When men think about their urinary systems, they usually focus on the lower urinary tract. It's understandable since lower urinary tract symptoms are a major cause of bother and discomfort for gents who have benign prostatic hyperplasia (BPH). But men should also spend a few minutes thinking about the upper urinary tract, especially the kidneys.
The kidneys don't get the respect they deserve. That's understandable, too, since many kidney diseases don't produce any symptoms until damage is severe. But that makes it all the more important for you to understand your kidneys, learn how to work with your doctor to spot problems early on, and — above all — know how to keep these vital organs healthy.
The burden of kidney disease
According to the National Kidney Foundation, 26 million Americans — about one of every nine adults — have chronic kidney disease. Another 20 million are at risk, but most don't know it. And men are more vulnerable than women.
Kidney disease is the ninth leading cause of death in the U.S., taking more than 85,000 lives annually. In addition, more than 475,000 people a year need dialysis or kidney transplants to stay alive. And since kidney failure is on the rise, that number is expected to swell to some 650,000 in 2010. These advanced treatments are wonderful, but they're also expensive. All told, the U.S. spends over $33 billion a year on kidney disease, and countless billions more on heart disease and other major problems triggered by kidney failure.
Normal kidney structure
Your two kidneys are located deep in the back of your abdomen on either side of your spine just below your lowest rib (see figure). Each is approximately 4.5 inches long and weighs about 5 ounces. And each kidney contains approximately one million functional units called nephrons. Every nephron consists of a glomerulus and a tubule. These glomeruli function as tiny filters. Blood passes through the glomeruli, which retain blood cells and large molecules such as proteins in the circulation while allowing fluid and small molecules to pass through to the tubules.
As fluid flows through the tubules, much of the liquid is absorbed back into the bloodstream. Depending on the body's needs, the tubules can also absorb small molecules such as sodium and potassium. Finally, the tubules join up to form each kidney's collecting system. At this point, the concentrated fluid has all the characteristics of urine. The urine flows from each collecting system into the ureter, a long muscular tube that carries the urine to the bladder.
The bladder stores the urine until you are ready to void. But in men, there is a final hurdle. The urethra, which carries the urine out through the penis, passes through the prostate, where enlarged tissue can pinch the tube and prevent urine from going with the flow.
Your kidneys and urinary tract
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Normal kidney function
The kidney's first job is to eliminate waste products. Although they are small organs, the kidneys receive more than 20% of the body's blood flow. Each day, some 200 quarts of fluid pass through the glomeruli into the tubules. The tubules return over 198 quarts to the circulation. But the 1 to 2 quarts that become urine contain waste products from the body's metabolism, including creatinine, urea, and various acids. As kidneys fail, these products build up in the blood, eventually producing symptoms such as fatigue, weakness, poor appetite, impaired mental function, disturbed sleep, itching, and muscle cramps. In end-stage kidney disease, seizures and other problems develop, leading ultimately to death.
Healthy kidneys rid the body of its natural waste products — and they can also excrete a variety of toxic chemicals that you might encounter. Many medications are also eliminated from the body by the kidneys, which is why doctors have to be very careful about the drugs they recommend and the doses they prescribe for people with kidney disease. And since kidney function declines with age, similar precautions apply to healthy senior citizens.
