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Priapism
An erection lasting more than 4 hours unrelated to sexual stimulation is priapism; the ischaemic (low-flow) type is painful, rigid and an emergency treated by aspiration and intracavernosal phenylephrine, and the non-ischaemic (high-flow) type after trauma is not urgent and is treated with observation or embolisation.
Why it matters in the exam
The central question is distinguishing the types, especially by the blood gases of blood aspirated from the corpus cavernosum. In ischaemic priapism the blood is dark, with pO2 below 30 mmHg, pCO2 above 60 mmHg and pH below 7.25. In non-ischaemic priapism the blood is bright red and the gases resemble arterial blood: pO2 above 90, pCO2 below 40 and pH around 7.40. Doppler ultrasound shows low or absent flow in the ischaemic type, and high flow or an arterial fistula in the non-ischaemic type.
Causes of ischaemic priapism: sickle cell disease (common in children), intracavernosal injections for erectile dysfunction, drugs (trazodone, antipsychotics, alpha-blockers), cocaine and haematological malignancies. Treatment is stepwise: aspiration of blood from the corpus cavernosum with or without saline irrigation, then injection of phenylephrine at 100 to 500 micrograms per mL, 1 mL every 3 to 5 minutes, with blood pressure and pulse monitoring, for up to one hour. If there is no response — a distal shunt between the corpus cavernosum and the glans, followed by a proximal shunt. In priapism lasting more than 36 to 48 hours immediate prosthesis insertion is considered, because the chance of preserving erection is low and fibrosis will make later implantation harder.
In a patient with sickle cell disease priapism is treated with the same penile aspiration and injection; hydration, oxygen and transfusion are not a substitute for local treatment. Non-ischaemic priapism follows perineal or penile trauma that creates an arterial-cavernosal fistula; the erection is partial and painless. Most cases close on their own, and if not — selective embolisation. "Stuttering" priapism is recurrent short episodes, mainly in sickle cell disease, and is treated by prevention.
Key points
- More than 4 hours = priapism.
- Ischaemic: pO2 below 30, pCO2 above 60, pH below 7.25.
- Ischaemic treatment: aspiration and phenylephrine.
- Failure — distal then proximal shunt.
- Non-ischaemic — observation or embolisation.
Summary table
| Feature | Ischaemic (low-flow) | Non-ischaemic (high-flow) |
|---|---|---|
| Pain and rigidity | Painful, very rigid | Painless, partly rigid |
| Cavernosal blood gases | pO2 below 30, pCO2 above 60, pH below 7.25 | pO2 above 90, pCO2 below 40, pH 7.40 |
| Cause | Sickle cell disease, injections, drugs | Trauma and arterial fistula |
| Doppler | Low or absent flow | High flow |
| Treatment | Aspiration and phenylephrine, then a shunt | Observation, selective embolisation |
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Sources
- AUA/SMSNA Guideline: Acute Ischemic Priapism, 2022 — Diagnosis and management
- EAU Guidelines on Sexual and Reproductive Health, 2025 edition — Priapism
- Campbell-Walsh-Wein Urology, 12th edition (2020) — Priapism
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.