and acidosis
  • High-flow priapism: bright red blood with normal arterial values
• Doppler ultrasound
  • Low-flow priapism: poor arterial influx
  • High-flow priapism: high arterial influx and adequate outflow
• Other: complete blood count and differential count, peripheral blood smear