Priapism is a prolonged erection, usually painful, that is unrelated to sexual stimulation and requires rapid etiologic stratification and targeted management.
Definition and Types
Priapism is an abnormal, persistent penile erection, typically painful and unrelieved by ejaculation, most often idiopathic but associated with systemic disease and drugs. An erection >4 hours is consistent with priapism.
Two key subtypes:
ISCHAEMIC (LOW-FLOW) PRIAPISM – cases: failure of venous outflow with hypoxic, hypercarbic, acidotic corporal blood; shaft rigid, glans soft; usually painful; true urologic emergency due to risk of corporal fibrosis and permanent ED.
NON-ISCHAEMIC (HIGH-FLOW) PRIAPISM : uncontrolled arterial inflow (often fistula/pseudoaneurysm after perineal/penile trauma); generally not painful, glans soft, well-oxygenated corporal blood and preserved arterial waveform.
Common Causes
- Haematologic: sickle cell disease, leukaemia, other hyperviscosity/thrombotic states.
- Medications/recreational drugs: intracavernosal ED agents (e.g., alprostadil), oral/injectable smooth-muscle relaxants, antidepressants (notably trazodone), cocaine, alcohol; PDE5 inhibitors and antipsychotics (e.g., risperidone) are recognised precipitants in broader research contexts.
- Trauma: perineal/penile (straddle) injury leading to high-flow arterial–sinusoidal fistula.
- Others: malignancy, spinal cord injury, fat embolism, antiphospholipid syndrome, idiopathic, and stuttering forms, especially in sickle cell disease
Key Diagnostic Considerations
- Immediate goal: distinguish ischaemic vs non-ischaemic.
- Corporal blood gas from aspirated corporal blood is essential in the emergency setting.
- Duplex doppler US helps differentiate low- vs high-flow and localise fistulae.
- Baseline labs: CBC, coagulation profile; haemoglobinopathy screen when indicated.
Major Management Principles
Ischaemic (low-flow) priapism
- Time-critical: start management as early as possible, ideally within 4–6h; durations >24h carry very high ED risk
- Stepwise therapy:
1. Corporal aspiration and saline irrigation via 18G needle until bright red blood.
2. Intracavernosal sympathomimetic (phenylephrine 300–500 mcg q5–10 min); continuous cardiac monitoring recommended