Proteinuria in glomerulonephritis is caused by:

In glomerulonephritis, proteinuria occurs primarily due to increased glomerular permeability. This condition is characterized by inflammation of the glomeruli, which are the tiny filtering units in the kidneys. When the glomeruli become inflamed and damaged, their ability to selectively filter substances is compromised. As a result, proteins, which are normally retained in the bloodstream, are allowed to pass through the glomerular membrane into the urine.

Increased permeability in the glomeruli leads to the loss of large proteins, particularly albumin, resulting in proteinuria. This leakage not only indicates the presence of kidney damage but can also contribute to further complications such as edema and the development of nephrotic syndrome if the condition is severe.

Other factors such as decreased glomerular filtration rate can also be involved in kidney disease processes, but it is the increased permeability that directly accounts for the presence of protein in the urine during glomerulonephritis. Additionally, excessive hydration and inflammation of the bladder do not directly cause proteinuria associated with glomerulonephritis; instead, they relate to other aspects of kidney and urinary tract health.