Comparison of sonographic and CT findings for the identification of renal nodules in dogs and cats

Abstract

Ultrasonography (US) and computed tomography (CT) are used to diagnose neoplastic and non‐neoplastic focal renal lesions in dogs and cats; however, comparative studies between these two diagnostic tools are lacking. The aim of this retrospective, methods comparison study was to evaluate and compare the performance of US compared to CT in identifying at least one renal nodule in animals with confirmed focal renal lesions. Imaging studies of animals with uni‐ or bilateral renal nodules smaller than 3 cm that underwent both US and CT and that had a pathologically confirmed diagnosis were reviewed. Animals with renal cysts and infarcts were excluded. Recorded features for both modalities included the following: shape, size, number, localization, margins, renal profile. For CT only, recorded features also included attenuation (HU) and pattern of enhancement. For US only, recorded features also included echogenicity, echostructure, and rate of visibility. Final diagnosis was obtained by cytology or histopathology. Using CT, lesions were identified in all 39 (100%) kidneys of 18 dogs and seven cats. Most lesions were multiple, cortical, well‐defined, iso‐attenuating (precontrast), hypo‐attenuating, and moderately enhancing (postcontrast). Using US, lesions were identified in 29 of 39 (74%) kidneys. Overall, nine (31%) lesions were poorly visible; 10 (26%) kidneys appeared normal; in 17 (59%) organs, lesions’ number was underestimated. Isoechoic, non‐protruding lesions were difficult to identify by US. Ultrasonography underestimated renal lesions compared to CT in 59% of the kidneys (P = 0.001). Final diagnoses included metastatic disease (n = 16), infiltration by feline lymphoma (n = 4), primary neoplasia (n = 3), and non‐neoplastic benign lesions (n = 2).

Ultrasonographic Renal Subcapsular Thickening in Cats with Primary and Metastatic Carcinoma

“…The most common cause of renal metastases is reported to be pulmonary carcinoma, which accounts for 25% of renal metastases in domestic animals [ 19 ]. Although no study has specifically investigated the cause of renal metastasis in cats, several studies have reported that feline pulmonary carcinoma can metastasize to the kidneys, with a prevalence ranging from 1.2 to 15.3% [ 10 , 11 , 12 ].…”

“…Metastatic lesions in the kidney are often microscopic, involving bilateral renal cortices [ 8 ]. Previous studies revealed that kidneys with metastasis from pulmonary carcinoma exhibited multifocal nodules on the renal capsular surface or within the parenchyma [ 11 , 19 ]. In contrast, our study identified renal nodules in only two out of six kidneys with metastatic pulmonary carcinoma.…”

“…Primary renal neoplasia is rare in cats, accounting for less than 2.5% of all feline tumors [4,5]. Although the kidney is a known metastatic site for various neoplasms in cats, such as pulmonary carcinoma [19], renal metastasis remains relatively infrequent. Even pulmonary carcinoma, the most common cause of renal metastases, has a low metastatic rate ranging from 1.2 to 15.3% [10][11][12].…”

“…Although intrathoracic metastasis is more likely to happen, the kidney is a relatively common extrathoracic metastatic site in cats with pulmonary carcinoma, with a prevalence of 1.5–15.3% of all metastatic cases [ 10 , 11 , 12 ]. Carcinoma is the primary cause of nodular renal metastasis in domestic animals, with pulmonary carcinoma occupying the majority [ 19 ]. Although nodular form of renal metastasis has been reported in cats with pulmonary carcinoma [ 11 , 19 ], ultrasonographic subcapsular thickening has not been described in previous reports as one of the manifestations of metastatic carcinoma in the feline kidney.…”

“…Carcinoma is the primary cause of nodular renal metastasis in domestic animals, with pulmonary carcinoma occupying the majority [ 19 ]. Although nodular form of renal metastasis has been reported in cats with pulmonary carcinoma [ 11 , 19 ], ultrasonographic subcapsular thickening has not been described in previous reports as one of the manifestations of metastatic carcinoma in the feline kidney.…”