Biochemical Parameters of Blood Serum in Cats with Nephrocardial Syndrome

Introduction. Nephrocardial syndrome (NCS) is a complex of interrelated disorders, which includes chronic kidney disease (CKD) resulting in development of secondary myocardial dysfunction and structural cardiac remodeling. CKD is one of the most common pathologies in older cats. Although cases of nephrocardial syndrome in cats have been described in the literature, its precise pathophysiological mechanisms are still poorly understood. Particularly insufficient are the scientific data regarding the role of systemic inflammation and protein and energy metabolism disorders related to NCS pathogenesis and progression. The aim of the study is to investigate the biochemical parameters of blood serum in cats with nephrocardial syndrome for identifying the specific patterns of disorders and developing the improved diagnostic and therapeutic techniques.
Materials and Methods. A retrospective analysis of 82 medical records of cats admitted to the Moscow veterinary clinics in the period of 2021 — 2025 was conducted. Two experimental groups of animals were formed (37 cats with NCS; 23 cats with CKD without cardiac complications) and one control group (22 healthy cats). Research methods included serum biochemistry (total protein, albumin/globulin fractions, C-reactive protein, azotemia and ketonemia markers), as well as instrumental methods (echocardiography, ECG).
Results. In cats with NCS, pronounced dysproteinemia was revealed: hypoalbuminemia (28.1±0.5 g/l versus 34.2±0.6 g/l in the control group), hyperglobulinemia (42.6±1.4 g/l), a significant decrease in the albumin to globulin ratio (0.69±0.03 versus 1.02±0.07 in the control group). The level of C-reactive protein in animals with NCS exceeded the values of both healthy cats (164.1±5.6 g/l versus 82.9±1.4 g/l) and the cats from the group with CKD without cardiac complications (128.5±3.2 g/l), which confirms the presence of systemic inflammation. Azotemia parameters (urea, creatinine, SDMA) did not significantly differ in groups with CKD and NCS, but were higher, compared to the control group.
Discussion and Conclusion. The increased ketogenesis was detected in cats with both pathologies, which is likely due to uremic intoxication and catabolic processes. NCS in cats is characterized by pronounced systemic inflammation, impaired protein metabolism, and metabolic shifts. The obtained results emphasize the importance of integrating inflammatory and metabolic markers interpretation into the diagnostics of NCS, as well as the need for further research to establish the cause-and-effect relationships within the nephrocardial continuum.

1. Conroy M, Brodbelt DC, O’Neill D, Chang YM, Elliott J. Chronic Kidney Disease in Cats Attending Primary Care Practice in the UK: A VetCompassTM Study. Veterinary Record. 2019;184(17):526. https://doi.org/10.1136/vr.105100/10.1136/vr.105100

2. Brown CA, Elliott J, Schmiedt CW, Brown S.A. Chronic Kidney Disease in Aged Cats: Clinical Features, Morphology, and Proposed Pathogeneses. Veterinary Pathology. 2016;53(2):309-26. https://doi.org/10.1177/0300985815622975

3. Spencer S, Wheeler-Jones C, Elliott J. Hypoxia and Chronic Kidney Disease: Possible Mechanisms, Therapeutic Targets, and Relevance to Cats. The Veterinary Journal. 2021;274:105714. https://doi.org/10.1016/j.tvjl.2021.105714

4. Summers S, Quimby J. Insights into the Gut-Kidney Axis Cats and Dogs. Veterinary Journal. 2024;306:106181. https://doi.org/10.1016/j.tvjl.2024.106181

5. Petrova NS, Glebov VV. Results of the Ultrasonic Study of Chronic Kidney Disease in Domestic Cats in the Territory of the Capital Megapolis. Bulletin of NSAU (Novosibirsk State Agrarian University). 2023;(2(67)):229-236. (In Russ.) https://doi.org/10.31677/2072-6724-2023-67-2-229-236

6. Bychkova VA, Goncharova AV, Kostylev VA. Proteinuria in Cats with Chronic Kidney Disease as a Factor of Additional Damage. Veterinary Morphology and Pathology. 2024;(3):36–41. (In Russ.) URL: https://disk.vetmorph.ru/2024-03/5_ВМП%202024-3_Протеинурия%20у%20кошек%20с%20хронической%20болезнью%20почек.pdf (accessed: 11.11.2025).

7. Inatullaeva LB, Vatnikov YuA, Vilkovyskiy IF, Voronina Yu.Yu. Gistologicheskiye izmeneniya v pochkah pri khronicheskoy bolezni pochek u koshek, svyazannyye s otlozheniyem amiloida. Veterinary, Zootechnics and Biotechnology. 2017;5:25–31. (In Russ.)

8. Vatnikov Yu.A., Sotnikova E.D., Byakhova V.M., Petrukhina O.A., Matveev A.V., Rodionova N.Yu., Rudenko A.A. Osobennosti razvitiya gepatokardial′nogo sindroma u sobak s dilatatsionnoy kardiomiopatiyey. Veterinariya. 2022;10:52–57. https://doi.org/10.30896/0042-4846.2022.25.10.52-57 (In Russ.)

9. Vatnikov YuA, Vilkovyskiy IF, Shchurov IV, Sotnikova ED, Byakhova VM, Petrukhina OA, Rudenko AA. Clinical and Echocardiographic Characteristics of Cardiorenal Syndrome in Dogs with Bicuspid Valve Endocardiosis. Bulliten of KSAU. 2025;(1):100–110. https://doi.org/10.36718/1819-4036-2025-1-100-110 (In Russ.)

10. Carvalho L, Kelley D, Labato MA, Webster CR. Hyperammonemia in Azotemic Cats. Journal of Feline Medicine and Surgery. 2021;23(8):700–707. https://doi.org/10.1177/1098612x20972039

11. Rogg S, Mochel JP, Kundu D, Tropf MA, Masters AK, Adin DB, et al. Frequency and Progression of Azotemia during Acute and Chronic Treatment of Congestive Heart Failure in Cats. Journal of Veterinary Internal Medicine. 2025;39(1):e17254. https://doi.org/10.1111/jvim.17254

12. Krofič Žel M, Nemec Svete A, Tozon N, Pavlin D. Hemogram-Derived Inflammatory Markers in Cats with Chronic Kidney Disease. Animals. 2024;14(12):1813. https://doi.org/10.3390/ani14121813

13. Chen H, Dunaevich A, Apfelbaum N, Kuzi S, Mazaki-Tovi M, Aroch I, Segev G. Acute on Chronic Kidney Disease in Cats: Etiology, Clinical and Clinicopathologic Findings, Prognostic Markers, and Outcome. Journal of Veterinary Internal Medicine. 2020;34(4):1496–1506. https://doi.org/10.1111/jvim.15808

14. Loane SC, Thomson JM, Williams TL, McCallum KE. Evaluation of Symmetric Dimethylarginine in Cats with Acute Kidney Injury and Chronic Kidney Disease. Journal of Veterinary Internal Medicine. 2022;36(5):1669–1676. https://doi.org/10.1111/jvim.16497

15. Jing H, Hsu WL, Wu VC, Tsai HJ, Tsai SF, Tsai PJ, et al. Urine Hemojuvelin in Cats with Naturally Occurring Kidney Disease. Journal of Veterinary Internal Medicine. 2020;34(3):1222–1230. https://doi.org/10.1111/jvim.15781

16. Wang IC, Hsu WL, Wu PH, Yin HY, Tsai HJ, Lee YJ. Neutrophil Gelatinase-Associated Lipocalin in Cats with Naturally Occurring Chronic Kidney Disease. Journal of Veterinary Internal Medicine. 2017;31(1):102–108. https://doi.org/10.1111/jvim.14628

17. Gorman L, Sharkey LC, Armstrong PJ, Little K, Rendahl A. Serum Beta Hydroxybutyrate Concentrations in Cats with Chronic Kidney Disease, Hyperthyroidism, or Hepatic Lipidosis. Journal of Veterinary Internal Medicine. 2016;30(2):611–616. https://doi.org/10.1111/jvim.13826

18. Polzin DJ, Churchill JA. Controversies in Veterinary Nephrology: Renal Diets Are Indicated for Cats with International Renal Interest Society Chronic Kidney Disease Stages 2 to 4: The Pro View. Veterinary Clinics of North America: Small Animal Practice. 2016;46(6):1049–1065. https://doi.org/10.1016/j.cvsm.2016.06.005