Priapism

A prolonged, rigid erection in the absence of appropriate stimulation. Any unwanted erection lasting 4 hours or longer and not relieved by ejaculation counts as priapism.

Incidence is roughly 0.73 to 5.4 cases per 100,000 men per year, with a bimodal age distribution peaking at 7-10 years and 20-50 years. Younger patients tend to have sickle cell disease; medication effects dominate in older men.

Classification

• Ischaemic (low-flow) — the common form. Failure of venous outflow traps blood, raising intracorporal pressure to a compartment-syndrome state with ischaemia, acidosis and pain. The corpora cavernosa are rigid and tender. A true emergency.
• Non-ischaemic (high-flow) — unregulated arterial inflow through a fistula, usually after perineal or penile trauma. Not painful, less than fully rigid, no tissue ischaemia. Not an emergency.
• Recurrent (stuttering) — repeated short ischaemic episodes, typically at night, gradually lengthening. Often sickle cell disease.

The glans and corpus spongiosum stay flaccid in priapism because they have a separate venous drainage — which is also why cavernosum-to-spongiosum shunting works.

Why the clock matters

Tissue damage does not begin at 4 hours. Microscopic change starts around 6 hours, permanent structural change in corporal smooth muscle at about 14 hours, and thrombus plus direct smooth-muscle damage leading to fibrosis by 36 hours.

• Beyond 24 hours, up to 90% of men cannot have normal intercourse afterwards
• Beyond 72 hours, erectile function is unrecoverable and prosthesis implantation should be considered

Duration before therapy is the single most important prognostic factor.

Causes

• Vasoactive drugs for erectile dysfunction — intracavernosal injections are the largest single group, thought to cause at least 25% of all cases
• Antidepressants and antipsychotics — trazodone alone accounts for about 16% of medication-induced cases; antipsychotics and trazodone are more than twice as likely to cause priapism as PDE5 inhibitors
• Haemoglobinopathies — sickle cell disease, thalassaemia, and any hypercoagulable state
• Illicit drugs and alcohol — amphetamines, cocaine; contributing in up to 21% of ischaemic cases
• Neoplastic — leukaemias, and pelvic malignancy by direct infiltration or venous obstruction
• Trauma — the usual cause of non-ischaemic priapism
• Rarer — amyloidosis, dialysis, Fabry disease, fat embolism, carbon monoxide poisoning, cauda equina syndrome, G6PD deficiency

Medicines reported to cause priapism (adapted from Salonia et al):

Medicine class	Examples
Antipsychotics & antidepressants	trazodone, risperidone, olanzapine, clozapine, chlorpromazine, quetiapine, sertraline, citalopram, escitalopram, lithium, fluoxetine, trifluoperazine, pericyazine
Vasoactive erectile agents	alprostadil, papaverine
Alpha-adrenergic receptor antagonists	doxazosin, tamsulosin, terazosin, prazosin
Antihypertensives	hydralazine, propranolol
Anticoagulants	heparin, warfarin
Hormones	testosterone, gonadotropin-releasing hormone
PDE5 inhibitors (reported, less common)	sildenafil, tadalafil
ADHD medications (reported)	methylphenidate, atomoxetine

Priapism in sickle cell disease

Prevalence among men with sickle cell disease is roughly 35-45%, and more than 95% of those episodes are ischaemic. It is uncommon under 18 years but affects about 42% of adults. Episodes typically occur at night in REM sleep and on waking.

Repeated ischaemic episodes cause permanent penile damage and erectile dysfunction in up to 40% of affected men.

History and examination

Ask the exact duration, any injection therapy used, erectile function before the episode, prior episodes and what worked, current medications, and any sickle cell disease or trauma to penis, pelvis or perineum.

In ischaemic priapism the corpora cavernosa are rigid, fully erect and tender, with a soft or only partly engorged glans. Painlessness, partial tumescence and palpable penile pulsations all point to non-ischaemic disease. Examine the perineum and abdomen for trauma or malignancy.

Investigations

Cavernosal blood gas is the discriminator. Aspirated ischaemic blood is dark, almost black; non-ischaemic blood is bright red.

• Ischaemic: pH below 7.2, pO2 below 30 mm Hg, pCO2 above 60 mm Hg
• Non-ischaemic: pH above 7.2, pO2 above 90 mm Hg, pCO2 below 40 mm Hg

Colour duplex ultrasound is recommended where available and can be used instead of blood gases. Absent cavernosal arterial flow indicates ischaemia; normal or increased flow indicates non-ischaemic priapism, and the fistula is identified in about 70% of cases. MRI or MR angiography can assess malignancy, thrombosis and corporal tissue viability.

Also send FBC, reticulocyte count, haemoglobin electrophoresis or haemoglobin S testing if sickle cell is even remotely suspected, plus blood alcohol and urine toxicology as appropriate.

Management

Ischaemic priapism — emergency

1. Treat as a true emergency; any episode of 4 hours or longer needs early intervention.
2. Oral pseudoephedrine may be tried while equipment is prepared. Oral terbutaline is no longer recommended — insufficient efficacy per both AUA and EAU guidelines, and oral therapy fails in around 75%.
3. Dorsal penile or ring block, then aspiration of the corpora with normal saline or heparinised irrigation. Aspiration alone works in only about a third of cases; with saline irrigation, detumescence is achieved in up to 66%.
4. Intracavernosal diluted phenylephrine is the preferred first-line sympathomimetic for its efficacy and safety profile, repeated at intervals until detumescence. Success is 58% with injection alone, rising to 81-86% when combined with aspiration and irrigation within the first 24-36 hours. Monitor continuously for arrhythmia and hypertension; use lower concentrations and volumes in children and severe cardiovascular disease.
5. Surgical shunting if medical therapy fails. Distal cavernosal-spongiosum shunts (Winter, Ebbehoj, Al-Ghorab, T-shunt) have broadly similar success; proximal shunts are not recommended. Duration over about 15.5 hours and failure of maximal phenylephrine predict the need for surgery.
6. Corporal tunnelling (“snake” manoeuvre) or penoscrotal decompression for refractory cases. Penoscrotal decompression achieved detumescence in 89.3% of otherwise intractable cases, preserving erectile function in 54.8%.
7. Penile prosthesis for priapism presenting beyond 48-72 hours, where recovery of erectile function is minimal. Implant early — ideally within 3 weeks — before the corpora become densely fibrotic.

Check eTG or AMH for the phenylephrine dilution and injection schedule.

Non-ischaemic priapism

Not an emergency. Manage conservatively with urology follow-up — 62% resolve spontaneously even without treatment. If intervention is wanted, the recommended approach is arteriography with selective arterial embolisation or direct ligation of the cavernous artery fistula. Overall success of selective arterial embolisation is 89% to 100%, with 75% to 86% retaining normal erectile capability afterwards, and recurrence in up to 30%.

Recurrent (stuttering) priapism

Acute episodes of 3-4 hours or more are treated exactly as acute ischaemic priapism. Chronic management aims at prevention: investigate for sickle cell disease, and avoid trazodone and alpha-blocking phenothiazines. Oestrogens are no longer recommended because of thromboembolic risk; antiandrogens and LHRH agonists work but carry significant adverse effects.

Evidence for preventive drug treatment in sickle cell disease is weak. A Cochrane review of three small randomised trials found we are uncertain whether stilboestrol, etilefrine or ephedrine reduce the frequency of stuttering priapism, and that sildenafil may make little or no difference.