Diagnostic Imaging in Erectile Dysfunction: Color Doppler Ultrasound (CDUS).
Stimulated Doppler Ultrasound is a reliable,
noninvasive diagnostic method that is used in the evaluation of men presenting with erectile dysfunction (ED).
This imaging and functional test provides objective quantification of erectile hemodynamics and can elucidate conditions such as corporal veno-occlusive dysfunction (venous leak),
penile arterio-venous shunts,
and Peyronie’s disease.
Ultrasound Normal Anatomy of penis:
The penis is composed of three cylindrical structures of erectile tissue: two dorsal corpora cavernosa and a ventral corpus spongiosum containing the penile urethra.
The spongiosum is smaller proximally but expands distally to form the glans penis.
The corpora cavernosa contain sinusoidal tissue which is markedly distensible and is essential to the erectile process.
non-distensible fibrous capsule,
the tunica albuginea,
invests the corpora cavernosa,
with a much thinner layer covering the corpus spongiosum.
There are two layers of fascia enveloping the shaft of the penis beneath the skin.
The dartos fascia is superficial and is in continuity with Scarpa’s fascia of the abdomen and the dartos fascia of the scrotum.
Deep to the dartos fascia lies Buck’s fascia,
which covers the corpora cavernosa and corpus spongiosum and attaches posteriorly to the suspensory ligaments of the penis,
allowing the erect penis to achieve a horizontal or greater angle Fig. 6 .
Fig. 6: Normal anatomy of penis.
CC: Corpora cavernosa.
CE: Corpus spongiosum.
Arrowheads: Tunica Albuginea.
Stars: Cavernosal arteries.
Arrow: Buck's fascia.
The normal arterial supply to the penis is via the internal pudendal artery (a branch of the anterior division of the internal iliac artery),
which divides into terminal branches,
the dorsal penile artery (supplying the glans penis),
the cavernosal artery (supplying the corpora cavernosa) and the bulbar artery (supplying the bulb and the corpus spongiosum) Fig. 7. Emissary veins pierce the tunica albuginea,
and drain into the deep dorsal vein via the spongiosal,
circumflex and cavernosal veins Fig. 8.
Fig. 8: Vascular Anatomy of penis.
References: Baxter GM and Sidhu PS. Ultrasound of the Urogenital System. Thieme, Stuttgart, 2006, Ch. 12.
Fig. 18: Schematic view of the complex venous drainage of the penis.
References: Rebonato A et al. Embolization of the Periprostatic Venous Plexus for Erectile Dysfunction Resulting from Venous Leakage. J Vasc Interv Radiol 2014; 25:866–872.
Indications of stimulated CDUS in Erectile Dysfunction:
- Patients with no satisfactory reponse to PDE-5 inhibitor treatment.
- Young patients that are candidates to arterial reconstructive surgery or endovascular therapies of venous-leaks.
- Pre-assessment of patients due to undergo revascularisation surgery
following penile trauma,
and to document vascularity prior to
surgery for Peyronie’s disease.
Stimulated CDUS: Pharmacological agents.
Prostaglandin E-1 (PGE-1/Alprostadil/Caverjet®) is the the most widely used agent for pharmacological stimulation of the penis.
The normal dosage of PGE-1 is between 10 and 20 μg.
but most commonly 20 μg is administered at the outset of the test.
PGE-1 is widely reported as a safe treatment but there is a small risk of priapism (less than 1%).
the second most commonly used stimulant,
has a reported incidence of iatrogenic priapism of up to 18%.
In patients with an erection lasting longer than 4 hours we recommend to come back to our institution and access to an on-site urology opinion to ensure prompt treatment if necessary.
Stimulated CDUS: Technique.
The stimulated CDUS examination should be performed in a setting that offers patient privacy with little possibility of interruption.
A high-frequency linear transducer is required.
Intra-cavernosal injection of PGE-1 is performed with a small-bore needle (typically 25-30G).
The ideal injection site is between the proximal and mid thirds of the shaft at the dorsolateral aspect. Following injection of the vasoactive substance the angle-corrected velocity of either the left or the right cavernosal artery is recorded at 5-minute intervals from baseline up to 30 minutes. Peak systolic velocity (PSV),
end diastolic velocity (EDV) and resistive index (RI) values are then
determined. Tumescence and rigidity are also documented.
Some studies have shown that hemodynamic measurements vary depending on the location of the transducer.
Those done at the “crus” (at the level of the peno-scrotal junction) may be significative for a better detection of veno-occlusive dysfunction (VOD),whereas an evaluation at “mid penis” (1/2 distance between peno-scrotal junction and coronal sulcus),
may be useful to diagnose better an arterial insufficiency (AI) Fig. 9.
Fig. 9: PGE-1 Stimulated CDUS of penis in Erectile Dysfunction Tecnique.
Left: Injection of 20 micrograms of PGE-1 with 30 needle inside the corpora cavernosa.
Right: Colour flow Doppler ultrasound of the cavernosal arteries should
be performed with the probe positioned at the base of the penis on
the ventral surface. The angle for Doppler analysis needs to be
optimised (<60°) with box-steering, angle correction and orientation
of the probe to ensure reproducible, valid measurements.
References: Berrkhim BM. Doppler Duplex Ultrasonography of the Penis. J Sex Med 2016;13:726e731
Stimulated CDUS in ED: Baseline Imaging.
Before injection of the stimulant,
a detailed B-mode US imaging is required to assess the anatomy,
the appropriate site for injection,
the presence of fibrotic plaques,
arterial calcification or tunica disruption.
The cavernosal arteries range in diameter from 0.3 mm in the flaccid state to 1.0 mm during erection.
The PSV of cavernosal artery in the flaccid penis is 10-15 cm/s Fig. 10.
Fig. 10: CDUS of right cavernosal artery before injection of PGE-1.
Artery diameter less than 1 mm and PSV <10 cm/s.
Stimulated CDUS in ED: Normal Response.
PSV greater than 35 cm/s,
EDV less than 5 cm/s or reversal flow RI >0.75 and deep dorsal vein velocity (DDVV) < 5 cm/s. Fig. 11 . Schwartz et al divided this process into stages:
- Phase 0: Prior to injection the dorsal arteries of the penis are more clearly identified than the cavernosal arteries.
The normal spectral waveform at this stage is monophasic with a high resistance pattern showing minimal or no diastolic flow Fig. 10.
- Phase 1: Follows pharmaco-stimulation and marks the onset of erection.
During phase 1 the systolic and diastolic flow increase results in continuous flow throughout the cardiac cycle.
In normal volunteers PSV is usually greater than 35 cm/s and the peak end-diastolic velocity (EDV) is greater than 8 cm/s.
- Phase 2: As pressure increases within the corpora cavernosa there is a progressive decrease in the diastolic flow.
The development of tumescence and subsequent veno-occlusion results in a reduction in diastolic flow.
- Phase 3: Corresponds to no diastolic flow.
- Phase 4: Characterised by reversal of diastolic flow and
- represents full erection.
- Phase 5: The final stage of rigidity,
usually not seen in clinical practice,
shows a decrease in systolic velocities,
which may approach zero.
Stimulated CDUS in ED: Arterial Insufficiency.
A PSV of ≥35 cm/s is unequivocally normal,
whilst a PSV of <25 cm/s following adequate stimulation indicates definite arterial insufficiency.
DDVV > 5 cm/s and RI <0,75 are associated. Fig. 12
Intermediate values are not specific and in this group sildenafil is often used as some will have mild to moderate arterial insufficiency and may benefit. Secondary diagnostic criteria for arteriogenic ED include asymmetry of 410 cm/s in PSV,
an increase in the diameter of the cavernosal artery by 75% postintracavernosal injection,
focal stenosis in the cavernosal artery and retrograde arterial flow.
Fig. 12: Stimulated CDUS after PGE-1 injection. Arterial Insufficiency. PSV of 20,3 cm/s, EDV of 3,4 cm/s, RI<0,75.
Stimulated CDUS in ED: Veno-oclusive dysfunction or venous-leak.
Ultrasound may be used to diagnose veno-occlusive dysfunction in
patients with normal arterial inflow.
Having established a normal
arterial response with a PSV >35 cm/s,
an EDV >5 cm/s and DDVV < 5 cm/s is usually accepted as the level above which a venous leak is present. RI may be used as an alternative measure for the diagnosis.
RI<0,75 with normal PSV is also regarded as diagnostic of a venous leak. Fig. 13.
Fig. 13: Stimulated CDUS of left cavernosal artery. Veno-oclusive (venous-leak) dysfunction. PSV of 30 cm/s, EDV of 10,3 cm/s, RI 0,82.
False Venous Leak concept: Anxiety following injection of PGE-1 may lead to a false positive result for venous leak due to elevated adrenergic tone.
Increase levels of adrenaline prevent complete relaxation of the sinusoidal smooth muscle in the corpora cavernosa and result in a failure of the normal veno-occlusive mechanism required for an erection.
This effect can be reduced by the use of Phentolamine (alfa-adrenoreceptor antagonist) injection in the corpora cavernosa.
Many authors recommend that intra-cavernosal phentolamine is necessary before a venous leak can be diagnosed by CDUS assessment in the younger patient.
Stimulated CDUS in ED: Mixed Aetiology.
Patients with PSV <25 cm/s,
EDV >5 cm/s,
DDVV >5 cm/s and RI < 0,75 reflects both arterial inflow insufficiency and venous leak. The diagnosis of mixed arterial and venous ED cannot be made using duplex Doppler sonography because venous competence cannot be assessed in a patient with arterial insufficiency. In this group of patients,
cavernosography and arteriography may be required. Fig. 14.
Fig. 15: Haemodynamic Parameters for Stimulated CDUS in ED.
Diagnostic Imaging of Veno-Oclusive Erectile Dysfunction: Conventional Cavernography and Caverno-Computed Tomography.
Anomalous Venous Drainage Classification.
Cavernosography with cavernosometry remains the diagnostic reference standard for the diagnosis of venous leak,
as this technique measures outflow resistance without the need for adequate arterial inflow as well as mapping the sites of incompetence.
Virag R et al proposed a new classification Fig. 17 of anomalous venous drainage based on computed tomography cavernography, after contrast media intracavernous injection under pharmacological stimulation.
Fig. 16: Caverno-CT images of 4 patients with ED. Anomalous Venous Drainage Classification.
A- Type A (no leakage). The cavernous bodies are both well opacified, without opacification of superficial vein either deep dorsal vein or opacification of the periprostatic plexus.
B- Type B leakage. The cavernous bodies are both opacified, with the deep dorsal vein and internal pudendal veins alone indicating a type B leakage.
C- Type C leakage. The cavernous bodies are partially opacified, with an obvious opacification of the superficial dorsal vein draining in the right great saphena vein, responsible for a type C leakage.
D- Type D leakage: The cavernous bodies are opacified, with an opacification of the two superficial dorsal veins draining in the right femoral vein, and also an opacification of the two deep dorsal veins and internal also pudendal veins responsible for a type D leakage.
References: Virad R, Paul JF.New Classification of Anomalous Venous Drainage Using Caverno-Computed Tomography in Men with Erectile Dysfunction.J Sex Med 2011;8:1439–1444.
Role of Interventional Radiology in the treatment of venous-leak.
Endovascular embolisation therapy.
In the last few years the role of interventional radiology in the management and treatment of veno-oclusive erectile dysfunction has become an alternative to restore sufficient penile erection using selective embolization of insufficient veins.
It has been clinically studied as an alternative to invasive surgical treatment.
Success of the interventional approach makes this procedure an attractive treatment option,
as it offers more long-term efficacy compared with nonsurgical treatments and is less invasive and more cosmetically pleasing than surgical option.
At our institution the embolisation procedure is performed using a femoral or braquial venous approach.
After inserting a 5F sheath,
a 4F diagnostic catheter is used to evaluate the individual venous anatomy.
First the internal iliac vein was intubed and the catheter was then placed into the internal pudendal vein.
A second selective embolisation catheter system was inserted through the diagnostic catheter into the target vessel.
We always try to get as close as possible to the dorsal penile vein confluence point into the venous prostatic plexus.
After the ideal position of the embolisation system is confirmed ,
we use coils and a mixture of N-butyl-2-cyanoacrylate tissue adhesive and lipiodol at a 1:2 to 1:3 ratio. The application was performed using valsalva’s manoeuver to prevent central embolisation or a pulmonary embolism.
the result (complete embolisation/partial embolisation) is confirmed by contrast media injection.
the procedure is repeated until the target vessels were completely embolised.
After retrieving all systems,
the patients received a compression dressing for 4 h and were maintained under observation for this time.
Hospitalisation was not required.
All of the patients had at least a six month (range 6 month to 24 month) postinterventional follow up.
Postinterventional evaluation included physical examination and report of therapeutic response.
Fig. 19, Fig. 20.
Fig. 19: Case 1. Patient with veno-oclusice erectile dysfunction.
A- Cavernography after PGE-1 injection in corpora cavernosa reveals a type B venous-leakage at he level of deep pelvic veins/periprostatic venous plexus on both sides (arrows in B)
B- Type B venous leakage with abnormal outflow towards deep pelvic veins and periprostatic venous plexus bilaterally (Arrows).
C- superselective retrograde venous angiography of right sided dilated venous periprostatic plexus and embolisation with coil (shor arrow) and glue (histoacryl-lipiodol)(long arrow).
D-Control cavernography after complete embolisation of both sides with filling of the target vessel system. There is no venous-leakage. Technical sucess was achieved.
Fig. 20: Case 2. Patient with veno-oclusive erectile Dysfunction with CDUS suggestive of venous-leak.
A- Cavernography after PGE-1 injection in corpora cavernosa shows a type C venous-leakage towards right external pudendal and great saphenous vein (arrow).
B - Superselective retrograde venous angiography of right external pudendal vein (arrow).
C- Embolisation with 1 coil and glue (histoacryl-lipiodol) up to complete filling of target vessel (arrow). Notice the
radiopaque appearance of the Lipiodol to control the result of embolisation.
D- Venous access in deep dorsal vein with micropuncture set.
E- 4 months later Control anterograde venous angiography using the deep dosal vein access. Notice the complete occlusion of the right external pudendal vein and recidive of venous-leak towards deep prostatix plexus. Technical success was achieved.