New CT Insights into Feline Ischiatic Lymph Nodes: Multicenter Study on 250 Cats

Computed Tomographic Features of Feline Ischiatic Lymph Nodes

Caterina Puccinelli, Mirko Mattolini, Daniele della Santa, Federica Rossi, Tina Pelligra, Simonetta Citi

Background

Lymph node imaging has become increasingly important for tumor staging and inflammatory disease assessment in veterinary medicine. However, data on feline lymph nodes, particularly the ischiatic lymph nodes, remain limited. These nodes, located dorsal to the ischiatic tuberosity and medial to the caudal gluteal vein, are known anatomically but not well characterized on CT. This study aimed to describe their prevalence and CT features in cats and assess their potential diagnostic significance.

Methods

This retrospective, multicenter anatomical study reviewed total-body pre- and postcontrast CT scans of 250 cats performed between January 2020 and January 2024 at three Italian veterinary hospitals. Lymph nodes were identified and characterized by location, size, shape, enhancement pattern, and symmetry. Measurements were made in multiple planes, and enhancement was graded as mild, moderate, or marked. Statistical comparisons assessed dimensional differences between sides and between normal versus diseased patients. CT lymphangiography was performed in six cats to trace drainage pathways.

Results

Ischiatic lymph nodes were visualized in 160 of 250 cats (64%). Bilateral nodes were observed in 84 cats, while 32 had only right and 44 only left nodes, totaling 242 nodes. Shapes varied (oval 49%, round 37%, irregular 11%), and nodes averaged 3.6 mm in length. Enhancement was mild to moderate in most cases and homogeneous in 80%. Fourteen cats had diseases in the drainage area (11 neoplastic, 3 inflammatory), and two had multicentric lymphoma, yet lymph node size did not differ significantly from the general population. CT lymphangiography in six cats revealed two drainage patterns from the popliteal lymph node—one to the medial iliac node and a second, less common, pathway to the ischiatic node.

Limitations

Only one lymph node underwent cytological evaluation, preventing definitive differentiation of normal versus pathological nodes. The retrospective design precluded ultrasound correlation, and the small number of young cats limited assessment of age effects on node size. Additionally, limited adipose tissue in some cats may have reduced visualization accuracy.

Conclusions

Feline ischiatic lymph nodes are identifiable by CT in most cats and typically appear as small, bilateral, oval structures with mild to moderate homogeneous enhancement. Visualization improves with greater surrounding adipose tissue. Although their role in lymphatic drainage and disease spread remains unclear, CT identification is feasible and clinically relevant for anatomical and oncological evaluations. Further CT lymphography and cytologic studies are needed to define their functional and pathological significance.

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