Kindey histopathology



When glomerulosclerosis takes place, how can we have BOTH protein leakage and toxin retention?

I mean protein leakage means that the glomeruli are very permeable while toxin retention means that they are little permeable.

I assume GFR decrease occurs due to glomerulosclerosis and the fluid cannot pass and produce the filtrate? But how protein leakage comes into play?

Any idea?

Also, what is the most common histopathology of chronic kidney disease? Is it the collagenation? Or anything else?