Nephrologist Winfred W. Williams, MD, explains why the kidneys are important, what causes kidney disease and how to keep the kidneys healthy.
Kidney Health Q&A with Winfred W. Williams, MD, of the Mass General Transplant Center
Q: What are the kidneys and what do they do?
A: Each person who has undergone normal development has two kidneys about the size of a fist on either side of the spine. The kidney is both a filtering unit and a processing unit. About 200 quarts of fluid pass through the kidneys every 24 hours. Of this fluid quantity, about two quarts are excreted as urine, and the other 198 quarts are recovered in the blood.
Winfred W. Williams, MD
Q: Why is kidney health important?
A: In addition to balancing the body’s fluids and regulating key electrolytes, the kidneys are responsible for other key metabolic and physiologic functions that are interconnected. The kidneys release a number of hormones that govern normal physiologic processes. For example, the hormone called renin plays an important role in the control of blood pressure. The kidneys also produce the active form of vitamin D that plays a prominent role in bone health by regulating calcium in the body. Finally, kidneys also produce the hormone called erythropoietin, which controls the production of red blood cells in the bone marrow.
Q: What are the leading causes of kidney disease?
A: Chronic kidney disease is defined as having some type of kidney abnormality that decreases kidney function for three months or longer. There are many types of chronic kidney disease but in the U.S. patients are primarily affected by diabetes and high blood pressure, also known as hypertension, conditions that often run in families.
Q: How prevalent is kidney disease?
A: About 26 million adults in the U.S. have chronic kidney disease and many more go undetected. Others have silent kidney disease and often associated high blood pressure.
Q: Who is at risk for kidney disease?
A: Patients who are not in the habit of having periodic annual health checkups, who may have an undetected elevation in blood pressure (the so-called silent killer) who may be pre-diabetic, or, frankly, are diabetic and who do not know that they have the disease, are at highest risk. Diabetic kidney disease accounts for 45% of the annual incidence of end-stage renal (kidney) disease in this country. Hypertension is a silent killer for many reasons, including its marked effect on cardiovascular health—causing strokes, heart attack and congestive heart failure.
Q: Are some populations more at risk for kidney disease than others?
A: Ethnic minorities— African Americans, Latinos and Native Americans— are at highest risk for kidney disease. African Americans have four to five times the risk of high blood pressure than whites and an approximately fourfold elevated risk of contracting chronic kidney disease. While African Americans constitute 12% of the U.S. population, they account for 35% of all patients on dialysis.
This disparity in the proportion of blacks with end-stage renal disease may be due in part to disparities in access to good health care, but also recent evidence points to a genetic predisposition to certain forms of chronic kidney disease.
Q: How do I know if my kidneys are healthy? What tests can be done and what symptoms should I look for?
A: There are straightforward tests to check kidney health. You have to look at three things:
1) Whether there is an elevated amount of protein in the urine,
2) Whether there is an elevation in the blood of the serum marker called serum creatinine (a breakdown product of the muscle constituent, creatine) and
3) Whether there is elevated blood pressure.
These three items alone will give you a good indication of kidney health; they are also influenced by other variables, including age, race and gender. That’s why you need a trained health professional to interpret the test results. These tests should be part of a yearly physical examination.
In order to have symptoms of kidney disease, your kidney damage has to be fairly advanced. In the advanced stages of kidney insufficiency, you might feel fatigued due to anemia, a decrease in exercise tolerance and/or physically not feel up to par. Kidney failure in far advanced stages can also be associated with a decrease in alertness and intellectual acuity. Patients who are not handling fluid well may have puffiness around their eyes and swelling of the hands and feet. More frequent urination, especially at night, and foamy urine may also be a sign that your kidney’s filtering apparatus may be off.
Q: What are the top ways to keep kidneys healthy?
A: When you’re an adult, once a year as part of a baseline physical examination, you should have your blood pressure, urine and blood creatinine checked, especially if there is a family history of high blood pressure and/or diabetes, or other kidney diseases, e.g., focal glomerulsclerosis (a.k.a, FSGS), hereditary nephritis or polycystic kidney disease.
Also remember to: