Your kidneys act as a highly selective filter or sieve, which allows certain waste elements to pass through to the urine but usually retains proteins. Diabetic nephropathy is a condition peculiar to diabetes the hallmark of which is a leakage of protein into the urine. Over a period of time this leakage worsens with progressive loss of kidney function and eventual irreversible kidney failure.
www.kidneypatientguide.org.uk/ site/kid_trans.html