The effect of proteinuria on the urine specific gravity in small animals

Abstract

Measuring urine specific gravity (USG) is a diagnostic tool frequently relied upon and widely accepted to evaluate the concentrating ability of the kidneys. It has a very close correlation with osmolarity but is not only influenced by the number of solutes inside the urine but also their mass. It is measured by refractometry a quick and cheap method based on the optical properties of the urine sample. The USG value measured with a refractometer has a good correlation with osmolarity and makes the determination of osmolarity unnecessary in most clinical situations. Both measuring USG and detecting proteinuria plays a key role in the early detection of kidney injury. However, the question has been raised; whether the increased mass of protein compared to other urine solutes in the case of proteinuria has an effect on the correlation of USG and osmolarity.