Duplex Ultrasound for Chronic Venous Insufficiency

Abstract: An advancing body of knowledge regarding chronic venous disorders and their diagnosis using duplex ultrasound has accumulated over the past two decades. Duplex ultrasound, primarily due to its low cost and reproducible nature, has impacted nomenclature and treatment technologies with its skillful application. Two distinct examination protocols have been developed and standardized, one for deep venous thrombosis and one for venous insufficiency (reflux). The duplex ultrasound protocol for chronic venous insufficiency and other insightful information regarding superficial reflux, anatomy, and concepts are presented.  

J INVASIVE CARDIOL 2014;26(11):E149-E155

Key words: duplex ultrasound, saphenous insufficiency, duplex insufficiency examination protocol, superficial venous reflux

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Duplex ultrasound has dramatically changed the diagnosis and intervention of chronic venous disorders (CVDs) over the past two decades, becoming the most widely used imaging technique for these applications.¹ There has been an explosion in the number of venous ablation procedures with an estimated 400% increase from 2005 to 2011, and expansion beyond vascular surgeons and phlebologists, an increasing numbers of cardiologists are providing venous ablation since 2008.² Duplex ultrasound is readily available, and the diagnostic approach for deep vein thrombosis (DVT) is considered well known and generally reliable. However, the diagnostic approach to evaluation of chronic venous insufficiency (CVI) is generally challenged with a lack of standardization, where physicians and sonographers alike have limited understanding and knowledge, as noted in the American Venous Forum’s INvestigating Venous Disease Evaluation and Standardization Testing (INVEST) study.³ This paper offers insightful information on performance, with comments on technical aspects and hemodynamic and anatomic considerations that can affect results. 

It is necessary to appreciate that an initial understanding of the concept that diagnosis for DVT is different than that for chronic venous disease (CVD) or its advanced form, CVI. This concept was clearly pointed out in a recent publication on CVI evaluations.⁴ These differences are noted in the venous standards, published by the Intersocietal Accreditation Commission, which indicate that “components of a venous examination vary depending on the indication” and a “complete examination includes the entire course of the accessible portions or each vein.”⁵ According to IAC standards, routine documentation for a normal study includes a minimum of 8 side by side compression images and 3 Doppler samples for a DVT examination and 6 side by side compression images and 6 Doppler samples for a reflux study (Table 1). Also, this author suggests adding 2 images for a DVT study and 5 spectral Doppler samples for a reflux study.  In the presence of pathology, additional images and spectral samples are required. The indications for these two types of venous exam are different; the information sought is similar, but different in its level of detail, and therefore different protocols exist. Another key consideration is that although superficial disease can be a focal point for the CVI examination, “when there is swelling out of proportion that cannot be explained by the reflux in the superficial veins and in the presence of skin damage the deep veins are examined in detail.”¹ As our investigation and understanding of superficial CVI has expanded, so has our knowledge of deep system disease. As noted by Lurie et al, “iliac vein obstruction is ubiquitous in the general population….in symptomatic (CEAP clinical class 3-6) primary and post-thrombotic CVI patients, such lesions are present in >90% when examined with [intravenous ultrasound].”⁶ Further, although typical duplex ultrasound includes examination of the bilateral common femoral vein Doppler wave forms, we need to appreciate that while the presence of an altered finding is highly suggestive of proximal disease, the absence of wave form changes is not sensitive enough to preclude a proximal lesion,⁷ a point unfortunately not well understood. 

Definition of Venous Reflux With Special Comment

The commonly understood definition of venous reflux is retrograde flow greater than 500 ms (0.5 sec) in the superficial system, and greater than 1000 ms (1.0 sec) in the femoral or popliteal segment.⁸ This duration of time needs to be determined using spectral Doppler tracings. These frozen image tracings allow for use of a calculation package to mark and determine measurement of the retrograde flow duration with the software of the duplex system. By contrast, using color and looking for a “flash of red” is not adequate to measure the duration of reflux, nor does this allow for proper documentation of reflux (without cineloops that show appropriate time duration indicators). Additionally, with the increase in performance of these studies, several authors have proposed the concept of performing the CVI duplex examination using a non-standing patient position. Many reasons are cited, most often including ergonomics and time efficiency. In the 2003 definition study noted above, patients were primarily studied standing, “of the 85 patients studied only 10 were examined in both the reversed Trendelenburg (RT) and standing (ST) positions, and differences in [positional] findings were interpreted by the authors as both increased specificity and sensitivity for detecting pathologic reflux in the standing position.”⁹  This point is critical to appreciate. Further, one needs to appreciate that variance from the methodology used (eg, standing position) when a “definition” was determined affects the validity or accuracy of applying that same definition to determinations that were made while not following the same techniques, such as patient in a supine or RT position. This conversation is ongoing; however, in their pivotal 2013 work, Carty and colleagues evaluated the standing versus supine (RT) evaluation for superficial venous reflux, perhaps due to this “mis-application” of the standing definition values. They noted that “reflux duration in the RT position was consistently greater at all levels along the extremity compared with the ST position. The average difference was a factor of 2.83.”  Further, they found that, “segmental reflux associated with an incompetent perforating vein was most accurately identified in the ST position…and…vein segments traveling outside the fascia plane were found to have significant overestimation of reflux duration in the RT position.”⁹ In their work, Carty et al showed that reflux values in the RT position are clearly longer when compared to the ST position. They state, “reflux durations equal or greater than 1.13 sec in the RT position always remain at or >0.5 sec, which is the universally accepted criterion for reflux positivity, when the test is repeated in the ST position (P<.001)…Therefore, we recommend that any extremity with a reflux between 0 and 1.13 sec in duration at the SFJ when supine be re-assessed in the standing position.”  (Figure 1). This has significant importance and implications to many who are following the 0.5 sec rule regardless of the position in which they are testing. Additionally, the author and others believe that proximal compression also has validity issues,^10,11 and therefore should not be used in superficial system evaluations. The conclusion is clearly that performance in a standing position with distal augmentation is preferred. If other positional methodologies are used, the validity of the 0.5 sec time appears to be in question. Aside from being a critical factor for the standardization of CVI duplex examinations, it demonstrates some of the nuances of venous hemodynamics that a person performing or interpreting the CVI duplex exam needs to consider.

CVI Duplex Protocol

In this work, the focus shall be the CVI examination. A primary goal is to create a “diagrammatic representation” or “vein map” showing the course of reflux (or location of obstruction), which will greatly assist in planning therapeutic intervention.¹² Figure 2 offers an example of a technical worksheet to be used during the examination. While creation of the vein map may seem daunting, using a technical worksheet and breaking it down into manageable steps as described below will be greatly helpful for the novice. Another key piece of information is an understanding of what to expect. A brief clinical examination will lead the diagnostician to determine the source of the patient’s condition and correlate diagnostic finding to clinical presentation. In this respect, understanding the prevalence of the distribution of disease is also helpful.  Table 2 shows that roughly 7 out of 10 patients examined will present with great saphenous vein (GSV) insufficiency, 2 of 10 with small saphenous vein (SSV) involvement, and about 1 out of 10 (~10%) will display non-saphenous issues.  

Typically, the deep venous segment of the reflux examination is performed first, with the patient in a supine position with the head elevated about 10°-15°, as is common.  Once complete, moving on to the superficial focus and vein mapping ensues; a protocol is described below. 

Vein Map: Step One

Ideally, the patient should be standing, with the bulk (~70%) of the patient’s weight on the contralateral leg. Examination of the posterior calf begins at the mid-calf level, where the saphenous compartment is easily identifiable. A “prescan” performed moving relatively quickly up and down the posterior aspect of the calf and thigh allows familiarization with the anatomy and observation of anatomic variants prior to documentation efforts. Interrogation of the SSV begins in the proximal calf with identification of the sapheno-popliteal junction (SPJ), measuring vein diameter and determination of reflux with spectral Doppler. Presence of the junction is reported to range from 11%¹³ to 25%¹⁴ in different studies, and is typically 4-5 cm above the popliteal crease. Similar diameter and reflux determinations are made at the mid-calf level. Attention to cross-over patterns between GSV and SSV networks, as described by Obermyer is important, especially when there is no SPJ reflux, and reflux is found at mid-calf or below.¹⁵ Next, examination of the thigh extension (TE) is made, seeking to determine which of the four possible terminations, only one of which is the Giacomini vein, is present.  At this stage, documenting diameter and reflux in the TE is performed. As will be noted later, identification and proximity of the sural, tibial, and sciatic nerves need to be a part of the examination. With this information, a diagram of the posterior aspect of the leg is made, and diameters and reflux noted on a worksheet.  

Vein Map: Step Two

Examination of the GSV of the thigh is critical. This is due to the high prevalence of GSV reflux in the CVI patient population. Easy identification of the true GSV can typically be made at the medial mid-thigh, and within the saphenous compartment (canal), which is located between the deep fascia and the saphenous fascia, forming the “Egyptian eye,” as it is sometimes referred. Although previously reported at a higher incidence, with clarification of nomenclature, the true incidence of a dual GSV is relatively low at 2%,¹⁶ with aplasia of the GSV at the knee noted in about 16%¹ of cases. Once again, a prescan is made of the thigh, seeking out the general anatomy with a focus on the saphenous compartment. Diameter and reflux determinations are made in the saphenous arch (the extended junction area that includes the terminal and preterminal valves), also at the mid-thigh, and at the knee. If these 3 reflux determinations are not consistent, additional sites of reflux determination are made between any 2 non-matching sites to isolate and identify where change occurs and understand the path of reflux. Change in size of the GSV within the compartment can be a “marker” for points at which the reflux begins or ends in the GSV. Once the native saphenous is understood, insonation of the anterior accessory great saphenous vein (AAGSV) within its own compartment is performed, again documenting diameter and reflux. This is also performed for the posterior accessory great saphenous (PAGSV), if present. Once the saphenous is documented, investigation into any epifascial vessels may be carried out. Typically, any tributary that does not have a diameter of at least 50% of the native saphenous vein can be disregarded in the absence of other suggestive pathology (50% rule).¹⁷ Other findings like bulbous areas, large tributaries, and significant perforators (>3.5 mm) are investigated. The information gathered is then reflected with a vein map diagram for the GSV in the thigh on the worksheet.    

Vein Map: Step Three

In the lower leg, the GSV is most easily found at the medial malleolus. Once again, a prescan is made, following the GSV in the sheath proximal to the level of the knee. Of note in this segment, the PAGSV of the leg can be seen, and is typically the vein to which the posterior tibial (previous Cockett’s) perforators connect, and is of interest in venous stasis ulceration. The paratibial (previous Boyd’s) perforators typically connect directly to the GSV just inferior to the knee. At least one location at mid-calf is selected for diameter and reflux determinations for the GSV, with additional sites if pathology is noted. Attention to the saphenous nerve along this segment is paid. Again, a diagram and notes of the findings in this segment of the leg are made on the worksheet.

Vein Map: Step Four

The fourth and final step(s) can be subdivided into two distinct areas: non-saphenous veins and perforators. In about 90% of situations, sources of reflux have been identified with the above steps. Keeping in mind that 9%-10% of patients have a non-saphenous origin for their varicosities, and up to 20% of patients with ulceration have no visible sign of varicose veins, at this point the curious investigator needs to also consider other sources of pathology. Non-saphenous pathology can come from multiple sources, such as pelvic sources or “leaks,” especially in the presence of varices in the area of the upper posterior thigh or medial to the SFJ including vulvar veins; various perforating veins are also potential sources. For any varicosities in which a source has not been found, scan directly over the varicosity with light probe pressure. Trace the veins proximally and distally, and typically the varices will increase in size as one is moving toward the source. These additional findings are then documented on the vein mapping worksheet. Figure 3 shows two examples of a complete vein map.

 Despite innumerous perforating veins (PVs) found in the lower limb, only about 20 become incompetent in patients with CVD.¹ PVs need to be subdivided into above-knee and below-knee segments. In most cases, the above-knee perforator (eg, the SFJ) can be an “exit perforator,” where higher pressure from the deep system causes blood to exit into the superficial (or epifascial) areas, causing reflux. On the other hand, a distal (or below-knee) perforator can be either an exit perforator, as noted above, or a terminal perforator.  A terminal or “re-entry” perforator is simply a conduit for descending hypertensive venous reflux to re-enter the deep system.¹⁸ Reduction in venous hypertension following therapeutic intervention to the superficial venous system can change the hemodynamics in play with perforating veins, normalizing 33% in one study.¹⁹ For these reasons, exhaustive examination of perforating veins upon initial presentation for possible treatment is very controversial. Flow direction diameter at the fascia defect, and outward flow of greater that 500 msec with a diameter of greater than 3.5 mm, are considered pathologic. Further, perforators adjacent to ulcerated areas have been termed “pathologic.”²⁰ The timing and necessity of treatment for perforators remains unclear. It is suggested that in the presence of gross saphenous reflux, examination of perforators be limited to only the largest PVs if present, and be considered a focal point for examinations subsequent to therapeutic intervention directed at the saphenous component.  

At this point, the vein map and CVI protocol are complete. Correlation of the examination’s findings with the clinical and symptomatic presentation needs to be considered. Similar to other diagnostic procedures, the ultrasonic findings are extremely operator dependent.

Concepts for Consideration

Current thinking is that the venous system is more complex than the arterial system.²¹ This is especially true with regard to venous reflux and hemodynamics. Presented in the following section are key concepts that can influence the performance and understanding of the information gathered in the CVI duplex examination.

Technical Concepts

• The CVI reflux study is best performed in the standing position to more closely mimic physiologic conditions when pathologic reflux exerts its influence.^{1,4,9,13,16,22} 
• The standing patient should be holding onto a frame or handle for stability, with the limb being imaged externally rotated and most of the weight (~70%) on the contralateral leg.
• “An advantage of the standing position is the easiness with which reflux sources and drainage points can be better evaluated…..and….venous dilation and 360° exposure of the calf to testing favor examination in the standing position.”²³
• The heel of the limb being examined should be flat on the floor surface to prevent calf systole.
• The Valsalva maneuver is most applicable to the SFJ, and used only when there is no reflux upon release of distal compression.   
• The “Valsalva maneuver has been found to produced adequate velocities at the common femoral level but not beyond.”⁹  
• Compression distal to the segment being tested is used with either manual compression or cuff inflation/deflation, and best if used over the varicose reservoir.
• Foot compression over Lejar’s plexus is helpful in examination of distal saphenous segments.²⁴
• Proximal compression, especially in the supine patient, can produce false reflux over the length of the compression.
• The Parana maneuver engages isometric contraction of the calf muscle pump and is gaining wider acceptance in CVI testing.
• Although color can be helpful the use of spectral Doppler waveforms, measuring superficial reflux in excess of 500 ms (0.5 sec), is required for adequate documentation (emphasis added).
• Reflux in the femoral or popliteal segment is measured at greater than 1000 ms (1.0 sec).
• Perforator reflux is measured at greater than 500 ms (0.5 sec).
• Junctional reflux is not required for gross or symptomatic GSV or SSV reflux to be present.²⁵
• As confirmed in the INVEST study, the severity of reflux is known to vary based on the time of day. Reflux can be more pronounced in the afternoon as compared to the morning.^3,17,26
• The magnitude of reflux is best characterized by time duration. Correlation to severity of disease is impractical for a myriad of reasons. The size and extent of the varicose reservoir has effects on the shape of the reflux curve, ie, “...when a large incompetent vein empties into a small capacitor, peak velocity is high, but duration is short. When the refluxing vein is small and the capacitor is large, velocity is low and retrograde flow duration is long…and no definite conclusions can be made.”^27,28

Anatomic and Other Considerations

• In CEAP 5 and 6 patients, superficial venous reflux alone, without perforator or deep venous reflux, is noted in 25% and 19%, respectively.²⁹  
• Patterns and degree of reflux are not static. CVI is a progressive disease process and serial examinations spaced greater than 6 months apart have shown progression of disease.
• Popliteal vein duplication can occur in up to 40% of patients.¹
• Femoral vein duplication can occur in up to 41% of patients.³⁰
• Varicosities of the saphenous trunk are rare (~2%), and therefore “negotiation of wires and catheters through saphenous veins should be straightforward in over 95% of patients.” ¹²
• Determination of the presence of reflux in the deep system, saphenous canal, the epifascial space, or both is critical for therapeutic planning.¹⁸
• The presence of AAGSVs is best identified in the saphenous canal using the “alignment sign.”¹⁴
• The AAGSV can be a source of recurrent reflux and is noted in 10% of patients.³¹
• Segmental deep vein reflux can be induced by incompetence of the SFJ or SPJ.³²
• Treatment of the superficial venous system can improve or resolve segmental deep reflux near junctions.³³ 
• Reflux distal to the junctions (and/or axial) represents true deep venous reflux and is common in post-thrombotic disease.¹ 
• The location of the sural nerve is important during ablation of the SSV.
• The location of the fascial curve (the curve of the SSV as it dives to meet the popliteal vein) and the tibial nerve is critical during ablation of the SSV.
• The location of the saphenous nerve is important during ablation of the GSV.
• Assessment of the saphenous vein bed after therapeutic intervention is important to assure successful treatment of the respective vein, GSV or SSV.¹
• Neovascularization can result in thin-walled, valveless vessels with significant reflux³⁴ and is rare following endovenous thermal ablation.
• Reflux progression is seen in antegrade and retrograde directions. “This contradicts the traditional assumption that primary reflux develops starting at the SFJ level and proceeds in a retrograde manner.”³⁵
• GSV diameter is a poor surrogate marker for assessing the effect of varicose veins on a patient’s quality of life; thus, it is inappropriate to use GSV diameter as a sole criterion for determining medical necessity for the treatment of GSV reflux.³⁶  Therefore, a small vein is not necessarily a “normal” vein.

Conclusion

With the development of advanced treatment techniques, our understanding of the venous system and hemodynamics has expanded. So too has the knowledge of diagnostic techniques for duplex evaluation for CVI. There are separate although overlapping protocols for a DVT or reflux duplex examination. Although the step-by-step protocol is important, especially for standardization of process, it can be relied upon too heavily at times. There also needs to be top of mind awareness for the technical and anatomic concepts presented in order for the most accurate and precise diagnostic evaluation to be performed. A relatively new (2010) Registered Phlebology Sonographer (RPhS) credential for physicians and sonographers has been developed by Cardiovascular Credentialing International for those specializing in this arena. The diagnostic sonography exam is extremely operator dependent; therefore, an inquisitive approach and extensive knowledge of the concepts presented herein are suggested. Recently, publications have shown “non-inferiority of the RT position for the diagnosis of superficial venous reflux if the test is performed with clear awareness and understanding of the potential pitfalls…”⁹ Lastly, those performing these studies are obligated to compare diagnostic findings with clinical and symptomatic presentation to ensure accurate diagnosis and facilitate appropriate treatment.

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From Veinz Phlebology Services, Kure Beach, North Carolina.

Disclosure: The author has completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. Mr Zygmunt is employed as the Director of Clinical Education for Covidien Vascular Therapies. This work was done and submitted privately. Covidien sells medical devices for treatment; however, the submitted document deals with diagnosis using duplex ultrasound, and is not conflicted by his employment. Mr Zygmunt is a longstanding member of the American College of Phlebology, a member of the American Venous Forum, and a board member of Cadiovascular Credentialing International.

Manuscript submitted March 14, 2014, provisional acceptance given May 14 2014, final version accepted May 27, 2014.

Address for correspondence: Mr Joseph A. Zygmunt, Jr, RVT, RPhS, Veinz Phlebology Services PO Box 267, Kure Beach, NC 28449. Email: veinz@aol.com