Diseases and conditions affecting the kidney
In the US, kidney disease is the eighth leading cause of death; diabetes and hypertension are the most common causes of chronic kidney failure. If you have diabetes or hypertension, you have a greater risk of developing kidney disease. (For links to more information, see the Related Pages, Elsewhere on the Web.) Any diseases that affect the blood vessels, including diabetes, hypertension, and atherosclerosis, can impair the kidneys' ability to filter blood and regulate fluids in the body. Disease and infection in other parts of the body can also trigger a kidney disorder. Because kidney impairment can be life-threatening, disorders and diseases that may affect the kidney deserve prompt attention. Kidney disease often causes no symptoms until late in its course and can lead to end-stage kidney failure, which is fatal unless a dialysis machine is used or a kidney transplant is performed. There are more than 100 disorders, diseases, and conditions that can lead to progressive destruction of the kidneys. Some of the more common problems are described here. Warning signs that should not be ignored are also listed.
The urinary tract can become blocked, or obstructed (for example, from a kidney stone, tumor, expanding uterus during pregnancy, or enlarged prostate gland). The buildup of urine can lead to infection and injury of the kidney. With a kidney stone, often the blockage is painful. Other obstructions may produce no symptoms and be detected only when a blood or urine test is abnormal or an imaging procedure, such as an x-ray or ultrasound, detects it.
Urinary tract infections, such as cystitis (an infection of the bladder), can lead to more serious infections further up the urinary tract. Symptoms include fever, frequent urination, sudden and urgent need to urinate, and pain or a burning feeling during urination. There is often pressure or pain in the lower abdomen or back. Sometimes the urine has a strong or foul odor or is bloody. Pyelonephritis is an infection of kidney tissue; most often, it is the result of cystitis that has spread to the kidney. An obstruction in the urinary tract can make a kidney infection more likely. Infections elsewhere in the body, including, for example, streptococcal infections, the skin infection impetigo, or a bacterial infection in the heart can also be carried through the bloodstream to the kidney and cause a problem there.
Glomerular diseases are those that attack the blood filtering units of the kidneys. Diabetes and hypertension can lead to glomerular disease. Diseases of this type cause more cases of chronic kidney failure than any other cause. The blood is continually filtered through microscopic clusters of looping blood vessels, called glomeruli. Attached to each glomerulus is a tiny tube (tubule) that collects the waste that has been filtered out. The filtering unit (glomerulus and tubule) is called a nephron.
Often, a glomerular disease is triggered by an abnormal reaction of the immune system. In this case, the body's own infection fighters mistakenly attack the kidney tissues. Sometimes, an autoimmune disorder such as systemic lupus erythematosus or Goodpasture syndrome is the cause. The attack on the glomerulus may also be the result of an inherited condition. An attack on the glomerulus may also occur after a bacterial infection in another part of the body, such as a strep infection of the throat or skin, the skin infection impetigo, or an infection inside the heart. Viruses, such as the HIV virus that leads to AIDS, can also trigger glomerular disease.
In diseases and conditions classified as glomerulonephritis (also called nephritis or nephritic syndrome), the glomeruli become inflamed. As blood filtering becomes impaired, urine output decreases, water and waste products accumulate in the blood, and blood appears in the urine. Because the blood cells break down, urine often becomes brown instead of red. Certain body tissues swell with the excess water (a condition called edema). Outcomes can vary: the condition may go away in a few weeks, permanently reduce kidney function, or progress to end-stage kidney failure.
In nephrotic syndrome, the blood loses protein to the urine because of damage to the membrane between the glomeruli and tubules. This damage causes the glomeruli to allow larger molecules than usual to pass through it. An example is albumin. As the amount of albumin, a major protein, decreases in the blood, parts of the body swell with fluid (often around the eyes or in the belly or legs). Other diseases and illnesses may lead to this syndrome, and complications such as blood clots and high cholesterol may develop. Childhood nephrotic syndrome usually responds well to Treatment and does not usually result in permanent kidney damage.
Any situation in which there is severe blood loss or reduced blood flow may prevent the kidneys from working correctly. Severe dehydration, some aortic and heart surgeries, a severe infection in the blood or heart, and severe heart failure are examples of events that can lead to sudden kidney problems. The damage is usually reversible; although with shock or severe infection, the damage may be permanent. Some medications and diagnostic agents can have toxic effects. In some cases, nonsteroidal anti-inflammatories (NSAIDS, such as over-the-counter ibuprofen and various prescription drugs), x-ray dye, ACE inhibitors, and certain antibiotics can damage the kidneys. Acute kidney failure may result, a condition that requires emergency medical treatment to prevent death.
Cancers involving the urinary system are not as common as those in other parts of the body. Kidney cancers are of two main types. One called Wilms tumor occurs in young children and is often detected as a firm swelling in the belly. Renal cell carcinoma, which occurs in middle-aged to older adults, can cause blood in the urine but is often not detected until it has spread to other parts of the body. Bladder cancers are more common, and often present with painless, bloody urine. In many cases, the blood is only detected when a urinalysis is performed. Because bladder cancers can be controlled when detected early, any urine bleeding in adults (except during a woman's menstrual period) should be checked by your doctor.