How Diabetes Affects the Kidneys

Kidneys are the body's water-treatment centers; they are responsible for controlling water levels and water quality.

The kidneys are shaped like, well, kidney beans. Or kidney-shape pools. You have two of them -- kidneys, not pools -- one on each side, just above the waist in the back of the abdomen. (In most people, the right kidney sits slightly lower than the left in order to make room for the liver above.)

Each kidney is about five inches long and weighs just four to six ounces. Yet these relatively small organs receive roughly 25 percent of the blood pumped from your heart. However, the kidneys quickly put all but a small fraction of that fluid back into circulation. In fact, while these hard-working organs process 200 quarts of blood per day, they only retain about 2 quarts, though they don't keep it for long.

The process goes like this: Kidneys receive blood from large vessels called renal arteries that branch from the aorta, the body's main artery, which delivers blood pumped from the heart. Once inside the kidney, the renal arteries divide into smaller blood vessels, which divide into even smaller blood vessels, and so on until they're just tiny capillaries that end in structures called nephrons.

There are about one million nephrons in each kidney. (Each nephron consists of two parts: clusters of capillaries called glomeruli, which are connected to tube-shape channels aptly known as tubules.) Since you have so many of them, nephrons must be pretty important, right? You bet -- nephrons filter excess, unnecessary, and downright dangerous stuff from the blood. Yes, it's true: Blood is full of junk. For example, when proteins in the body outlive their usefulness, they break down into waste products. When cells use food as a source of energy and to rebuild tissue, they toss out the leftovers. And it all ends up in the blood, like toxic sludge dumped into a river.

The nephrons act like mini water treatment plants, filtering out all this gunk. Nephrons also remove excess water from the blood. As this crude urine passes through the tubules, much of it returns to circulation. That's because it contains substances your body needs, including protein and electrolytes such as sodium, phosphorus, and potassium. (Electrolytes are molecules that control various processes in the body.)

The kidneys determine whether current levels of these chemicals in the blood need adjustment and reabsorb whatever is necessary through the renal veins to achieve a healthy balance. The waste-filled fluid left behind is plain old urine, which the kidneys ship south to be eliminated.

The kidneys do more than just control water quality and levels in the body, however. As a side job, these hard-working organs also release an array of hormones, enzymes, and other critical substances, including the following:

  • Calcitriol, the hormone made from vitamin D that's necessary for healthy bones, among other things.
  • Erythropoietin, a hormone that regulates the manufacture and distribution of red blood cells from bone marrow.
  • Renin, an enzyme that the kidneys produce when blood pressure dips too low; it causes the blood to make angiotensin, which constricts blood vessels, causing blood pressure to stabilize. Angiotensin, meanwhile, also causes the adrenal gland to release a hormone called aldosterone, which acts on the tubules to regulate electrolytes. 

To learn more about diabetes and how it can wreak havoc on your kidneys, visit the following links:

  • Diabetes sufferers can develop diabetic kidney disease, which can lead to complications such as kidney failure. Find out how you and your doctor can spot the warning signs at the main Diabetic Kidney Disease page.
  • The classic signs of diabetes are insatiable thirst and excessive urination. Visit the main Diabetes Symptoms page to learn more about the common symptoms of this dangerous ailment.
  • Diabetes is a growing health problem in the United States, now affecting approximately 20.8 million Americans. Go to the main Diabetes page to learn about type 1 and type 2 diabetes.
  • Your kidneys are responsible for regulating the composition of your blood, stimulating the production of red blood cells, maintaining your calcium levels, and regulating your blood pressure. Learn all about these essential organs in How Your Kidneys Work.

This information is solely for informational purposes. IT IS NOT INTENDED TO PROVIDE MEDICAL ADVICE. Neither the Editors of Consumer Guide (R), Publications International, Ltd., the author nor publisher take responsibility for any possible consequences from any treatment, procedure, exercise, dietary modification, action or application of medication which results from reading or following the information contained in this information. The publication of this information does not constitute the practice of medicine, and this information does not replace the advice of your physician or other health care provider. Before undertaking any course of treatment, the reader must seek the advice of their physician or other health care provider.

How Diabetic Kidney Disease Works

Spaghetti, anyone? The handy kitchen device known as a colander works by letting water pass through its tiny holes, leaving behind pasta or whatever food you're straining. But what if the holes in a colander suddenly expanded to the size of, say, the pockets on a pool table? Obviously, the noodles would slip through easily, dropping into the sink and possibly down the drain. Result: You go hungry.

The nephrons in your kidneys are kind of like colanders, allowing very small waste particles to pass through but holding back proteins and other larger molecules, ushering them back into circulation. However, elevated blood sugar fouls up this process. Glucose reacts with proteins in the body to produce demon compounds called advanced glycosylation end products, or AGEs.

Over time, if blood sugar is not well controlled, AGEs accumulate on the walls of the blood vessels in the kidneys, which makes the nephrons' filters too porous or leaky. As a result, protein molecules begin to slip through the kidneys' filters and into the urine. This phenomenon is called proteinuria, though when it's detected at an early stage doctors call it microalbuminuria (albumin is a simple form of protein).

At first, losing a little protein in the urine is no big deal. In fact, you won't even notice the problem, though as proteinuria progresses, you may observe that your urine looks a bit frothier. (If you're in the habit of observing such things.) Even though some of your nephrons are struggling, each kidney packs a million of the filtering units, so the organs are able to keep up with the body's demands for the first few years. (The body is capable of running just fine if you donate a kidney or one of yours quits working.)

Over time, however, exposure to high glucose levels -- as well as the effects of hypertension, smoking, and certain other conditions -- begins to destroy huge numbers of glomeruli, dramatically reducing the kidney's filtering capacity. Not only does the body lose protein, but more waste products remain in the blood, especially substances called creatinine and urea. About 80 percent of type 1 diabetes patients who develop persistent microalbuminuria but don't receive adequate medical care will progress to full-blown kidney failure within 10 to 15 years.

Symptoms of advanced kidney failure may include

  • high blood pressure (though hypertension causes kidney problems, too; more on that later)
  • swelling, especially around the eyes or ankles. Excess amounts of protein and salt in the urine cause water to pool in tissues. This may be accompanied by weight gain.
  • loss of appetite
  • nausea, vomiting
  • headache
  • itchiness
  • fatigue and poor sleep
  • frequent need to urinate at night
  • difficulty concentrating
  • an all-around blah feeling
  • and, of all things, frequent bouts of the hiccups, which for some reason often accompany kidney failure

To learn more about diabetes and how it can wreak havoc on your kidneys, visit the following links:

  • Diabetes sufferers can develop diabetic kidney disease, which can lead to complications such as kidney failure. Find out how you and your doctor can spot the warning signs at the main Diabetic Kidney Disease page.
  • The classic signs of diabetes are insatiable thirst and excessive urination. Visit the main Diabetes Symptoms page to learn more about the common symptoms of this dangerous ailment.
  • Diabetes is a growing health problem in the United States, now affecting approximately 20.8 million Americans. Go to the main Diabetes page to learn about type 1 and type 2 diabetes.
  • Your kidneys are responsible for regulating the composition of your blood, stimulating the production of red blood cells, maintaining your calcium levels, and regulating your blood pressure. Learn all about these essential organs in How Your Kidneys Work.

Timothy Gower is a freelance writer and the author of several books. His work has appeared in many magazines and newspapers, including Prevention, Health, Reader's Digest, Better Homes and Gardens, Men's Health, Esquire, Fortune, The New York Times, and The Los Angeles Times.

ABOUT THE CONSULTANTS:

Dana Armstrong, R.D., C.D.E., received her degree in nutrition and dietetics from the University of California, Davis, and completed her dietetic internship at the University of Nebraska Medical Center in Omaha. In private practice for 21 years, she has developed educational programs that have benefited more than 5,000 patients with diabetes. She is the cofounder and program director of the Diabetes Care Center in Salinas, California..

Allen Bennett King, M.D., F.A.C.P., F.A.C.E., C.D.E., received his degrees and training at the University of California, Berkeley; Creighton University Medical School; the University of Colorado Medical Center; and Stanford University Medical Center. He is the author of more than 50 papers in medical science and speaks nationally on new advances in diabetes.

This information is solely for informational purposes. IT IS NOT INTENDED TO PROVIDE MEDICAL ADVICE. Neither the Editors of Consumer Guide (R), Publications International, Ltd., the author nor publisher take responsibility for any possible consequences from any treatment, procedure, exercise, dietary modification, action or application of medication which results from reading or following the information contained in this information. The publication of this information does not constitute the practice of medicine, and this information does not replace the advice of your physician or other health care provider. Before undertaking any course of treatment, the reader must seek the advice of their physician or other health care provider.