Last update:
10-Sep-2020

The original relevant works by Hippocrates, Galen, Anonymi Medici Minores, Stephanus, Theophilus, Aetius, Joannes Zacharias Actuarius and Avicenna's Canon were read in order to find out if they contained any reference to urine specific gravity (s.g.) and its correlation with the natural history of renal diseases. The term "specific gravity" was of course never mentioned by ancient and medieval writers. Indirectly, they referred to it by discussing the different location of a semisolid formation in the matula (urine examination vial). If it lay on the bottom, it was cold "hypostasis" (sediment), if suspended in the middle "enaeorema" (suspension) and if floating on the top "nephelion" (nebulum). All above medical authors agreed that sediment usually testifies a healthy condition and a floating formation a very severe disease. The suspension could either be a sign of recovery if it followed a nebulum and was thus descending or of deterioration if it followed a sediment and was thus assenting. As its location depended on the difference in weight between the semisolid formation and the liquid part of the urine, in a sense, it measured its specific gravity. Very recently, urine specific gravity gained ground as an accurate renal function marker, equal to creatinine clearance.

Key words: Byzantine medical authors, Classical medical authors, Proteinouria, Specific gravity, Urinometer.