Erectile dysfunction

Penile Doppler (papaverine induced colour duplex Doppler) is an excellent and highly accurate means of assessing patients with erectile dysfunction¹.

Introduction

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

Physiology of erection

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

Aetiology of erectile dysfunction

• psychogenic (~10%)
  • stress
  • anxiety
  • depression
• organic 
  • endocrine disorders
    • Cushing's syndrome
    • Addison's disease
    • hyperthyroidism
    • hypothyroidism
    • hypogonadism
    • hyperprolactinemia 
  • neurogenic
    • spinal tumor
    • 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 doppler procedure

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

High frequency transducer (7.5-9.0 MHz) is used for penile doppler 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 velocity.

60 mg of papaverine (2 ml ampoule of 30 mg/ml) is injected intracavernosally. 10-15 micrograms of PGE1 can also be injected. Combination of papaverine and phentolamine may also be used.

Corpora cavernosa is localized as two well defined oval compartments with central cavernosal artery on both sides of bulbus spongiosa (urethra is in center of bulbus spongiosa). Insulin syringe is used for injection under sonographic guidance.

Post 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: it is a multiphasic event.

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