When it comes to chronic kidney disease, new guidelines call for a bolder approach
From the October ACP-ASIM Observer, copyright © 2002 by the American College of Physicians-American Society of Internal Medicine.
By Margie Patlak
As rates of chronic kidney disease in this country reach record levels, generalists are being urged to rethink how they approach the condition—and to play a more active treatment role.
In the last 10 years, the incidence of kidney failure—end-stage renal disease—has doubled. According to the National Kidney Foundation (NKF), one out of nine Americans suffers from chronic kidney disease, which the Foundation defines as the presence of kidney damage or decreased level of kidney function for at least three months. While some experts use a more conservative estimate that cuts that figure in half, all agree that kidney disease has shown dramatic growth.
In the last 10 years, end-stage renal disease has doubled.
Making matters worse, most people with kidney disease don't know they have it, while just as many other patients are at heightened risk for developing the disease. With a shortage of nephrologists in many parts of the country, the burden of caring for these patients has landed squarely on the shoulders of primary care physicians.
To help doctors detect and treat kidney disease, the NKF earlier this year released new clinical care guidelines. Recognizing that kidney disease is silent until patients lose most of their kidney function, the guidelines make a strong case for routine kidney disease screening among much broader segments of the adult population.
The new guidelines also call for more aggressive monitoring and treatment of patients already diagnosed with chronic kidney disease, and for intervention years before patients teeter on the brink of kidney failure. The guidelines also underscore the fact that physicians' traditional approach—treating only the disease that triggers loss of kidney function, but not the kidney disorder and its complications—will spell trouble for your patients down the line.
"As a nation, our care of people with decreased kidney function is poor," said nephrologist Josephine Briggs, MD, director of the division of kidney, urologic and hematologic disorders at the National Institute of Diabetes & Digestive & Kidney Diseases (NIDDK). "We can do a lot better."
The good news is that by acting early, you can stop or stall the progressive loss of kidney function and prevent premature death from the cardiovascular disease that often accompanies chronic kidney disease. Early screening and intervention can not only extend the lives of many kidney disease patients by several years but save them from becoming tethered to a dialysis machine.
As is true for most treatable chronic diseases, the earlier you detect chronic kidney disease and start treatment, the better the outcome. According to Dr. Briggs, however, most physicians don't think of screening patients for kidney disease unless they find a red flag like diabetes or possibly high blood pressure.
Part of the problem is that experts don't universally agree on screening guidelines. Some experts, for example, argue that only diabetics, hypertensives and those with a family member with kidney failure should be screened for chronic kidney disease. Tom Hostetter, MD, who heads the National Kidney Disease Education Program, said that because these are the people most likely to have kidney disease, expanding screening to other risk groups is not warranted.
Nor does the U.S. Preventive Services Task Force currently recommend routine screening for kidney disease in healthy adults. But given the wealth of evidence that has recently come to light showing the growing prevalence of chronic kidney disease and the benefits of early treatment, Andrew Levey, MD, chair of the committee that wrote the NKF guidelines, said he hopes the task force will reevaluate its position.
The new guidelines recommend screening all patients who have an elevated risk of developing kidney disease. Besides targeting patients with diabetes and hypertension, you should also consider screening individuals with the following risk factors:
- family history of kidney disease;
- autoimmune diseases such as lupus;
- heightened exposure to drugs such as analgesics that can cause loss of kidney function;
- systemic infections such as HIV or hepatitis;
- age greater than 60 years;
- high-risk ethnic backgrounds (black Americans, Hispanics and Native Americans); and
- history of acute kidney failure.
The guidelines don't specify which or how many of these risk factors patients should have to justify screening for chronic kidney disease. But because the burden of testing is fairly low, "it might not be unreasonable to recommend testing for all members of an at-risk group, such as African Americans," Dr. Levey said.
According to Dr. Briggs, physicians are already ordering many of the tests they need to screen for kidney disease for other reasons. The following four simple tests will detect most cases of kidney disease:
- blood pressure;
- spot urine dipstick test for protein (preferably albumin) or protein-to-creatinine ratio;
- urine sediment examination or dipstick test for white or red blood cells; and
- serum creatinine to measure glomerular filtration rate (GFR).
While experts used to think that cumbersome 24-hour urine collections were needed to adequately detect signs of kidney damage, recent studies have found that first-morning or random spot urine tests are just as effective for most patients.
Albumin in the urine is a more sensitive marker than total urine protein for the most common forms of kidney disease in adults, such as those due to diabetes, hypertension and glomerular diseases. An albumin dipstick can also detect lower levels of protein than a dipstick for total protein.
Experts suggest repeating tests that yield abnormal results. False positives may be a result of exercise, urinary tract infection or menstruation, all of which can boost the level of albumin or protein in the urine.
Because some kidney diseases don't produce protein in the urine, you also need to examine urine sediment for red or white blood cells. You can detect these cells with a dipstick as well.
While urine tests can reveal markers of kidney damage, the guidelines emphasize that the best estimate of kidney function is the patient's GFR. You can calculate GFR using equations in which you plug the serum creatinine concentration, as well as patients' age, gender, race and/or body size. (These equations are online.) Some labs will do the calculation for you.
Although serum creatinine was once seen as the gold standard for detecting kidney damage, the measure alone is no longer considered adequate, explained Ronald Perrone, FACP, associate chief of nephrology of Tufts New England Medical Center.
"A creatinine of 1.5 in a 350-pound linebacker for a professional football team does not have the same meaning as a creatinine of 1.5 in an 85-year-old woman who weighs 100 pounds," he said. "The 85-year-old woman probably has half or less of the GFR of this linebacker, despite having the same creatinine." Also, a relatively minor increase in creatinine level within or near the normal range (0.3, for example) can translate into a major loss of GFR that has clinical significance, he added.
According to the guidelines, you can assume patients have chronic kidney disease if they test positive in any of the urine tests and/or have a GFR of less than or equal to 60 mL/min/1.73 m2 for three months or more. High blood pressure (greater or equal to 140/90 in adults) does not indicate chronic kidney disease unless it is accompanied by urine indicators of kidney damage or a GFR of less than 60. But high blood pressure can indicate faster progression of chronic kidney disease and the development of cardiovascular disease.
All kidney disease patients should be monitored at least yearly for signs of progression, as indicated by GFR and levels of protein or other signs of kidney damage in the urine. And you should thoroughly review any drugs—both prescribed and over-the-counter—your kidney disease patients take. Many common drugs, such as NSAIDs and certain antibiotics, can cause acute kidney dysfunction or damage and should be avoided. In addition, you need to tailor medication dosages to patients' GFRs.
The new guidelines also recommend using ultrasound or other imaging exams for patients who have an increased risk of developing polycystic kidney disease. Also consider using imaging technology to diagnose chronic kidney disease due to urinary tract stones, infections, obstruction or vesico-uretal reflux. Stay clear of imaging studies that use iodinated contrast agents, however, as these can cause acute kidney damage that can be problematic for someone with hampered kidney function.
Slowing the disease
Depending on the cause, you can stop or reverse some types of kidney damage. Using steroid therapy for lupus and removing kidney stones, for example, can effectively treat certain forms of kidney disease.
Most types of kidney disease, however, are caused by chronic conditions such as diabetes and hypertension that continue to chip away at kidney function. Chronic kidney conditions often seem to take on a life of their own and continue to progress even when the original cause is no longer a factor.
"Once kidney mass falls below a critical value," Dr. Briggs said, "kidney diseases progress inexorably by common mechanisms that are independent of what caused the original injuries."
But research has definitively shown that you can slow the progressive decline of irreversible forms of chronic kidney disease—if you take the right measures. Here are some strategies that have been proven to work:
- strict glycemic control with diet, exercise and/or medications for patients with diabetic nephropathy;
- ACE inhibitors or angiotensin-receptor blockers for both diabetic and nondiabetic patients, especially if they have protein in the urine; and
- strict blood pressure control (less than 130/85 mm Hg).
Studies suggest that ACE inhibitors or angiotensin-receptor blockers can cut the rate of kidney disease progression in half. "The earlier these people are identified and put on effective therapy, the more time off dialysis you'll buy," noted Dr. Hostetter from the National Kidney Disease Education Program.
The NKF guidelines also state than all patients with chronic kidney disease—even those you catch at an early stage—fall into the high-risk category for cardiovascular disease. Cardiovascular disease is the leading killer of even nondiabetic patients with chronic kidney disease, making them much more likely to die from a heart attack or stroke than to experience kidney failure. You should aggressively treat patients with lifestyle interventions or lipid-lowering drugs to bring their LDL cholesterol below 100 mg/dL and eliminate as many cardiovascular disease risk factors as possible.
But just treating the causes of chronic kidney disease, slowing its progression and boosting cardiovascular disease prevention efforts are not enough. You also have to deal with the many complications that accompany declining kidney function. They include anemia, bone disorders, malnutrition and neuropathy, and they tend to surface once the GFR dips below 60.
According to the new guidelines, patients with a GFR between 30 and 60 should be monitored for the following conditions:
- anemia (hemoglobin level);
- nutritional status (dietary energy and protein intake, weight, serum albumin and serum total cholesterol);
- bone disease (serum levels of parathyroid hormone, calcium and phosphorus); and
- functioning and well-being (questionnaires).
While the guidelines don't spell out the proper treatments for these conditions, you can find other protocols for treating various complications of kidney disease at the NKF Web site.
Finally, you should measure serum creatinine to update patients' GFRs biannually or every three months if their GFRs fall below 60. The guidelines state that patients should be referred to a nephrologist only when their GFRs dip below 30. (Subspecialist care is recommended before then if primary physicians don't have adequate resources to evaluate kidney disease patients or carry out an effective treatment plan.)
This means that many internists will have to bone up on kidney disease and its complications. "Nephrologists know they have to deal with the anemia, cardiovascular risk and abnormal calcium and phosphorus metabolism of people with kidney disease," noted Dr. Perrone from Tufts. "But other physicians and health providers need to be aware of these issues as well. The kidney is great when it's working well, but when it doesn't, things really fall apart."
Dr. Perrone hopes the new guidelines will bring chronic kidney disease to the forefront of primary care screening and treatment efforts. "Everyone thinks about HDL and LDL and colon cancer screening," he said, "but we think screening for chronic kidney disease is equally important."
Margie Patlak is a freelance science writer in Elkins Park, Pa.
The information included herein should never be used as a substitute for clinical judgment and does not represent an official position of ACP-ASIM.
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