The kidneys perform several functions vital to life. These functions include:
• Eliminating waste products from the body.
• Regulating the composition of minerals, salts, and other dissolved substances in the body.
• Controlling the amount of water in the body.
• Regulating blood acidity (pH).
• Making and releasing the hormone, erythropoietin, which controls red blood cell production.
• Activating vitamin D, critical in controlling calcium in the body.
• Regulating blood pressure.
There are many ways to measure kidney function. One of the most reliable is to determine the amount of blood filtered by kidneys in a period of time. This is known as the glomerular filtration rate (GFR). The GFR of a healthy adult is around 120 millimeters per minute (mL/min). GFR normally declines as we age. It can be measured or estimated through calculations of creatinine, a waste product produced by muscle that can be measured in the blood. In general, elevations in creatinine concentration usually correlate with impaired kidney function. It is important to note that creatinine concentration is dependent on several factors and is not always a reliable measure of kidney function.
Any disease or process capable of permanently injuring the kidneys can cause CKD. CKD is a spectrum classified by grades. Grade 1 is the least severe and is defined as a damaged kidney with a normal or increased GFR. Grade 5 or kidney failure (KF) is the most severe form of CKD. In patients with KF, the GFR less than 15 mL/min. Kidney failure is sometimes referred to as end stage renal disease (ESRD)
There are many causes of CKD. Diabetes and high blood pressure (hypertension) are two of the most important. Other causes include autoimmune diseases such as glomerulonephritis, certain drugs, infections, and blockage (obstruction) of the lower urinary tract. Treating these conditions may delay or prevent a decline in kidney function.
Knowing the functions of normal kidneys, you may be able to predict what happens when kidney function deteriorates.
• Waste products accumulate in the body.
• The composition of minerals, salts and other substances in the body is abnormal.
• Calcium handling in the body is abnormal and bones become brittle.
• The amount of water in the body tends to increase. Excess water retention (edema) may accumulate in the lungs making it difficult to breath. Excess water may cause swelling of the legs and abdomen.
• Blood pressure tends to increase due (in part) to fluid retention.
• The body becomes very acidic due to an inability to maintain normal pH.
• A deficiency of erythropoietin results in anemia. Anemia causes fatigue and is a risk factor for developing heart failure.
Many people with early stages of CKD are asymptomatic. By the time one develops kidney failure, most people will have multiple symptoms. These include:
• Fluid retention
• Fatigue
• Impaired mental function and sleep
• Diffuse itchiness (pruritis)
• A tendency to bleed or bruise easily
• A tendency to urinate at night (nocturia)
• Nausea and possibly vomiting
• Muscle cramps
• The development of yellow or gray pigmented skin
Ideally, patients with chronic kidney disease will be identified at an early stage. Optimal management of their underlying disease(s), such as diabetes and hypertension, may delay or prevent further decline in their kidney function. Once CKD is present, it tends to worsen with time. Early referral to a physician specializing in kidney diseases (nephrologist) has been shown to delay the progression of CKD and decrease mortality. These patients may also benefit by receiving nutritional counseling from specially trained dieticians. Important aspects of management include:
• Strict attention to diet and fluid consumption
• Vitamin D supplementation
• Administration of recombinant erythrpoietin
• Medications to help eliminate excess fluid (diuretics) and control blood pressure.
Patients with kidney failure will usually require some form of renal replacement therapy to stay alive. Options include dialysis and kidney transplantation. Dialysis is a procedure that helps eliminate waste products, acid, and excess fluid. Dialysis may be performed on blood (hemodialysis) or by using a body membrane in the abdomen (peritoneal dialysis). Patients receiving dialysis continue to use the treatments mentioned previously. Kidney transplantation involves the placement of a working kidney into the body of a patient with kidney failure. Patients who receive a kidney transplant must take medication to prevent their immune system from rejecting the new kidney.
What this means to you:
• Ask your physician if you have or are at risk for developing chronic kidney disease.
• If you are at risk for developing CKD, take action to reduce your risk. This usually involves treating the underlying cause of kidney diseases such as diabetes and hypertension.
• If you have CKD, inquire about early referral to a nephrologist and a registered dietician with experience in CKD.
