Chapter 191 - Erectile dysfunction Flashcards by Gary Yang

Prevalence of erectile dysfunction

50% of men > 40

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Erectile dysfunction definition

recurrent or consistent inability to maintain penile erection for satisfactory sexual performance

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Anatomy of the penis

1) paired dorsal corpora cavernosa - supported by tunica albuginea
2) ventral corpus spongiosum (urethra)

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Blood flow to penis

internal pudendal artery –> common penile artery –>

1) dorsal
2) cavernosal
3) bulbourethral

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Accessory pudendal artery origin

1) EIA
2) obturator
3) vesicle
4) femoral

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Cavernosal arteries terminate at what

helicine arteries

provide tumescence of penis

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Venous drainage of the penis

DEEP VEIN
Lacunar space –> subtunical venules –> emissary veins –>

1) cavernosal veins
2) deep dorsal vein
3) spongiosal veins

–> prostatic venous plexus or internal pudendal veins

SUPERFICIAL VEIN
Superficial dorsal vein –> saphenous vein

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Innervation of the penis

1) somatic nerve
2) parasympathetic nerve
3) sympathetic nerve

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Somatic nerve function for the penis

1) sensory

2) contraction of bulbocavernosus and ischiocavernosus muscle

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Parasympathetic nerve for penis origin

S2-S4 - hypogastric plexus

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Sympathetic nerve for penis origin

T12-L2 - pelvic plexus

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Autonomic nerves coalesce into this nerve before entering penis

Cavernous nerve

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Pathway of the cavernous nerve into penis

Posterolateral aspect of prostate –> urogenital diaphragm along with urethra

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Innervation of the cavernous nerve

Helicine arteries

Trabecular smooth muscle

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Physiology of erection

1) sexual stimulation
2) increase parasympathetic activity
3) cavenous nerve stimulation
4) penile smooth muscle relaxation (NO pathway)
5) increase bloodflow through penile arteries
6) sinusoid expansion
7) compressiong of subtunical venules (veno-occlusive mechanism)
8) increase intracavernous pressure

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Cellular mechanism of nitric oxide in erection

NO –> cAMP and cGMP –> decrease Ca2+ intracellular –> smooth muscle relaxation

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Causes of erectile dysfunction

1) psychogenic (10-15%)
2) neurogenic (uncomon)
3) endocrinologic
4) vasculogenic
5) drug-induced

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Psychogenic ED feature

1) good nocturnal erection

2) sudden-onset ED with intermittency

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Neurogenic ED subclassification

1) supraspinal
2) spinal
3) peripheral

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Supraspinal ED causes

1) tumor
2) stroke
3) Parkinson
4) dementia
5) temporal lobe epilepsy

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Spinal ED causes

1) MS
2) spinal cord injury
3) transverse myelitis
4) myelodysplasia
5) lumbar disc disease/surgery

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Peripheral neurogenic ED causes

1) lower motor neuron lesion
2) trauma
3) pelvic pathology
4) pelvic surgery (radical prostatectomy)

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Endocrine ED causes

1) androgen ? no clear link
2) hyperprolactinemia –> inhibit LH –> low libido
3) hypothyroidism –> low LH
4) hyperthyroidism –> high estradiol

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Vasculogenic ED risk factors

1) CAD
2) DM
3) HTN

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Vasculogenic ED theoretical mechanisms

1) flow-limiting stenosis 2) lower oxygen tension (low PGE1, high E2, high TGF beta1 (collagenization of cavenous smooth muscle) 3) endothelial dysfunction lack of NO 4) Corporal veno-occlusive dysfunction

Rate of abnormal ECHO in patients with vasculogenic ED

20%

5 year risk of cardiovascular events in patients with ED

45%

Peyronie disease in ED

scar tissue resulting in deranged drainage of the cavernous tissue

Drugs associated with ED

1) thiazide 2) non-selective beta blocker 3) ARB 4) SSRI 5) antiandrogen (prostate cancer use) 6) 5-alpha reductase inhibitor (finasterid, dutasteride) 7) digoxin

Penile brachial index

Cuff at base of flaccid penis no evidence not used

Intracavernosal injection testing

``` Vasodilatory meds (PGE1, papaverine, phentolamine) injected test for erection and detumesce ``` if no relaxation after 1 hour then phenylephrine given no evidence largely unused

Duplex ultrasound of the penis how its done

vasodilator use erection obtained then measure velocities transducer frequency 7.5 - 12 MHz

Duplex of penis cutoffs

PSV < 25 cm/s = arteriogenic ED sen 100 spe 86 > 10 cm/s difference between sides = atherosclerotic lesion EDV > 5cm/s = CVOD RI < 0.75 = abnormal

Dynamic infusion cavernosometry and cavernosography indications

1) young men with trauma for revascularization 2) young men failed pharmacotherapy to rule out CVOD 3) primary ED to rule out CVOD 4) medicolegal case 5) Peyronie disease with ED to rule out CVOD

DICC steps

CAVERNOSOMETRY 1) butterfly needle in each corporal body - one to pressure transducer, one to heparin 2) inject vasoactive drugs 3) record 4 things: 1) equilibrium pressure in corpus cavernosum - assessment of intracavernosal pressure 10-15 min after vasoactive agent 2) cavernosal artery inflow gradient for both sides - difference between brachial artery SBP and cavernosal artery occlusion pressure 3) flow to maintain a given intracavernosal pressure 4) pressure decay in mmHg/30s = pressure drop after raising intracavernosal pressure to 150 mmHg CAVERNOSOGRAPHY 1) radioopaque non-ionic dye into intracavernosally 2) rule out CVOD

DICC normal values

1) cavernosal artery occlusion pressure < 30 mmHg 2) flow to maintain ICP < 5 ml/min 3) pressure decay < 45 mmHg/30 seconds

DICC result interpretation

Plot flow to maintain against ICP 1) curvilinear pattern = CVOD 2) parabolic pattern = excessive sympathetic tone

Selective internal pudendal angiography indication

1) arterial insufficiency without CVOD 2) focal occlusion in one or both common penile or cavernosal arteries 3) perforating branches traveling from dorsal to cavernosal artery 4) at least one patent inferior epigastric artery as donor artery 5) at least one patent dorsal artery as recipient artery 6) patient with high flow priapism

Treatment of ED algorithm

1) lifestyle 2) PDE5 inhibitor + psychosocial 3) intracavernosal injection, intraurethral suppository, vacuum constriction device 4) penile implant surgery, vascular surgery

PDE5 inhibitor types, Tmax and half life

Sildenafil (1998) Viagra - Tmax 60 min; half life 4 hours vardenafil (Levitra) - Tmax 42 min; half life 4.5 hours tadalafil (Cialis) - Tmax 120 min; half life 17.5 hours Avanafil (Standra) - Tmax 45 min; half life 5.1 hours

PDE5 inhibitor mechanism of action

PDE5 normally degrades cGMP | Prolonged cGMP --> decrease intracellular calcium --> smooth muscle relaxation

Side effects of PDE5 inhibitors

1) headache 2) flushing 3) nasal congestion 4) heartburn 5) altered color vision 6) n/v 7) cardiovascular 8) diarrhea 9) dizziness 10) myalgia

Contraindication of PDE5 inhibitors

1) nitrate use | 2) antiarrhythmic (Type 1A or 3) for vardenafil only = long QT

Intracavernosal injection therapy types

1) PGE1 (alprostadil/Caverject) 2) phentolamine 3) papaverine Trimix has all 3 Bimix doesn't have PGE1

Mechanism of PGE1

Activate prostaglandin receptor --> increase cAMP

Mechanism of phentolamine

non-selective alpha antagonist --> relax SMC

Mechanism of papaverine

nonspecific PDE inhibitor --> increase cAMP and cGMP --> erection

Response time of ICI

5-10 minutes

Success rate of PDE5

69%

Success rate of ICI

89%

Complication of ICI

Priapism 0.25 - 7.3%

Reversal of prolonged erection

Alpha-adrenergic agonist Phenylephrine - intracavernosal administration

Intraurethral PGE1 suppository steps, success and complication

1) small plastic device into urethral meatus 2) pellet deposited into urethra variable efficacy 33% get pain 5% get bleeding

Maximum time of vacuum constriction device with compression ring

30 min

Implantable penile devices

1) malleable | 2) hydrualic (two piece or three piece)

Satisfaction after penile implant

75-97%

Infection after penile implant

0.7-3%

Surgical revascularization in ED

Inferior epigastric artery to dorsal artery bypass

Success after surgical revascularization in ED

55%

Key selection for surgical revascularization in ED

``` young < 40 focal lesion otherwise healthy no other underlying disease no CVOD ```

Complication after surgical revascularization in ED

1) failure to improve 2) inguinal hernia 3) penile shortening 4) loss of penile sensation 5) glans hyperemia if dorsal vein used

Venous ligation in crural enous leaks success rate

82-93%

Rate of ED preop in AAA and AIOD

22-39% historically higher in contemporary data with better definition

Aneurysm detection and management ADAM study on ED

1136 patients with 4-5.4 cm AAA surveillance vs immediate open repair Impotence higher in immediate repair 18months to 4 years higher ED over time also noted = progression of disease