ISSM – Research Summary – Duplex Doppler Ultrasound in the Evaluation of Patients With Erectile Dysfunction
A Critical Analysis of Methodology Pitfalls in Duplex Doppler Ultrasound in the Evaluation of Patients With Erectile Dysfunction: Technical and Interpretation Deficiencies
Bruno Nascimento, MD; Eduardo P. Miranda, MD, PhD, FECSM; Jean-Etienne Terrier, MD, PhD; Felipe Carneiro, MD, PhD; John P. Mulhall, MD, MSc, FECSM
FIRST PUBLISHED: July 3, 2020 – The Journal of Sexual Medicine
First described in 1985, penile duplex Doppler ultrasonography (PDDU) provides a less invasive method for assessing hemodynamic parameters in men with erectile dysfunction (ED). These parameters include peak systolic velocity (PSV), a direct assessment of the arterial supply, the end-diastolic velocity (EDV), and the Resistive Index (RI), which “indirectly evaluates the venocclusive mechanism.”
PDDU protocols vary widely in published medical literature. Scientists may approach the following aspects in different ways:
- intracavernosal vasoactive agents to induce erection before ultrasound
- redosing schedules
- assessment of erectile rigidity
- timing of hemodynamic assessments
- hemodynamic parameter cutoffs
High rates of false diagnoses of corporal venocclusive dysfunction (CVOD – also called venous leak) and arterial insufficiency might be explained by discrepancies in PDDU protocols.
Through a PubMed literature search, 86 full-text studies published in 2005 or later were deemed eligible for this review. The following elements were evaluated:
- intracavernosal vasoactive agents used
- use of a redosing protocol
- means of rigidity assessment
- report of at-home best quality erection (BQE)
- normative criteria for PSV and EDV
- use of time-based hemodynamic assessment
Results, Discussion, and Recommendations
Vasoactive Agents and Redosing
Findings: Half of the studies used prostaglandin E1 alone as a vasoactive agent. Papaverine was used by 16%, trimix by 12%, and bimix by 7%. Other agents were used by 3% of the studies, and 12% did not identify the agent used.
The starting dose also varied. For example, among studies using prostaglandin E1, 44% used 20 mcg and 35% used 10 mcg.
Only 26% of studies mentioned the use of a redosing protocol.
Comments: Although the combination of agents (bimix or trimix) appears to be more effective in inducing erection, “neither the agent nor the starting dose is critical to the excellent conduct of a PDDU. Ultimately, maximal corpus cavernosum smooth muscle (CCSM) relaxation is the goal, and the possibility of redose may be a key point”. “Robust” evidence shows that redosing “improves the accuracy of penile hemodynamic evaluation.” However, the fact that only 26% of the studies mentioned redosing protocols raises concerns.
Recommendation: All clinicians should use a redosing schedule for more reliable results.
Findings: No form of rigidity assessment was mentioned in 56% of the studies. For those reporting rigidity, the Erection Hardness Scale was the most frequently-used tool, reported by 14% of the studies.
Comments: Erection rigidity can play a role in redosing decisions and data interpretation, so having a systematic way to assess and report it is important.
Recommendation: Rigidity should be assessed when the penis is scanned. It should be recorded separately for right and left cavernosal arteries as this is a dynamic parameter and it may change.
Findings: Fifty-nine percent of the studies used a time-based protocol for hemodynamic assessment. In this group, 84% used multiple time assessments. The most common protocol involved assessments after 5, 10, and 20 minutes.
Comments: Choosing the moment to perform the hemodynamic assessment according to rigidity may be a more useful approach than guiding it with time after injection. “The idea that patients should be scanned at timed intervals, for example, every 10 minutes, makes little sense if erection rigidity is poor.”
Hemodynamics Parameter Cutoffs
Findings: The studies showed “great variability” in hemodynamic parameter cutoffs. About a quarter of the studies did not mention which cutoffs were used.
Comments: “The process of finding the cutoff involves the choice of a value with optimal sensitivity and specificity.” The ISSM SOP indicates that normal hemodynamic parameters should be a range rather than a specific single value. Negative EDV may also be considered.
Recommendation: “We encourage clinicians to use a PSV value < 30 cm/sec to diagnose arterial inflow insufficiency. Likewise, while normative EDV values have been cited between 3 and 7 cm/sec, we recommend a value greater or equal to 5 cm/sec to diagnose venous leak.”
- Only properly trained clinicians should perform PDDU and analyze results. Clinicians should also know how to reverse a prolonged erection. Patients should provide full consent to PDDU procedures.
- PDDU equipment should allow clinicians to “visualize penile structures, measure erectile hemodynamics, and interpret data appropriately.”
- Because PDDU is not 100% accurate, clinicians should use their judgment when analyzing results.
Clinical Implications and Conclusion
This review showed that:
- Measurement guidelines for PDDU are not standardized.
- This lack of standardization makes it challenging to interpret the results of studies and compare them to others.
“Despite its widespread use, analysis of the literature on PDDU use in the ED population shows marked protocol heterogeneity, rendering data interpretation a problem.”