Chronic kidney disease (CKD) is a leading cause of death in dogs and cats. Based on a survey conducted in 2005, U.S. veterinarians indicated that 10.8% of cats and 5.2% of dogs brought in for evaluation had CKD. In geriatric CKD patients, the peak prevalence in clinic patients reaches 10% of dogs and 30% of cats over 15 years of age.

CKD in dogs and cats generally progresses along a continuum from an initial non-azotemic stage to end-stage uremia. The International Renal Interest Society (IRIS) has proposed a classification system for CKD which provides a staged approach to CKD in dogs (Table 1) and cats (Table 2). This classification scheme uses serum creatinine concentration to estimate the degree of decline in glomerular filtration rate (GFR) caused by the kidney disease. However, it should be noted that the degree of azotemia in cats is not synonymous with that in dogs.

Note also that the Antech Diagnostics normal references ranges for creatinine are 0.5–1.6 mg/dL for dogs and 0.6–2.4 mg/dL for cats. This must be taken into account when using the IRIS classification guidelines. Taking the creatinine results obtained from Antech and applying them directly into the IRIS classification scheme would result in over-diagnosis of kidney disease.

In the initial stage of CKD, the animal is not azotemic and generally has no observable clinical signs.

This stage of CKD occurs when there is sufficient loss of renal tissue such that azotemia is now present, usually without clinical signs. During this stage, slowing progression of the disease is an important factor. The rate of progression is often slow in cats (months to years) but erratic and more rapid in dogs (weeks to months).

This stage reflects the effects of further decline in GFR and increased likelihood of clinical signs of advancing CKD. Both progression and uremia are concerns in this stage.

Patients in this stage generally have clinical signs, referred to as the uremic syndrome. Prospectively identifying and alleviating these complications is critical in this stage.