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Abstract Background Urinary liver‐type fatty acid‐binding protein (uL‐FABP) is a promising biomarker to detect early chronic kidney disease (CKD) in cats. Few healthy cats show increased uL‐FABP for unknown reasons. Objectives The objective of this study was to evaluate uL‐FABP in a large healthy elderly cat population comparing cats with and without International Renal Interest Society (IRIS) stage 1 CKD and with and without borderline proteinuria. Methods This was a cross‐sectional study. One hundred ninety‐six clinically healthy client‐owned cats of ≥7 years old were subdivided based on two criteria: (1) having either IRIS stage 1 CKD or no evidence of CKD and (2) having borderline proteinuria or no proteinuria. Urinary L‐FABP was measured using a validated commercially available feline L‐FABP ELISA. Results Overall, uL‐FABP was detectable in 6/196 (3%) healthy elderly cats. For the first subdivision, nine (5%) cats had IRIS stage 1 CKD, 184 cats had no evidence CKD and three cats were excluded. All cats with IRIS stage 1 CKD had uL‐FABP concentrations below the detection limit, whereas 6/184 (3%) cats without IRIS stage 1 CKD had detectable uL‐FABP concentrations (median 1.79 ng/ml, range 0.79–3.66 ng/ml). For the second subdivision, 47 (24%) cats had borderline proteinuria, 147 cats had no proteinuria and two cats were excluded. One of the borderline proteinuric cats had a detectable uL‐FABP concentration, whereas the other five cats with detectable uL‐FABP concentrations were non‐proteinuric. Conclusion With the current assay, the screening potential of uL‐FABP as an early biomarker for feline CKD is limited as uL‐FABP was rarely detected in clinically healthy elderly cats independently of the presence of either IRIS stage 1 CKD or borderline proteinuria.

Abstract Serum creatinine concentration, the classical biomarker of chronic kidney disease (CKD) in cats, has important limitations that decrease its value as a biomarker of early CKD. Recently, serum symmetric dimethylarginine concentration was introduced as a novel glomerular filtration rate biomarker for the early detection of CKD in cats. However, data on its specificity are still limited. The limitations of conventional biomarkers and the desire for early therapeutic intervention in cats with CKD to improve outcomes have prompted the discovery and validation of novel renal biomarkers to detect glomerular or tubular dysfunction. Changes in the serum or urinary concentrations of these biomarkers may indicate early kidney damage or predict the progression of kidney before changes in conventional biomarkers are detectable. This review summarizes current knowledge on renal biomarkers in CKD in cats, a field that has progressed substantially over the last 5 years.

Abstract Background Liver‐type fatty acid‐binding protein (L‐FABP) and neutrophil gelatinase‐associated lipocalin (NGAL) are candidate biomarkers for the detection of early chronic kidney disease (CKD) in cats. Objective To evaluate urinary and serum L‐FABP and NGAL concentrations in CKD cats and in hyperthyroid cats before and after radioiodine (131I) treatment. Animals Nine CKD cats, 45 healthy cats and hyperthyroid cats at 3 time points including before (T0, n = 49), 1 month (T1, n = 49), and 11 to 29 months after (T2, n = 26) 131I treatment. Methods Cross‐sectional and longitudinal study. Serum L‐FABP (sL‐FABP), serum NGAL (sNGAL), urinary L‐FABP (uL‐FABP), and urinary NGAL (uNGAL) were compared between the 3 groups and between hyperthyroid cats before and after treatment. Data are reported as median (min‐max). Results CKD cats had significantly higher sL‐FABP (13.50 [3.40‐75.60] ng/ml) and uL‐FABP/Cr (4.90 [0.97‐2139.44] µg/g) than healthy cats (4.25 [1.34‐23.25] ng/ml; P = .01 and 0.46 [0.18‐9.13] µg/g; P < .001, respectively). Hyperthyroid cats at T0 had significantly higher uL‐FABP/Cr (0.94 [0.15‐896.00] µg/g) than healthy cats (P < .001), thereafter uL‐FABP/Cr significantly decreased at T2 (0.54 [0.10‐76.41] µg/g, P = .002). For the detection of CKD, uL‐FABP/Cr had 100% (95% confidence interval [CI], 66.4‐100.0) sensitivity and 93.2% (95% CI, 81.3‐98.6) specificity. There were no significant differences in sNGAL and uNGAL/Cr between the 3 groups. Conclusions and Clinical Importance L‐FABP, but not NGAL, is a potential biomarker for the detection of early CKD in cats. Utility of uL‐FABP to predict azotemia after treatment in hyperthyroid cats remains unknown.

A 10-year-old, spayed, female poodle was presented at Prasuarthon Animal Hospital, Faculty of Veterinary Science, Mahidol University for further investigation on abdominal enlargement, anorexia and frequent vomiting for 1 week. Upon an abdominal palpation, a firm abdominal mass was noted in the cranial abdomen. Hematology and blood chemistry values were within normal limits, except elevated symmetric dimethylarginine (SDMA). Ultrasonography reported a large oval shaped mass at the left retroperitoneal area of unknown origin. The computed tomography (CT) result revealed that the left kidney was severely enlarged with an irregular shape. The dog was diagnosed with a renal mass. An exploratory laparotomy and nephrectomy were performed for diagnosis and treatment. The renal mass was submitted for a histopathological examination and was reported to be a clear cell renal cell carcinoma (ccRCC). The patient was clinically healthy and was under follow up for 24 weeks without any sign of metastasis. [ABSTRACT FROM AUTHOR]