Priapism: Comprehensive Overview

Definition and Classification

Priapism is a persistent penile erection lasting greater than 4 hours that is unrelated to sexual stimulation, representing a urologic emergency requiring immediate evaluation to prevent permanent erectile dysfunction. 1, 2

The condition affects only the corpora cavernosa (the paired cylindrical erectile bodies responsible for penile rigidity), while the corpus spongiosum and glans typically remain flaccid. 1, 3

Three Distinct Subtypes:

Ischemic (Low-Flow) Priapism - 95% of cases:

Non-sexual persistent erection with little to no cavernous blood flow 4, 5
Characterized by rigid, tender corpora cavernosa with severe pain 1
Abnormal blood gases: pO2 <30 mmHg, pCO2 >60 mmHg, pH <7.25 2, 3
This is a true urologic emergency - permanent erectile dysfunction occurs in 90% of cases after 48 hours 2, 6

Non-Ischemic (High-Flow) Priapism - 5% of cases:

Persistent erection from unregulated arterial inflow, typically post-traumatic 1, 3
Penis is neither fully rigid nor painful 1
Normal arterial blood gas values 1, 2
Not an emergency - many resolve spontaneously 2, 7

Stuttering (Intermittent) Priapism:

Recurrent self-limiting episodes of ischemic priapism with intervening detumescence 1
Each acute episode must be managed as ischemic priapism 4, 5

Anatomy and Physiology

Normal Erectile Anatomy:

Two corpora cavernosa: paired cylindrical structures responsible for penile rigidity 3
Corpus spongiosum: surrounds the urethra and forms the glans, remains flaccid during priapism 3
Normal erection involves coordinated arterial inflow and venous outflow regulation through smooth muscle relaxation/contraction 3

Normal Detumescence Mechanism:

Sympathetic nervous system activation causes smooth muscle contraction 1
Venous outflow channels open, allowing blood drainage 3
Alpha-adrenergic receptors mediate this vasoconstriction 1

Pathophysiology

Ischemic Priapism:

Venous outflow obstruction causes blood stagnation in corpora cavernosa 3, 8
Progressive hypoxia, hypercarbia, and acidosis develop 1
Failure of normal detumescence mechanism - smooth muscle cannot contract 3
Prolonged ischemia leads to smooth muscle necrosis, fibrosis, and permanent erectile dysfunction 3
Functions as penile compartment syndrome with time-dependent tissue damage 8

Non-Ischemic Priapism:

Traumatic arterio-cavernosal fistula formation allows unregulated arterial inflow 3, 7
Blood remains oxygenated - no ischemic damage occurs 1, 2
Perineal or penile trauma is the most common etiology 1, 8

Differential Diagnosis and Etiologies

Ischemic Priapism Causes:

Medications: intracavernosal vasoactive agents (most common iatrogenic cause), PDE5 inhibitors, antipsychotics, antidepressants, antihypertensives 1, 6
Hematologic disorders: sickle cell disease (most common in children), leukemia, multiple myeloma, thalassemia 1, 9
Neurologic conditions: spinal cord injury, cauda equina syndrome 7
Malignancy: penile metastases, pelvic tumors 8
Idiopathic: 30-60% of cases have no identifiable cause 1

Non-Ischemic Priapism Causes:

Perineal or penile trauma (blunt or penetrating) - 90% of cases 1, 8
Iatrogenic arterial injury during penile procedures 7

Anatomic Risk Factors:

Peyronie's disease, penile angulation, cavernosal fibrosis 9, 10
These predispose to priapism with PDE5 inhibitor use 9, 10

Diagnostic Approach

Immediate History Elements:

Duration of erection (critical for prognosis) 3, 8
Pain severity (severe = ischemic; minimal/absent = non-ischemic) 1, 2
History of trauma (suggests non-ischemic) 1, 3
Medication use: PDE5 inhibitors, intracavernosal injections, antipsychotics, antidepressants 6, 3
Previous priapism episodes (suggests stuttering pattern) 1, 3
Underlying conditions: sickle cell disease, hematologic malignancies 1, 2

Physical Examination:

Palpate corpora cavernosa: completely rigid and tender = ischemic; partially tumescent and non-tender = non-ischemic 1, 6
Assess glans and corpus spongiosum: should remain flaccid in both types 1, 3
Examine perineum: look for trauma, ecchymosis suggesting non-ischemic etiology 8

Gold Standard Diagnostic Test:

Cavernosal blood gas analysis - aspirate blood from corpora cavernosa with 19-21 gauge needle 2, 3:

Ischemic priapism values:

pO2 <30 mmHg
pCO2 >60 mmHg
pH <7.25 2, 3

Non-ischemic priapism values:

Normal arterial blood gas (pO2 >90 mmHg, pCO2 <40 mmHg, pH >7.35) 1, 2

Alternative Diagnostic Test:

Color Doppler ultrasound (if blood gas unavailable):

Ischemic: minimal to absent cavernosal arterial flow 1, 2
Non-ischemic: high arterial flow with visible fistula 2, 4

Management of Ischemic Priapism

Critical Timing Considerations:

Intervention must begin within 4-6 hours to preserve erectile function 2
Risk of permanent erectile dysfunction increases dramatically after 24 hours 2, 6
90% permanent erectile dysfunction rate after 48 hours 2, 3

Step 1: Immediate Corporal Aspiration + Phenylephrine Injection

This is the first-line treatment for all ischemic priapism, regardless of etiology. 2, 6

Technique:

Use 16-19 gauge butterfly needle inserted into lateral aspect of proximal corpora 2
Aspirate 20-30 mL of dark, deoxygenated blood 2
Inject phenylephrine 100-500 mcg/mL concentration 2
Maximum dose: 1000 mcg within first hour (to avoid systemic cardiovascular effects including hypertension and reflex bradycardia) 2, 6
Repeat injections every 3-5 minutes as needed before considering surgery 2, 6
Success rate: 43-81% 2, 3

Critical Pitfall: Never delay ischemic priapism treatment waiting for spontaneous resolution or attempting conservative measures alone - every hour increases permanent erectile dysfunction risk 2

Step 2: Surgical Shunting (if phenylephrine fails)

Distal shunts (first surgical option):

Winter, Ebbehoj, or T-shunt procedures 6
Create communication between corpora cavernosa and corpus spongiosum 4
Success rate: 60-80% 6
Lower erectile dysfunction risk than proximal shunts 6

Proximal shunts (if distal shunts fail):

Quackels or Grayhack procedures 6
Create communication between corpora cavernosa and saphenous vein 5
Higher erectile dysfunction risk but necessary for refractory cases 6

Step 3: Penile Prosthesis (last resort)

Immediate prosthesis implantation if all other measures fail and >48 hours elapsed 1
Preserves penile length and allows future sexual function 7

Management of Non-Ischemic Priapism

Initial management should be observation, as many cases resolve spontaneously without intervention. 2, 3

Conservative Management:

Observation for 2-4 weeks - spontaneous resolution occurs in majority 2, 7
Ice pack application to perineum 11
Avoid sexual stimulation 8

Selective Arterial Embolization (if patient requests treatment or priapism persists):

Use temporary absorbable materials (e.g., autologous clot, gelfoam) 2
Success rate: 74% 2
Erectile dysfunction rate: only 5% with temporary materials 2

Critical Pitfall: Never use permanent embolization materials as first-line - 7-fold higher erectile dysfunction rate (39% vs 5%) 2

Critical Pitfall: Never treat non-ischemic priapism as an emergency with aspiration and sympathomimetics - this provides no benefit and risks complications 2

Management of Stuttering Priapism

Acute Episode Management:

Treat each acute episode identically to ischemic priapism with aspiration and phenylephrine 4, 5
Episodes typically last <3 hours but require same urgent approach 1

Prevention of Future Episodes:

Patient education for home management:

Teach self-administration of intracavernosal phenylephrine for episodes approaching but not yet meeting 4-hour threshold 2, 6
Counsel on injection technique, dosing, systemic side effects, and when to seek emergency care 6

Preventive pharmacotherapy:

PDE5 inhibitors (sildenafil, tadalafil) taken daily reduce recurrence frequency 2, 6
Hormonal therapy options based on underlying etiology 2
Consider gonadotropin-releasing hormone agonists in refractory cases 7

Special Population: Sickle Cell Disease

Patients with sickle cell disease presenting with ischemic priapism should receive immediate urologic intracavernosal treatment identical to other ischemic priapism cases, without delay for systemic sickle cell interventions alone. 2, 3

Management Approach:

Immediate corporal aspiration and phenylephrine injection (same as non-sickle cell patients) 2, 6
Provide concurrent systemic sickle cell management (hydration, oxygen, exchange transfusion) alongside urologic intervention, not as substitute 2, 3
Systemic sickle cell treatments alone resolve priapism in only 0-37% of patients 3

Critical Pitfall: Never delay urologic intervention in sickle cell patients waiting for systemic treatments to work - this leads to permanent erectile dysfunction 2, 3

PDE5 Inhibitor-Related Priapism

Risk Factors from FDA Labels:

Sildenafil: Use with caution in patients with anatomical penile deformation or conditions predisposing to priapism (sickle cell anemia, multiple myeloma, leukemia) 9

Tadalafil: Should be used with caution in patients with conditions predisposing to priapism or anatomical penile deformation 10

Patient Counseling Requirements:

Seek emergency medical attention if erection lasts >4 hours 9, 10
Priapism >6 hours can result in irreversible erectile tissue damage and permanent potency loss 9, 10
Do not combine multiple PDE5 inhibitors 9

Management of PDE5 Inhibitor-Induced Priapism:

Treat identically to other ischemic priapism with immediate aspiration and phenylephrine 2, 6
Do not discontinue PDE5 inhibitor acutely during emergency 6
After resolution, discuss whether dose adjustment or discontinuation is warranted 6

Conservative Measures (Limited Evidence)

Exercise Trial:

Lower-limb exercise (specifically stair climbing) may redirect blood flow away from penis 11
Minimal risk if access to definitive treatment not delayed 11
Can be attempted while awaiting urologic evaluation, but never delay aspiration/phenylephrine 11

Other Conservative Measures (Weak Evidence):

Ice pack application to penis/perineum 11
Cold showers 11
These lack sound evidence but have minimal risk if definitive treatment not delayed 11

Critical Pitfall: Conservative measures should never delay aspiration and phenylephrine injection in ischemic priapism - time is erectile tissue 2, 11

Verification of Resolution

Ischemic Priapism Resolution:

Penis returns to completely flaccid, non-painful state 1
Persistent penile edema, ecchymosis, and partial erections can occur and may mimic unresolved priapism 1
Verify resolution with repeat cavernosal blood gas (normalized values) or color duplex ultrasound (restored normal flow) 1

Non-Ischemic Priapism Resolution:

Complete return to flaccid penis 1
Confirm with ultrasound showing closure of arterio-cavernosal fistula 2

Common Pitfalls Summary

Never delay ischemic priapism treatment waiting for spontaneous resolution - every hour increases permanent erectile dysfunction risk 2
Never treat non-ischemic priapism as emergency with aspiration and sympathomimetics - provides no benefit and risks complications 2
Never use permanent embolization materials for non-ischemic priapism first-line - 7-fold higher erectile dysfunction rate 2
Never exceed 1000 mcg phenylephrine in first hour - risk of systemic cardiovascular effects 2, 6
Never delay urologic intervention in sickle cell patients waiting for systemic treatments alone 2, 3
Never assume resolution based on clinical appearance alone - verify with blood gas or ultrasound as edema/ecchymosis can mimic persistent priapism 1

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