Erectile dysfunction

Penile Doppler (papaverine inducedin erectile dysfunctionor papaverine-induced colour duplex Doppler) is an excellent and, is a highly accurate means of assessing patients with erectile dysfunction (ED).

Pathology

Penile erection is a result of a complex interaction between the nervous, arterial, venous and sinusoidal systems. Any defect in one of these linkscomponents can lead to erectile dysfunction.

Physiology

Psychological factors (mental impulse) causescause transmission of parasympathetic impulses to the penis. This causes relaxation of arterioles and corpora cavernosa sinusoids. As the sinusoidal spaces start filling, the corporal veno-occlusive mechanism activates, adand the fibrous tunica albuginea compresses the emissary veins of the corpora, and rigid erection is achieved.

Aetiology

• psychogenic (~10%)
  • stress
  • anxiety
  • depression
• organic 
  • endocrine disorders
    • Cushing's syndrome
    • Addison's disease
    • hyperthyroidism
    • hypothyroidism
    • hypogonadism
    • hyperprolactinemiahyperprolactinaemia 
  • neurogenic
    • spinal tumortumour
    • traumatic nerve injury
    • multiple sclerosis
    • Parkinson disease
    • stroke
  • arteriogenic impotence (~30%) 
    • diabetes 
    • peripheral vascular disease
  • venogenic impotence (~15%)
    • penile venous insufficiency
  • combined arteriogenic and venogenic (~10%)
  • morphological penile abnormalities
    • Peyronie's disease
    • hypospadias
  • drugs
    • antipsychotics
    • anticonvulsants
    • diuretics
    • ACE inhibitors
    • corticosteroids
  • excessive alcohol and smoking

Radiographic features

Angiography

Angiography with selective internal iliac angiography is the gold standard for arteriogenic impotence. However, it is invasive and not recommended for screening or primary diagnosis.

Ultrasound

Penile dopplerDoppler procedure

Procedure should be explained in detail prior to the examination. It is advisable to stop smoking 3three days prior to the examination. A proper drug history and cardiac status should be inquiredenquired.

HighA high frequency transducer (7.5-9.0 MHz) is used for penile dopplerDoppler examination. Patient is placed in supine position and penis is positioned in its anatomical position along the anterior abdominal wall. Doppler angle is set at 30-60 degrees.

Pre-injection measurements: inner diameter of cavernosal artery (normal value is 0.3-0.5 mm), baseline peak systolic velocity and end diastolic-diastolic velocity.

60 mg of papaverine (2 mlmL ampoule of 30 mg/ml/mL) is injected intracavernosally. 10-15 micrograms of PGE1prostaglandin E1 (PGE1), also known as alprostadil, can also be injected. Combination of papaverine and phentolamine may also be used.

Corpora cavernosa isare localized as two well defined-defined oval compartments with central cavernosal artery on both sides of bulbus spongiosathe corpus spongiosum (urethra is in centercentre of bulbus spongiosacorpus spongiosum). Insulin syringe is used for injection under sonographic guidance.

Post injection-injection measurements (at 5, 10, 15, 20 minutes): inner diameter of cavernosal artery (normal value is 0.6-1.0 mm), peak systolic velocity, end diastolic velocity, visual tumescence and erection.

Assessment of erection following papaverine injection

• phase 1: sudden increase in both systolic and diastolic flow velocity in cavernosal artery with minimal tumescence
• phase 2: with further increase in intracavernosal pressure, there is a decrease in diastolic flow with a classical 'dicrotic' notch
• phase 3: as the intracavernosal pressure increases, diastolic flow reaches zero with further increase in tumescence
• phase 4: diastolic flow reversal occurs with maximum systolic velocity; this is associated with penile rigidity
• phase 5: decrease in the systolic flow velocity occurs; this is usually 15 minutes post injection-injection which is associated with reduction in tumescence and rigidity

Interpretation

In flaccid state, monophasic flow is seen with absent/minimal diastolic flow. With onset of erection, systolic and diastolic flow both increases. With further increase in pressure, 'dicrotic notch' appears with dip in diastolic flow. End diastolic-diastolic flow may go down to zero or reversal may be seen. Then monophasic flow is seen with sharp systolic peak, corresponding with visual full erection.

Peak systolic velocity is the best Doppler indicator of arteriogenic impotence. Its value <30 cm/sec during the examination indicates arterial dysfunction. Some people consider <25 cm/sec as definite arterial dysfunction and 25-30 cm/sec as borderline case. Less than 60% increase in cavernosal diameter after papaverine injection is also an indicator of arterial impotence.

End diastolic-diastolic velocity is the best dopplerDoppler indicator of venogenic impotence. Its value >5 cm/sec indicates venous dysfunction. A good diastolic reversal virtually rules out venous insufficiency.