Category : Kidney
Like the rest of your organs, I am unappealing in appearance – reddishbrown, shaped like a bean, about the size of fist. I am your right kidney; my partner is on the other side of your lower spine. You have a very low opinion of me. You may think about me as the producer of an unglamorous fluid mine and as a kind of secondary garbage disposal unit.
Brother! Actually, I am the master chemist of your body and your intestinal tract is not the main waste disposal system – I am. Blood passes through me continuously and I clean and filter it, ridding it of wastes that are potentially deadly. I help production of red blood cells; watch over potassium, sodium chloride and other substances in your blood – a whisper too much or too little of any of them can be lethal. I control vital water balance in your body. Too much water and your cells would drown, too little and you would simply dry up. I also see to it that your blood is neither too acidic nor too alkaline. As a matter of fact, I do so many things for you that the doctors still do not have a complete catalogue of my activities.
Look at my anatomy. Although I weigh only 140 grams, I contain more than a million little filtering units- nephrons. Under a high power microscope one of these looks something like a bigheaded worm, with a twisted tail called a t u b u l e . U n t a n g l e and stretch out my tubules and there would be 105 kilometers of them!
Each hour my partner and I filter twice the total blood in your body. And it is mighty tricky filtering, I might add. I do not allow red blood cells or large particles of essential blood proteins to pass through my fine filters. Otherwise they might be lost in urine causing catastrophic result. In my tubules, 99 percent of the fluid is reabsorbed. Essential vitamins, amino acids, glucose, hormones and so on are also returned to the bloodstream but excess of any of them is discarded in urine.
Thus, if you have eaten two big slabs of custard pie, your urine may show enough sugar to fool a doctor into thinking you have diabetes. When you eat a big portion of salted fish or any other particularly salty food, you might be in real danger if I did not extract the salt. Salt holds water. If it were permitted to remain in the blood, excess fluid would start accumulating in the blood and inter cellular spaces. Your face, feet and abdomen would puff up; and eventually to your heart, pumping against the growing load of liters of retained fluid, would simply falter and stop.
Potassium, mainly from meal and fruit juices requires my equally vigilant attention. Too little and muscles begin to fail, particularly breathing muscles. A little high and it acts like a brake on the heart and can bring it to a full halt. I simply discard the excess. Or, if your diet is not providing enough essential potassium, I hoard the existing supply like a miser.
The biggest waste I have to deal with is urea, the end product of protein digestion. Like everything else, this must be kept in precise balance. Too little means there has been damage to my upstairs neighbor, the liver. Too much and there sets in one of the ugliest diseases any doctor is apt to see – uremic poisoning. The name simply means urine in the blood. Unchecked, it can lead to shock, coma, death. As it piles up in the blood, the body makes a heroic effort to rid itself of this killer. Whitish crystals of urea may even appear on the skin indicates that sweat glands are helping to rid the body of the stuff. You must not worry about it. You can eat anything you want and I will handle any resulting excess of urea.
Doing my job, I produce urine continuously-about a liter a day each for my partner and me. Microscopic droplets of this waste- laden fluid pass out of each of my million tubules and feed into a tiny reservoir at my center. This connects with the bladder and the bladder with the outside. Wavelike muscular action occurs every 10 to 30 seconds, pushing the fluid along the exit tubes. At night, I slow down activity to about a third of daytime levels; otherwise, you would be up every hour or so.
Like everyone else, you have noticed that certain things step up my activity. When you chilled for example the blood supply to your skin is reduced to preserve internal heat. This means an increased flow of blood to internal organs, including me. With more blood, I make more urine.
Anger in you produces much the same result. Your blood pressure rises and I get an increased supply of blood for processing. Result: increased urine output.
Alcohol produces the same result via another, quite complex route. One of my main bosses is the pituitary gland on the under- side of your brain. It produces an anti-diuretic hormone. Left to my own devices, I might produce too much urine and you would become dangerously dehydrated. The hormone prevents this. The alcohol in your beer or martinis has no direct effect on me. But it does retard the pituitary’s production of the braking hormone, so I produce urine more rapidly. If you have too many drinks, you may become mildly dehydrated. That is why you crave water next morning.
Caffeine in coffee has a similar action. The nicotine in cigarettes has the opposite effect – it steps up production of the hormone. When you smoke heavily, you need to urinate far less frequently.
Like you, I am now 47 years old and beginning to show my age. I am a candidate for a lot of ills floating kidneys, for example. You need not worry here, mainly because you do watch your weight.
You may avoid the formation of kidney stones by maintaining an adequate fluid intake and anti-oxidants. The equivalent of nine glasses of water a day – most of which comes from food, is about right. Meat is 50 percent water; bananas are 90 percent, watermelon – 93 percent.
My really big problem is damage to my filters, or nephrons. Infection is one villain. It usually creeps from the urinary tract below. Fortunately, such infections are usually promptly controlled by antibiotics. Large bums can cause my nephrons severe damage, wastes from destroyed tissue pile up more rapidly than I can dispose off and blood essentials weep from wounds faster than I can replace them.Injury – from a kidney punch or an auto accident, for example – is also troublesome to my nephrons, as are many drugs and poisons.
As a rule, all these things cause only temporary damage – readily repairable, since I have striking regenerative powers. A steady concern, however, is the hardening of the arteries that seems to be a part of the ageing process. My arteries harden, narrow and become inelastic, just as they do elsewhere in the body, thereby reducing my blood supply. In time, your heart may lose some of its pumping power. This, too, cuts my blood supply. In these situations I begin to fall down on my job of laundering blood. I let toxic wastes pile up, and allow sodium, potassium, chloride and other things to get out of normal balance.
Some of this already has happened to you; quite a few of my nephrons have been destroyed. Fortunately, my partner and I have a big reserve capacity. We can do a pretty job even if 90 percent of our nephrons stop functioning. Wise medical and dietary management can still provide years of life if such a point is reached. This means keeping an ever vigilant eye on salt, potassium and other substances in food to maintain them in exact balance. And fluid intake must be exactly balanced with losses via lungs, perspiration and urine. There are drugs, too, that now help in situations once considered hopeless.
The medical profession has come up with some remarkable tests to determine the exact nature of the problem when I give trouble. The basic test, of course, is the urinalysis. Does the urine contain protein? It should not, except in the minutest amounts. The presence of protein indicates that my filters are letting it escape from the blood. Are there “casts”? When my tubules are inflamed, solid matter (cells, fats, proteins) solidifies to the exact shape of the tubule and then time to time these casts are flushed out by urine.
Blood, too, helps in diagnosis. Does it contain excess urea? If so, I am falling down on my job of ridding your of protein wastes. In another test, a dye is injected in your bloodstream. The time it takes to pass this material out in urine is measured: the longer it takes the more trouble I am in. There are dozens of tests like these.
What can you do to ease my jobs? Watching weight and blood pressure are major things. Exercise helps, but not violent exercise. Overworked muscles produce excess lactic acid, which is a burden on me. An extra glass or so of water a day helps; most people drink too little fluid. If your urine becomes cloudy, smoky or mahogany colored, you should get to a doctor fast. If you note puffiness of face, nausea, blurred vision and weariness, it is likely that I am ailing and want immediate attention.
I am not asking you to dwell on me or to fret about me. I am asking only that if you hear a cry for help from me you listen attentively I am far too important to you for any trifling.