Friday, February 15, 2013

The aging kidney starts sooner than you may think

I was reviewing medical articles this morning and noticed that metformin , this very old medication , is mention in a new medical article almost daily. Today I noticed an article on the controversial risk of lactic acidosis and metformin use in " older " people.  I believe it was 1968 with a drug in the same family as metformin was taken off of the market because of it's association with lactic acidosis. Metformin was approved for the treatment of Type 2 diabetes but has alway had the cloud of lactic acidosis in its family pedigree. This risk is increased in people with liver  or kidney problems.

 Most doctors are concerned about starting metformin in " older people " because of the known deterioration of kidney function with increasing age.

 Another problem of getting older is the loss of muscle mass complicating the interpretation of a commonly used test, Creatinine. The test result will  be lower and and becomes a less accurate test of kidney function as we age.

 This leads to todays topic , the effects of age on kidney function.

Aging Kidneys
A good discussion of the aging kidney was discussed in an article published in ;
Clinical Geriatric Medicine 2009August;25 (3) : 331-358
Acute Kidney Injury in the Elderly

The bad news
Our kidneys lose mass , get smaller and lose function with increasing age
 *  Kidney mass can decrease by 75 to 80 % by age 80 to 90
 *  A reduction in blood  flow to the kidneys of up to 50% can occur from age 20 to age 80
 *  Decreased function of our kidney can be observed by age 30 resulting in increased problems
     handling salt and water.

A word of caution
  Medication dose adjustment may be needed as we get older.

The good news
 Despite all of the above , "the kidneys of healthy elderly people are able to compensate  and maintain homeostasis under normal conditions". Also 30 % of people do not demonstrate the age related decrease in function.

Have Fun , Be Smart and take care of your body and it will take care of you
David Calder,MD


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Your comments and questions are appreciated. David Calder,MD