N-acetyl-beta-D-glucosaminidase activity in urine of cows with renal parenchymal lesions

OBJECTIVE: To measure N-acetyl-beta-D-glucosaminidase (NAG) activity in urine of cows with renal diseases and to correlate values for NAG activity with renal lesions. ANIMALS: 8 lactating Holstein cows and a Japanese Shorthorn cow, all of which had renal disease. PROCEDURE: Urine samples were collected, and urinary NAG activity and creatinine concentration were measured. The NAG activity was expressed as units per gram of creatinine (NAG index). Cows were euthanatized, necropsy was performed, and correlations between results for urinary NAG index and histopathologic findings for the kidneys were evaluated. RESULTS: The NAG activity and NAG index in urine samples obtained from cows with interstitial nephritis were high, ranging from 4.2 to 13.6 U/L and 3.5 to 23.0 U/g, respectively. A cow with renal amyloidosis also had high values for urinary NAG activity and NAG index. Histologic examination of the kidneys revealed various kinds of parenchymal lesions. However, urinary NAG index in cows with enzootic bovine leukosis was low. CONCLUSIONS AND CLINICAL RELEVANCE: Cows with renal diseases had high urinary NAG indexes that correlated well with their renal lesions, except for cows with enzootic bovine leukosis. Therefore, measurement of NAG index in urine samples has the potential to provide new perspectives on clinical diagnosis of renal disease in cattle.