Characterization of thyroid lymphatic drainage on real-time contrast-enhanced ultrasound: A mapping study in vivo

The in vivo lymphatic drainage pattern of the thyroid gland is a critical but poorly understood determinant of prognosis in papillary thyroid carcinoma (PTC), as conventional imaging cannot dynamically visualize these pathways. This study aimed to systematically characterize these patterns using lymphatic contrast-enhanced ultrasound (LCEUS).

This prospective study enrolled 30 PTC patients. A microbubble contrast agent was injected into the tumor-bearing lobe. The origin, anatomical course, and terminal draining lymph nodes (LNs) of lymphatic vessels (LVs) were dynamically observed and quantitatively analyzed.

Following injection, complete enhancement of the ipsilateral lobe was achieved in all cases. Contralateral communication was observed in 76.7 % (23/30) of patients. LVs originated evenly from all poles (P ≥ 0.05). The "Anterior to Carotid" course was the most prominent pathway for LVs (P < 0.05). Levels III and IV were the primary draining basins for LNs (P < 0.05). Notably, a significant right-sided predominance in the total number of draining LNs was identified (median 8.0 vs. 4.0; P = 0.005). No drainage to Level V was observed. No significant differences were found in patients with or without Hashimoto's thyroiditis.

LCEUS provides the first detailed, real-time map of thyroid lymphatic drainage, revealing a high incidence of contralateral communication and a previously uncharacterized right-sided anatomical predominance. These findings challenge conventional concepts of lymphatic compartmentalization and establish a novel methodology for lymphatic research.