The kidneys are twin, fist-size organs located at the bottom of the rib cage on either side of the spine. They perform several functions, the most important of which is filtering waste products, excess water, and other impurities out of the blood. These waste products are stored in the bladder and later expelled from the body as urine.
In addition, the kidneys regulate pH, salt, and potassium levels in the body, and they produce hormones that regulate blood pressure and control the production of red blood cells. The kidneys are also responsible for activating a form of vitamin D that helps the body absorb calcium to build bones and modulate muscle function.
When Things Go Wrong
A little more than one in 10 Americans over the age of 20 show evidence of kidney disease. Some forms of kidney disease are progressive, meaning that they get worse over time. When the kidneys no longer effectively remove waste from the blood, this can lead to kidney failure. Waste builds up in the body, causing serious problems including death, until the blood is filtered artificially through dialysis or a new kidney is transplanted into the body.
Types of Kidney Disease
Chronic Kidney Disease
The most common form of kidney disease is chronic kidney disease, caused by high blood pressure. Because the kidneys are constantly processing the body's blood supply, they are exposed to about 20 percent of the total blood volume of the body every minute.
High blood pressure is dangerous for the kidneys because it can lead to increased pressure on the glomeruli, which are the functional units of the kidney. In time, this high pressure compromises the filtering apparatus of the kidney, and kidney function begins to decline.
Eventually, kidney function will deteriorate to the point where the kidney can no longer properly perform its job, and a person will be required to go on dialysis. Dialysis filters fluid and wastes out of the blood, but it is not a long-term solution when the kidneys stop functioning. Eventually, kidney transplant may be an appropriate next move, but each circumstance will be different.
Diabetes is also a major cause of chronic kidney disease. Over time, uncontrolled blood sugar will damage the functional units of the kidney, leading to kidney failure.
One other common kidney problem is kidney stones. Minerals and other substances in the blood crystallize in the kidneys, forming solid particles (stones) that usually pass out of the body with urine. Passing kidney stones can be extremely painful but rarely causes significant problems.
Glomerulonephritis is an inflammation of the glomeruli, microscopic structures inside the kidneys that perform the actual filtration of the blood. Glomerulonephritis can be caused by infections, drugs, congenital abnormalities, and autoimmune disease. This condition often gets better on its own or is responsive to immunosuppressive medications.
Polycystic Kidney Disease
Polycystic kidney disease is a genetic disorder that causes many cysts—round sacs of fluid—to grow inside and on the surfaces of the kidneys. These cysts can interfere with kidney function. (Individual kidney cysts are fairly common and almost always harmless; polycystic kidney disease is a separate, more serious condition.)
Urinary Tract Infections
Urinary tract infections (UTIs) are bacterial infections of any of the components of the urinary system. Infections in the bladder and urethra are most common. They are easily treatable and cause few long-term effects. However, if left untreated, these infections could spread to the kidneys and lead to kidney failure. A kidney infection is also known as pyelonephritis.