Kidney disease: a stealthy killer

VIEW ON HEALTH

Kidney disease has become a serious public health problem in the United States, affecting one out of nine Americans.

The Centers for Disease Control and Prevention estimates that 20 million American adults have chronic kidney disease and another 20 million are at increased risk due to diabetes, hypertension and other conditions. Nearly half of adults with declining kidney function are unaware of it.

According to the CDC, 11 percent of Americans over age 65 who do not have diabetes or high blood pressure have “moderate to severely decreased kidney function.” In other words, merely aging is a risk factor for kidney disease.

Diseased and failing kidneys place a gigantic burden on the American health-care system. Anyone with kidney disease, regardless of age, is eligible for Medicare funding. People with kidney disease represent less than 1 percent of the Medicare population, but treating them consumes 6.4 percent of total health-care expenditures by the Centers for Medicare and Medicaid services. According to the U.S. Renal Data System, Medicare provided approximately two-thirds of the $22 billion spent on kidney patients in 2001.

It is a stealthy disease. There are often no symptoms of kidney disease until the advanced stages, when it can cause dry and itchy skin, fatigue, trouble concentrating and poor appetite. Insomnia and muscle cramps may occur at night. Feet and ankles may become swollen, and puffiness may occur around the eyes, especially in the morning. Frequent urination, especially during the night, can be a sign of kidney disease.

There are other factors making kidney disease a public health issue. According to a CDC report, kidney disease is underdiagnosed and undertreated. Many people afflicted with high blood pressure and diabetes do not know that these conditions can cause chronic kidney disease. (Even diabetics with good control of their blood sugar are more likely to develop kidney disease than non-diabetics.) There are also kidney disease risks associated with the overuse of some over-the-counter painkillers.

Vipul Shah, M.D., a transplant nephrologist at University Medical Center of Southern Nevada at Las Vegas, says many people have chronic medical conditions and aren’t aware of them, such as diabetes, hypertension or high cholesterol. These conditions can cause damage to the kidneys, which often goes undetected, just as the underlying condition goes undetected.

“One of the best things a primary care physician can do is check for protein in the urine,” Shah said. “Protein in the urine can be an indication of kidney damage.”

The kidneys purify blood and regulate the amount of water and electrolytes in the body. They also release hormones that help regulate blood pressure, make red blood cells and strengthen bones.

When kidneys aren’t functioning properly, they become less efficient at removing wastes and toxins from the bloodstream. As kidney disease worsens, the kidneys fall behind in their job of purifying and regulating the body’s fluids. Waste products begin to build up in the bloodstream and tissues. Anemia and high blood pressure can result. Bones weaken. Nerves can become damaged. Risk of cardiovascular disease increases dramatically.

In advanced stages of kidney failure, the waste products normally eliminated in urine accumulate in the bloodstream and eventually reach a toxic level. This condition is known as uremia, a term that literally means “urine in the blood.” It can cause nausea, vomiting, loss of appetite, fatigue, weight loss, severe itching and muscle cramps.

Kidney function can deteriorate very slowly over time. The good news is that three simple tests allow your physician to accurately assess the health of your kidneys.

Urinalysis allows the most sensitive test for diminished kidney function. The presence of protein in urine can be detected in the early stages of kidney disease and allow treatment and lifestyle changes that can stop the deterioration and prevent its progression to kidney failure. An increase in blood pressure can be a sign of declining kidney function, and a blood test gives the most accurate measurement of kidney function. Doctors check for the presence of creatinine in the blood serum. Creatinine is a breakdown product of creatine, a substance found in healthy muscle tissue. As kidney function decreases, the kidneys filter less creatinine from the bloodstream, so the less creatinine in the bloodstream, the better the kidneys are functioning.

This can be a symptom of diabetic nephropathy, which results from damage to tiny blood vessels in the kidneys that filter impurities from the bloodstream. All diabetics should have regular tests to measure kidney function.

“Loss of kidney function is not always irreversible, although in many cases it is,” Shah said. “Sometimes getting better blood sugar control in a diabetic can restore some function. But even if function can’t be restored, good control of the underlying condition (such as diabetes or hypertension) can prevent further loss of function.”

As kidney function diminishes, damage to the cardiovascular system can become severe. Heart disease is the most common cause of death for people with chronic kidney disease.

Kidneys functioning at about 10 to 15 percent of normal are considered to be failing, and dialysis or transplantation is necessary. Dialysis is a process in which a machine is used to filter toxins from the bloodstream of a patient whose kidneys have failed.

Hemodialysis is the most common type of dialysis. It involves circulating a patient’s blood through a machine with a special filter. The machine can also remove the excess fluid that can accumulate in the tissues and bloodstream of a patient with chronic kidney failure.

Dialysis patients with chronic kidney failure typically go to a clinic three times a week for three or four hours per session. Paul S. Kellerman, M.D., who is a kidney specialist, director of dialysis and associate professor at the University of Wisconsin-Madison Medical School, said patients who undergo dialysis feel better after the process.

“It removes cellular toxins and uremic waste products,” Kellerman said.

Dr. Kellerman said research has shown that shorter, more frequent sessions of kidney dialysis are more effective. However, Medicare only pays for three sessions per week.

In 1973, Congress passed a law requiring Medicare to provide funding for dialysis to any patient who needed it.

“That was when there were about 6,000 dialysis patients. Now there are about 400,000,” Dr. Kellerman said. “It’s enormously expensive.”

On June 28, 2005, the U.S. House of Representatives introduced the “Kidney Patient More Frequent Dialysis Quality Act,” which would provide payment under Medicare for more frequent dialysis. It was referred to the Subcommittee on Health and never made it to the floor for a vote.

According to the U.S. Renal Data System, 72,000 patients were on the kidney transplant waiting list in 2007. There were 17,513 kidney transplants performed that year.

Meanwhile, dialysis patients have high mortality rates, with 25 percent dying within one year and 75 percent within five years. The average wait for a kidney transplant in the United States is two to four years.

What’s the answer? “Educate the public,” Dr. Kellerman said. Patients should be aware of the risk factors for kidney disease and discuss kidney function with their physicians. The National Kidney Foundation is working to provide primary care doctors with guidelines that can help them refer patients to kidney specialists earlier.