Clinical progression of cats with early‐stage chronic kidney disease fed diets with varying protein and phosphorus contents and calcium to phosphorus ratios

Abstract

Background Dietary protein and phosphorus (P) restriction is the mainstay for nutritional management of chronic kidney disease (CKD). However, adequate restriction levels for cats with early CKD remain unclear. Objectives To investigate responses in cats with early CKD to varying dietary protein, P, and calcium (Ca) : P ratio. Animals Nineteen research colony cats with International Renal Interest Society stages 1‐2 CKD. Methods In an opportunistic longitudinal case study, cats were fed a low protein (59 g/Mcal), low P (0.84 g/Mcal) dry diet (LP‐LP; Ca : P = 1.9) for 18 months and later transitioned onto a moderate protein (76‐98 g/Mcal), moderate P (1.4‐1.6 g/Mcal) dry‐wet diet regimen (MP‐MP; Ca : P = 1.4‐1.6) for 22 months. Fold‐changes in serum creatinine, total Ca (tCa) and P (primary outcomes) and fibroblast growth factor 23 (FGF23) were assessed by linear‐mixed models. Results While feeding LP‐LP, mean serum creatinine decreased (0.87‐fold, 95% confidence interval [CI] 0.81, 0.93, P < .001) to within reference range after 6 months, while increases in total Ca (tCa; 1.16‐fold, 95% CI 1.11, 1.22, P < .001) and FGF23 (2.72‐fold, 95% CI 1.72, 4.31, P < .001), but not in P (1.03‐fold, 95% CI 0.945, 1.124, P = .94), were observed after 17 months. On MP‐MP, mean creatinine, tCa and P remained within reference ranges and did not significantly change (P = .11, P = .98, and P = 1, respectively), while FGF23 significantly decreased (0.58‐fold, 95% CI 0.36, 0.95, P = .02) after 22 months. Conclusions and Clinical Importance Cats with early CKD developed hypercalcemia after long‐term feeding of a highly P‐restricted diet. Increasing dietary P and reducing Ca : P ratio maintained renal markers, while improving Ca‐P balance. Cats with early CKD could benefit from moderately protein‐ and P‐restricted diets.

Ionized hypercalcemia in cats with azotemic chronic kidney disease (2012‐2018)

“…It could be hypothesized that the pathophysiology is different between cats with ionized hypercalcemia at diagnosis of azotemic CKD and cats that developed ionized hypercalcemia during follow‐up. Some studies suggest an association with feeding a clinical renal diet, as it was reported that ionized hypercalcemia developed in 2/15 cats on 84 and 149 days after starting a phosphate and protein‐restricted clinical renal diet, 13 total calcium increased in cats with IRIS stage 1 and 2 CKD fed different clinical renal diets for 6 months, 30 and ionized hypercalcemia developed after 17 months of feeding a phosphate‐restricted diet in 76% of cats with IRIS CKD stage 1 and 2 14 . Moreover, hypercalcemia was reported to resolve after discontinuation of stringent dietary phosphate restriction 13,21 .…”

“…Some studies suggest an association with feeding a clinical renal diet, as it was reported that ionized hypercalcemia developed in 2/15 cats on 84 and 149 days after starting a phosphate and protein‐restricted clinical renal diet, 13 total calcium increased in cats with IRIS stage 1 and 2 CKD fed different clinical renal diets for 6 months, 30 and ionized hypercalcemia developed after 17 months of feeding a phosphate‐restricted diet in 76% of cats with IRIS CKD stage 1 and 2. 14 Moreover, hypercalcemia was reported to resolve after discontinuation of stringent dietary phosphate restriction. 13 , 21 Cats in the present study were also offered a phosphate restricted clinical renal diet following the diagnosis of azotemic CKD, and most cats were fed this diet >50% of their daily food intake.…”

“…The percentage of cats with CKD diagnosed with hypercalcemia based on total calcium concentration varies between 10% and 20%, 2,3,11,12 while ionized hypercalcemia is observed in 10% to 30% of cats with CKD 2,3 . In previous studies of cats with azotemic CKD, the development of ionized hypercalcemia was observed in 13% to 76%, 13,14 and the development of hypercalcemia based on plasma total calcium concentration in 60 of 191 (31%) cats 1 . The majority of cats in the latter study lacked information on ionized calcium concentration, which is the physiologically relevant fraction of the plasma total calcium concentration 15 .…”

>b<Perfil aminoacídico plasmático e composição corporal de gatos doentes renais crônicos alimentados com dieta formulada com teor de proteína recomendado para gatos em manutenção e baixo fósforo>b<

“…Conforme já mencionado, o HPSR é comum em gatos com DRC, chegando a acometer 84% dos pacientes felinos, mas pode chegar a 100% em estádios mais avançados da doença, nos quais pode-se observar hiperplasia da paratireoide e osteodistrofia renal Elliot;. Estudos mais recentes têm demonstrado aumento nas concentrações séricas do PTH e Cai nos estádios iniciais da doença (CORTADELLAS et al, 2010;GIOVANINNI, et al, 2013), sugerindo a hipótese de que a diminuição da excreção de fósforo e, consequente retenção sérica, se inicia nos estádios iniciais da DRC.…”

“…Nos tempos T0, T30 e T60, 67%; 50% e 83% dos gatos doentes renais estádio 1 e 89% (nos tempos T0 e T30) e 100% em T60, dos gatos estádio 2 eram hiperfosfatêmicos. Em estudo conduzido porSchauf et al (2021), a concentração sérica de fósforo de gatos com DRC nos estádios iniciais, manteve-se dentro do intervalo de referência durante todo o estudo mas, foi maior que 4,5mg/dL após 3, 6 e 17 meses de consumo do alimento com baixos teores de proteína e fósforo em comparação ao alimento com moderado teor destes nutrientes.A hiperfosfatemia é uma complicação frequente observada em gatos com DRC e pode ocorrer já nos estádios iniciais da doença (BARBER;ELLIOTT, 1998;ELLIOTT, 2016). Por isso, a introdução de alimentos restritos em fósforo é recomendada a partir do estádio 2 ou quando a concentração de fósforo for maior que 4,5mg/dL (IRIS, 2019b) com o objetivo de minimizá-la.…”