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Page 6 of 11 Hara et al. Plast Aesthet Res 2023;10:42 https://dx.doi.org/10.20517/2347-9264.2023.11

Among these indicators, C was the most reliable. Caution should be exercised in the presence of lymphatic
malformations, as lymphatic-venous communication may be observed; however, C is approximately 100%
sensitive. A video of lymphatic ultrasound can be seen on YouTube (https://www.youtube.com/
watch?v=IYrxIgB9c-Q).

SELECTION OF PROBE
Hayashi et al. reported the usefulness of ultra-high-frequency ultrasonography (70 MHz) for observing
[31]
lymphatic vessels . We usually use a linear probe of 18 MHz (Noblus EUP-L65; Hitachi Medical Corp.,
Tokyo, Japan), which is similar to that used for general lower-extremity veinous ultrasound. Lymphatic
vessels are usually about 1 cm deep from the skin surface in lymphedema of the lower extremities, and this
probe is suitable for observing the depth around it. However, when observing the lymphatic vessels in the
upper extremities, dorsum of the feet, lower legs of lean individuals, and extremities of healthy individuals,
the subcutaneous fat layer is thin; therefore, lymphatic vessels often exist at a depth of approximately 5 mm
from the skin surface, and it is difficult to observe them with an 18 MHz linear probe. In such cases, we used
a higher frequency 33-MHz linear probe (Aplio i900, Canon Medical Systems Corp., Tokyo, Japan) to
[33]
observe the superficial layers [Figure 5] . Furthermore, as the resolution generally increases with higher
probe frequencies, it is considered that observing small lymphatic vessels is more feasible at higher
frequencies. A disadvantage of using ultrahigh-frequency probes such as 33 MHz and 70 MHz is that the
penetration is insufficient, making it difficult to observe deep layers of 1 cm or more. However, recent
advances in ultrasound equipment have led to the development of ultrahigh-frequency equipment that can
observe objects as deep as 1-2 cm. Especially in infant patients, the subcutaneous tissue is very thin;
therefore, an ultrahigh-frequency probe would be useful [45,46] . It is expected that even better equipment will
be developed in the future.

EVALUATION OF ADIPOSE TISSUE FOR LIPOSUCTION
Ultrasonography can also diagnose the presence or absence of edema [47,48] . Lymphoedema-affected limbs
become stiff, but it is sometimes difficult to ascertain by palpation alone whether the stiffness is due to the
accumulation of tissue fluid or fibrosis. In addition, when the affected limb is thick, it may not be possible to
determine only by palpation whether the limb is thick due to the accumulation of tissue fluid or fat. If tissue
fluid is retained, lymphatic drainage treatment, such as compression therapy [49-51] , LVA, and lymph node
transplantation, is required, but liposuction is indicated if there is fat accumulation. Accurate diagnosis is
also important when choosing appropriate treatment, including lymphatic reconstructive surgery,
liposuction, or conservative treatment. Ultrasonography is useful for selecting treatment methods because
the differences between both causes can be observed at a glance.

Case 1
A 52-year-old woman underwent hysterectomy and bilateral ovarian resection for ovarian cancer when she
was 32 years of age. Thirteen years later, lymphedema developed in the left leg. Although she wore elastic
stockings, lymphedema gradually worsened, and she consulted our hospital [Figure 6A].

Lymphoscintigraphy revealed dermal backflow in the left thigh and slightly around the right inguinal lymph
node [Figure 6B]. In addition, we found line patterns that indicated the presence of functional lymphatic
vessels, and we decided to apply LVA. In multi-point ICG lymphography, we found a greater number of
lymphatic vessels than in lymphoscintigraphy [Figure 6A]. We then performed ultrasonography to detect
the dilated lymphatic vessels and a suitable vein. We designed incision sites at 4 points with dilated
lymphatic vessels and well-sized veins [Figure 6C]. At each site, lymphatic vessels and veins consistent with
ultrasonographic findings were observed intraoperatively and successfully anastomosed. The time taken to