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The urine gamma-glutamyl transferase (GGT)-to-creatinine ratio has been used to monitor patients at risk of acute renal injury. We validated the spectrophotometric quantification of GGT in urine in a commercial biochemistry analyzer. The assay was precise, accurate, and linear. Intra-assay precision was 3.59% in 4 samples, with GGT concentrations of 47-195 U/L. Inter-assay precision in 3 samples with activities of 11-51 U/L was 7.74%. Accuracy was 97.3%, with an absolute bias of 2.7 U/L. Urine GGT was unaffected by hematuria, hemoglobinuria, or bacteriuria. Urine GGT was stable at 20°C and 4°C for up to 3 d. Storage by freezing at -20°C resulted in a significant reduction in enzyme activity. A pH outside the range of 6.5-8 resulted in reduced GGT activity. The biological variation of urine GGT-to-creatinine ratio provided an index of individuality of 1.6, indicating that a population-based reference interval (RI) can be used. The reference change value was calculated, and an increase in consecutive measurements >43% is required to be regarded as significant. The urine GGT-to-creatinine ratio RI obtained in a population of 41 healthy dogs was 8.5-28.5 U/g.

Polycystic kidney disease is the most common inherited disorder in cats. Renal cysts progressively increase in size and number, resulting in a gradual decrease in kidney function. An autosomal dominant mutation in exon 29 of the polycystin-1 gene has been identified, mostly in Persian and Persian-related breeds. This case study describes polycystic kidney disease in four British shorthair cats, of which two had the same genetic mutation reported in Persian and Persian-related cats. This likely reflects introduction of this mutation into the British shorthair breeding line because of previous outcrossing with Persian cats. An infected renal cyst was diagnosed and successfully treated in one of the cats. This is a commonly reported complication in human polycystic kidney disease, and to the authors' knowledge has not previously been reported in cats with polycystic kidney disease., (© 2015 British Small Animal Veterinary Association.)