Background

Lymphography in veterinary medicine has largely focused on canines, with limited data available for felines. Current clinical approaches for assessing feline lymphatic drainage often extrapolate from canine studies, despite possible species-specific anatomical differences. This study addresses the knowledge gap by evaluating the feasibility of using indocyanine green (ICG) fluorescence lymphography to map superficial lymphatic drainage territories (lymphosomes) in the head and hind limbs of cats, aiming to determine the predictability of lymphatic pathways and identify deviations from known canine patterns.

Methods

This exploratory study involved 33 adult cat cadavers, both owned and unowned, which were frozen or refrigerated post-mortem. Lymphography was performed on 84 selected cutaneous regions (26 head, 58 hind limbs), each marked based on anatomical landmarks. After intradermal injection of ICG dye and massage/flexion movements, near-infrared fluorescence (NIRF) imaging was used to track lymphatic drainage and identify draining lymphocentrums (LCs). Success was defined by fluorescent lymph node detection, and correspondence with canine-based expectations was assessed.

Results

ICG lymphography succeeded in 75% (63/84) of cases. Drainage to expected LCs based on canine models occurred in only 44% of successful cases; the remainder showed partial (additional unexpected LCs) or complete non-correspondence. Migration times were shorter in the head than in hind limbs (median 4 vs. 10 minutes), and drainage pathway lengths were likewise shorter in the head. Certain regions (e.g., auricular and medial crural) had high failure rates. Use of half-volume injections correlated with fewer failures and re-injections. Unexpected drainage to medial iliac LCs was observed from distal hind limb regions, bypassing popliteal and superficial inguinal LCs.

Limitations

The study's limitations include a small number of refrigerated cadavers, a relatively limited number of repetitions per region (4–5), and potential variability introduced by cadaveric changes affecting lymphatic integrity. Additionally, the focus on paired regions and exclusion of midline structures may limit anatomical generalizability.

Conclusions

NIRF-ICG lymphography is a feasible technique for mapping superficial lymphatic pathways in feline cadavers. However, lymphatic drainage patterns in cats differ significantly from canine models, particularly in the hind limbs. The unpredictability and individual variability in drainage routes underscore the need for species-specific mapping in clinical applications such as sentinel lymph node detection. Future research should aim to map the complete superficial lymphatic system, including midline and unpaired regions.

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