When should we start to treat feline CKD: A narrative review of early diagnosis and the evidence for pre-azotaemic intervention

Chronic kidney disease (CKD) is a common and important disease in ageing cats. Increased awareness and availability of a novel biomarker for detecting glomerular filtration rate reduction (symmetric dimethylarginine), alongside efforts by the International Renal Interest Society to standardise diagnosis and staging, have led to earlier detection of CKD and an ability to study and trial interventions in sub-populations based on disease severity. As weight loss and phosphorus dyshomeostasis are present in non-azotaemic cats, and progression to azotaemic CKD may occur over time, earlier diagnosis and management represent a compelling opportunity for optimising management of this disease. To date, however, dietary modification (particularly protein- and phosphorus-restriction) in cats with azotaemic CKD is the only intervention demonstrating robust evidence for improving survival times and slowing disease progression. The purpose of this article is to review the available literature supporting criteria currently used to diagnose non-azotaemic CKD and evidence for early intervention, with a focus on dietary modification.