After initial preparation, under local anesthesia and ultrasound guidance, GSV puncture was tried below the knee level (at this level GSV diameter was 4 mm). Due to thick subcutaneous adipose tissue, it was not feasible to enter GSV, despite multi-level attempts up to 10-12 cm above the knee. Then, we decided to make a puncture from the groin level to the GSV downwards. Under ultrasound guidance, the guide-wire was placed (Figures 1, 2). The access point for the GSV was about 3 cm distal of the SFJ (Figure 3). After placing the introducer, RF catheter was pushed downwards through the introducer. However, at 13-15 cm distally from the junction, the RF catheter was unable to be advanced forward due to the vein valve resistance. The patient was taken to reverse Trendelenburg position, and was told to make a long Valsalva's maneuver. The RF catheter was pulled back a little and pushed down simultaneously. The catheter, then, passed downwards to below the knee level without any difficulty. Tumescent anesthetic solution was given routinely (starting from below the knee level where the tip of RF catheter was to the SFJ). The procedure was completed following ablation. The GSV was completely ablated from below the knee level to the 3 cm distal of SFJ.

Figure 1: The retrograde puncture of the great saphenous vein on the groin level (Case 1).

Figure 2: B-mode ultrasound view: common femoral vein, great saphenous vein, common femoral artery and guide-wire.

Figure 3: B-mode ultrasound view: radiofrequency catheter in great saphenous vein 3 cm distal of saphenofemoral junction.

Case 2– A 51-year-old female with a weight of 88 kg and height of 1.59 cm was admitted. She was obese with a body mass index of 34.8 kg/m². She was admitted due to visible varicose veins and edema on left leg. Physical examination findings were remarkable for palpable varicosities on cruris and venous congestion. Duplex examination showed a four-second reflux of the left SFJ in erect position during Valsalva's maneuver and the GSV diameter was 6 mm at the junction level. Radiofrequency ablation for GSV was scheduled.

In this case, the GSV puncture was not also feasible below the knee level, where its diameter was 3.5 mm. The GSV was also easily cannulated downwards from the groin. The access point for the GSV was about 2 cm distal from the SFJ. Without any difficulty, the RF catheter was advanced downwards below the knee and was stuck there (15 cm from the knee). After tumescent anesthetic solution was given, ablation was made and the procedure was completed.

In the first week, repeated ultrasound showed an occluded GSV without any complication (Figure 4).

Figure 4: B-mode ultrasound view: great saphenous vein is occluded without complication, the first week control visit.

In addition, it brings several questions together when retrograde junction puncture for GSV firstly come to mind, i.e. injury of femoral vein or artery or attachment of the catheter to vein valves. In one of our cases, valve resistance occurred during the retrograde passage of the catheter, however the catheter was advanced downwards very easily with saphenous filling (reverse Trendelenburg position and Valsalva's maneuver). Puncture of GSV at the groin level was made initially under ultrasound in both patients without any arterial or venous complication.

There is a limited number of data in the literature regarding modified accesses for the GSV for thermal ablation.

In conclusion, retrograde puncture to GSV and retrograde passage of radiofrequency catheter from the groin to below the knee may be an alternative access to GSV for thermal ablation treatment.

Declaration of conflicting interests
The author declared no conflicts of interest with respect to the authorship and/or publication of this article.

Funding
The author received no financial support for the research and/or authorship of this article.

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