Priapism

Overview

Priapism is a pathologically prolonged and persistent penile erection for >4 hours that is not associated with sexual stimulation or interest. It is an emergency requiring urgent treatment.

Types

Priapism can be divided into two types with different management based on their pathological cause:

• Ischaemic priapism – more common, due to occluded venous drainage of the penis
• Non-ischaemic priapism – due to increased arterial inflow to the penis with blood entering more quickly than it can be drained

Stuttering priapism is when recurrent episodes of priapism occur that do not last for at least 4 hours.

Causes

Causes of ischaemic priapism lead to occluded venous drainage of the penis either due to a blockage (e.g. thrombi) or narrowed veins:

• Hypercoagulable states – (e.g. thrombophilias and thrombocytosis)
• Haemoglobinopathies – sickle cell disease, thalassaemia
• Neurological disorders – cauda equina syndrome, spinal cord injury, multiple sclerosis
• Malignancy
• Drugs – drugs used in erectile dysfunction (e.g. phosphodiesterase-5 (PDE-5) inhibitors such as sildenafil), alcohol, cocaine

Causes of non-ischaemic priapism lead to more arterial inflow than venous drainage. This is often idiopathic or due to trauma.

Stuttering priapism often occurs due to the same causes as ischaemic priapism and is usually managed as the same.

Presentation

Overview

Features include:

• Persistenterection lasting >4 hours that is not associated with sexual stimulation
  • Stuttering priapism is when recurrent episodes lasting <4 hours occur
• Pain suggests ischaemic priapism
  • The absence of pain can suggest non-ischaemic priapism
• There may be a known history of a predisposing condition or use of a causative drug 

Investigations

Overview

The diagnosis of priapism is mainly clinical, however, investigations are performed to identify whether it is ischaemic or non-ischaemic, look for underlying causes, and identify complications. Some tests include:

• Full blood count (FBC):
  • May show leukocytosis suggesting infection
  • May show thrombocytosis, suggesting a hypercoagulable state
  • May show reticulocytosis, which may be present in haemoglobinopathies
• Corpus cavernosum blood gas analysis:
  • Blood is aspirated from the corpus cavernosum
  • If ischaemic: pO₂ and pH are reduced, and pCO₂ is increased
  • If non-ischaemic: pO₂, pCO₂, and pH may be normal
• Colour duplex ultrasound:
  • May be considered instead of blood gas analysis to assess penile blood flow

If non–ischaemic priapism is present, spinal trauma should be considered and investigated if necessary. 

Management

Overview

The management of ischaemic priapism involves:

• If >4 hours or stuttering:
  • 1^st-line: aspiration of blood from corpora cavernosa. Irrigation with saline is often used to clear out any pooled blood
    • If unsuccessful: intracavernosal injection of a sympathomimetic (e.g. phenylephrine) – usually every 5 minutes for up to an hour
  • If medical treatment fails: surgery is indicated
• If <4 hours, observation may be appropriate or treat as above

The management of non-ischaemic priapism is more conservative with observation and supportive treatment.

Complications

• Penile ischaemia and necrosis
• Erectile dysfunction – thought to occur in >50% of people with 24-48 hour episodes