Characterizing Normal Upper Extremity Lymphatic Flow with ^99mTc In-House Dextran: A Retrospective Study

Lymphoscintigraphy evaluates the lymphatic system using radiocolloid compounds like ^99mTc-sulfur colloid and ^99mTc-nanocolloid, which vary in particle size and distribution timing. A local in-house Dextran kit (15-40 nm) was developed in 2005 and began clinical use in 2008 to localize sentinel lymph nodes; diagnose lymphedema; and detect lymphatic leakage. The normal drainage pattern remains unexplored. We retrospectively analyzed 84 upper extremity lymphoscintigraphies from 2008 to 2021. ^99mTc in-house Dextran was intradermally injected into both hands, followed by whole-body imaging at specified intervals (≤15 min; 16-30 min; 31-45 min; 46-60 min), with some receiving delayed imaging. Visual and quantitative analyses recorded axillary and forearm lymph nodes and liver, kidney, and urinary bladder activity. Results showed 92% (77/84) upper extremity lymphatic tract visualization within 45 min. Axillary node detection rates increased from 46% (≤15 min) to 86% (46-60 min). Delayed imaging further revealed nodes. Epitrochlear or brachial node visualization was rare (4%, 3/84). Hepatic, renal, and urinary bladder activity was noted in 54%, 71%, and 93% at 1 h, respectively. The axillary node uptake ratio was minimal (<2.5% of injection site activity; median 0.33%). This study characterizes normal upper extremity lymphatic drainage using ^99mTc in-house Dextran, offering insights into its clinical application.