How does my doctor know that I have kidney disease?

A person's kidney function is best determined by a blood test called serum creatinine. This is routinely included on the panel of blood tests performed on patients. If the creatinine level in the blood is elevated, it indicates that the kidneys are not filtering the blood normally. It is common that patients with evidence of kidney disease on their blood work do not have any symptoms. The best way to monitor kidney function is by regularly drawing blood to measure the creatinine level.

How does the care that I receive from a nephrologist differ from what I would receive from a urologist?

Urologists treat surgical problems associated with the kidneys and urinary tract. Nephrologists treat medical problems associated with abnormal kidney function. A similar example is how a cardiologist monitors heart function and medically treats heart failure, while a cardiac surgeon performs bypass surgery for blocked coronary arteries. Many of our patients also see a urologist. The care urologists and nephrologists provide do not overlap; our care complements one another.

The amount of urine I produce has not decreased. Doesn't that mean my kidneys are functioning alright?

The kidneys still produce the same amount of urine up to - and even after - a patient with kidney failure first starts dialysis. Kidney function is described using the term "glomerular filtration rate," or GFR. The GFR in a person with normal kidney function is 120 milliliters (4 fluid ounces) per minute. This means that each minute 120 milliliters is filtered from the blood into the kidneys. After three minutes, the amount filtered by the kidneys from the blood is about the same amount of fluid as in a can of soda. Over a 24-hour period, the total fluid filtered by the kidneys from the blood in a patient with normal kidney function is roughly 50 gallons! Of course, people do not produce 50 gallons of urine per day. That is because the kidneys reclaim over 99% of the water and minerals filtered by the kidney into roughly two quarts of urine. Therefore, a patient with kidney function that is 20% of normal will still filter 10 gallons of fluid from the blood per day. That person still produces two quarts of urine just like someone with normal kidney function, but only eliminates 20% of the kidney poisons in the urine compared to a person with normal kidney function.

How can I know if the GFR of my kidneys is normal or low?

There is a mathematical formula that takes into account a person's age, gender, race and blood creatinine level to give an estimated GFR (eGFR) value. The eGFR value is also reported with the panel of labs that include the creatinine level. The National Kidney Foundation classifies various stages of chronic kidney disease based on the eGFR value:

  • Normal Kidney Function: GFR 120 mL/min
  • Chronic Kidney Disease Stage 1: eGFR > 90 mL/min
  • Chronic Kidney Disease Stage 2: eGFR 60-90 mL/min
  • Chronic Kidney Disease Stage 3: eGFR 30-59 mL/min
  • Chronic Kidney Disease Stage 4: eGFR 15-29 mL/min
  • Chronic Kidney Disease Stage 5: eGFR < 15 mL/min

Once the GFR drops below 15 milliliters per minute, patients can become sick with uremic poisoning from accumulation of kidney poisons in the body. Patients in this condition require dialysis to replace the kidney function; their own kidneys can no longer adequately clean the kidney poisons from their blood.

The blood creatinine value and eGFR value are not fixed numbers. They will usually fluctuate to some degree within a range of values. The fluctuation of the blood creatinine and eGFR is often due to fluctuation in the fluid status of a person, which indicates how hydrated a patient was at the time the blood sample was drawn.

What can I do to protect my kidney function?

There is no single answer because each patient's conditions may vary from person to person; however, here are a few important common considerations:

  • Manage high blood pressure
  • Control diabetes
  • Avoid substances that can damage the kidneys (x-ray, dye, anti-inflammatory drugs)

Also, patients with chronic kidney disease have more risk for heart disease than those without. Therefore, patients should also:

  • Maintain healthy levels of cholesterol
  • Quit smoking
  • Maintain ideal body weight

Do my kidneys do anything in addition to filtering the blood?

Yes, kidneys also are involved in other functions in the body. A couple of the most prominent are:

  • Stimulate bone marrow to make red blood cells
  • Regulate calcium/phosphorus/vitamin D metabolism

That's why nephrologists routinely monitor hemoglobin levels to assess patients for anemia and perform a blood test called PTH to assess the calcium/phosphorus/vitamin D status in a patient. If either condition occurs due to abnormal kidney function, specific therapy is prescribed to improve those parameters.

Other than drawing blood to monitor lab values, what else is involved in good nephrology care?

There are subtleties in caring for patients with abnormal kidney function. The board-certified nephrologists of RenalCare Associates, S.C., partner with primary care physicians, endocrinologists and cardiovascular specialists to help treat patients with kidney disease, including those who must rely on dialysis or a kidney transplant, as well as related conditions - abnormalities in the body's water or mineral balance (electrolyte disorders), difficult-to-manage hypertension and diabetes-related kidney diseases.

How is kidney disease monitored?

Your doctor will perform a blood test known as serum creatinine to check for elevated creatinine levels. Elevated levels mean that your kidneys aren’t functioning the way they should. Since you might not have any obvious symptoms of kidney disease, this test allows your doctor to monitor your kidney function on a regular basis. Your doctor will combine creatinine level results with other factors, such as your age, to estimate your glomerular filtration rate (GFR). This rate determines whether kidney function is normal or low. Your creatinine levels and GFR can fluctuate over time depending on your fluid levels.