Diabetic nephropathy (kidney disease) is the leading cause of kidney failure in the United States. That’s the bad news. The good news is that the outlook for protecting your kidneys has gotten much brighter over the past decade or so. There are now a number of measures you can take that have been scientifically proven to protect your kidneys and lower the risk of developing diabetes-related kidney disease. Here’s what the research shows.
When good kidneys go bad
Your kidneys, which are each about the size of your fist, are located near the middle of your back, just below the rib cage. By no coincidence, they are shaped like kidney beans. One of their jobs is to filter waste products and extra water from the bloodstream. This waste and excess water, in the form of urine, flow through tubes called ureters and into the bladder. The bladder stores urine until it is full enough to create the urge to urinate.
How does this filtering process work? Each kidney is made up of about one million tiny filtering units called nephrons. Tiny blood vessels called arterioles deliver blood to the nephrons. Within each nephron, the blood vessels form a complex called a glomerulus. It is within these glomeruli that the filtering activity actually takes place. The filtered blood leaves through another arteriole and is eventually carried back to the heart. Meanwhile, the material filtered from the blood passes through a tubule, where it is converted to urine, and then carried to the bladder through the ureters. (See “The Function of a Kidney” for more information about kidney anatomy.)
Diabetes sets the stage for kidney damage. Chronic high blood glucose levels, often in combination with high blood pressure, damage the glomeruli and progressively diminish kidney function. (High blood pressure alone is the second-leading cause of kidney failure behind diabetes.) This type of kidney dysfunction is known as diabetic nephropathy. In its earliest stages, it has no symptoms; however, the “silent” damage going on behind the scenes can still pave the way for kidney failure.
In the first stage of diabetic nephropathy, called hyperfiltration, the kidneys filter larger quantities of blood than usual in an attempt to compensate for damaged nephrons. Hyperfiltration is the first stage of the problem, but it does not necessarily lead to kidney failure. In fact, some people may stay in this stage and not progress further, especially if they maintain control of their blood glucose and blood pressure levels.
If damage from high blood glucose levels (and high blood pressure) continues for many years, this may lead to the second stage, called microalbuminuria. Normally, the kidneys do not allow significant amounts of proteins from the bloodstream into the urine. However, once they become damaged, tiny amounts of protein leak into the urine. The appearance of small amounts of the protein albumin in the urine indicates the start of diabetic nephropathy. (Albumin in the urine can also signal the possibility of glomerular disease or chronic high blood pressure, while the presence of other types of protein would raise suspicions of other types of kidney disease.) Laboratory tests can detect this small amount of albumin while kidney disease is still fairly treatable. However, your doctor must specifically request a microalbumin test of your urine, because standard urine tests are not sensitive enough to notice these small amounts of albumin.