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Erectile Dysfunction — A Complete Urological Overview

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1. DEFINITION

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2. EPIDEMIOLOGY

• 52% of all respondents reported some degree of ED
• Breakdown: 17% mild, 25% moderate, 10% complete
• Prevalence of complete ED tripled from 5% at age 40 → 15% at age 70
• Incidence per 1,000 man-years: 12.4 (age 40–49), 29.8 (50–59), 46.4 (60–69)

• Hypertension, hyperlipidemia, diabetes mellitus, cardiovascular disease
• Smoking (dose-dependent)
• Metabolic syndrome (each additional component increases ED risk)
• Depression and psychosocial disorders
• Prostate cancer treatment (surgery, radiation)
• Chronic renal failure, cirrhosis, COPD

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3. ANATOMY & PHYSIOLOGY OF ERECTION (Prerequisite for Understanding Pathophysiology)

3.1 Penile Anatomy

• Two corpora cavernosa (paired dorsolateral cylinders) — enclosed in the tunica albuginea (a bilayered, inelastic fibrous sheath)
• Corpus spongiosum — surrounds the urethra and forms the glans
• The cavernous sinusoids are trabeculated spaces lined by endothelium, surrounded by smooth muscle

3.2 Vascular Mechanism of Erection

1. Psychogenic/sensory stimulation → activation of the parasympathetic sacral erection center (S2–S4) and medial preoptic area (MPOA) of the hypothalamus
2. Cavernous nerves release nitric oxide (NO) from NANC (non-adrenergic, non-cholinergic) nerve terminals AND from vascular endothelium
3. NO activates soluble guanylyl cyclase → ↑cGMP → activates protein kinase G → opens K⁺ channels, closes Ca²⁺ channels → ↓ intracellular calcium → smooth muscle relaxation
4. Arterial dilation and sinusoidal expansion → blood rushes in
5. Veno-occlusive mechanism: expanding sinusoids compress the subtunical venular plexuses against the rigid tunica albuginea → venous outflow blocked → intracavernous pressure rises to ~100 mmHg (systolic BP) → rigid erection
6. With ischiocavernosus muscle contraction, intracavernosal pressure can exceed 200 mmHg (full rigidity phase)

3.3 Detumescence

• Sympathetic discharge (via T11–L2) releases norepinephrine → α₁-adrenergic receptor activation → smooth muscle contraction → venous channels open → detumescence
• PDE5 (phosphodiesterase type 5) degrades cGMP → facilitates detumescence

3.4 Key Molecular Players (Campbell Walsh Table 68.8)

3.5 Types of Erection

1. Psychogenic — from auditory, visual, olfactory, imaginative stimuli → higher cortical centers → sacral/thoracolumbar pathways
2. Reflexogenic — from tactile stimulation of the genitalia → sacral reflex arc (S2–S4); preserved in upper motor neuron lesions
3. Nocturnal (REM sleep) — testosterone-dependent; occurs 3–5 times per night; used diagnostically

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4. CLASSIFICATION

4.1 Organic ED

• A. Arteriogenic (arterial insufficiency — most common organic cause)
• B. Cavernosal/venogenic (veno-occlusive dysfunction — failure of the veno-occlusive mechanism)
• C. Mixed (arterial + venogenic)

• Central: brain lesions, spinal cord injuries, multiple sclerosis
• Peripheral: diabetic neuropathy, post-surgical (radical prostatectomy, APR, radical cystectomy), pelvic radiation

• Peyronie's disease, penile fibrosis, congenital curvature, micropenis, hypospadias, phimosis

• Hypogonadism (primary/secondary), hyperprolactinemia, hypothyroidism/hyperthyroidism, Cushing's syndrome

• Antihypertensives (β-blockers, thiazides), antidepressants (SSRIs, TCAs), antipsychotics, antiandrogens, opioids, alcohol, LHRH agonists/antagonists

4.2 Psychogenic ED

• Generalized unresponsiveness: primary lack of sexual arousability; aging-related decline
• Generalized inhibition: chronic disorder of sexual intimacy

• Partner-related: lack of arousability in specific relationship; sexual object preference issues; conflict
• Performance-related: situational anxiety (fear of failure); associated with other sexual dysfunctions (e.g., premature ejaculation)
• Psychological distress/adjustment: negative mood states (depression), major life stress

4.3 Mixed ED

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5. ETIOLOGY & PATHOGENESIS (by Category)

5.1 Vasculogenic (Most Common Organic Type)

• Atherosclerosis, hypertension, hyperlipidemia, DM → endothelial dysfunction → reduced NO bioavailability → impaired vasodilation
• Peak systolic velocity (PSV) <25 cm/s on Doppler ultrasound = arteriogenic insufficiency
• Pelvic cycling trauma → perineal compression of pudendal artery → bicycle rider's ED

• Degenerative changes in smooth muscle and collagen (aging, DM, smoking)
• Abnormal communication between cavernosal sinusoids and emissary veins
• Peyronie's disease fibrosis preventing sinusoidal expansion
• End-diastolic velocity (EDV) >5 cm/s on Doppler = venous leak

5.2 Neurogenic

• MPOA and paraventricular nucleus (PVN) of hypothalamus — key integration centers
• Parkinson's disease, stroke, temporal lobe epilepsy, Alzheimer's disease, traumatic brain injury → disrupt dopaminergic/oxytocinergic pathways
• Spinal cord injury: reflexogenic erections preserved in 95% of complete upper motor neuron lesions (intact sacral reflex arc); psychogenic erections lost. Complete lower motor neuron (conus/cauda equina) lesions abolish both.

• Radical prostatectomy — cavernous nerve injury is the key mechanism; Walsh's nerve-sparing technique:
  • 86% potency recovery at 18 months (Walsh data)
  • Age <65, bilateral NVB preservation, preoperative potency → best outcomes
  • Recovery is gradual: 38% at 3 months → 54% at 6 months → 73% at 12 months → 86% at 18 months
• Abdominoperineal resection, radical cystectomy, pelvic radiation
• Diabetic autonomic neuropathy: NO-dependent selective nitrergic nerve degeneration; decreased nNOS and eNOS activity

5.3 Endocrinologic

• Testosterone (T) modulates sexual desire centrally and maintains NOS activity in cavernous tissue
• DHT (via 5α-reductase) is important peripherally for penile tissue health
• Castration → decreased NOS activity in corpus cavernosum → reduced erectile activity
• Nocturnal erections are androgen-dependent; visually-stimulated erections are relatively androgen-independent
• Finasteride 5 mg → ~5% ED; post-finasteride syndrome (persistent ED months–years after stopping) reported

• Prolactin-secreting pituitary tumors → elevated prolactin → suppresses GnRH → hypogonadotropic hypogonadism → ↓ testosterone → ED + decreased libido

• Independent risk factor for ED; visceral adiposity → ↑ aromatase activity → ↑ estrogen → ↓ testosterone
• Prevalence of ED increases with each additional metabolic syndrome component

5.4 Diabetic ED (Multimechanistic)

• Macrovascular: atheromatous lesions in large vessels, stenosis in pudendal/iliac arteries
• Microvascular: small vessel disease, thickening of basal lamina, endothelial cell loss
• Neuropathy: decreased nNOS and eNOS activity (NO-dependent nitrergic degeneration)
• Biochemical: advanced glycation end products (AGEs) deposit in cavernous tissue → impaired smooth muscle relaxation; increased expression of inducible arginase (arginase II) depletes L-arginine substrate for NO production; increased oxidative stress → free radical scavenging of NO; reduced cAMP production
• Result: decreased response to PDE5 inhibitors compared to non-diabetic patients

5.5 Drug-Induced ED

5.6 Psychogenic Mechanism

1. CNS-mediated: Anxiety/depression → increased cortical inhibitory tone via serotonergic overactivation → suppresses pro-erectile signals from hypothalamus and limbic system
2. Adrenergic: Excessive sympathetic activation → elevated peripheral catecholamines → increased cavernous smooth muscle tone → prevents sinusoidal relaxation
   • Men with psychogenic ED have higher serum norepinephrine than healthy controls or vasculogenic ED patients (Kim and Oh, 1992)

5.7 Aging-Related Changes

• Progressive decline: longer latency to erection, reduced turgidity, shorter duration, increased refractory period
• ↓ penile sensitivity to tactile stimulation
• ↓ testosterone concentration
• ↑ cavernous smooth muscle tone
• ↓ smooth muscle:collagen ratio → reduced compliance

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6. CLINICAL PRESENTATION: SYMPTOMS AND SIGNS

6.1 Primary Symptom

• Onset failure — cannot achieve erection at all (suggests severe arteriogenic or neurogenic cause)
• Maintenance failure — achieves partial erection that dissipates before or during intercourse (suggests venogenic/veno-occlusive dysfunction)
• Reduced rigidity — erection present but insufficient for penetration

6.2 Distinguishing Organic vs. Psychogenic ED (Clinically Critical)

6.3 Associated Symptoms to Assess

• Libido/sexual desire: If absent → suggests endocrine cause (hypogonadism, hyperprolactinemia) or depression
• Ejaculatory dysfunction: Premature ejaculation, anejaculation, retrograde ejaculation
• Penile deformity/pain: Suggests Peyronie's disease
• LUTS (lower urinary tract symptoms): BPH frequently coexists; both respond to PDE5I
• Cardiovascular symptoms: ED is a cardiovascular risk equivalent — ask about angina, exertional dyspnea, claudication
• Neurological symptoms: Saddle anesthesia, weakness, MS symptoms, Parkinson's features

6.4 Validated Questionnaire: IIEF-5 (International Index of Erectile Function)

6.5 Signs on Physical Examination

• Genitalia: Penile plaques (Peyronie's), phimosis, testicular size/consistency (small testes → hypogonadism), varicocele, hernias
• Secondary sex characteristics: Body hair distribution, gynecomastia (suggesting androgen deficiency or estrogen excess)
• Blood pressure and heart rate: Hypertension, pulse quality, peripheral pulses
• Neurological: Bulbocavernosus reflex (S3–S4), perineal sensation, lower limb reflexes
• Rectal examination: Prostate size, nodules (important before testosterone therapy)
• Body habitus: Central obesity (metabolic syndrome), muscle mass

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7. DIAGNOSIS

7.1 Basic Workup (Recommended for ALL patients)

1. Detailed sexual, medical, and psychosocial history (most important single step)
2. Physical examination (as above)
3. Validated questionnaire (IIEF-5)
4. Laboratory tests:
   • Fasting glucose (or HbA1c if diabetic)
   • Fasting lipid profile
   • Morning total testosterone (8–11 AM — diurnal variation)
   • Calculated free testosterone (if T borderline or SHBG likely abnormal)
   • Complete blood count
5. Additional hormones if clinically indicated:
   • Prolactin (if ↓ libido, low T, or gynecomastia)
   • LH and FSH (to distinguish primary vs. secondary hypogonadism)
   • TSH (thyroid disease)
   • PSA (before initiating testosterone therapy)

7.2 Specialized Investigations

• RigiScan monitors frequency, duration, and rigidity of nocturnal erections
• Normal: ≥3 episodes per night, ≥10 min each, ≥70% rigidity at tip and base
• Preserved NPT → psychogenic origin (erection center intact)
• Absent/reduced NPT → organic cause
• Note: depression and sleep disorders can suppress NPT and produce false-positive results

• Performed with intracavernosal injection of vasoactive agent (prostaglandin E1 / papaverine / phentolamine — Tri-Mix)
• Measurements taken at 5, 10, 20, 30 minutes post-injection
• Peak Systolic Velocity (PSV):

  • 25 cm/s = Normal arterial function

  • 25–35 cm/s = Borderline
  • <25 cm/s = Arteriogenic ED
• End-Diastolic Velocity (EDV):
  • <5 cm/s = Normal veno-occlusion
  • >5 cm/s = Venogenic ED (venous leak)
• Resistance Index (RI) = (PSV–EDV)/PSV; RI >0.9 = normal
• The test also identifies high-flow priapism (post-traumatic cavernous artery–sinus fistula)

• Papaverine, phentolamine, or alprostadil injected directly
• Full rigid erection = adequate vascular function (rules out significant arterial insufficiency or venous leak)
• Partial response = vascular cause likely

• Cavernosometry: measures maintenance flow rate required to sustain pharmacologically induced erection → assesses veno-occlusive function; >120 mL/min maintenance flow = significant venous leak
• Cavernosography: contrast injection to visualize leaking venous channels
• Reserved for patients being considered for venous surgery

• Internal iliac → pudendal arteriogram with pharmacological erection
• Reserved for: young men with post-traumatic arteriogenic ED being evaluated for penile revascularization surgery
• NOT indicated routinely in older men with systemic arterial disease

• Biothesiometry (vibration perception threshold) — assesses peripheral nerve function of penile skin; threshold >25V = significant neuropathy
• Bulbocavernosus reflex latency (BCR) — normal <35–40 ms; tests pudendal nerve and sacral arc
• Pudendal nerve somatosensory evoked potentials (SSEPs)
• Corpus cavernosum electromyography (CC-EMG) — research tool

• IIEF, Beck Depression Inventory, State-Trait Anxiety Inventory
• If psychogenic ED strongly suspected, referral to sex therapist/psychologist

• Dynamic infusion cavernosometry: cavernosal alpha-smooth muscle biopsy in complex cases

7.3 Risk Stratification for Cardiovascular Safety (Princeton Consensus)

• Low risk (stable, well-controlled cardiovascular disease, no symptoms): Can treat immediately
• Intermediate risk (unstable): Defer until cardiologically stabilized
• High risk (recent MI <6 weeks, unstable angina, uncontrolled hypertension): Contra-indicated until stabilized

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8. TREATMENT

• First-line: Lifestyle modification + oral pharmacotherapy (PDE5Is)
• Second-line: Intracavernosal injections, intraurethral therapy, vacuum erection devices
• Third-line: Penile prosthesis implantation

8.1 Lifestyle Modification and Treatment of Underlying Conditions

• Treat dyslipidemia, hypertension, diabetes (metabolic control improves erectile function)
• Weight loss and exercise — proven to restore erectile function in obese men; 30 minutes of aerobic exercise daily
• Smoking cessation — reversal of endothelial dysfunction
• Review and modify medications contributing to ED (e.g., switch β-blockers to ARBs/CCBs)
• Pelvic floor physiotherapy (Kegel exercises) — especially post-prostatectomy

8.2 Psychosexual Therapy

• For psychogenic ED: cognitive behavioral therapy (CBT), sensate focus (Masters & Johnson technique), relationship counseling, treatment of depression/anxiety
• Combination of psychotherapy + pharmacotherapy more effective than either alone in mixed ED

8.3 First-Line: PDE5 Inhibitors (Oral)

• Headache, flushing, nasal congestion, dyspepsia
• Visual disturbances (blue tinge, blurred vision) — sildenafil has some PDE6 inhibition (retinal)
• Myalgia and back pain — tadalafil (due to PDE11 inhibition)
• Hypotension

• Nitrates in any form (organic nitrates, amyl nitrate) — severe refractory hypotension
• α₁-blockers (relative; use with caution and dose separation — high risk of hypotension)
• Severe hepatic impairment
• Recent stroke or MI (<6 weeks), unstable angina, uncontrolled hypertension
• Severe aortic stenosis, obstructive hypertrophic cardiomyopathy
• Retinitis pigmentosa (sildenafil)
• Use of ritonavir, ketoconazole (potent CYP3A4 inhibitors — increase PDE5I levels)

8.4 Hormone Replacement

• Indicated only in confirmed symptomatic hypogonadism (morning total T <300 ng/dL, confirmed on two occasions, with symptoms)
• Does NOT work in eugonadal men
• Routes: IM injection (testosterone cypionate/enanthate), transdermal gel, transdermal patch, subcutaneous pellets, intranasal
• Monitoring: DRE + PSA at 3 and 6 months, then annually; CBC (polycythemia risk), liver function, lipid profile
• Absolute contraindications: Active prostate cancer, breast cancer, severe BPH with high post-void residual, erythrocytosis (hematocrit >54%), untreated obstructive sleep apnea

8.5 Second-Line: Intracavernosal Injection Therapy (ICI)

• Dose: 2.5–40 mcg; titrated by physician
• Onset: 5–20 minutes; duration 30–60 minutes
• Efficacy: 70–85% satisfactory erections (better than oral therapy in post-prostatectomy and diabetic patients)
• Tri-Mix (papaverine + phentolamine + alprostadil) — most effective combination; success rates >90%
• Complications:
  • Priapism (erection >4 hours) — medical emergency; aspirate + phenylephrine injection; risk 1–5% with PGE1
  • Penile pain (most common with alprostadil ~50%)
  • Penile fibrosis/nodules with long-term use
  • Syncope (vasovagal)
  • Hematoma at injection site
• Contraindications: Patients on anticoagulants (relative), those with history of priapism, sickle cell anemia

8.6 Second-Line: Intraurethral Alprostadil (MUSE — Medicated Urethral System for Erection)

• Alprostadil pellet 125–1000 mcg inserted into urethra via applicator
• Absorption through urethral mucosa into corpus spongiosum → corpus cavernosum
• Efficacy: ~43–65% (less effective than ICI)
• Side effects: urethral burning/discomfort, dizziness, hypotension
• Requires urination prior to use to moisten urethra

8.7 Second-Line: Vacuum Erection Device (VED)

• External cylinder placed over penis → negative pressure creates erection → constrictive ring at base maintains erection
• Non-invasive; no systemic side effects
• Success rates: 60–90%
• Limitations: unnatural appearance, penile ecchymosis, pivoting erection (ring at base), petechiae, ejaculatory dysfunction
• Best suited for: elderly men, poor surgical candidates, those anticoagulated, post-prostatectomy rehabilitation
• Penile rehabilitation: Regular VED use post-prostatectomy prevents cavernosal fibrosis and aids recovery

8.8 Third-Line: Penile Prosthesis (Implant Surgery)

1. Semirigid (Malleable) Prosthesis (e.g., AMS Spectra, Coloplast Genesis):
   • Constant semi-rigid state; manually positioned
   • Simpler surgery, lower mechanical failure rate
   • Acceptable rigidity; less natural appearance/concealment
2. Inflatable Penile Prosthesis (IPP):
   • 2-piece: Two cylinders + combined reservoir-pump in scrotum (e.g., AMS Ambicor)
   • 3-piece (Gold standard): Two cylinders + separate scrotal pump + abdominal reservoir (e.g., AMS 700 CX/LGX, Coloplast Titan)
     • Most natural appearance and function
     • Activated: squeeze pump → fluid from reservoir → cylinders inflate
     • Deactivated: press deflation valve → fluid returns to reservoir
     • Patient satisfaction: 85–95% (highest of all ED treatments)
     • Partner satisfaction: ~80%
     • Mechanical survival: ~93–95% at 5 years; ~60–80% at 15 years

• Infection: Most feared; S. epidermidis/S. aureus; risk 1–3% in non-diabetics, up to 8% in diabetics
  • AMS 700 has InhibiZone coating (rifampin + minocycline); Coloplast Titan has hydrophilic coating → reduces infection risk to <1%
• Mechanical failure (cylinder aneurysm, tubing disconnection, pump failure)
• Erosion (cylinder erosion through urethra or glans — rare)
• Penile shortening (most common patient complaint)
• Autoinflation
• Reservoir migration/herniation

8.9 Emerging and Regenerative Therapies

• Acoustic waves applied to penile tissue → neovascularization, nNOS upregulation, endothelial regeneration
• Most evidence in mild-to-moderate vasculogenic ED
• Systematic review 2024 (PMID 39419772, J Sex Med): Li-ESWT, platelet-rich plasma (PRP), and stem cell therapy show significant improvements in IIEF scores; Li-ESWT has best current evidence
• May restore response to PDE5Is in prior non-responders

• Concentrated autologous growth factors injected intracavernosally
• Emerging evidence; not yet FDA-approved specifically for ED

• Adipose-derived or bone marrow-derived mesenchymal stem cells
• Targets nNOS restoration and cavernous smooth muscle regeneration
• Still experimental/clinical trial phase

• eNOS gene transfer, Rho-kinase inhibition, Maxi-K channel gene therapy — research phase

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9. SPECIAL CLINICAL SCENARIOS

9.1 ED as a Cardiovascular Risk Marker

• ED and coronary artery disease share the same endothelial dysfunction pathophysiology
• Penile arteries are 1–2 mm diameter vs. 3–4 mm coronary arteries → smaller arteries occlude first
• ED precedes clinical CAD by 2–5 years in many patients → "canary in the coal mine"
• All men with ED should have cardiovascular risk stratification (BP, lipids, glucose, BMI, smoking)
• Princeton Consensus Guidelines: classify cardiac risk before prescribing any ED treatment

9.2 Post-Prostatectomy ED

• Nearly universal immediately post-surgery (>90%)
• Mechanism: cavernous nerve neuropraxia → temporary loss of NO-mediated relaxation → cavernosal smooth muscle hypoxia → fibrosis
• Penile rehabilitation strategy:
  • Early use of PDE5Is (daily low-dose tadalafil 5 mg) to maintain oxygenation and prevent fibrosis
  • VED use post-catheter removal
  • ICI with alprostadil for more aggressive rehabilitation
  • Timeline: recovery may take 18–24 months with nerve-sparing; less likely without

9.3 ED in Spinal Cord Injury

• Depends on level and completeness:
  • Complete upper motor neuron lesion → reflexogenic erection preserved (sacral arc intact); psychogenic erection absent
  • Complete lower motor neuron (conus/cauda) → both types lost
  • Incomplete lesions → variable preservation
• Treatment: PDE5Is effective if sacral parasympathetics functional; ICI for complete lower lesions

9.4 Varicocele and ED

• Systematic review 2024 (PMID 38960064): Varicocele is significantly associated with both hypogonadism and erectile dysfunction; varicocelectomy may improve testosterone and erectile function

9.5 ED and Beta-Blockers

• Systematic review 2025 (PMID 39269577, Endocrine): β-blockers, especially older non-selective agents, are associated with increased ED risk; newer vasodilatory β-blockers (nebivolol — releases NO) have less sexual side effect burden

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10. PROGNOSIS

• Psychogenic ED: Excellent prognosis with psychosexual therapy ± PDE5Is; 50–70% respond
• Mild-moderate vasculogenic ED: Good response to PDE5Is (65–82%), especially if underlying risk factors managed
• Diabetic ED: Poorer response to PDE5Is (40–60%); often requires combination or second-line therapy; strict glycemic and metabolic control is critical
• Post-prostatectomy ED: Depends on age, pre-op potency, and whether bilateral NVB was spared; 50–90% partial recovery over 18–24 months; penile rehabilitation improves outcomes
• Complete neurogenic ED (bilateral pelvic nerve loss): PDE5Is largely ineffective; ICI or penile prosthesis required
• Hypogonadal ED: Excellent response to TRT when confirmed hypogonadism; testosterone alone may restore function without PDE5Is in mild cases
• Penile Prosthesis: Highest long-term satisfaction (85–95%) and durability of all treatment options; patient and partner satisfaction remains high at 5+ years

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11. SUMMARY ALGORITHM

ED confirmed (IIEF-5 + history)
        ↓
Basic workup: glucose, lipids, morning testosterone, CBC
        ↓
Underlying cause identified?
  → Hypogonadism: TRT first
  → Psychogenic: Psychosexual therapy ± PDE5I
  → Drug-induced: Modify medications
  → Systemic disease: Optimize (DM, HTN, dyslipidemia)
        ↓
FIRST LINE: PDE5 Inhibitor (on-demand or daily tadalafil)
  → Failed 4–6 adequate trials at max dose?
        ↓
SECOND LINE: ICI (alprostadil or Tri-Mix) OR MUSE OR VED
  → Failed or refused?
        ↓
THIRD LINE: Penile Prosthesis (3-piece IPP preferred)
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Consider Li-ESWT for mild-moderate vasculogenic ED
(may restore PDE5I response)

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Key High-Yield Facts for Urology Exams

1. ED is defined by a 6-month duration of inability to achieve/maintain erections sufficient for intercourse
2. NO → cGMP → PKG → smooth muscle relaxation is the core molecular pathway; PDE5 degrades cGMP
3. Arteriogenic ED = PSV <25 cm/s on CDDU; Venogenic ED = EDV >5 cm/s
4. IIEF-5 score 5–7 = severe ED; 22–25 = no ED
5. PDE5Is are absolutely contraindicated with nitrates — risk of fatal hypotension
6. Nocturnal erections (NPT) distinguish organic (absent) from psychogenic (preserved) ED
7. ED precedes coronary artery disease by 2–5 years — it is a cardiovascular sentinel event
8. Alprostadil ICI has highest efficacy among second-line treatments (~70–85%)
9. 3-piece inflatable prosthesis has the highest patient satisfaction (~90%); placing it permanently abolishes natural erections
10. Diabetic ED is the most treatment-refractory — multimechanistic (vascular + neurogenic + biochemical)
11. Psychogenic ED mechanism: excess sympathetic tone + high catecholamines prevent smooth muscle relaxation
12. Penile rehabilitation post-prostatectomy with early PDE5Is/VED prevents cavernosal fibrosis
13. Nebivolol among antihypertensives has the least ED side effect (releases NO)
14. Li-ESWT is the most promising emerging regenerative therapy

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