Gettysburg Medical News
 The Clinical View
 by P.E. Hoffsten, MD
 22 February 2006

WHAT IS KIDNEY FAILURE?

            For every person there needs to be a balance between what that person eats and drinks and how much waste product the person excretes.  For an adult, these two items are supposed to be equal every day.  If you drink a certain amount of fluid, that amount of fluid has to be excreted out of the body.  In addition, there needs to be a sensing mechanism that can figure out how much fluid the person took in, how much they lost from perspiration and therefore, how much urine the person has to put out as water.  This is also true for salt, potassium, calcium, and magnesium which are all essential body nutrients.  But they all become waste products when there is too much of them.  Lastly, the body needs a way to get rid of chemicals in food when the food is burned up for energy.  The major waste product from the body’s food burning process is carbon dioxide that comes out through the lungs.  But when a person eats protein that they do not use to build body parts, there are a number of chemical waste products left over when the protein is burned.  These are sulfates, and phosphates, and nitrogen products which can only be excreted by the kidney in the urine.

            One of the favorite questions to ask a medical student is, “What is the kidney’s most important waste product?”  It is an unusual student that recognizes that the most important waste product excreted by the kidney is water.  That is the product that will cause the most problems for an individual when kidney failure occurs.  The kidneys are able to excrete as much as 20 quarts of water a day if needed (usually only after college beer drinking parties).  Or if the person is very dehydrated the kidneys can maintain balance while only putting out 1 pint of urine per day.  The kidneys are so smart they know just how much urine to make each day, not too much so the person becomes dehydrated and not too little so the person becomes fluid overloaded.

            Thus in response to the above question, “What is kidney failure?”; the answer is kidney failure is what happens when the kidneys fail to put out the appropriate amount of a waste product.  The accumulating waste product builds up in the body and causes “uremic poisoning”.

            The most common cause of kidney failure occurs slowly over an extended period of months or years.  Kidneys can fail because they don’t get enough blood supply the same way that an arterial block in the heart can cause a heart attack or an arterial block in the brain can cause a stroke.  An arterial block to the kidney can damage kidney tissue which then leads to decreased kidney function.  A second reason that kidneys might fail is the outlet tubes that carry urine to the bladder get stopped up or if the exit tube from the bladder to the outside gets stopped up.  The latter problem is very common in men with prostate disease.  The third reason that kidneys fail is because of intrinsic disease of the kidney itself of which there are many causes.   Most of these develop slowly over years of time.

            When does kidney failure become an issue?  Many people have heard of a person who donated a kidney to relative for transplant purposes.  The answer is that both the patient and the donor of the kidney just do fine.  There is plenty of kidney function for both people even though they only have one kidney each.  It is expected that the amount of waste product in the blood will double compared to the normal state but the person can live very well even though they have twice as much waste product in their blood.  If the person were to lose another half of their kidney function so that now they only have 25% of normal, the amount of waste product would double again.  They would still do relatively well although not have the normal stamina.  If the amount of kidney tissue gets decreased in half again, they now only have 12.5% of their normal kidney function left; now the person will be sick.  Normal function of their body and their activity will not be normal and special diets and medications will be required.  Soon after that, if the kidney function continues to deteriorate, the need for kidney transplant or chronic or artificial kidney treatments will be needed.

            In addition to getting rid of waste products and measuring how much of each waste product needs to be gotten rid of each day, the kidney also has hormonal functions to generate blood for the body and to control the blood pressure.    These functions become abnormal also as kidney tissue is damaged from disease states or loss of blood supply or blocking off the urine exit routes.

             In the past few years, it has become very apparent that chronic kidney failure is a marker for a number of other problems.  Heart disease and strokes and high blood pressure are all accompaniments with chronic kidney failure.  People that have heart disease and develop kidney problems have a much more unfavorable prognosis than those without kidney problems.  Thus it is critically important that kidney functions be protected as can be done.

            To protect your kidneys in the long run, it is important to monitor how well the kidneys are doing on a periodic basis.  This is especially true for people that have heart problems, diabetes, high blood pressure or prostate problems.  Some individuals have hereditary factors with familial kidney problems.  These people should be monitored very carefully.

            Fortunately, there are steps that can be taken to protect and preserve kidney function over the long run.  It is well worth the effort.  Even when end stage kidney failure finally occurs and the person needs a transplant or an artificial kidney treatment, there are steps that can be taken to restore a normal life.  Next week, I will describe a patient who received her kidney transplant in 1964 from her sister.  Forty-two years later, they are both alive and well.  They provide an interesting and inspirational story.