What is the pathophysiology, diagnosis, and management of priapism, a urologic emergency characterized by a prolonged erection of the penis?

Priapism: Pathophysiology, Diagnosis, and Management

Clinical Presentation and History

All patients presenting with priapism must be evaluated emergently to identify the subtype, as acute ischemic priapism represents a true urologic emergency requiring immediate intervention to prevent permanent erectile dysfunction. 1

Key Historical Elements to Obtain:

• Duration of erection (critical threshold: >4 hours defines priapism) 2
• Pain characteristics: Ischemic priapism presents with painful, rigid erection; non-ischemic priapism is painless and not fully rigid 3, 4
• Trauma history: Perineal or penile trauma suggests non-ischemic etiology 2
• Medication exposure: Intracavernosal injection therapies (papaverine, phentolamine, alprostadil) have the highest incidence; PDE-5 inhibitors (sildenafil, tadalafil) also implicated 2
• Sickle cell disease status: These patients require concurrent urologic and hematologic management 1
• Recurrent episodes: Suggests stuttering (recurrent ischemic) priapism 1

Physical Examination Findings:

• Ischemic priapism: Rigid corpora cavernosa with flaccid glans penis 1
• Non-ischemic priapism: Partially tumescent, non-rigid corpora 3

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Classification and Pathophysiology

Three Distinct Types:

1. Ischemic Priapism (Low-Flow, Veno-Occlusive)

• Pathophysiology: Venous outflow obstruction creates compartment syndrome with hypoxic, hypercarbic, acidotic blood in corpora cavernosa 1
• Natural history: Untreated cases progress from painful erection to widespread smooth muscle necrosis, blood vessel attrition, trabecular fibrosis, and permanent erectile dysfunction within days to weeks 1, 5
• This is a medical emergency 1, 2

2. Non-Ischemic Priapism (High-Flow, Arterial)

• Pathophysiology: Unregulated arterial inflow, typically from arterio-cavernosal fistula following trauma 2, 3
• Blood gases: Similar to normal arterial blood 6
• Not an emergency; most episodes are self-limiting 1, 4

3. Stuttering (Recurrent Ischemic) Priapism

• Pathophysiology: Recurrent episodes of ischemic priapism with intervening detumescence 1, 2
• Common in sickle cell disease patients 1
• Acute episodes require emergency management; long-term focus is prevention 1

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Diagnostic Approach

Immediate Diagnostic Steps:

Cavernous Blood Gas Analysis (Gold Standard for Classification):

• Ischemic priapism: pO₂ <30 mmHg, pCO₂ >60 mmHg, pH <7.25 1
• Non-ischemic priapism: Blood gases similar to arterial blood 6

Color Duplex Ultrasonography:

• Ischemic: Little to no cavernous arterial flow 1
• Non-ischemic: Normal to high cavernous arterial flow, may identify fistula 3

Adjunctive Laboratory Testing:

• Complete blood count: Evaluate for sickle cell disease, leukemia 1
• Hemoglobin electrophoresis: If sickle cell disease suspected 1
• Toxicology screen: If drug-induced priapism suspected 3

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Management Strategies

Acute Ischemic Priapism (Time-Dependent Emergency):

Stepwise Algorithmic Approach:

Step 1: Intracavernosal Phenylephrine (First-Line)

• Phenylephrine is superior to other sympathomimetics due to demonstrated efficacy and limited systemic side effects 5
• Dose: 100-500 mcg intracavernosal injection, may repeat every 5-10 minutes up to 1 hour 1
• With or without aspiration/irrigation 1
• Monitor blood pressure and cardiac status during administration 5

Step 2: Aspiration and Irrigation

• If phenylephrine alone fails, proceed to corporal aspiration with saline irrigation 1, 5
• May be combined with phenylephrine injections 1

Step 3: Surgical Shunting

• Distal shunts (Winter, Ebbehoj, or Al-Ghorab procedures) if medical management fails 1
• Novel tunneling techniques for refractory cases 1
• Proximal shunts reserved for distal shunt failures 3

Step 4: Early Penile Prosthesis Placement

• For prolonged ischemic priapism (>36-48 hours) with anticipated permanent erectile dysfunction, consider early (non-emergent) penile prosthesis placement 1
• This prevents corporal fibrosis and preserves penile length 1

Non-Ischemic Priapism Management:

Conservative Approach (Not an Emergency):

• Observation: Most resolve spontaneously 1, 4
• Ice packs and compression may be attempted 4
• Selective arterial embolization: If persistent and bothersome to patient 1
• Treatment based on patient objectives, available resources, and clinician experience 1

Stuttering (Recurrent Ischemic) Priapism:

Dual Management Strategy:

• Acute episodes: Treat as acute ischemic priapism with phenylephrine 1
• Prevention:
  • Oral sympathomimetics (pseudoephedrine, terbutaline) 1
  • Hormonal therapy (GnRH agonists, antiandrogens) for refractory cases 1
  • PDE-5 inhibitors (paradoxically preventive in low doses) 1

Special Population: Sickle Cell Disease

Concurrent Management Approach:

• Primary focus: Urologic relief of erection using standard ischemic priapism protocols 1
• Concurrent interventions: Hydration, oxygenation, analgesia, exchange transfusion 1
• Do not delay urologic intervention for hematologic management 1

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Complications of Delayed or Inadequate Treatment

Ischemic Priapism Complications:

Time-Dependent Tissue Damage:

• <12 hours: Minimal smooth muscle damage, excellent erectile function recovery 1
• 12-24 hours: Progressive smooth muscle necrosis begins 5
• >24 hours: Widespread necrosis, vascular attrition, nerve damage 5
• >48 hours: Irreversible trabecular fibrosis and permanent erectile dysfunction highly likely 1, 5

Long-Term Sequelae:

• Erectile dysfunction: Most significant complication, occurs in majority of cases with delayed treatment 1
• Penile fibrosis and shortening 1
• Psychological and socioeconomic morbidity 4

Surgical Complications:

• Distal shunt procedures: Glans necrosis, urethral injury (rare) 1
• Proximal shunts: Higher risk of permanent erectile dysfunction 3

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Critical Clinical Pitfalls and How to Avoid Them

Common Errors:

1. Delaying Urologist Involvement

• Early urologist consultation when patient presents to emergency department is essential 1
• Do not attempt prolonged conservative measures in ischemic priapism 1

2. Misclassifying Priapism Type

• Always obtain cavernous blood gas analysis before treatment 1
• Treating non-ischemic priapism as ischemic emergency causes unnecessary interventions 1

3. Using Wrong Sympathomimetic Agent

• Avoid epinephrine and norepinephrine due to significant cardiovascular side effects 5
• Phenylephrine is the recommended agent 1, 5

4. Confusing Iatrogenic Prolonged Erection with True Priapism

• Prolonged erection following intracavernosal vasoactive medication requires different treatment protocols than spontaneous priapism 1
• These typically respond more readily to conservative measures 1

5. Inadequate Patient Counseling

• Counsel all patients about high risk of erectile dysfunction, especially with delayed presentation 1
• Discuss penile prosthesis as definitive option for refractory cases 1

6. Waiting for Hematologic Interventions in Sickle Cell Patients

• Urologic detumescence takes priority; do not delay for exchange transfusion or other sickle cell therapies 1

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Application to Clinical Practice

Emergency Department Protocol:

Immediate Actions (<30 minutes):

• Obtain focused history (duration, pain, trauma, medications, sickle cell status) 1
• Perform cavernous blood gas analysis 1
• Consult urology immediately 1
• If ischemic priapism confirmed, initiate intracavernosal phenylephrine 1, 5

Within 1-2 Hours:

• If phenylephrine fails, proceed to aspiration/irrigation 1
• Prepare for surgical shunting if medical management unsuccessful 1

Patient Education:

• Explain time-dependent nature and risk of permanent erectile dysfunction 1
• Discuss realistic expectations for erectile function recovery 1
• For stuttering priapism, provide prevention strategies and action plan for future episodes 1