Priapism

Priapism is a persistent penile erection lasting more than 4 hours, unrelated to sexual stimulation or continuing beyond it. It is a urological emergency in its ischaemic form, as prolonged ischaemia causes irreversible corporal fibrosis and erectile dysfunction.

Types

• Ischaemic (veno-occlusive, low flow; about 95% of cases): the corpora are rigid and painful, with absent or minimal arterial inflow. Blood is hypoxic, hypercapnic and acidotic. Irreversible smooth muscle damage begins at 6 to 12 hours, and fibrosis is established after 24 to 48 hours.
• Non-ischaemic (arterial, high flow): the erection is not fully rigid and painless. It follows perineal or penile trauma that causes a laceration of the cavernosal artery, forming an arteriovenous fistula with unregulated inflow. It is not an emergency.
• Stuttering (recurrent, intermittent ischaemic) priapism: repeated self-limiting painful erections lasting less than 3 to 4 hours, with escalating risk of a major ischaemic episode, particularly in sickle cell disease.

Epidemiology

• Incidence about 1.5 per 100,000 men per year, with a bimodal peak in boys 5 to 10 years (sickle cell disease) and men 20 to 50 years. About 30 to 45% of men with sickle cell disease will have an episode of priapism by adulthood.

Causes

• Haematological: sickle cell disease (commonest in children), thalassaemia, leukaemia (especially chronic myeloid), myeloma, polycythaemia, thrombophilia, and fat emboli with parenteral nutrition.
• Drugs: intracavernosal vasoactive agents (alprostadil, papaverine, phentolamine, the most common cause in adults), phosphodiesterase inhibitors (rare, with overuse), antipsychotics (risperidone, chlorpromazine, clozapine), trazodone, antidepressants, alpha blockers, antihypertensives (hydralazine, prazosin), anticoagulants (heparin, warfarin), cocaine, cannabis, alcohol, and testosterone.
• Neurogenic: spinal cord injury, cauda equina syndrome, autonomic neuropathy, and epidural anaesthesia.
• Malignancy: penile and metastatic infiltration of the corpora (prostate, bladder, renal, rectal).
• Trauma: perineal or straddle injury (non-ischaemic), and pelvic fractures.
• Infection and systemic: malaria, rabies, scorpion sting, Fabry disease, and amyloidosis.
• Idiopathic: 30 to 50%.

Pathophysiology of ischaemic priapism: impaired detumescence from persistent smooth muscle relaxation, with venous outflow obstruction, blood stasis and sludging, falling pH and PO2, and rising PCO2, lactate, and tissue damage. In sickle cell disease, there is also dysregulation of nitric oxide and phosphodiesterase 5 activity, and sickling in the corpora.

Ischaemic priapism:

• Fully rigid erection of the corpora cavernosa (the glans and corpus spongiosum are soft), increasing pain with duration, tenderness, and no improvement with sexual release.
• Duration over 4 hours, often longer. History of onset, medications, injections, drugs, trauma, sickle cell history, previous episodes, and prior erectile function.
• Late features: edema of the penile shaft, dusky discolouration, ecchymosis, and reduced rigidity as the tissues become fibrotic.

Non-ischaemic priapism:

• Partial erection, usually not painful, can vary with sexual stimulation, may occur days after perineal trauma. Penile shaft is semi-rigid and normal in colour. Perineal bruising or tenderness may be seen.

Stuttering priapism:

• Recurrent episodes (often nocturnal or on waking) lasting from minutes to a few hours, resolving spontaneously, in sickle cell disease patients, and sometimes preceding a prolonged event.

Examination:

• Palpate the corpora cavernosa (rigid) versus glans and spongiosum (soft), assess tenderness, perineum, abdomen and spine, neurological examination (perineal sensation, tone), and signs of haematological disease (pallor, splenomegaly, lymphadenopathy).

Differential diagnosis: normal erection, post-ejaculatory refractory state, Peyronie disease, penile thrombosis (Mondor disease), urethral injury, and penile fracture.

Red flags: duration beyond 4 hours, severe pain, history of sickle cell disease or leukaemia, injection of vasoactive agents, spinal cord injury, and fever.

Classify as ischaemic or non-ischaemic urgently, as treatment differs.

Clinical features and history (rigidity, pain, duration, trauma, drugs).

Corporal blood gas analysis (from a needle in the corpus cavernosum, 19 to 21 gauge butterfly needle at 3 or 9 o'clock position at the base of the penis):

• Ischaemic: dark, deoxygenated blood with PO2 below 30 mmHg, PCO2 above 60 mmHg, and pH below 7.25.
• Non-ischaemic: bright red, oxygenated blood with PO2 above 90 mmHg, PCO2 below 40 mmHg, and pH about 7.40.
• Intermediate values: mixed, consider time course.

Colour duplex Doppler ultrasound of the penis and perineum:

• Ischaemic: absent or minimal cavernosal arterial flow.
• Non-ischaemic: normal or high-velocity arterial flow with turbulent fistulous jet (arteriovenous fistula or pseudoaneurysm).

Laboratory:

• CBC with differential, reticulocyte count, haemoglobin electrophoresis or sickle solubility test (if not known), coagulation profile, renal function, toxicology screen, and peripheral smear for leukaemia. Haemoglobin S percentage in sickle cell disease patients.
• Further investigations for recurrent episodes: drug and medication review, spinal MRI, tumour screening, thrombophilia work-up.

Selective pudendal arteriography for non-ischaemic priapism planned for embolisation.

Ischaemic priapism: emergency treatment (start within 4 to 6 hours, ideally earlier) Step-wise approach:

• Analgesia and general measures: pain control (penile dorsal nerve block with 1% lidocaine without adrenaline, or ring block), oxygen, IV fluids, and sedation if required. Ice packs, exercise and ejaculation are ineffective.
• Cavernosal aspiration (with or without irrigation): aspirate 20 to 50 mL of blood until bright red blood returns, then irrigate with saline 0.9%. Success rates 30%.
• Intracavernosal sympathomimetic injection:
• Phenylephrine 100 to 500 micrograms (diluted to 100 to 500 micrograms/mL) injected every 3 to 5 minutes for up to 1 hour (maximum about 1 mg/h), with the penis at the 3 or 9 o'clock position. Combined with aspiration it resolves 60 to 80% of cases.
• Monitor blood pressure and ECG, as hypertension, headache, bradycardia and arrhythmia can occur. Use lower doses in cardiac disease, with careful monitoring, and in children (reduced dose 0.5 to 1 microgram/kg). Alternatives are etilefrine 5 to 10 mg or adrenaline 10 to 20 micrograms/mL, but phenylephrine is preferred.
• Surgical shunting if detumescence fails after 1 hour of aspiration and injection (or for episodes lasting more than 48 to 72 hours):
• Distal shunts: Winter (percutaneous needle puncture through the glans into corporal body using a Tru-Cut biopsy needle), Ebbehoj (scalpel stab), T-shunt (T-shaped scalpel with tunnelling), and Al-Ghorab (excision of a segment of the tunica at the tip of the corpora, with gentle squeeze). T-shunt with tunnelling is most efficacious (~74%), and complications include urethral injury, fistula and infections.
• Proximal shunts (Quackels corporospongiosal anastomosis, Grayhack with saphenous vein, saphenous vein to corpora): reserved for failed distal shunts, with higher complications (fistula, urethral injury, deep vein thrombosis, pulmonary embolism).
• Immediate penile prosthesis insertion: for episodes over 36 to 48 hours (late presentation), when corporal fibrosis is expected, to prevent penile shortening and maintain length. Frozen section or biopsy of cavernosal tissue guides the decision.

Sickle cell disease specific

• Hydration, oxygen, analgesia, alkalinisation. Initial aspiration with injection of phenylephrine remains the priority, since other measures delay care.
• Exchange transfusion or simple transfusion to reduce haemoglobin S to below 30% (not as a first resort, as ASPEN syndrome (association of sickle cell disease, priapism, exchange transfusion, and neurological events) is a concern). Hydroxyurea 15 to 35 mg/kg daily may help.
• Stuttering priapism prevention: pseudoephedrine 30 to 60 mg at bedtime, oral phenylephrine, hydroxyurea, sildenafil 25 mg daily (or tadalafil 5 mg daily) as a controlled PDE5 inhibitor regimen that reduces recurrences in sickle cell (counterintuitive and requires specialist supervision), GnRH agonists or antiandrogens (bicalutamide 50 mg daily, ketoconazole, finasteride 5 mg daily, stilboestrol 1 to 5 mg), intracavernosal self-injection of phenylephrine 200 micrograms (training), and gabapentin 300 mg daily.

Non-ischaemic priapism

• Not an emergency. Observation (spontaneous resolution in 60% within 1 year), cold packs, perineal compression.
• Selective arterial embolisation (autologous blood clot, absorbable gelatin sponge, or coils) if persistent and desired by the patient, with success in 75 to 90%, and a risk of erectile dysfunction (5 to 20%). Surgical ligation for failed embolisation.
• Avoid shunt procedures.

Treat the cause

• Stop offending drugs, treat leukaemia (leukapheresis, chemotherapy) or myeloma, treat spinal cord pathology, and correct coagulopathy. In children, distinguish and treat sickle cell disease, and counsel.

Prevention of recurrence

• Education on early presentation. Avoid triggers (dehydration, alcohol, cold, sexual activity in sickle cell, trigger drugs).
• For intracavernosal injection users: start with the lowest dose, avoid injection frequency more than 3 times weekly, and teach emergency reversal (oral pseudoephedrine 60 mg and exercise).

Outcomes and follow-up

• Erectile function recovery depends on duration: preserved in most with detumescence within 12 hours, about 50% preserved at 24 hours, and under 10% after 48 to 72 hours.
• Follow-up with erectile function assessment (IIEF-5), penile Doppler, early penile rehabilitation with PDE5 inhibitors, and psychological support. Penile prosthesis later for permanent erectile dysfunction.