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Page 4 of 11 Hara et al. Plast Aesthet Res 2023;10:42 https://dx.doi.org/10.20517/2347-9264.2023.11

We performed ultrasonography when designing the incision site for the LVA. With the patient in a supine
or long-sitting position, imagining the position of the lymphatic vessels in [Figure 1], we applied the probe
to the skin, perpendicular to the long axis of the lymphatic vessels. For lower extremity venous ultrasound,
the probe is placed parallel to the long axis of the vein, but lymphatic vessels are very thin (0.11 mm) and
often tortuous in lymphedematous limbs; therefore, long-axis images are often difficult to observe.
Therefore, we observed a short-axis view of the lymphatic vessels.

After placing a probe on the skin and finding a vessel (a circle with a black interior and white
circumference) beneath the superficial fascia, we moved the probe proximally and distally, tracing the
vessel. If the circle has a long continuous structure, it is considered a type of vessel. If it disappears quickly
when the probe is moved, it may be fibrous tissue between the subcutaneous fat. Specifically, we identified
lymphatic vessels using D-CUPS as a clue in the next chapter.

In lymphatic ultrasound, the short-axis image of lymphatic vessels is observed; therefore, the degree of
lymphatic sclerosis can be morphologically diagnosed [28,29] . We previously reported the process of lymphatic
degeneration (NECST classification: normal, ectasis, contraction, and sclerosis types), and LVA was most
effective when dilated lymphatic vessels were anastomosed [3,12,13] ; however, conventional ICG lymphography
and lymphoscintigraphy did not reveal whether the lymphatic vessels were dilated or sclerosed. We
previously reported that normal lymphatic vessels, dilated lymphatic vessels, and sclerotic lymphatic vessels
coexist in linear lymphatic vessels on ICG lymphography . By performing lymphatic ultrasound, dilated
[12]
lymphatic vessels can be reliably identified and effective LVA can be performed [23-25] . Lymphoedema may
also be diagnosed using lymphatic ultrasound by evaluating the morphology of lymphatic vessels [28,30] .

Another advantage of lymphatic ultrasound is that it does not require a contrast agent. There is no concern
about allergies and it does not cause pain in the patient. In lymphoscintigraphy and ICG lymphography,
which enhance lymphatic vessels with medicines, the visualized lymphatic vessels are limited depending on
where the medicine is injected. Not all lymphatic vessels can be visualized, even with multi-point ICG
lymphography. As Yang et al. reported previously, some lymphatic vessels are flow-positive, but ICG
[44]
enhance-negative . They reported that LVA was also effective when the lymphatic vessels were
anastomosed. Lymphatic ultrasound is useful as a preoperative examination for LVA because it is contrast-
independent and can identify all dilated lymphatic vessels, that is, all lymphatic vessels suitable for LVA.

D-CUPS IN LYMPHATIC ULTRASOUND
When performing lymphatic ultrasound, it is essential to distinguish lymphatic vessels from the veins. To
achieve this, we established an index, D-CUPS [23,28] .

D (Doppler): Veins are colored in Doppler mode, but lymphatic vessels are not [Figure 2A and B].
However, thin veins may not be colored in the Doppler mode.

C (Cross): Veins merge with nearby veins, but lymph vessels cross past veins [Figure 3].

U (Uncollapsible): Lymphatic vessels in lymphedema-affected limbs, in particular, have high internal
pressure, so they are less likely to collapse than veins when compressed with a probe.

P (parallel): Two or three lymphatic vessels may run side by side without merging [Figure 4]. The frequency
of this phenomenon is approximately 20%.