Kidney Disease

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The main functions of the kidneys are to regulate the body's fluid balance and electrolyte levels and to eliminate waste products. They perform these important tasks by filtering the blood and removing unnecessary water and soluble wastes, including excess amounts of minerals, which are excreted in the urine. About twenty times every hour, all of the blood in your body passes through your kidneys. The kidneys are also involved in the regulation of blood pressure. They secrete a hormone called rennin, which causes the formation of another hormone, angiotensin, in the blood. Angiotensin is a potent blood-vessel constrictor, and acts to increase blood pressure.

The kidneys are located at the lack of the abdominal cavity, just above the waist, on either side of the spinal column. The right kidney is situated under the liver, and the left is under the spleen. In the average adult, the kidneys are about four to five inches long and weigh about six ounces apiece. A renal artery enters each kidney and then branches out into a network of progressively smaller blood vessels, culminating in clusters of tiny capillaries called glomeruli. The term glomerulus comes from the Latin glomus, which, roughly translated, means "ball of yarn". The glomeruli are the main filtering units of the kidney, and each kidney houses many of them. Membranes in these tiny structures filter nutrients and wastes structures called tubules. The tubules are surrounded by blood vessels that absorb essential nutrients from the liquid. Once that has been accomplished, the material that has been removed from the blood is concentrated to become urine. Urine continually trickles down the tubules, through the uterus, and into the bladder, where it is stored until it is passed. The cleansed and filtered blood, meanwhile, passes into the renal vein and returns to the circulation.

Together, glomeruli and tubules make up nephrons, which are the basic functional units of the kidneys. During the natural aging process, the number of functioning nephrons declines. A baby enters the world with about a million more working nephrons, but the average forty-year-old has only around 375000 still functioning. By the age of eighty, that number has been reduced t approximately150000. Certain diseases also reduce the number of functioning nephrons.

The term nephritis denotes any condition characterized by inflammation of the kidneys. Glomerulonephiritis is inflammation of the glomeruli, the filtering units of the kidneys. This condition usually develops because of an immune response to infection. For example, infection with Streptococcus bacteria can precipitate glomerulonephiritis, just as it can lead to rheumatic fever. Symptoms can include fluid retention and bloating, decreased frequency of urination, nausea and vomiting, fever, exhaustion, abdominal and/or lower back pain, elevated blood pressure, and dark or bloody urine. Pyelnephritis refers to inflammation of the kidney itself, including the entire kidney and the renal pelvis, the area connecting the kidney to the top of the ureter, the tube that carries urine to the bladder. This condition can cause chills, fever, pain, nausea, and vomiting.

The causes of the above kidney diseases include infections that migrate upward from the urinary tract and exposure to certain drugs or toxins. Kidney problems are often a complication of other disorders, such as diabetes, lupus, high blood pressure, and liver disease. If kidney function is seriously impaired, toxic wastes cannot be properly eliminated and may accumulate in the blood stream, resulting in uremic poisoning, and a sign of potential kidney failure.

Kidney failure can be acute or chronic. Acute failure can itself be divided into three separate types: prerenal, renal, and postrenal. Prerenal failure is also called prerenal azotemia, meaning that there are excess nitrogen waste products left in the bloodstream that the kidney was supposed to have filtered into the urine for removal, but did not. This is a sign of poor filtration due to an inadequate flow of blood reaching the kidney, not disease within the kidney itself. This can be due to dehydration, excessive blood loss, and blockage of the artery that serves the kidney, liver disease that inhibits blood flow, heart failure, and the use of certain drugs. The two drugs best known for doing this are angiotensin - converting enzyme (ACE) inhibitors, used to treat high blood pressure, and the type of painkiller known as nonsteroidal anti-inflammatory drugs (NSAIDs). Postrenal failure, or postrenal azotemia, results from blockage of the outflow tract can be compressed. Other possible causes include stones in the bladder and severe trauma. These conditions are not common, but they are the most treatable, as they tend to be localized and, as long as the problem is caught early, there is no disease in the kidney itself.

Failure within the kidney itself, known as intrinsic failure, takes many different forms, depending on exactly which part of the filtering unit is damaged. Usually it is due to chemical damage or acutely low blood flow to the kidney. Chemical damage can be a result of using certain drugs, the worst of which are the so-called aminoglycoside antibiotics, x-ray contrast material used for visualizing the kidney, and the immune-system suppressant cyclosporine.

Some forms of kidney disease are hereditary. In cystic kidney disease, multiple cysts-fluid-filled cavities of different sizes - form within the kidneys, ultimately destroying kidney tissue. This condition tends to be more severe and progress more rapidly in children than in adults, and kidney failure is often the eventual result. Other types of hereditary kidney disease include Bartter's syndrome, Fanconi's syndrome, Hartnup disease, and Liddle syndrome. All of these disorders are characterized by improper functioning of the kidneys that results in metabolic problems, principally electrolyte imbalances, which in turn can lead to nutritional deficiencies and blood-pressure disturbances.

Tests to measure kidney function include urinalysis, in which urine is examined microscopically for blood cells, pus and infectious agents. Kidney function can also be evaluated by measuring the concentration in the blood of substances, such as urea, that are normally eliminated from the body by healthy kidneys. X-ray and ultrasound scans may also be performed.

Prevention

anytime you suspect a urinary tract infection, seek treatment promptly. Left untreated, an infection can migrate up through the uterus to the kidneys.

If you have a history of kidney infection, consider taking 500 milligrams of cranberry extract daily on an ongoing basis.

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