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Liang et al. Plast Aesthet Res 2023;10:71 https://dx.doi.org/10.20517/2347-9264.2023.81 Page 9 of 13

counterparts.

Mihara et al. first described the macroscopic appearance of lymphatics, establishing the NECST
[38]
classification . Lymphatics can be classified into the following subtypes: normal, ectasis, contraction, and
sclerosis, representing a spectrum of severity in ascending order. This macroscopic appearance is correlated
to their ultrasonographic appearance . Since normal, ectasis, and contraction subtypes all have patent
[23]
lumens, these lymphatics are amenable for use in LVA, with ectasis vessels yielding the best results [39-41] .
Extrapolating on this pioneering work, we found that, rather than rigidly shoehorning lymphatics into
distinct categorical subtypes, for most practical purposes, detecting patent lymphatics denoted by a clearly
hypoechoic center is sufficient to successfully perform an LVA. This simplified approach helps reduce the
learning curve for surgeons who may be less adept at ultrasonography.

While lymphatic assessment is well documented, preoperative evaluation of the venous system has received
less emphasis in literature. Several authors have described the use of vein visualizers to detect venules
preoperatively [42-45] . These non-contact and non-invasive devices use infrared and laser light to detect
differences in hemoglobin concentrations between subcutaneous veins and their surrounding tissues before
[44]
superimposing their positions directly on the skin. They can detect venules as small as 0.5 mm in size .
However, like most infrared-based technologies, vein visualizers can only image superficial venules up to 1.5
cm below the skin. This depth may be sufficient for use in early lymphedema cases, and even then, only in
anatomical sites with thin, soft tissues such as the hand, wrist, foot, and ankle. For more advanced cases or
[46]
obese patients, this technology is likely unhelpful .

Ultrasonography for detecting veins for LVA surgery is scarcely reported. This modality is very sensitive
and theoretically capable of imaging blood vessels as small as 0.3 mm in diameter . Mihara reported
[47]
ultrasonographic assessment of subcutaneous veins for use in LVA surgery of the lower limb, allowing the
identification of larger venules, performing more microanastomoses, and achieving a better postoperative
[48]
reduction in limb circumference . However, we find that ultrasonography serves a purpose beyond merely
locating subcutaneous veins; it also aids in determining the presence of reflux. Even in cases of advanced
lymphedema, venous pressure remains higher than lymphatic pressure [49-51] . This discrepancy occurs due to
competent valves in veins that allow unidirectional flow and maintain a favorable pressure gradient for
LVAs to drain lymphatic fluid into the venous system. However, when reflux flow occurs in the recipient
vein, lymphatic drainage is retarded, and anastomotic thrombosis can occur, resulting in surgical
failure [52-54] . Visconti et al. coined the BSO classification, which delineates three patterns of recipient venules
after the completion of microanastomoses. Outlet (O) venules showed no backflow of blood and more
intense fluorescence compared to the lymphatics in ICG lymphography. Slack (S) venules had initial mild
backflow that was washed out and appeared similar in fluorescent intensity. Backflow (B) venules had
minimal lymph flow and low fluorescent signal, highlighting an unfavorable pressure gradient. Patients with
backflow venules had 3.32 times the odds of having poor surgical outcomes compared with those showing
outlet or slack patterns . Bianchi et al. analyzed 1,000 LVAs and concluded that LVAs should not be
[25]
performed on veins showing high reflux, and if no suitable recipient venules are detected, it is
recommended to abandon the incision .
[26]
Preoperative assessment of anti-reflux veins is thus of paramount importance to allow optimized placement
of incisions. Several authors have demonstrated the efficacy of detecting reflux by employing vein
visualizers and “milking” veins on the skin surface [45,55] . However, based on the images and videos, the veins
tested appear to be of large dimensions; the sensitivity of this method may be reduced for the smaller
venules more commonly used in LVA. The absence of reflux in main venous trunks may not necessarily