There are many causes of kidney disease, but having diabetes is a common one. Both elevated blood glucose and high blood pressure (another frequent problem among those with diabetes) damage blood vessels in the kidneys, just as they harm blood vessels throughout the body. In fact, a vicious cycle may develop. As your kidneys weaken, blood pressure often rises, and that in itself damages the kidneys further.
Diabetic nephropathy or kidney disease develops slowly over the course of years. And long before any physical manifestations are present, kidney disease leaves a clue that allows doctors to detect it early: microalbuminuria, or small quantities of the protein albumin in the urine.
When elevated blood glucose and blood pressure damage blood vessels in the kidneys' filters, protein starts to leak into the urine. At first, the leaks are tiny, so only small amounts of proteins like albumin slip through. At a later stage, the amount of protein in the urine, or proteinuria, increases.
You should be screened each year for microalbuminuria if you have type 2 diabetes or have had type 1 diabetes for at least five years (microalbuminuria is rarely present at the time of diagnosis of type 1). Screening is done with a simple "spot" urine test, meaning that it can be done any time of day with just one sample of urine. The lab measures the ratio of albumin to creatinine. Normal results are usually less than 20 or 30 mg albumin per gram of creatinine (less than 20 or 30 mg/g), depending on the lab.
One positive test (over 30 mg/g) should be confirmed, because simple things like a urinary tract infection, menstruation, or even exercise can give a positive result. If confirmed, though, microalbuminuria should be taken seriously.
What about blood tests? The fact is that no abnormalities show up in the blood until kidney disease has progressed beyond microalbuminuria. Once you do have a positive early urine test, though, you should have blood levels of serum creatinine measured at least once a year. Creatinine is a waste product and its blood levels indicate how well your glomeruli (network of tiny blood vessels) are filtering blood. The higher the blood creatinine level, the lower the glomerular filtration rate (GFR) and the more severe the kidney disease. A GFR of 60 to 89 mL/min indicates mild kidney disease or simple aging; 30 to 59 mL/min, moderate disease; 15 to 29 mL/min, severe disease; and less than 15 mL/min is a sign of kidney failure.
