Year : 2019 | Volume
: 7 | Issue : 1 | Page : 74--77
What is a venous duplex study anyway? Redefining ultrasound protocols in modern venous practice
M Angelson1, Douglas L Wooster2,
1 Department of Surgery, Toronto West Vascular Lab, Toronto, ON, Canada
2 Department of Surgery, Toronto West Vascular Lab; Department of Surgery, University of Toronto, Toronto, ON, Canada
Dr. Douglas L Wooster
Department of Surgery, University of Toronto, 46 Van Dusen Blvd, Toronto, ON M8Z 3E7
Introduction: Venous duplex ultrasound (VDU) is the diagnostic standard for deep venous thrombosis (DVT); however, modern venous practice requires information for a variety of other venous disorders. Protocols and standards may not have kept pace with these demands. Our aims were to (1) identify disease-specific study standards, (2) survey the community practice of VDU, and (3) consider if there is a practice gap. Methods: A web-based search was conducted to identify standards for VDU studies under the headings of DVT, superficial vein thrombosis (SVT), chronic venous insufficiency (CVI), venous reflux (VR), venous mapping, and prevenous ablation studies. Only those returns that gave specific protocol recommendations were included for analysis. Fifty VDU reports from six community facilities were analyzed using an audit tool; these were compared to a specialized “index” laboratory. Gaps were identified by comparing the recommendations to the interpretation reports. Results: The search returned approximately 50,000 citations (range 855–21,000). Recommendations from recognized authorities (Society for Vascular Ultrasound, Intersocietal Accreditation Commission Vascular Laboratory (ICAVL), College of Physicians and Surgeons of Ontario, and Radiological Society of North America) and peer-reviewed publications were used to define appropriate study protocols. Studies used a “DVT protocol” (38/50 = 76%), regardless of the indication; all studies in the index laboratory used focused protocols. For SVT, it was not related to connections to the deep system (0%); index laboratory 100%. For CVI, VR level was noted in 25%; index laboratory 100%. For patients with venous ulceration, arterial assessments were not added to the venous study. For patients with other nonvenous findings, these were not described in the studies. The comparison of findings from the community laboratories to the index laboratory confirms practice gaps in the assessment of all areas of venous disease. Venous mapping and prevenous ablation studies were only done in specialized facilities. Conclusion: A significant gap is present between community VDU practice and recommended standards and index laboratory protocols for the spectrum of venous disease. Advocacy for established standards and redefined study protocols is required for appropriate VDU practice and quality care of these patients.
|How to cite this article:|
Angelson M, Wooster DL. What is a venous duplex study anyway? Redefining ultrasound protocols in modern venous practice.Arch Med Health Sci 2019;7:74-77
|How to cite this URL:|
Angelson M, Wooster DL. What is a venous duplex study anyway? Redefining ultrasound protocols in modern venous practice. Arch Med Health Sci [serial online] 2019 [cited 2020 Aug 13 ];7:74-77
Available from: http://www.amhsjournal.org/text.asp?2019/7/1/74/260017
Venous duplex ultrasound (VDU) is the diagnostic standard for lower extremity deep venous thrombosis (DVT). Study protocols and interpretation criteria are defined by a variety of ultrasound authorities and widely used in practice. Analyses show VDU study sensitivity of 95%–97% and specificity of 94% for DVT in the popliteal and more proximal veins; the study sensitivity and specificity for calf vein DVT approximate 63%–74%. Definitive treatment for DVT is offered or withheld on the basis of the duplex findings without need for further study. Controversies do exist, however, with respect to the relevance of calf (tibial and muscular vein) DVT or the need for more proximal (iliac and inferior vena cava) studies. In addition, guidance on follow-up and “completion” VDU is variable.
Despite the proven utility of VDU for DVT, modern venous practice requires additional information in patients suspected of having DVT. Venous thromboembolism (VTE) profiles include pulmonary embolism, DVT, and superficial vein thrombosis (SVT). VDU protocols have been described for both the superficial and deep systems by the Society for Vascular Ultrasound (SVU),, Intersocietal Accreditation Commission (IAC), American Institute for Ultrasound in Medicine (AIUM), American College of Radiology (ACR), and College of Physicians and Surgeons of Ontario (CPSO). Patients presenting with leg pain and swelling may raise a concern regarding DVT or VTE but instead may have chronic venous insufficiency (CVI) in the deep system. Or, alternatively, they may have superficial vein thrombosis (SVT) with a risk of extension into the deep system. There are venous ultrasound protocols described to characterize CVI and/or SVT.,,,,
Patients having varicose veins may also have evidence of CVI and require detailed venous imaging studies to identify both deep and superficial vein reflux. Some patients may have concomitant chronic deep or superficial vein occlusion. In addition, in patients considered for directed venous therapy, identification of reflux at the saphenofemoral junction (SFJ) or small saphenopopliteal junction (SSPJ) is required to plan intervention. Protocols for preintervention planning and postprocedure follow-up have been described.
However, the implementation of study and interpretation protocols for a variety of venous disorders encountered in the community may not have kept pace with the demands of modern venous practice.
Our aims in this study were to (1) identify disease-specific study standards, (2) survey the community practice of VDU, and (3) consider if there is a practice gap.
A web-based search of published articles and recommendations in English was conducted to identify standards for VDU studies under the headings of DVT, superficial phlebitis (SVT), CVI, venous reflux, venous mapping, and prevenous ablation studies. Only those returns that gave specific protocol recommendations were included for analysis; recommendations from recognized authorities, such as the SVU, the IAC (Vascular and Venous), ACR, Radiological Society of North America (RSNA), CPSO, Society for Vascular Surgery (SVS), American Venous Forum, and CHEST (American College of Chest Physician) were given priority.
Focused studies in the “index laboratory” were used for each indication for VDU study. For all studies, the “index laboratory” used detailed standard-based protocols. For DVT, the study follows a defined protocol consistent with the recognized sources. The studies for SVT include characterization of the SVT and its relationship to the junctions and perforators connecting to the deep system, as well as a deep system assessment for DVT. Studies for CVI include assessment of the deep system for valvular incompetence, as well as deep system obstruction. Patients with venous ulcer have similar studies with addition of an ankle: brachial index. Patients with varicose veins also have reflux assessment, in the deep and superficial systems and at the SFJ and SSPJ and any identified perforators. Lesions identified in the differential diagnosis of leg swelling are characterized for both the lesion itself and its relationship to arterial and venous circulation.
Fifty VDU reports from six community facilities were analyzed using a previously developed audit tool. This tool allowed numeric comparisons of eight domains relevant to venous ultrasound interpretation.
The results were compared to the specialized index laboratory.
Care gaps were identified by comparing the literature recommendations and index laboratory approach to the interpretation reports from the community facilities.
The web-based literature search returned approximately 50,000 citations (range 855–21,000 for differing testing modalities). Recommendations from recognized authorities (SVU, IAC, CPSO, RSNA, AIUM, and SVS) and peer-reviewed publications were used to define appropriate study protocols.,,,,,
The literature search revealed varying levels of information on VDU studies for differing indications for the study. A “DVT protocol” was well established from a variety of sources; there was good consistency of protocol definition across these sources. Although recommendations for follow-up studies of patients with DVT are available in the clinical guideline literature, specific ultrasound protocols do not address these issues. Similarly, the clinical guideline literature defines indications for venous ultrasound studies in patients with SVT, but the study protocols are not well defined. The SVU standards do include an SVT protocol. Protocols for assessing patients with varicose veins, venous ulcers, or other findings, suggestive of CVI with reflux, are defined in the literature. Protocols to characterize findings in the differential diagnosis of leg swelling in patients considered for the assessment for DVT are not well-defined.
Studies from the community laboratories used a “DVT protocol” (38/50 = 76%), regardless of the indication; all studies in the index laboratory used focused protocols. The DVT protocol included assessment of the calf veins in 50% and the iliac veins in 30%. The index laboratory included the calf veins in 100% and iliac veins in 88%. Of the patients assessed for DVT, 6 of 38 (16%) were positive for proximal thrombus and 2 (5%) showed calf vein DVT; all were recommended for the treatment with anticoagulation. The index laboratory findings confirmed the proximal DVT findings and identified a further 8 (20%) calf vein DVT findings. No patients showed iliac vein DVT. For studies for SVT, the description of the findings did show the level of thrombus (100%) but did not identify the character of the thrombus, its length, or relationship to connections to the deep system; in the index laboratory, these findings were identified in 100% of studies. For patients with CVI, level of reflux and vein effected were noted in 75% of studies in the community and 100% in the index laboratory; reflux at the SFJ was documented in 50% in the community and 100% in the index laboratory. No patients had DVT in either assessment. Arterial testing with ankle: brachial index was done in two patients with venous ulcer at the index laboratory but in none of the other laboratories' results. For the two patients with other findings in the leg, such findings were neither described nor fully defined in all patients. A significant care gap exists in the application of venous duplex studies for all these indications.
Venous mapping and prevenous ablation studies were only done in specialized facilities and could not be analyzed.
VDU is the diagnostic standard for lower extremity DVT., Study protocols and interpretation criteria are defined by a variety of ultrasound authorities and widely used in practice. Contemporary studies show study sensitivity of xx% and specificity of yy% for DVT in the popliteal and more proximal veins; the study sensitivity and specificity for calf vein DVT approximate aa% and bb%, respectively. Definitive treatment for DVT is offered or withheld on the basis of the duplex findings without need for further study., This study confirms the application of such protocols in venous practice for DVT in the popliteal, femoral, and more proximal veins. Management of these patients is determined without need for further VDU or any other confirmatory studies. The proximal vein DVT findings from the community laboratory studies were confirmed in the index laboratory in this study.
Specifics of VDU protocol application for assessment of DVT in below knee veins remain controversial despite clinical practice and ultrasound standards recommendations that support this practice. Published protocols define these studies but many laboratories do not include the calf veins in their protocols. In this study, below knee (tibial and muscular branch), DVT was missed in the VDU protocols that did not include this component but was identified effectively in the more detailed protocols used in the index laboratory. This practice gap could be addressed with wider acceptance of known evidence regarding calf vein thrombosis and general application of published testing standards.
Similarly, clinical practice guidelines recommend ultrasound at the completion of treatment for DVT to serve as a baseline in the event of future assessments. The published ultrasound protocol recommendations do not provide guidance for these studies. There was no evidence that these clinical recommendations were applied in this study.
The finding of superficial venous thrombosis (SVT) has been correlated with the presence of DVT and the potential for extension of the SVT into the deep system in approximately 20% of patients (range 8%–45%).,, This can be related to an underlying coagulopathy or direct extension of the SVT into the deep system via the SFJ, short saphenous-popliteal junction, or perforators. The characteristics of the SVT, as well as patient characteristics, have been related to the potential for extension and are therefore important clinically. Some defined focused protocols are now available in the literature; repeat studies at 7–14 days have been recommended to assess these patients for progression of disease. The index laboratory studies for SVT include characterization of the SVT and its relationship to the junctions and perforators connecting to the deep system, as well as a deep system assessment for DVT. Application of a DVT-only protocol in these circumstances misses significant information that is important clinically. A care gap exists; this gap could be addressed by greater appreciation of the natural history of SVT and routine application of focused SVT-specific protocols.
Clinical guidelines for the assessment of patients with CVI with or without varicose veins or venous ulcers recommend VDU assessment to guide intervention. Studies for CVI require assessment of the deep system for valvular incompetence, as well as deep system obstruction. This study confirms a practice gap in this application. Patients with venous ulcer need similar studies with addition of an ankle: brachial index. Again, a practice gap exists in these patients. Patients with varicose veins also need reflux assessment at the SFJ and any identified perforators. Such protocols are defined in the literature. Comparison of the community studies with a focused index laboratory protocol shows a care gap in applying VDU to these patients. General utilization of such protocols could address this gap.
Clinical gaps in the management of venous disease can be effectively addressed through consistent application of complete venous studies that include the deep and superficial systems and assess both reflux (insufficiency) and thrombosis (occlusion). Recognition of the importance of venous pathology at all levels proximally, both in the thigh and in the lower leg, is essential to comprehensive assessments.
Many patients present to the vascular laboratory for assessment of leg swelling with a concern for the presence of deep vein thrombosis. When no DVT is identified, the differential diagnosis includes a variety of vascular and soft-tissue lesions. Lesions identified in the differential diagnosis of leg swelling should be fully characterized for both the lesion itself and its relationship to arterial and venous circulation. Apart from the finding of a popliteal cyst, such findings are rarely described or fully characterized in VDU reports. Such detail is important to clinical practice and subsequent assessment of these patients with other imaging modalities. The identified care gap can be addressed with acceptance of the importance of full studies and the use of defined assessment strategies and focused protocols to apply to such patients.
The assessment of patients with DVT requires detailed VDU studies; practice guidelines recommend complete studies including the calf veins. Similarly, detailed baseline study at the completion of therapy of DVT requires appropriate protocols. As well, the spectrum of venous disease encountered in clinical practice extends beyond DVT; clinical practice guidelines identify the need for detailed focused venous duplex studies to identify and characterize superficial venous thrombosis, CVI, and the lesions identified in the differential diagnosis of patients with leg swelling. Standards and protocols exist to inform these areas of VDU. This study shows that laboratories frequently use only DVT protocols that do not fully define the spectrum of venous disease. This care gap needs to be addressed with well-defined, widely-accepted, and generally-applied focused protocols specific to the spectrum of indications for VDU.
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