True renal disease is indicated by which type of proteinuria?

True renal disease is indicated by glomerular proteinuria because it reflects a dysfunction of the glomeruli, the structures in the kidneys responsible for filtering blood. In glomerular proteinuria, proteins that are normally retained in the bloodstream, such as albumin, leak into the urine due to changes in the permeability of the glomerular membrane. This condition is commonly seen in various renal diseases, including glomerulonephritis and diabetic nephropathy, and is often utilized as a diagnostic marker for underlying kidney damage.

In contrast, tubular proteinuria occurs when the renal tubules are unable to reabsorb proteins effectively, representing a problem primarily at the tubular level rather than the glomerular level. Post-renal proteinuria is a result of protein leakage from the urinary tract after urine has exited the kidneys, such as due to infections or inflammation of the bladder or urethra. Pre-renal proteinuria is related to conditions outside the kidneys that lead to excess production of low molecular weight proteins. These conditions do not reflect true renal pathology but rather indicate influences from other bodily processes. Thus, glomerular proteinuria is the most direct indicator of true renal disease.