Priapism

Classification

1. Ischemic (Low-Flow) Priapism

Pathophysiology

• Venous outflow from the corpora cavernosa is obstructed
• Stagnant blood becomes hypoxic, hypercapnic, and acidotic
• A cascade of endothelial and smooth-muscle damage leads to progressive fibrosis
• Conceptually analogous to compartment syndrome of the penis
• Cavernosal blood gas: ↓PO₂, ↑PCO₂, ↓pH

Causes

• Sickle cell disease (most common in children; occurs in 2–29% of affected males — sickled RBCs occlude sinusoids during sleep-related mild hypoventilatory acidosis)
• Leukemia, other hemoglobinopathies, G6PD deficiency

• Intracavernous vasoactive agents: papaverine, phentolamine, prostaglandin E1 (alprostadil)
• Antipsychotics (especially chlorpromazine, trazodone)
• Anticoagulants, antihypertensives
• PDE5 inhibitors (rare)

• Spinal cord injury
• Pelvic/perineal malignancy
• Cocaine use (underreported)
• Idiopathic (most common overall)

⚠️ Pseudopriapism (non-deflating penile prosthesis or malignant corporal replacement in prostate/bladder cancer) must be distinguished from true priapism.

2. Nonischemic (High-Flow) Priapism

Pathophysiology

• Typically follows trauma to the perineum or penis
• Injury to the cavernosal or helicine artery → arteriocavernous fistula
• Unregulated arterial inflow causes partial, painless tumescence
• Venous drainage is preserved → no ischemia
• This is not a medical emergency

3. Stuttering (Recurrent) Priapism

• Periodic painful erections of shorter duration with spontaneous detumescence
• Most common in sickle cell disease patients
• Involves dysregulation of PDE5, nitric oxide (NO), and cGMP signaling
• Episodes often occur during sleep

Evaluation

History

• Duration and onset, pain, prior episodes
• Medications, drug use (cocaine), sickle cell history
• Prior trauma (points toward nonischemic)

Physical Examination

• Ischemic: fully rigid, tender corpora; soft glans
• Nonischemic: partial tumescence, soft/non-tender corpora, often palpable perineal bruit

Investigations

• Corporal blood gas (or color Doppler ultrasound): key diagnostic test
  • Low-flow: pO₂ <30 mmHg, pCO₂ >60 mmHg, pH <7.25
  • High-flow: blood gas resembles arterial values
• CBC/blood film: sickle cell, leukemia
• Color Doppler ultrasound: identifies arteriovenous fistula in nonischemic type
• CT angiography: locates the damaged vessel in nonischemic priapism

Management

Ischemic Priapism — Step-up Approach

• Subcutaneous or oral terbutaline 0.25–0.5 mg SQ (repeat in 15 min) or 5 mg PO
• Less effective than direct injection but may be tried first

• Phenylephrine 200–500 μg every 5–20 min (up to 3 doses) — drug of choice due to selective α1 activity without cardiac β effects
• Inject at 10 o'clock or 2 o'clock position at base of penis (25–27 gauge needle), avoiding the dorsal neurovascular bundle
• Because the corpora communicate, unilateral injection suffices

• Aspirate 20–30 mL of dark corporal blood (using 21-gauge butterfly)
• Irrigate with saline or dilute phenylephrine
• Visible change from dark venous to bright arterial blood = success

• For duration 1–2 days: T-shunt + anticoagulation
• For duration >2 days: T-shunt + tunneling + anticoagulation
• Perioperative anticoagulation: heparin 5000 units SQ + aspirin 325 mg immediately; continue aspirin 325 mg + clopidogrel 75 mg PO daily for ≥5 days postoperatively (reduces shunt closure)

• Considered when ischemia has lasted >48 hours and shunting fails
• Implantation within 4 weeks yields fewer complications (erosion, infection, shortening) vs. delayed implantation
• Malleable prosthesis allows later upsizing to inflatable device

Nonischemic Priapism — Conservative to Selective

1. Observation + compression: may resolve spontaneously
2. Androgen ablation (1–3 months): reduces sleep erections, allows vascular injury to heal
3. Selective arterial embolization: autologous clot, gel foam, or coiling — preferred over surgery
4. Surgery: last resort

Stuttering Priapism — Prevention

• Oral pseudoephedrine or other α-agonists at bedtime
• PDE5 inhibitors (long-term, low-dose): paradoxically prevent recurrence by restoring normal PDE5/cGMP homeostasis (Burnett hypothesis)
• Sickle cell–directed: hydration, oxygenation, alkalization, analgesia, exchange transfusion to reduce HbS concentration
• Home self-injection kits for patients with frequent recurrences

Complications

• Erectile dysfunction: >1/3 of patients with severe priapism develop permanent ED despite treatment — risk increases with duration
• Penile fibrosis: irreversible smooth muscle damage from prolonged ischemia
• Hematoma, infection from corporal procedures
• Systemic hypertension from α-adrenergic agents (monitor BP during injection)

Key Takeaways

• Ischemic priapism = urologic emergency; treat within hours to preserve potency
• Phenylephrine is the preferred intracavernous drug (selective α1, minimal cardiac risk)
• Duration determines surgical strategy: <24 h → aspiration/injection; 1–2 days → T-shunt; >2 days → T-shunt + tunneling
• Nonischemic priapism is painless, not urgent, and treated conservatively/with embolization
• Sickle cell disease is the leading secondary cause, especially in children