Impact of Duplex Ultrasound Scanning in Varicose Vein Surgery.

Philip D Coleridge Smith DM FRCS

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Summary
The use of duplex ultrasonography in the assessment of patients with venous incompetence and varicose veins has become widespread in recent years. The availability of good quality colour duplex machines combined with a developing understanding of what they may show has lead to their enthusiastic use in many western countries. They may be used in the assessment of patients with primary varicose veins, recurrent varices and venous leg ulcers. Surgeons may be helped to locate perforating veins, residual saphenous trunks and veins in the popliteal fossa with the help of pre-operatively skin marking.

Published evidence shows that duplex ultrasonography detects more incompetent veins than clinical examination, hand-held (CW) Doppler ultrasound or phlebography. Little data has been published to allow an objective judgement to be reached as to whether duplex ultrasonography improves the outcome of superficial venous surgery. Those who use this method as part of their practice immediately realise that no other technique can give them the same precision of information and do not need to be convinced by randomised clinical trials! The use of duplex ultrasonography will become more widespread in the future and I believe that this will result in the improved management of patients with all types of venous disease.

Introduction
How has duplex ultrasonography modified the management of varicose veins?

Colour duplex ultrasonography is a technology that became widely available from about 1990, although duplex ultrasonography offering pulsed Doppler analysis of blood flow has been available since the early 1980s. There has been a rapid expansion in its use for the investigation of patients with venous disease, as well as for arterial problems. Although several papers have been published comparing angiographic techniques of investigating venous and arterial diseases, no study has so far addressed the question of whether an improvement in outcome of treatment can be expected following duplex assessment of either venous or arterial disease.

There is a number of reasons why this information has not become available for lower limb venous disease. Those who use duplex ultrasonography to assess patients with varicose veins realise that no other technique can provide such precise information about the anatomical distribution of veins and their function! , , , Colour duplex machines have only become widely used in the last five or six years so few centres have had the opportunity to follow-up patients for long enough to provide an answer. The design of varicose vein studies necessitates follow-up of at least 3 - 5 years for reliable data to be obtained and so these take a number of years to complete.

What are the alternative methods of investigation in patients with varicose veins?
Clinical examination of the venous system has been widely used to assess varicose veins but it is well know that this technique is unreliable , especially in patients with complex problems such as recurrent varices or leg ulceration. Many surgeons now employ hand-held continuous wave (CW) Doppler ultrasound to detect venous valvular incompetence. The sapheno-femoral junction can be reliably assessed in the majority of patients using this device. In many cases sapheno-popliteal incompetence may also be detected. However, CW Doppler is not reliable in distinguishing deep from superficial venous incompetence, especially in the popliteal fossa.

Phlebography provides excellent anatomical information and may also be used to assess venous valvular incompetence. Until recently this investigation was widely used to assess all aspects of venous disease. Intravenous injection of contrast media and exposure to ionising radiation are significant disadvantages. With the rapid expansion of duplex ultrasonography, phlebograpy is being used much less often.

Appropriate use of duplex ultrasonography - which are the clinical situations where it may be useful?
Duplex ultrasonography is helpful in many stages of the management of varicose veins and venous disease. Pre-operatively this technique is used to identify the diseased veins in primary disease. During the peri-operative period it is useful in the identification of veins which cannot be easily localised by clinical examination. Examples of these include the sapheno-popliteal junction, calf and thigh perforating veins and residual segments of saphenous vein. Patients who have previously been operated upon for their varicose veins may present with recurrent varices from many possible sources. These include a recurrence from the original site of ligation or from another source, as a consequence of progression of disease or failure to identify this source at the previous operation. Duplex ultrasonography is invaluable for this purpose. Many patients presenting with venous ulceration may be suitable for treatment by varicose vein surgery. Recent studies in which duplex ultrasonography has been used as the method of assessment have reported that up to 50% of patients with venous leg ulcers have superficial venous incompetence alone. This compares with as few as 10% of patients in which the diagnosis was achieved by earlier methods of diagnosis.

Duplex ultrasonography has rapidly received acceptance at the ‘gold standard’ for investigation in venous disease. Evidence for its use comes from comparative studies to other techniques.

Pre-operative assessment
The outcome of varicose vein surgery is dependent on accurate preoperative assessment as well as competent surgery, to achieve long term cure of varicose veins. If, after clinical examination, the surgeon decided to ligate the sapheno-femoral junction when the patient actually had sapheno-popliteal junction incompetence, success is unlikely. The most important point at which duplex ultrasonography may modify management is at the assessment stage prior to surgery. An accurate diagnosis here will ensure that the correct operation is selected.
Clinical examination may be misleading. Varices apparently arising from the sapheno-popliteal junction (SPJ) may come from the long saphenous system. Sapheno-femoral (SFJ) and sapheno-popliteal junction incompetence may co-exist. A previous, unsuspected deep vein thrombosis may have occluded or seriously damaged the deep veins. Removing the superficial veins may deprive the limb of a collateral route of venous drainage.

It is essential to assess each of these veins since valvular incompetence may occur in isolation at any of these, or at a number of sites:
* Sapheno-femoral junction
* Long saphenous vein (LSV)
* Sapheno-popliteal junction
* Short saphenous vein (SSV)
* Perforating veins
* Deep veins

Clinical examination, C.W. Doppler or duplex ultrasound?
Duplex ultrasonography has been compared against clinical assessment and continuous wave (C.W., hand-held) Doppler ultrasound. , , DePalma et al 6 investigated 40 patients with varicosities in the distribution of the long saphenous vein. They compared clinical examination and CW Doppler with colour duplex ultrasonography, which they used as the reference standard. Clinical examination and CW Doppler examination were equally sensitive (48%) in detecting long saphenous vein incompetence, missing a startling 26 of 50 incompetent long saphenous veins. In 22 patients who had previously had sapheno-femoral ligation, the groin recurrence present in 9 subjects on duplex was missed by CW Doppler. CW Doppler examinations in this study were carried out by an experienced vascular surgeon.

In a study carried out by McMullin et al 7 CW Doppler was compared with duplex ultrasonography in 136 patients present with varicose veins. CW Doppler detected 73% of the long saphenous veins found to be incompetent on duplex ultrasonography. Sensitivity in the popliteal fossa for sapheno-popliteal incompetence was worse at only 33%, and 48% for deep vein incompetence. The reason for inaccuracy in this region is that CW Doppler is poor at resolving complex anatomy (fig. 1). Somjen et al studied 123 limbs with popliteal fossa venous incompetence. In 91 cases there was a single source of incompetence, but in the remaining limbs multiple sources of incompetence were found. In 48 of the cases reflux in the popliteal vein above the knee or superficial femoral vein was found although in most cases the popliteal vein below the knee was competent.

The clinical advantage of duplex ultrasonography remains difficult to judge. A study in which patients were first examined by a surgeon using clinical examination and CW Doppler has been conducted in 48 patients, 10 of whom were being operated upon for the second time.8 An operation plan was devised for each patient based on this information. Patients were then examined by colour duplex ultrasonography and the operation plan revised in 18 of 68 limbs. Escape points between the superficial and deep venous system would have been left intact in 14 limbs had duplex ultrasonography not been performed. This study show that duplex ultrasonography is more reliable than CW Doppler, especially where complex anatomy is to be expected. It also suggests that improved outcome of treatment might be expected with the use of duplex ultrasonography.

How does duplex ultrasonography compare with phlebography?
Phlebography is not widely used for the investigation of primary varicose veins, but has been studied in comparison with duplex ultrasonography in the diagnosis of deep vein incompetence. Duplex ultrasonography is as sensitive as phlebography in the femoral region and detects more cases of popliteal vein incompetence. The difference here is that descending phlebography relies on demonstrating reverse flow in veins into which a hypertonic contrast medium has been injected. This investigation has to be performed at rest. Competent proximal valves may prevent the demonstration of incompetence in the (important) popliteal segment, since contrast medium never descends to this section of the venous system. Duplex ultrasonography relies on the flow of blood in veins and is not restricted by the need for injection of contrast material and is usually carried out with the patient standing, the position in which venous reflux is clinically significant.

The ability of duplex ultrasonography to reveal a wide range of patterns of venous valvular incompetence has lead some authors to suggest that varicose vein surgery should be precisely tailored to each patients needs. Whether this actually improves the results of surgery has not been tested systematically.

Duplex assessment of patients with recurrent varicose veins.
Recurrent varicose veins are a difficult problem to assess clinically and the type of surgery performed by the previous surgeon may not be obvious from the skin incisions or recorded in the patients hospital notes. The use of an imaging technique to determine their origin is widely accepted. 5 The most common source of recurrence following surgery of the long saphenous system is the sapheno-femoral junction, (fig 2, 3, 4). , , However, this only accounts for 40% of new varices, and investigation is necessary to establish whether veins fill from other sources.

In planning a further operation it is highly desirable to have the following information available:
* Is there a recurrence at the SFJ or SPJ?
* Was the LSV or SSV stripped previously?
* Where do recurrent varices fill from?
* Is incompetence present in a previously unoperated junction (SFJ or SPJ)?
* Are the deep veins normal?

Clinical examination is as unreliable here as it is in other situations. Bradbury et al studied an unselected series of 36 patients who has previously undergone ligation of the sapheno-femoral junction. 5 At operation three-quarters were found to have a patent SFJ. Of 26 cases with an operative diagnosis of a patent SFJ, 17 were identified clinically, and 23 using CW Doppler. However, both these techniques identified further cases where a patent SFJ was not found at operation, resulting in poor specificity for these tests. C.W. Doppler examination may be unreliable in assessment of recurrent SFJ incompetence since in the groin communications between the superficial abdominal veins and the thigh varices may simulate the sounds from a recurrent sapheno-femoral junction. Only an imaging technique can resolve this problem.

A frequently reported problem is persisting reflux in an un-stripped long saphenous vein following earlier sapheno-femoral ligation. The anatomy of this and its filling points cannot be resolved without an examination that provides imaging information. In fact, incompetence of the LSV trunk may occur in the presence of a competent SFJ, even before surgical intervention, in one third of patients with primary LSV varices .

Recurrent varices in the popliteal fossa are particularly difficult to treat. Inappropriate exploration may result in damage to important nerves or veins. An exact anatomical map is required before commencing an operation in this region. Duplex ultrasonography is very reliable when used in to assess this area, giving 100% concordance with phlebography in a series of patients with recurrent SPJ varices.

In many instances, recurrent varices are identified in a limb where previous surgery has been performed, but in a vein that was not operated upon previously. This is probably due to progression of disease into unaffected veins. This has been reported in one clinical study using an objective measure of outcome. In this study 36 patients were examined clinically, by colour Duplex scanning and photoplethysmography and 56 limbs with superficial venous incompetence identified. The same patients were re-examined after 20 months in which no treatment was given and an additional 10 sources of superficial venous reflux identified.

Many authors recommend the use of duplex ultrasonography for assessment of recurrent varicose veins. Interpretation of the findings from duplex ultrasonography requires experience, but basing management on objective data seems to be a logical advance.

Patients with venous ulceration.
In patients presenting with venous leg ulcers, up to half of the cases will have only superficial venous incompetence. , , In these patients, ligation and stripping of the superficial veins usually achieves rapid ulcer healing. There is unlikely to be any advantage to varicose vein surgery in patients with deep vein incompetence, especially if this involves the popliteal vein. , , , Removal of superficial veins where there is occlusion of the deep veins may makes the problem worse. The aim of venous investigation in these circumstances is to identify the extent of the problem in the superficial veins, but confirm that the deep venous system is normal. Clinical examination and C.W. Doppler are unreliable at confirming that the deep venous system is patent and competent. Duplex ultrasonography reliably assess patency of the deep veins. Investigation in this group of patients aims to define the location and nature of the venous problem (superficial veins or deep veins, incompetence or obstruction) and to assess the overall venous function of the limb using a plethysmographic method.

In summary, the following information will determine the treatment plan in a patient presenting with chronic venous insufficiency:

* Is incompetence confined to the superficial venous system?
* Are the deep veins competent?
* Have the deep veins been damaged by a previous deep vein thrombosis?
* Is there residual obstruction of the deep veins?

Pre-operative vein localisation.
The most common situation in which vein localisation is helpful is the popliteal fossa. There is a wide range of anatomical patterns in this region. The location of the junction of the short saphenous vein with the popliteal vein is very variable. Identification of this point using an imaging technique has been widely advocated, but never assessed to determine whether it actually improves the outcome of venous surgery (fig. 5). Such localisations greatly assist the surgical procedure and hopefully reduce the likelihood of neurological injury following popliteal fossa exploration. The marking of perforating veins and residual segments of the long saphenous vein is also reported and greatly facilitates their ligation and removal at surgery.

Conclusions.
Those who regularly use duplex ultrasonography in the management of venous disease are convinced of its value, but no objective study has ever been carried out to prove this. Good surgery depends on full pre-operative assessment of patients, and it is in this part of the treatment process where duplex ultrasonography may influence management. At the sapheno-femoral junction duplex is more accurate than clinical assessment and CW Doppler in patients with primary varicose veins. In recurrent varices, duplex ultrasonography is the most reliable investigation. In the popliteal fossa clinical examination and CW Doppler are less sensitive to sapheno-popliteal junction and popliteal vein incompetence than duplex ultrasonography. Duplex is helpful in resolving the complex anatomy of the popliteal fossa. In patients with recurrent varices it provides a precise indication of the surgery that was conducted previously, indicating where this has failed or if recurrence has occurred in some other part of the superficial venous system.

In patients presenting with venous ulceration, duplex ultrasonography is as reliable as phlebography in demonstrating the status of the deep veins, and identifies a substantial proportion of patients who may benefit from varicose vein surgery.

The exact role of duplex ultrasonography has not been objectively demonstrated in the management of patients with varicose veins - and it probably never will. This will not prevent its widespread application in the management of such patients!

Figure legends.

Figure 1.
Longitudinal ultrasound anatomy of the popliteal fossa showing the complexity of the veins in this region.

Figure 2.
Ultrasound image of sapheno-femoral recurrence.

Figure 3.
Sources of recurrent varices in a study by Quigley et al.13

Figure 4.
Source of recurrence in 36 patients re-operated for recurrent varices following previous SFJ ligation. 5

Figure 5.
Pre-operative duplex ultrasound localisation of the short saphenous vein in the popliteal fossa.

Figure 1.

Figure 2.

Figure legends:
Figure 1:
Anatomy of the superficial veins of the lower limb.

Figure 2.
Method of scanning the lower limb veins for valvular incompetence.

Figure 3.
Colour duplex ultrasound image showing reflux at the sapheno-femoral junction.

Figure 4.
Pre-operative localisation of the sapheno-popliteal junction.

Figure 5.
Longitudinal ultrasound anatomy of the popliteal fossa.

Figure 6.
Diagrammatic representation of duplex findings in a vascular laboratory report.

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