Lymphoscintigraphic Evaluation of Systemic Tracer Uptake in Patients With Primary Lymphedema.

Background: Lymphoscintigraphy is used to confirm the diagnosis of lymphedema. One end point for the test is to ensure a patent thoracic duct by uptake of tracer in the organs. The purpose of this study was to evaluate transit of radiolabeled colloid to the organs to gain insight into the etiopathophysiology of primary lymphedema.

Methods: Patients treated in our Lymphedema Program between 2009 and 2018 were reviewed. Only subjects with bilateral lower extremity primary lymphedema were included (individuals with unilateral leg lymphedema were excluded because the tracer will reach the venous circulation and organs through the normal extremity). Disease severity and lymphoscintigraphy findings were documented.

Results: Sixty-one patients were included. Ten subjects had no radiolabeled tracer transit to the inguinal lymph nodes on lymphoscintigraphy. However, 8 of these individuals had tracer uptake to the liver, kidney, and/or bladder, illustrating clearance of tracer into the systemic venous circulation. All 8 patients had infant-onset primary lymphedema and mild disease. The 2 patients who did not have clearance of tracer to the systemic venous circulation developed lymphedema in adolescence and had clinically moderate or severe disease.

Conclusions: Patients with primary lower extremity lymphedema often have pathways for lymph fluid to reach the venous circulation other than through the inguinal nodes and thoracic duct. Documentation of systemic tracer uptake during lymphoscintigraphy to confirm a patent thoracic duct has limited clinical significance in subjects with primary disease of the legs.