Mini-Med at McGill: Question and Answer Corner

Mini-Med Study Corner

PHYSIOLOGY: KEEPING OUR BODIES IN BALANCE
Sarah Prichard

Written Question and Answer Section:

1. What are the main causes of kidney failure?

In Canada the top 3 causes are Diabetes, Hypertension (high blood pressure) and other vascular disease and glomerulonephritis.

2. Why do we only transplant one kidney if we normally have two and both fail when kidney failure occurs?

Our 2 normal kidneys do more work that they really need to do to keep us healthy. To maintain normal salt and water balance for example, we only need about one third of our normal total kidney function. To keep ourselves completely free of waste products, we need most of our kidney function but we can remain healthy with a small increase in blood levels of these things e.g. creatinine (a waste product of muscle metabolism). In addition, in someone who has only one kidney, that single kidney compensates and does more work than normal. Thus we can safely donate one of our kidneys and a renal failure patient can be made healthy by receiving one kidney.

3. What are the consequences of having too much creatinine in our bodies? Does this happen and why?

Creatinine itself is not toxic but if its level is high in the blood that indicates that the kidneys are not functioning normally. The kidney excretes many other waste products too and if the kidneys are failing these more toxic substances accumulate and can make you sick. We talk about the creatinine in kidney failure because it is easy to measure in blood tests . The only time it rises significantly in blood is in kidney failure, but it can be modestly elevated in cases of muscle breakdown (such as a crush injury of a muscle) and in body builders who have a very large muscle mass.

4. How important is it to drink 8 glasses of water per day?

For the kidneys to function normally we simply need to be adequately hydrated but we do not need to be excessively hydrated. That is, we need to drink enough to stop ourselves from being thirsty. However, passing large amounts of water through the urinary tract may help to prevent bladder infections and helps prevent kidney stones.

5. When one is on dialysis, how often do they have it per week? Does dialysis cut down your life expectancy?

Hemodialysis is usually done 3 times per week for 4 hours each time. But some patients do it more often. Some patients do home peritoneal dialysis which involves putting fluids into the abdominal cavity as an alternative method. I refer you to the web site www.kidneydirections.com for further information on the various forms of dialysis. Dialysis patients tend to have a shortened life expectancy to normal.

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