Definition
Priapism is defined as a prolonged penile erection (>4 h) which is maintained without sexual stimulation and persists despite ejaculation and orgasm. Priapism is a medical emergency requiring an accurate diagnosis and urgent medical intervention.
Types
The two main subtypes of priapism are:
- Ischaemic priapism (also referred to as low-flow priapism)
- Non-ischaemic priapism (also referred to as high-flow priapism)
- Stuttering or recurrent priapism - a rarer subtype defined by frequent prolonged and painful erections which are generally self-limiting and are common in patients with sickle cell disease (SCD)
Causes
Ischaemic Priapism
- Thromboembolic/hypercoagulable states
- Haemoglobinopathies (e.g. sickle cell disease, thalassaemia)
- Thrombocytosis
- Heparin-induced platelet aggregation
- Neoplastic disease
- Penile carcinoma, prostatic adenocarcinoma
- Metastatic neoplasia
- Neurological disease
- Spinal cord injury
- Cauda equina syndrome
- Multiple sclerosis
- Vasoactive agents and drugs
- PDE5 inhibitors
- Antihypertensives
- Antipsychotics
- Alcohol and cocaine
Non-Ischaemic Priapism
- Traumatic injuries
- Straddle injury
- Coital trauma
- Pelvic fractures
- Birth canal trauma to newborns
- Vascular erosions from metastatic cancer
Pathophysiology
Ischaemic Priapism
Results from an imbalance in vasoconstrictive and vasorelaxatory mechanisms. Features vascular stasis and reduced venous outflow, leading to trapped deoxygenated blood, venous congestion, tissue ischemia, and increased pressure within the corporal bodies.
Non-Ischaemic Priapism
Results from unregulated cavernous arterial inflow, typically trauma-induced. Creates an arteriolar-sinusoidal fistula with excessive arterial inflow and pooling of blood in sinusoidal spaces. Not a medical emergency as blood gases remain normal.
History and Examination
History
- Duration of erection (<48h, 48-72h, >72h)
- Onset of erection
- Underlying haematological disorders
- Current medications
- Illicit drug use
- Previous episodes
- Recent trauma
Examination
- Differentiate ischaemic (painful, rigid) vs non-ischaemic (painless, less rigid)
- Abdominal and digital rectal exam for malignancy
- Neurological examination
- Evidence of perineal/penile trauma
Comparison of Priapism Types
| Ischaemic Priapism |
Non-Ischaemic Priapism |
| Veno-occlusive or low flow |
Arterial or high-flow |
| Little or absent intracorporeal blood flow |
Elevated vascular flow within corpora |
| Associated with systemic disease or pharmacotherapy |
Usually follows penile/perineal trauma |
| Painful, progresses with duration |
Typically painless |
| Penis fully rigid |
Tumescence without full rigidity |
| Abnormal cavernous blood gases |
Normal blood gases |
| Medical emergency |
Not a medical emergency |
Investigations
- Blood tests: FBC, blood film, autoimmune screen
- Cavernous blood gas analysis: Hypoxia, acidosis and glucopenia confirm ischaemic priapism
- Imaging:
- Penile Doppler study
- Penile MRI for refractory cases
- Abdominal/pelvic CT/MRI for possible malignancy
Management Timeline
Duration <48h
Immediate Intervention
- Analgesia + antibiotics
- Penile aspiration
- Phenylephrine instillation
- Shunt if refractory
Duration >72h
Critical Situation
- Unlikely viable muscle
- Urgent prosthesis consideration
- High complication risk
Management
Ischaemic Priapism Management Algorithm
Duration <48h:
- Provide analgesia and broad-spectrum antibiotics
- Arrange Doppler but don't delay aspiration
- Penile block and aspirate with 19-gauge needle
- If persists, instill phenylephrine 200-250µg aliquots (max 1000µg)
- If continues, perform shunt surgery (Winter or T-shunt)
Duration 48-72h:
- Attempt aspiration and phenylephrine if duration uncertain
- Refractory cases need shunt surgery
- Consider penile prosthesis if perfusion absent
Duration >72h:
- Unlikely to have viable smooth muscle
- Attempt aspiration/phenylephrine if duration uncertain
- Urgent referral for possible penile prosthesis
Non-Ischaemic Priapism Management
- Initial management can be conservative
- If fistula demonstrated, attempt duplex compression
- Failure requires referral for superselective arteriography and embolisation
Stuttering Priapism Management
- Idiopathic cases: hormone manipulation with antiandrogens (avoid in prepubertal boys)
- SCD patients: manage with haematology team
- Etilefrine may be useful for SCD (named patient basis)
Key Points
- Ischaemic priapism is painful, rigid with abnormal blood gases - medical emergency
- Arterial priapism is painless, not fully rigid - not an emergency
- Start ischaemic priapism management within 4-6 hours
- Reduce phenylephrine dose in children
- Monitor BP/ECG with phenylephrine - contraindicated in cerebrovascular disease
- SCD patients need additional supportive measures (IV hydration, oxygen, bicarb)
- Inject/aspirate at 3 or 9 o'clock position
Complications
- Penile ischaemia
- Penile fibrosis and deformity
- Erectile dysfunction