Gettysburg Medical News
 The Clinical View
 by P.E. Hoffsten, MD
10 August 2005

WHAT IS KIDNEY FAILURE?

            The patient was 57 years old with a 25 year history of diabetes mellitus.  He used insulin but had never really paid attention to his blood pressure.  Unfortunately, his blood pressure had been high over the last 10-15 years and only modest gestures of control had been achieved.  Blood pressures were in the vicinity of 160-170/ 90-100 and he said that this was the blood pressure that he felt best at.  Unfortunately, diabetes and high blood pressure are the commonest cause of kidney failure in the United States today.

            A waste product in this gentleman’s blood called creatinine was being monitored.   A normal value of blood creatinine is 1 milligram %.  The kidney can be thought of as a large filter.  If a person loses 50% of their kidney filtering area, the value of the blood creatinine goes to 2 milligram %.  This is what would happen if a person were to donate a kidney for transplantation to a relative.  There is no detrimental effect of this loss of kidney filtering capacity. If they lose another 50% of what they have left, the blood creatinine goes to 4 milligram %.  This would be the same as losing half of the remaining kidney.  Now the person would feel some fatigue, loss of appetite, and meat just would not taste as good as it used to.  But the person would still be able to function relatively normal.  If the person were to lose 50% of the ¼ normal function they have left, creatinine raises to 8 milligram %.  It is at this point that most people would require artificial kidney treatment in order to stay alive and comfortable.

            The above gentleman’s creatinine had risen to 7 milligrams % 3 months ago and now was at 8.5 milligram %.  He was feeling more fatigued than usual.  His appetite was poor.  He was vomiting occasionally and he indicated that he could no longer function normally in his occupation as an executive for a local firm.  He said that he just couldn’t concentrate or keep ideas straight.

            It was explained to him that he had end stage kidney failure and was going to require artificial kidney treatments.  These are given 3 times a week for about four hours each.  There is some surgery necessary to prepare the person for kidney treatments.  The treatments are not painful but they are very time consuming and inconvenient.  Once started, the treatments are life long unless the person is lucky enough to receive a kidney transplant.

            As one might imagine, this was a surprise and an unexpected disappointment for him.  He was asking how this could happen.

            It was first explained to him that kidney failure is a lot like other medical conditions.  It happens slowly and is found suddenly.  It may seem that the problem has happened all of a sudden when really it has been developing over a long period of time.  Finally, the crunch point comes where symptoms begin to occur but unfortunately then it is too late to reverse the process.  By then the situation is rather like trying to unstrike a match.  The most important single step for any diabetic is to control their blood pressure at 120/80 or less and thereby prevent the slow progressive loss of kidney function.

            He volunteered that he was still urinating very frequently and said that he didn’t know how his kidneys could be failing when he seemed to pass so much urine.  He felt that his kidneys were working well.  It was explained to him that the most important waste product that the kidney excretes is water itself.  That ability to excrete water is guarded and maintained by the body as long as it can be done.  But while water excretion is maintained relatively well, other waste products that are toxic for the body buildup and cause the symptoms of fatigue and loss of appetite with nausea and vomiting.

            The gentleman wanted to know more about how the kidneys worked.  This is a very complex question. The kidney’s basic function is to filter the blood and remove the waste products that accumulate.  These waste products are concentrated by the kidney into a very small amount of urine and passed out through the bladder.  The gentleman had measured his urine output as part of several tests that were done in his evaluation and he knew that he was excreting about a quart and a half of urine per day.  He said that surely that was plenty of urine to get the waste the products out of his blood.  It was then explained to him that in the normal state, the kidneys filter about 150 quarts of blood per day.  They concentrate the waste products from 150 quarts of blood down into the quart and half of urine that he excretes.  As kidneys fail, they filter less blood until eventually they are only filtering 15 quarts of blood per day or less instead of 150.  The result is that the body accumulates 10 times a much waste product and these waste products make the person sick.  Through all of this, water balance can be maintained until very late in the course of kidney failure.

            There are steps to take to prevent kidney failure if it is detected early.  Control of blood pressure is the most important step.  In addition to that, the person’s diet can be modified so that the number of waste products generated is decreased.  Most of the kidneys waste products come from protein that is eaten but not needed.  A standard South Dakota steak is at least a pound.  In fact the body only needs a fourth of a pound of protein per day to maintain protein balance.  That other ¾ of a pound of beefsteak gets broken down and burned for energy but the waste products from breaking down protein are all excreted by the kidney.  Thus, a person with chronic kidney failure needs to cut back the amount of protein in their diet, something that is almost un-American to a South Dakota native.  In addition, virtually all of the salt that a person eats comes out in the urine.  A relatively small amount is excreted in perspiration and thus the amount of salt in a person’s diet needs to be cut back if they have kidney failure.  This is also true for potassium and phosphorus containing foods.

            Kidney failure is one of the strongest indicators that a person is going to have a stroke and heart attack.  The healthcare providers at your local clinics monitor kidney function on a routine basis especially in people that have high blood pressure or diabetes.  When the waste product called creatinine begins to increase in the blood, a new urgency and importance to address the blood pressure and diabetes becomes apparent.  The healthcare providers at your local clinics are well aware of these problems and can help in preventing kidney failure especially when it is detected early.