Introduction

The determination of fractional excretion of electrolytes is an easy and low expensive method to evaluate the tubulointerstitial function of kidneys, but is not commonly used.

Objective

The aim of the present study was to evaluate the utility of the urinary fractional excretion of three electrolytes: sodium (FENa), chloride (FECl) and potassium (FEK), in the diagnosis of canine kidney disease (CKD) in dogs.

Methods

A group of 20 patients from the Teaching Hospital, diagnosed in different stages of CKD according to the International Renal Interest Society, were included: IRIS I (2); IRIS II (4); IRIS III (8); IRIS IV (6). Twenty healthy dogs were the population control.

The serum and urine concentrations of sodium, chloride and potassium were measured using the selective ion electrode technique. Urinary fractional excretion of electrolytes was calculated using a spot clearance method.

Results

Statistical analysis of data showed that in dogs with CKD, the FENa, FECl and FEK was 5, 7 and 8 times significantly higher, respectively, than in healthy dogs (p < 0,001). In the group of renal patients, FENa and FEK showed a significantly correlation with serum creatinine and phosphorus (r = 0,80); and FECl with urinary protein- to-creatinine (r = 0,70). FENa, FECl and FEK were up 10 times higher in IRIS IV than in early stages.

Conclusion

Urinary fractional excretion of electrolytes showed to be a sensitive and easy technique to use in the diagnosis and evaluation of the progression of CKD.