The purpose of this study was to: (1) evaluate the mechanism of lymph drainage through a vascularized lymph node (VLN) flap, and (2) investigate if the number of VLNs impacts lymph transit time through the flap.Methods
Twenty-seven axillary VLN flaps were elevated in 14 Sprague-Dawley rats and divided into three groups (n = 9 each) based on the number of lymph nodes present: group 1 (0-VLNs), group 2 (2-VLNs), and group 3 (4-VLNs). Indocyanine green (n = 8/group) and Alexa680-albumin (n = 1/group) were injected into the edge of flaps and the latency period between injection and fluorescence in the axillary vein was recorded. Stereomicroscopic fluorescent lymphography was performed to directly visualize lymphatic transit through VLNs.Results
Fluorescence was detected in the axillary vein after 229s [47-476], 79s [15-289], and 56s [16-110] in group 1, 2, and 3, respectively (p < 0.01). There was a negative correlation between the number of VLNs in the flap and the latency period (r = −0.59; p < 0.05). Median flap weights were comparable in group 1, 2, and 3 (258 mg [196-349], 294 mg [212-407], 315 mg [204-386], respectively; p = 0.54). Stereoscopic lymphography allowed direct visualization of lymphatic fluid transit through VLNs.Conclusion
Lymphatic fluid in VLN flaps drains into the venous system mainly by passing through the afferent lymphatics and lymph nodes. A secondary mechanism appears to be the diffusion of fluid into the venous system via intratissue lymphaticovenous connections created during flap elevation. Increasing the number of lymph nodes in the flap is associated with a more rapid transit of fluid.