CT Clues Reveal Key Differences Between Feline Kidney Tumors

Veterinary Sciences 2025

Author

Obi Veterinary Education
January 30, 2026

Choye Shin, Kidong Eom, Jaehwan Kim, Aryung Nam, Yewon Joo, Inseong Jung, Jihee Park, Noh-won Park, Minsu Lee, Dong-gil Lee, Seunghak Yeo, Heejung Yu

Background:
Renal cell carcinoma (RCC) and lymphoma are the most common feline renal tumors but require different management strategies. Differentiating between these neoplasms non-invasively is challenging. This study aimed to characterize computed tomography (CT) features that distinguish RCC from renal lymphoma in cats to aid diagnosis and guide clinical decisions.

Methods:
A retrospective, multicenter study evaluated CT images from 25 cats with histologically or cytologically confirmed renal tumors (15 RCC, 10 lymphoma) between 2016 and 2024. Qualitative features (tumor distribution, growth pattern, enhancement type) and quantitative parameters (tumor size, attenuation values) were analyzed across pre- and post-contrast CT phases. Statistical comparisons were performed to identify significant differentiators between RCC and lymphoma.

Results:
RCC typically presented as unilateral (93%) and solitary (93%) masses with expansile growth and heterogeneous contrast enhancement. Tumor vessel enhancement was exclusive to RCC. Lymphomas were more often bilateral (60%), multifocal (80%), and showed infiltrative growth with homogeneous enhancement. RCC tumors were significantly larger than lymphomas and exhibited higher attenuation values in the delayed nephrographic/early excretory phase (p < 0.001). Necrosis and hemorrhage were significantly more common in RCC, whereas lymphadenopathy was more frequent in lymphoma. Some overlap occurred, especially in cases of papillary RCC, which could mimic lymphoma imaging features.

Limitations:
The study's retrospective design, small sample size, and incomplete triphasic CT data for some cases limit the generalizability of findings. Not all tumors or suspected metastases underwent histopathological confirmation. CT imaging timing varied slightly across institutions, and only RCC and lymphoma were studied.

Conclusions:
Distinct CT characteristics, particularly regarding lesion distribution, enhancement patterns, internal features, and attenuation values, can aid differentiation between feline RCC and renal lymphoma. These findings enhance non-invasive diagnostic capabilities but highlight the continued importance of histopathologic confirmation, especially in atypical cases. Triphasic contrast-enhanced CT is recommended for comprehensive renal tumor evaluation in cats.

Contrast-enhanced computed tomography (CT) images of renal tumors in different cats. (A) Lymphoma with a heterogeneous and irregular appearance. (B) Papillary renal cell carcinoma (RCC) presents as a relatively hypoenhancing mass, mimicking the solitary hypoenhancing mass observed in the lymphoma. Partially nonenhancing hypoattenuating regions corresponded to extensive internal necrosis observed in the histopathological analysis. (C,D) Incidental findings of small RCCs in two different cats demonstrating increased vascularity and heterogeneity without significant alteration of kidney shape.

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