erectile dysfunction Flashcards
what is erectile dysfunction?
The persistent inability to attain and maintain an erection sufficient to permit satisfactory sexual performance
what happens physiologically for erection to occur?
- brain sends a signal via the spinal cord through the parasympathetic nervous system
- causes release of nitric oxide, NO, a neurotransmitter which chemically relaxes the smooth muscles in thecorpora cavernosa, the two expansion chambers in the penis
- This enables enhanced blood flow into the lacunar spaces of the corpora, a mechanical process, causing expansion of the erectile tissue
- there is concomitant constriction of venous outflow resulting in blood containment, penile enlargement and rigidity = corporeal veno occlusive mechanism
what is the arterial supply of the penis?
the internal pudendal artery branch of the internal ileac artery
the internal pudendal artery branches into the dorsal penile artery, cavernosal artery and bulbar artery
which part of the penis does the dorsal penile artery supply?
the glans penis
which part of the penis does the bulbar artery supply?
bulb
spongiosum
glans penis
which part of the penis does the cavernosal artery supply?
corpora cavernosa
describe how the blood supply of the penis changes between the flaccid and erect state
flaccid: the penile smooth muscle is contracted, the helicine arteries are constricted, the cavernosal sinusoids are empty and the emissary veins are open
erect: the penile smooth muscle is relaxed, helicine arteries are dilated and so fill the cavernosal sinusoids which in turn compress the emissary veins against the tunica albuginea, resulting in reduced venous outflow
what are the different routes of venous drainage of the penis?
subtunical plexus which drains into the circumflex veins and deep dorsal vein
the coropora cavernosa is drained by the cavernous veins to the crural veins and internal pudendal veins
what type nerve supply causes the erection and what spinal levels is this?
parasympathetic
S2-4
what type of nerve supply causes ejaculation and what spinal levels is this?
sympathetic
T11-L2
what nerve carries both the parasympathetic and sympathetic nerve supply to the penis?
cavernous nerve
In the flaccid state, the penile smooth muscle is contracted, what is the biochemistry behind this?
noradrenaline release from sympathetic nerve terminals causes smooth muscle contraction
(also neuroppeptide Y released form sympathetic nerve terminals and endothelin and prostanoids released from the vascular endothelium cause contraction of smooth muscle)
in the erect state, the trabecular smooth muscle relaxes, what is the biochemistry behind this?
NO is released from the parasympathetic nerve terminals
NO is also released by the vascular endothelium after the endothelium has been stimulated by Ach from parasympathetic nerve fibres
which hormone is required for normal erectile function?
testosterone
what are the causes of low testosterone?
- primary - hypopituitarism, hypothalamic dsiease
- secondary - tumour of the testis, testicular injury, drugs
- congenital - Klinefelters, Noonans
How does NO cause smooth muscle relaxation?
- NO stimulates guanylate cyclase
- guanylate cyclase converts GTP to cyclic guanosine monophosphate (cGMP)
- cGMP causes protein kinase G to close calcium channels and open potassium channels
- the reduction in cytoplasmic calcium concentration results in smooth muscle relaxation
How is the action of cGMP terminated?
phosphodiesterase converts cGMP to the inactive guanosine monophosphate GMP
How does viagra (ie sildenafil) work?
it is a phosphodiesterase inhibitor, so inhibits the conversion of cGMP to GMP which normally terminates the erection
what are the different causes of erectile dysfunction?
vasculogenic neurogenic hormonal anatomical drug induced psychogenic
what are the risk factors of ED?
(same as those of CVS disease) obesity lack of exercise smoking hypercholesterolaemia metabolic syndrome diabetes
list some specific conditions that can cause ED?
DM cardiovascular dsiease - MI and hypertension liver disease alcohol renal failure trauma - eg pelvic fracture iatrogenic - prostatectomy
can ED be improved by lifestyle modification?
yes
can ED be an early sign of cardiovascular disease
yes
What are the indicators of psychological aetiology?
sudden onset ED
good nocturnal and early morning erections
situational ED
younger pt
What are the components of the physical examination for ED?
BP and HR hepatosplenomegaly genitalia - for Peyronie's disease prostatic enlargement or cancer hypogonadism - small testis, lack of secondary sexual characteristics
What questionnaire is used for assessment of sexual history?
IIEF (International index for Erectile Function)
what are the components of the international index for erectile function?
Erectile function, orgasmic function, sexual desire, ejaculation, intercourse and overall satisfaction
What lab investigations are commonly done for ED?
fasting glucose (diabetes)
lipid profile
morning testosterone (as this is when testosterone is highest)
if testosterone is low, perform prolactin, FSH and LH
what are the specialised tests that can be done for ED (rarely)
Nocturnal penile tumescence (how swollen it is) and rigidity
Intracavernosal injection test
Duplex USS of penile arteries
Arteriography
In most pts a cause for their ED is found T or F?
False - in most causes no cause is found and results of tests are normal
How is ED treated?
identify the causes and treat if reversible
lifestyle and risk modification
pt and partner involvement in education and counselling to help psychologically
How are hormonal causes of ED treated?
testosterone deficiency is treated with gels and injections containing testosterone
When is testosterone therapy contraindicated?
if history of prostate cancer
What is monitored in pts who are on testosterone therapy?
- check DRE and PSA beforehand and monitor through therapy as it does increase your risk of prostate cancer
- monitor for hepatic or prostatic disease
What is the first line therapy for ED?
phosphodiesterase PDE5 inhibitors
what are the second line treatments for ED?
intracavernous injections
intraurethral alprostadil
vacuum devices
How are the treatments assessed?
Therapeutic response
Side effects
Satisfaction with treatment
if there is an inadequate outcome, then make sure the pt is doing the treatment correctly
What is the last resort for ED?
penile implant (two types, one is malleable and one is a pump device)
Do phosphodiesterase type 5 inhibitors stimulate erection?
no - needs sexual stimulation
How do you
test whether the medication is working or not?
6 attempts at maximum dosage after advising pt on how to take the drug properly with adequate sexual stimulation, waiting long enough for the drug to work
how does the second line agent sublingual apomorphine work?
centrally acting dopamine agonist
what are the side effects of the vacuum pump?
pain inability to ejaculate petechiae bruises numbness
what are the contraindications for the vacuum device?
bleeding disorders
anticoagulants
what are the complications of intracavernosal injections?
penile pain
priapism
fibrosis
bruising
what is a priapism?
an erection that lasts more than 4 hours
risk of permanent ischaemic damage to the corpora and permenant erectile dysfunction
what are the side effects of intraurethral alprostadil?
pain
dizziness
urethral bleeding
what are the complications of prosthesis?
infection
mechanical failure
