Priapism is a persistent penile erection, typically defined as lasting longer than 4 hours and is not associated with sexual stimulation. Priapism can be described as either ischaemic or non-ischaemic with both categories having a different pathophysiology. Ischaemic priapism is typically due to impaired vasorelaxation and therefore reduced vascular outflow resulting in congestion and trapping of de-oxygenated blood within the corpus cavernosa. Non-ischaemic priapism is due to high arterial inflow, typically due to fistula formation often either as the result of congenital or traumatic mechanisms.
Epidemiology
- Age at presentation has a bimodal distribution, with peaks between 5-10 years and 20-50 years of age
- incidence has been estimated at up to 5.34 per 100,000 patient-years
Causes
- Idiopathic
- Sickle cell disease or other haemoglobinopathies
- Erectile dysfunction medication (e.g. Sildenafil and other PDE-5 inhibitors), this also includes intracavernosal injected therapies.
- Other drugs both prescribed (anti-hypertensives, anticoagulants, antidepressants etc) and recreational (specifically cocaine, cannabis and ecstasy).
- Trauma
Patients typically present acutely with:
- A persistent erection lasting over 4 hours
- Pain localised to the penis
- Often a history of either known haemoglobinopathy or use of medications listed above
- Patients may, more rarely, present with either a non-painful erection or an erection that is not fully rigid: these are both suggestive of non-ischaemic priapism.
- History of trauma to the genital or perineal region: also suggestive of non-ischaemic priapism.
Investigations:
- Cavernosal blood gas analysis to differentiate between ischaemic and non-ischaemic: in ischaemic priapism pO2 and pH would be reduced whilst pCO2 would be increased.
- Doppler or duplex ultrasonography: this can be used as an alternative to blood gas analysis to assess for blood flow within the penis.
- A full blood count and toxicology screen can be used to assess for an underlying cause of the priapism.