Have You Been Screened for Kidney Disease?

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Forty million Americans either have it or are at increased risk, but most don't know it

ARE YOU at least 60? Or do you have diabetes or high A blood pressure? What about a family history of kidney disease, heart attack, or stroke? Are you of African, Hispanic, Pacific Island, or Native American descent?

People in any of those groups should make particularly A certain that their next doctor's visit includes having a urine sample checked for a protein called albumin and a blood sample checked for a waste product of muscle metabolism called creatinine, says Andrew S. Levey, MD, Chair of the National Kidney

Foundation work group that recently authored new guidelines for the detection and treatment of chronic kidney disease, as well as the Gerald J. and Dorothy R. Friedman professor of medicine at the Tufts University School of Medicine. The presence of albumin in the urine is a sign of chronic kidney disease, as is a slow rate of removal of creatinine from the blood, and the populations mentioned above are at increased risk.

The tests are crucial because chronic kidney disease cannot be "felt" in its early and, often, mid-stages. Indeed, while more than one in 10 US adults (20 million people) have it, and another 20 million may be at elevated risk, most don't know it. That's particularly unfortunate because kidney disease is a progressive condition that can worsen over time. Let it go unchecked, and it can lead to serious and sometimes deadly complications.

Perhaps the most obvious is kidney failure, which requires treatment with dialysis or kidney transplantation. Another is heart and blood vessel disease. People with kidney failure have a 10- to 30-fold increased risk for dying from cardiovascular problems. They are also at higher risk for anemia, weakened bones, and, of course, eventual kidney failure death. But if you identify and treat kidney disease early on, you have the best chance Of slowing or even halting its progression through lifestyle changes and medication.

Exactly how wide is the gap between the existence of kidney disease and people's knowledge of their condition? Consider results released last October from the National Kidney Foundation's Kidney Early Evaluation program (KEEP), a nationwide screening program designed to identify people in the early stages of the disease. More than 11,000 people with at least one risk factor for kidney disease underwent testing to check their kidney function. While nearly half the group was found to already have kidney disease, only 2 to 3 percent knew it.

The fallout of that lack of awareness is staggering. In 2000, more than 350,000 people with kidney failure were treated either by dialysis or a kidney transplant.

Dialysis requires being hooked up to a machine several times a week to filter out waste from the blood that the kidneys can no longer handle. But it replaces only about 10 percent of kidney function, with most dialysis patients continuing to have some symptoms of kidney failure. A kidney transplant replaces more than 50 percent of kidney function, allowing most patients to actually feel better and resume many activities of daily living, but the number of kidneys donated falls far short of the number of people on the transplant waiting list. And the situation is expected to worsen. In 2010, the number of Americans with kidney failure will reach an estimated 650,000. The increase is due largely to the rise in diabetes and high blood pressure, which together are responsible for two in three cases of kidney disease. There's also the rise in obesity--which can lead to diabetes and high blood pressure.

How the kidneys work
The kidneys are two fist-sized organs in the back, located just below the rib cage, and serve many purposes. For instance, they convert vitamin D to its active form, a necessary step for bone maintenance and, research suggests, muscle maintenance, too. They also manufacture a hormone required for red blood cell formation, and they help control blood pressure. Their main function, however, is to filter the blood, eliminating waste and excess body fluid in the urine. They also regulate the body's sodium, potassium, and acid balance, thereby maintaining the consistency of body fluids.

The kidney filters are called glomeruli, and the filtration system can be likened to a fine cheesecloth. In a healthy person, about 175 quarts of fluid flow through them every single day--a glomerular filtration rate (GFR) of about 120 milliliters of fluid a minute. About two quarts of that fluid are excreted from the body every day as urine. The rest gets routed back into circulation via the bloodstream, but not before undesirable materials such as waste products like creatinine "fall through" the finely webbed cheesecloth to be eliminated from the body in the urinary flow.

The finely working kidney filters don't just cause undesirable materials to go through them and out of the body. They also make sure desirable materials that the body needs to recycle don't fall through. If the consistency in the filtering "cloth" is not just so, it cannot do this part of its filtering job properly, leaking some materials into the urine that should have remained.

This is where the urine test for the protein albumin comes in. Albumin is usually retained in the bloodstream. If it is detected in the urine, it signifies that the kidney filter has lost its proper "texture" and that kidney damage has occurred.

The reason for the other test that checks kidney function--a blood test for creatinine--is that the level of creatinine in the blood, plugged into an equation with your age, gender, race, and body size, provides an estimate of your GFR. Whereas a very healthy GFR is about 120, a GFR of less than 60 for more than 3 months indicates more serious kidney damage than can be identified by albumin in the urine alone. Indeed, even if the test for urine albumin is negative, a GFR under 60 indicates chronic kidney disease.

If you are diagnosed with chronic kidney disease, your GFR will be used to determine which of the rive stages of the illness you are at, which is an indication of how severe the condition is. Someone with a GFR of at least 60 and kidney damage detected by the presence of albumin in the urine has normal-to-only-mildly-reduced GFR, indicating stage 1 or 2. If the GFR is 30 to 59, it's moderately reduced-stage 3; 15 to 29, severely reduced-stage 4; and less than 15, kidney failure requiring dialysis or a kidney transplant--stage 5.

Unfortunately, very few people have their blood creatinine checked to estimate their GFR. Too few even have their urine evaluated for protein. According to one estimate, only 30 to 40 percent of people are tested for protein in their urine at their physicals. The National Kidney Foundation recommends that at the very least, everyone with high blood pressure (that's 60 million Americans right there) or diabetes, as well as those whose age, ethnic, or genetic background puts them at risk, be tested for kidney disease.

Diet and other treatments
Much of eating to treat kidney disease is eating to treat the disorders that lead to it, namely, diabetes and hypertension. Since both of those conditions tend to go hand in hand with excess weight, losing some extra pounds can be one of the goals for slowing the damage created by the disease. (You may not be able to reverse kidney disease once it has taken hold, but you can retard, and sometimes halt, its progression.)

Eating a diet more moderate in protein than the typical American diet is appropriate, too. It doesn't necessarily have to be low in protein, but people in the US currently average twice as much protein as is necessary, and in someone with kidney disease, the extra protein--in the form of large amounts of meat and dairy products--can place more of a burden on an already compromised system.

Unfortunately, says Heather Bell, a dietitian with a master's degree in public health who treats chronic kidney disease patients at the Tufts-New England Medical Center, "a lot of primary care physicians are recommending high-protein diets across the board" for patients who want to lose weight. For someone who may have kidney disease, a high-protein plan is not just a fad diet; it's a potentially dangerous one.

Other dietary considerations for someone with kidney disease revolve around a number of minerals, sodium and phosphorus among them. Too much sodium in the American diet is an old story, with about 80 percent of it coming not from the salt shaker at the stove or table but from processed foods at the supermarket and restaurant foods, including fast food. The excess can burden the kidneys.

So can excess phosphorus. Diseased kidneys may not be able to remove phosphorus from the blood. And a high blood phosphorus level can work to cause calcium losses from the bones, which weaken them and make them more prone to break easily. Not everyone with kidney disease has to maintain a diet limited in phosphorus, but those who do need to stick to prescribed amounts of high-phosphorus foods, including dairy products, dried beans, nuts, and beverages such as cocoa and cola-based sodas. The National Kidney Foundation says that people with impaired kidney function whose disease is far enough along that they need to follow a special diet may be referred by their doctor to a kidney disease dietitian who can work to get the diet where it needs to be depending on the stage of the disease.

Unfortunately, dietary adaptations alone are not always enough to slow the progression of kidney disease, and sometimes medications are needed. For instance, people with hypertension who have kidney disease are often prescribed drugs called ACE inhibitors or ARBs, which not only keep down blood pressure but also appear to directly help the kidneys.

If your doctor does prescribe drugs to help keep your kidney disease in check, take them faithfully. This is definitely not something you want to play around with because by working to rein in kidney disease in its earlier stages, you're better assured of living to a ripe old age--with as few compromises in your lifestyle as possible.

The aorta, the body's main artery, carries blood from the heart to all of the body's other organs, including the kidneys, via a network of smaller arteries.
Blood flows from the aorta into the renal arteries before entering the kidneys.
Filtering occurs in the kidneys themselves. Some substances, like protein, are retained in the blood, while waste is discarded.
Filtered (cleaned) blood exits the kidneys via the renal veins.
The filtered blood flows from the renal veins into the vena cava, the body's main vein, which carries the blood back to the heart.
Waste and excess water form urine that flows through two ureters into the bladder.
Urine is stored in the bladder until urination takes place.
Source: National Kidney Foundation

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