

The production of very concentrated urine (USG >1.050) can be seen when reduced renal perfusion results from hypovolaemia, haemoconcentration or heart failure. If the patient is not azotaemic, this finding is generally considered incompatible with a diagnosis of substantial kidney disease, although kidney disease, with loss of up to 2/3 of normal nephron function may still be present.* However, USG values in some cats with chronic kidney disease (CKD) and azotaemia may be as high as 1.040 or 1.045, so kidney disease could still be suspected in a cat if these values are accompanied by persistent azotaemia. A substantial number of functioning nephrons is needed to produce urine of this concentration, so the simultaneous presence of azotaemia suggests there is likely to be a large pre-renal component to the azotaemia this conclusion can be confirmed by determining if the azotaemia reverses on rehydrating the animal. Cats typically produce more highly concentrated urine than dogs, but similar variation might be expected for normal cats.Ĭoncentrated urine: USG >1.030 (dog) or >1.035 (cat)Įxcretion of urine that is concentrated like this indicates that significant modification of glomerular filtrate (which has specific gravity of 1.008 to 1.012) has occurred by means of active resorptive processes in the renal tubules. In healthy animals, urine concentration can change substantially over time, and 2 to 3 fold variations have been observed within 2 hours in some dogs. It is important to note that any USG value could be considered 'normal' in a patient, depending on certain other factors, including the patient's hydration status.

What USG values are considered ‘normal’?Ī wide range of USGs can be encountered in healthy animals – 1.001 to >1.075 for dogs and 1.001 to >1.085 for cats – although values encountered typically for normally hydrated individuals are often closer to 1.015 to 1.045 for dogs, and 1.035 to 1.060 for cats. The USG can also help verify the presence of polyuria (USG is inversely related to 24 hour urine volume), assist evaluation of urinary losses of protein, bilirubin and glucose, and aid assessment of the patient's state of hydration. It is measured using a refractometer, and provides an approximate guide to urinary solute concentration that is sufficiently accurate for clinical purposes. USG measurement is used frequently in veterinary practice to help evaluate renal function by assessing whether water is being excreted or conserved appropriately, according to need. Original Authors: ADJ Watson, Sydney, Australia, HP Lefebvre, Toulouse, France and J Elliott, London, UK Why measure urine specific gravity (USG)? The dipstick is a rapid method of determining the specific gravity.Using urine specific gravity (revised by J Elliott in 2022) However, urine output is a consequence of fluid intake, thus there is a considerable variance of specific gravity in urine in the same individual, or between individuals. All urine including that from healthy individuals contains dissolved solids. Other commonly excreted metabolic products such as urea, and creatinine also make up a portion of the dissolved solids. Most commonly these salts include the ions sodium, potassium and chloride. The specific gravity is primarily a measure of the salts excreted in final urine. Specific gravity is a property of urine that is dependent upon the amount of solids dissolved in urine.
