Significance of popliteal lymph nodes visualization during radionuclide lymphoscintigraphy for lower limb lymphedema

To examine the frequency and significance of visualization of popliteal nodes during lymphoscintigraphy for the investigation of lower extremity swelling.

Technetium-99m-labeled nanocolloid was injected subcutaneously in the first web spaces of both feet of 90 patients (24 males, 66 females; age range, 4-70 years) who had clinical evidence of lower limb lymphedema and were referred for routine lymphoscintigraphy; imaging was performed 5, and 90 minutes after injection without any vigorous exercise between the injection and imaging.

According to the scan findings, patients were divided into two groups; group I included 63 patients without popliteal nodes visualization on scanning, and group II included 27 patients with positive popliteal nodes uptake. None of patients with primary lymphedema (N = 22) due to agenesis or hypoplasia showed popliteal node uptake, whereas, patients with secondary lymphedema (N = 68) had either severe (N = 23) or partial (N = 45) lymphatic obstruction. A high positive association of popliteal node uptake with the severity of lymphatic obstruction was noted. Popliteal nodes were visualized in 26 of 57 patients with dermal back flow (46%), and in only 1 of 33 patients without dermal back flow (3%). There was a strong association between skin rerouting and popliteal node visualization (P < 0.01). Skin changes were detected in 24 patients (38%) with positive popliteal node uptake.

Popliteal lymph nodes uptake during lymphoscintigraphy for clinical lymphedema of the lower limb indicates lymph rerouting through the deep system and raises a diagnosis of higher severity and longer duration of lymphatic dysfunction.