By Terry Davis, M.D., family physician, Providence Medical Group - Wilsonville
"Know your numbers" is a message that health care providers have been pushing for years, with positive results. Chances are good that you, your friends and your family members now pay closer attention to your blood pressure and cholesterol numbers. But what about your GFR?
Never heard of it? Most people haven't – but I encourage you to get to know it.
GFR, short for glomerular filtration rate, is a measure of how well your kidneys are doing their job. It's a number that doesn't get much attention, but you'd be wise to watch it - especially if you have diabetes, high blood pressure or other risk factors for kidney disease. A drop in this number may be the first and only indication that your kidneys are starting to have problems. And problems with the kidneys can affect just about every other organ and function of your body.
A moment of appreciation for healthy filtration
The heart gets a lot of press. The lungs get a lot of press. But the kidneys, which play a vital role as your body's filtration system, are underappreciated.
Besides filtering waste products and excess fluid out of your body, these wonderful, hard-working organs also regulate your electrolyte balance, red blood cell production and blood pressure, and can affect your calcium metabolism, as well. Yet as important as they are, we don't pay as much attention to our kidneys as we should - not, that is, until we're faced with the prospect of spending the rest of our life on kidney dialysis. Unfortunately, with type 2 diabetes becoming more common, that prospect is growing more likely for a lot more people.
Doing a number on your kidneys
Some causes of kidney disease can't be controlled - these include family history, genetic conditions, aging and race (African Americans, Native Americans, Hispanic Americans, Asians and Pacific Islanders are at higher risk). But most of the things that lead to chronic kidney disease and kidney failure are things that we do, often unwittingly, to ourselves. Topping the list of controllable risk factors are the following:
- Poorly managed type 2 diabetes: Type 2 diabetes that is not managed well is the leading cause of chronic kidney disease, responsible for about 40 percent of all cases.
- Uncontrolled high blood pressure: Hypertension that is undetected or poorly managed is the second leading cause of chronic kidney disease.
- Too much protein: Compared to the rest of the world, most Americans eat huge amounts of protein, which puts a toxic load on the kidneys.
- Overuse of over-the-counter pain relievers: You don't hear much about this, but non-steroidal anti-inflammatories, such as ibuprofen (Advil) and naproxen (Aleve), put a heavy burden on the kidneys.
- Dehydration: Drinking too little water stresses the kidneys.
- Smoking: On top of all the other harm that smoking does, it's also hard on the kidneys.
Each of these alone increases the risk of chronic kidney disease. A person with several risk factors - for example, a smoker with poorly controlled diabetes who eats a lot of meat and takes ibuprofen frequently - could seriously be looking at kidney failure and dialysis in the future.
And it isn't a pretty future. Dialysis means having to travel to a clinic two or three times a week to be tethered to a machine for half of the day. The machine does the work that your kidneys no longer can do, and it leaves you feeling pretty washed out. You are chronically anemic, you may need hormone injections, and you have to change your diet radically. It is definitely something you want to avoid if at all possible.
That's where knowing your GFR comes in.
What's your number?
GFR is the earliest and most accurate predictor of declining kidney function. Tracking this number gives you the power to detect a problem early enough to do something about it.
Your GFR calculation begins with a blood test for creatinine, a waste product normally filtered out by the kidneys. High levels of creatinine are the first clue to a potential kidney problem, but a complete GFR goes further. It also factors in your age, race, gender and body mass to provide a very accurate measure of your kidneys' functioning. The lower your GFR, the lower your kidney function.
A GFR between 130 and 90 is considered normal for most people, but that can vary depending on a person's body size and race. Kidney disease is ranked in five stages:
- Stage 1: GFR 130 to 90 - A person may be considered in stage 1 if his kidneys are damaged due to injury or other factors, but are still functioning normally
- Stage 2: GFR of 90 to 60 - damaged kidneys with mildly reduced function
- Stage 3: GFR of 60 to 30 - kidney disease with moderately functional kidneys
- Stage 4: GFR of 30 to 15 - severe kidney disease
- Stage 5: GFR below 15 - kidney failure; kidney dialysis or transplant is necessary for survival
A person can progress to stage 4, when dialysis is just around the corner, with no symptoms whatsoever. That's why knowing your GFR is so important: a drop in this number gives you a heads-up that trouble is brewing. When we discover kidney disease earlier, we can intervene with diet and lifestyle changes that can do an enormous amount of good, preserving a lot of kidney function and forestalling or potentially avoiding dialysis.
TLC for your GFR
If some of the risk factors for kidney disease apply to you, ask your doctor to calculate your GFR at your next checkup. If you find that your GFR is abnormal, work closely with your doctor to develop and follow a plan to preserve your kidney function. If your number is healthy - and especially if it's not - start giving your kidneys some much-deserved attention and work on reducing your controllable risk factors:
- Get screened regularly for diabetes and high blood pressure: If you are diagnosed with either of these, work closely with your physician to keep them well under control.
- Don't overdo it on protein: For most people, the U.S. Dietary Guidelines recommend 5 to 6½ ounces of meat, fish or poultry per day from a variety of healthy sources.
- Take fewer pain medicines: For mild aches and pains, try other options such as breathing deeply, drinking water, and applying heating pads or ice.
- Stay hydrated: Drink two quarts of water every day, especially if you already have reduced kidney function.
- Don't smoke: If you do smoke, ask your doctor to help you quit.