• Clinical science



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.



  • Priapism can affect individuals of all age groups.
  • Race: no racial predilection


Epidemiological data refers to the US, unless otherwise specified.


Low-flow priapism

Drug use (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!

High-flow priapism

  • Less common
  • Pathophysiology
    • Excessive arterial influx with sufficient venous outflow
    • No penile ischemia
  • Etiology
    • Blunt perineal trauma (e.g., saddle injury) and/or penetrating injury (e.g., local penile injections) → injury to the cavernosal arteryfistula between the cavernosal artery and corpus cavernosum
    • Congenital vascular malformations


Clinical features

  • Low-flow (ischemic) priapism
  • High-flow (non-ischemic) priapism
    • 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



  • One or both of the following tests are used to differentiate high-flow from low-flow priapism:
    • 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
  • Complete blood count and differential count, peripheral blood smear



Low-flow priapism

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

High-flow priapism

  • Usually no treatment is necessary.
  • Persistent high-flow priapism can be treated electively with selective arterial embolization.



  • Low-flow priapism
  • High-flow priapism has a good prognosis, with most cases resolving spontaneously.


Peyronie disease

  • Definition: Fibroproliferative disorder affecting the tunica albuginea of the penis that leads to an abnormal curvature of the penis.
  • Pathogenesis: repeated penile microtrauma during intercourse followed by abnormal wound healing fibrous plaque formation [14]
  • Clinical features
  • Differential diagnosis
  • Treatment:
    • First-line: oral pentoxifylline
    • Second-line: intralesional collagenase injections
    • Third-line: surgical repair

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last updated 08/03/2020
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