The presence of protein in the urine was detected by Frederick Dekkers of Leyden in 1694, found in dropsical patients by Cotugno in 1764, and related to renal disease by Richard Bright in 1827. It remains to this day the most important and often the most sensitive sign of renal disease.
Most healthy subjects excrete less than 100 mg of protein per 24 hours, but less rigid criteria are employed in clinical practice. In the present state of knowledge, quantities less than 250 mg/24 hr are best regarded as normal for employment and insurance purposes. Excretion of protein in excess of 300 mg/24 hr, unless associated with transient physiological or pathological states, is indicative of kidney disease.1 The converse however does not always hold true; disorders such as renal artery stenosis, pyelonephritis, obstructive uropathy and, at times, glomerulonephritis may occur in the absence of proteinuria. Intermittent or orthostatic proteinuria
Dunea G, Freedman P. Proteinuria. JAMA. 1968;203(11):973-974. doi:10.1001/jama.1968.03140110065013