Chronic kidney disease (CKD), also known as chronic renal disease, affects 17 percent of adults aged 20 or older in the United States. CKD is defined as a progressive loss of kidney function taking place over months to years. In the U.S., diabetes and hypertension are the leading causes of kidney disease, but other conditions may also contribute to a decline in kidney function, such as autoimmune disease (sometimes leading to what we call glomerulonephritis, or inflamed kidney filters), vascular problems, polycystic kidney disease, kidney stones, and blockage of urine.
Screening for CKD usually includes a urinalysis (UA), and a blood test called a creatinine level. The normal creatinine value varies with age and amount of muscle mass.
The kidneys perform many functions, most importantly the filtering of blood and clearing toxins, and by removal of excess salt, water, and electrolytes from the body. The kidneys are also involved with creating red blood cells, and with bone health. Symptoms of CKD include fatigue, intolerance to cold temperature, and nausea. In later stages, some might experience anemia (low blood count), fluid overload, high blood pressure, and problems with electrolytes including calcium, phosphorus, and potassium.
The stages of Chronic Kidney Disease are determined by a patient’s GFR, or glomerular filtration rate. The GFR is the amount of blood cleaned by the kidneys per minute. Normal GFR value for a male is 130 mL per min and normal for a female is 120 mL per min.
There are five “stages” of CKD:
- Stage I = GFR >90 mL/min with some evidence of structural problems involving the kidneys, perhaps blood or protein in the urine
- Stage II = GFR 60-89 mL/min
- Stage III = GFR 30-59 mL/min
- Stage IV = GFR 15-29 mL/min
- Stage V = GFR 0-14 mL/min
Some describe a sixth stage of kidney disease, or end-stage renal disease (ESRD).
Patients with ESRD require a transplant or dialysis to survive. Most patients with CKD, however, do not succumb to kidney failure, but rather cardiovascular disease, which is quite prevalent in patients with kidney disease. The best ways to slow the progression of CKD are by obtaining goal blood pressure levels (usually with medications that block the renin-angiotensin-aldosterone pathway such as ACE inhibitors or ARBs), by controlling blood sugars in those with diabetes, and by avoiding NSAIDS (nonsteroidal anti-inflammatory drugs).
Typically a nephrologist (kidney specialist) will get involved once the kidneys are functioning below a GFR of 60 mL/min. Nephrologists can help slow the progression of CKD and can treat some of the sequelae of kidney disease (e.g. anemia, bone disease), and can prepare patients if dialysis is approaching.