Abstract
The present study was aimed to determine the ultrasonographic morphologic characteristics of the feline Medullary rim sign (MRS) and its association with chronic kidney disorder (CKD) in Persian cats. In order to examine the correlation between MRS morphologic characteristics and CKD based on clinical, laboratory and renal ultrasonographic parameters.70 Persian cats were examined through an ambispective study (retrospective cohort: historical medical records of 55 cats, previously examined between December 2021 and December 2024, were reviewed and analyzed, in addition to a prospective cohort: 15 active cases, during the last year, were enrolled and followed clinically. The Persian cats were divided into 4 groups; MRS and CKD (n=12), MRS and no CKD (n=12), CKD and no MRS (n=31), and cats Neither MRS Nor CKD (n=15). Receiver operating characteristic (ROC) analysis was performed for diagnostic performance evaluation of ultrasonographic and laboratory parameters. Cats with CKD showed significantly increased serum creatinine and BUN levels and decreased USG when compared to cats without CKD (P<0.05). A thin and well-defined MRS-line was more commonly found in cats without CKD (83.3%) as compared to a thick and ill-defined MRS-band that was significantly related to CKD (75.0%; P = 0.004). Poor corticomedullary differentiation was the most useful ultrasonographic sign for the diagnosis of CKD (AUC = 0.744), whereas serum creatinine (AUC = 0.867) and BUN (AUC = 0.856) were the tests with the highest diagnostic accuracy.The morphological appearance of MRS might provide additional diagnostic information regarding CKD in Persian cats.A thin, well-defined MRS-line was commonly associated with cats without (CKD), whereas a thick, ill-defined MRS-band was strongly associated with CKD. Although serum creatinine and blood urea nitrogen remained the most accurate diagnostic markers, ultrasonographic assessment of MRS morphology and corticomedullary differentiation offered valuable complementary information for the diagnosis of CKD.

Key words: Persian cat, chronic kidney disorder, renal ultrasonography, medullary rim sign