Comparative study of urinary N-Acetyl-Beta-D-Glucosaminidase levels in cats with chronic kidney disease, Feline Idiopathic Cystitis and Cystic Calculi

Abstract

Comparative study was performed to measure urinary N-acetyl-beta-D-glucosaminidase (NAG) in cats with chronic kidney disease (CKD), idiopathic cystitis and cystic calculi. Information regarding age, gender, breed, type of food consumed and environment factors were asked through standard questionnaire. Urine samples were collected from 19 clinically normal cats, 19 cats with CKD, 19 cats with idiopathic cystitis and 9 cats with cystic calculi. The urinary NAG activity was quantified by colorimetric method. NAG index was calculated by NAG activity to urine creatinine ratio. The results showed that the risk factors of FIC and cystic calculi were age (3 to 7 years old), weighing more than four kilograms, and/or consuming only dry commercial food. CKD cats had significantly higher NAG index (8.32 ± 2.16 U/g) than the clinically normal cats (2.14 ± 0.48 U/g) (p < 0.01) while the average of NAG index in feline idiopathic cystitis (FIC) (4.79 ± 1.53 U/g) and cystic calculi group (3.53 ± 2.08 U/g) had an increased trend of 2 times and 1.5 times when compared with the clinically normal cat group, respectively (p > 0.05). In FIC group, log urine protein to creatinine ratio was positively correlated with log NAG index at moderate level (r2 = 0.512, p < 0.05). Based on the results, NAG index could not be used to indicate early CKD. In FIC cats, the increased NAG index may be related to the increased proteinuria before azotemia occur. Further study is needed to address NAG role in the pathological abnormalities in cats with idiopathic cystitis.