In this retrospective study, 54 feline medical records at the veterinary hospital at the University of Pennsylvania from 1999 through 2005 were reviewed to determine the association between renal hypoechoic subcapsular thickening seen on ultrasonography and presence of renal lymphosarcoma in cats. Ultrasound features of feline renal lymphosarcoma (LSA) are often nonspecific because they can also be seen with such abnormalities as infections, toxicity, and metastatic neoplasia. Ultrasound findings seen with renal LSA include renomegaly, abnormally shaped kidneys, masses, hypoechoic nodules or hyperechoic cortices, and subcapsular effusion.The authors also noticed hypoechoic subcapsular effusion in several cats with this type of neoplasia.Data collected included age, gender, and ultrasound findings as well as cytology, biopsy, or necropsy results.The ultrasound was first reviewed by a board-certified radiologist (who was blinded to the history and final diagnosis of each case) and then classified based on the presence or absence of hypoechoic subcapsular thickening. A final diagnosis for each cat was made based on cytologic, histopathologic, or necropsy findings. Hypoechoic subcapsular thickening was seen on ultrasonography in 21 of the 54 cats (38.9%).Of these 21, 17 cats (81%) were diagnosed with renal LSA.Other renal changes in these 17 cases included renomegaly, irregularly shaped kidneys, hyperechoic cortices, and pyelectasia. The remaining 33 cats showed no evidence of hypoechoic subcapsular thickening; however, 11 of these 33 cats (33%) were diagnosed with renal LSA.Based on these data, renal LSA was higher in the group of cats with hypoechoic subcapsular thickening than in the group without this ultrasound finding.

COMMENTARY: While hypoechoic subcapsular thickening, when seen on ultrasonography, is not a specific indicator of lymphosarcoma, the diagnosis should be considered. In this study, cats without LSA but with hypoechoic subcapsular thickening had undifferentiated malignant neoplasia, renal anaplastic carcinoma, and chronic active nephritis. The definitive diagnosis would still need to be made via cytology or biopsy.

Association between renal hypoechoic subcapsular thickening and lymphosarcoma in cats.Valdéz-Martínez A, Cianciolo R, Mai W. VET RADIOL ULTRASOUND 48:357-360, 2007.