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Chronic Kidney Disease
Chronic renal failure (CRF)—is now called chronic kidney disease—is the gradual loss of the kidneys' ability to filter waste and fluids from the blood. Chronic kidney disease can range from mild dysfunction to severe kidney failure Figure 01. The kidneys serve as the body's natural filtration system, removing waste products and fluids from the bloodstream and excreting them in the urine. The kidneys maintain the body's salt and water balance, which is important for regulating blood pressure. When the kidneys are damaged by disease or inherited disorders, they no longer function properly, and lose their ability to remove fluids and waste from the bloodstream. Fluid and waste products building up in the body can cause many complications. Most systems in the body, including the respiratory, circulatory, and digestive systems, are adversely affected by chronic kidney disease (CKD).
Figure 01. Anatomy of the renal system
Kidney disease can exist without symptoms for many years. Renal failure progresses so gradually that CKD may not be detected until the kidneys are functioning at less than 25% of their normal capacity.
CKD occurs in 1 of every 5,000 people. Chronic kidney disease usually occurs in middle-aged and older people, although children and pregnant women are also susceptible. Chronic kidney disease can lead to total kidney failure, also known as end-stage renal disease (ESRD). People with ESRD require either dialysis or a kidney transplant. If not properly managed, ESRD is fatal.
Underlying disease is usually responsible for CKD Table 01. Diseases leading to kidney damage may be confined to the kidney, as in kidney infections, or may affect multiple organs, as in hypertension or diabetes. Approximately 40% of CKD patients have the disease as a result of diabetes, 30% have it as a result of hypertension, and 10% have it as a result of a disease called glomerulonephritis. Glomerulonephritis is a kidney disease that causes decreased output of urine, the spilling of blood and protein into the urine, and body swelling.
Diabetes mellitus is the most common cause of CKD. Diabetes, a disease that disrupts the way the body uses blood sugar (glucose), can lead to kidney damage and CKD. The high levels of sugar damage the kidneys over several years, and results in a reduced ability to filter blood and excrete waste products in the urine.
High blood pressure that is ignored or inadequately treated for many years can lead to CKD Figure 02. Hypertension, or high blood pressure, is a disorder that leads to damage of small blood vessels. When small blood vessels in the kidneys that filter the blood are damaged, kidney failure results. For this reason, it is important to keep blood pressure under control with medications, if necessary.
Figure 02. Blood pressure categories
CKD can result from a chronic kidney disease called glomerulonephritis, or from kidney infections. Glomerulonephritis may cause a small output of urine, the spilling of blood and protein into the urine, and body swelling. Glomerulonephritis may have no symptoms for many years, but may eventually cause enough damage to the kidneys to lead to CKD. Long-term or repeated kidney infections can also damage the structure of the kidneys, reducing the kidney's capacity to filter blood.
Kidney stones and other blockages can lead to CKD. Any obstruction in the natural flow of urine causes a back-flow of pressure in the kidney, which can damage the kidney's functional units, the nephrons. Nephrons are tiny tubular structures in the kidney that filter the blood. Each kidney has millions of nephrons. This damage can occur slowly over several years, and can ultimately lead to CRF.
Over-the-counter and prescription medications can contribute to CKD. Several drugs cause damage to the kidneys, including over-the-counter pain medications and certain very powerful antibiotics. If taken regularly over long periods, these medications act like poisons to the kidneys. People with even mild kidney disease must be very careful about the prescription drugs and non-prescription drugs they use. If you have known kidney disease, you should discuss all medication usage with your doctor.
Other diseases and conditions may lead to CKD as part of their natural progression. These include Alport syndrome, which is a rare kidney disease that causes kidney failure and hearing loss; lupus erythematosus; connective tissue diseases; kidney cancer; liver disease (cirrhosis); polycystic kidney disease; and abnormalities present at or before birth (congenital abnormalities).