Odds and Limitations of Duplex Sonography in the Diagnosis of PeVD
Advancing knowledge and addressing challenges in venous therapy was the order of business this afternoon, with experts gathered to discuss topics including pelvic venous disorders, May-Thurner syndrome, venous stenting trials, chronic thromboembolic pulmonary hypertension, antithrombotic therapy, filters, inflow assessment, endophlebectomy, and Nutcracker syndrome. Tobias Hirsch, from the Practice for Internal Medicine and Vascular Diseases, in Halle, Germany, spoke to LINC Today to offer a glimpse into his presentation on duplex sonography in the diagnosis of pelvic venous disorders (PeVDs), touching on benefits, advancements, challenges and future perspectives.
Duplex sonography is widely used in vascular diagnostics. What makes it particularly suited for evaluating PeVDs, and what unique challenges does it address?
Ultrasound is also the first-line method for examining the pelvic and retroperitoneal veins. It is ubiquitously available, cost-effective, has no known side effects and can be repeated. In addition, the pelvic vein system is closely connected to the system of the leg veins, which is routinely explored using ultrasound.
What are the odds of duplex sonography providing a definitive diagnosis for PeVD compared to other imaging modalities, such as computed tomographic/ magnetic resonance venography (CTV/MRV)?
The major advantage of duplex sonography is that it allows for the detection of hemodynamic abnormalities. In particular, reflux (e.g. from the ovarian veins and the internal iliac vein) can be detected by modifying the position of the person being examined (supine vs upright). Consecutive changes in topography, such as those between the abdominal aorta, left renal vein and anterior mesenteric artery, can also be shown. These are findings that are not revealed by cross-sectional imaging.
What are the most significant limitations of duplex sonography in diagnosing PeVD, and how can clinicians mitigate these issues?
One challenge is that there is a significantly higher degree of examiner and patient dependency. The learning curve is longer. The limitations of sonographic imaging are often linked to the constitution of the patient. Obesity and intestinal gas can significantly disrupt the examination. So can restlessness. But above all, time pressure. The use of a tilt table is recommended, which allows for a comfortable and relaxed patient position even when upright in a 45° position. It also makes sense to start with a full bladder and continue after voiding.
How does the accuracy of duplex sonography depend on experience? Are there specific techniques or protocols you recommend?
The examination depends heavily on the examiner’s training. There is no fixed protocol. It is important to have the technical equipment with linear and convex probes and to make a smart selection of the probes used. Duplex sonography allows for dynamic evaluation of venous flow.
How important is this feature in identifying reflux or obstruction in PeVD cases?
In my opinion, the importance of dynamic flow analysis is greatly underestimated. However, it plays an essential role because the vascular calibers or vascular crossings that can be excellently measured in cross-sectional diagnostics do not necessarily correlate with significant pathological hemodynamic phenomena.
How do you see duplex sonography being used to select patients for further diagnostic evaluation or interventional procedures for PeVD?
Duplex sonography can be used for patient selection to determine whether further examinations such as MRV are useful. On the other hand, it can also be used to analyze anatomical results with regard to their hemodynamic significance, in order to enable a correct indication for an intervention or the selection of a method.
When and how should duplex sonography be integrated with other imaging modalities to achieve a comprehensive diagnostic workup for PeVD?
Duplex sonography should not be viewed as a competing method to radiological imaging. Rather, they are complementary methods in the diagnosis of a complex disease.
Are there recent advancements in ultrasound technology that improve the diagnostic yield of duplex sonography for PeVD?
There are various manufacturer-specific modalities that enable the visualization of slow flow phenomena, such as B-Flow or SMI. However, the anatomical and technical skills of the examiner and the availability of suitable probes for the best possible B-image are crucial.
How often do you encounter false positives or negatives in duplex sonography for PeVD, and what are the most common causes of these errors?
The pre-test probability of positive ultrasound findings is quite high. However, there is no reliable data on this. A registry that also includes ultrasound diagnostics would be helpful here. The issues are often complex and I would not say that ultrasound and MRV or CTV are competing techniques, but rather that they complement each other. Ultimately, the meticulous study of the patient’s history and the exclusion of possible differential diagnoses of a PeVD are crucial. And one must always be aware that, on the one hand, venous reflux and topographical intersections can also be observed in asymptomatic patients, and on the other hand, nonvascular causes must be considered for all symptoms of PeVD.
Looking ahead, what role do you see for duplex sonography in the evolving diagnostic landscape for PeVD, and what research or technological advancements are needed to enhance its utility?
Ultrasound diagnosis of the pelvic and retroperitoneal veins, including hemodynamic maneuvers, should be given a higher priority in vascular medicine training despite the greater time required.
