Chronic Kidney Disease: Pathophysiology, Progression and Interventions

chronic kidney disease (CKD) in dogs and cats occurred late in the course of disease, usually aft er kidney function loss of 75% or more. Late recognition of CKD is largely due to insensitivity of serum creatinine concentration as a measure of kidney function. A new kidney function test, symmetric dimethylarginine (SDMA), has been reported to diagnose CKD in dogs and cats with a decline in kidney function as little as 25% to 40%. It has been hoped that earlier diagnosis of CKD may lead to recognition of primary kidney diseases that cause CKD and thereaft er specific therapy directed at these diseases. However, despite earlier recognition of CKD, diagnosis of a treatable primary kidney disease remains rare. Failure to diagnose kidney diseases that initiate CKD in dogs and cats may result from insuff iciently aggressive diagnostic evaluations and/or limited or inadequate diagnostic testing options for dogs and cats with early International Renal Interest Society (IRIS) CKD Stage 1. It is also possible that dogs and cats with CKD do not develop kidney disease subsequent to a single identifiable primary kidney disease (e.g., pyelonephritis, immunemediated glomerular disease, amyloidosis, etc.). An alternative scenario is that CKD may result from a series of smaller individual renal insults of diverse origin leading to suff icient loss of kidney function to prompt compensative processes that help sustain renal function but ultimately lead to self-perpetuating loss of nephrons and progressive CKD. Regardless of which of these possibilities are in fact the causes of CKD as we recognize it clinically, they ultimately are all characterized by processes in the injured kidney that promote progressive CKD. It is useful to recognize these processes, their impact on the kidneys and what therapies that may be useful in managing CKD, with the ultimate goal of maximizing length and quality of life.