Assessment of renal function and damage in animal species . A review of the current approach of the academic, governmental and industrial institutions represented by the animal clinical chemistry association

There are a wide variety of laboratory tests available to assess damage to and functional impairment of the kidneys, although the effectiveness of these tests varies greatly depending upon the site specificity of the damage and to a lesser extent upon the animal species involved. Several traditional tests of renal dysfunction and damage, including plasma creatinine and urea, and urinalysis (dipstick and/or quantitative protein), can be used in the first instance to detect nephrotoxicity. A second tier of specific, targetted indicators (concentration test, urinary enzymes, clearance of analytes, specific proteins, etc.) may then be applied to identify further the site of the lesion and the functional status of the kidneys. The glomerular filtration rate (GFR) may be estimated from the clearance of exogenous and endogenous substances. The difficulty in obtaining accurately timed urine samples limits the value of these tests in small animals, although methods that do not involve urine collection are available. The kidney is the origin of several enzymes found in urine that can be used to monitor the toxic effects of chemicals and therapeutic substances. Selective measurement of enzyme activities in urine can be used to detect the site of the renal lesion after traditional tests have established the presence of renal injury. Separation of proteins in urine by electrophoretic techniques may also be used to discriminate damage to different parts of the nephron. Renal cell excretion in urine is a sensitive but unreliable indicator of acute damage to the proximal tubule. The rate of cell excretion is not a good predictor of the severity of tubular injury. The tests available, and their use in toxicological investigations, have been reviewed in the light of current practice in the UK.