CT Clues to Canine Renal Tumors: Collateral Vessels Point to RCC

Computed tomographic features of renal neoplasms in dogs: introduction of the collateral vessel sign in veterinary medicine

Michele Occhiuzzi, DVM; Swan Specchi, DVM, PhD, DACVR; Roberto Rabozzi, DVM; Simone Teodori, DVM; Caterina Puccinelli, DVM, PhD; Erica Visconti, DVM; Samuele Berti, DVM; Laura Brizzi, DVM; Simonetta Citi, DVM, PhD

Background

Renal neoplasms in dogs are rare, with primary renal tumors accounting for a very small proportion of canine cancers. Ultrasonography has limited sensitivity and specificity for renal lesion characterization, whereas computed tomography (CT) offers multiplanar assessment and improved lesion detection. In human medicine, CT features—including enhancement patterns and collateral vessels—aid in renal tumor characterization, but analogous veterinary data are limited. This study aimed to describe CT features of canine renal neoplasms and evaluate CT’s ability to differentiate tumor types, introducing the “collateral vessel” (CV) sign in veterinary medicine.

Methods

This retrospective multicenter study included 32 dogs with cytologically or histopathologically confirmed primary or secondary renal neoplasia that underwent pre- and postcontrast CT between 2017 and 2024. Qualitative CT features (eg, lesion size and type, margins, laterality, enhancement pattern, mineralization, lymphadenopathy, pulmonary metastases, hemorrhage, and collateral vessels) and quantitative features (lesion diameter and attenuation values) were assessed by blinded radiologists. Lesions were categorized as masses (≥ 3 cm) or nodules (< 3 cm). Statistical analyses included Shapiro-Wilk testing and Fisher exact tests to compare imaging features across diagnostic groups.

Results

Primary renal tumors (17/32), multicentric lymphoma (5/32), and metastatic renal lesions (10/32) were identified; renal cell carcinoma (RCC) was the most common primary tumor (12/32). Primary tumors typically appeared as unilateral, large mass lesions, whereas lymphoma and metastatic disease more often presented as bilateral, multifocal nodules. RCCs most frequently showed heterogeneous postcontrast enhancement, intralesional mineralization, and collateral vessels. Collateral vessels were significantly more common in RCC than in lymphoma or metastatic lesions and were also associated with mass-size lesions. Multicentric lymphoma demonstrated homogeneous enhancement and bilateral, multifocal nodules. No CT feature reliably distinguished among different primary renal tumor subtypes.

Limitations

Limitations included the retrospective design with nonstandardized CT protocols, incomplete histopathologic and immunohistochemical confirmation for all cases, small subgroup sample sizes, absence of a control group, and potential selection and interpretation biases inherent to referral-based imaging cohorts.

Conclusions

CT provides valuable information for characterizing canine renal neoplasms and identifying patterns suggestive of tumor type. The presence of collateral vessels is a novel CT feature in dogs and was most strongly associated with RCC and with mass-size lesions, supporting its potential role in differential diagnosis and surgical planning. Despite overlapping imaging features among tumor categories, CT findings—particularly lesion distribution, enhancement pattern, and collateral vessels—can help guide clinical decision-making, although definitive diagnosis still requires cytologic or histopathologic confirmation.

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