When normal kidneys fail
Dialysis compared with normal kidneys
Many think that dialysis duplicates or approaches normal kidney function and that, once dialysis starts, normal or near-normal kidney function is returned.
Sadly, this is not so …
Dialysis does a good job but …
Current dialysis falls far, far short of ‘optimum’ kidney function
The following comparisons may surprise you, but they are true:
CKD (pre-dialysis) ~8 ml/min
4x3 HD (mean Kt/V = 1.3, 3 times/wk) = 13 ml/min
NHHD 6/wk (Qd = 300ml/min) = 50 ml/min
2 normal kidneys = 100ml/min
As you can see, even ‘optimal’ dialysis falls far short of two normal kidneys.
So …
What makes normal kidneys so much better?
What is normal kidney function?
What do normal kidneys do?
Knowing the answers to these questions will help you to better understand
How dialysis works
And …
How the various ‘dialysis options’ might differ
Normal kidneys work solidly and consistently, 24 hrs/day, 7 days/week.
The way normal kidneys work is well shown at:
Yet …
When people with chronic kidney failure start dialysis, dialysis is most commonly prescribed for just 12 hrs/week
For the other 156 hours of the week, it’s …
…..……..‘Sorry, but we’re out to lunch’!!
Normal kidneys
What then do normal kidneys do? They …
Work non-stop 24 hrs/day, 7 days/wk.
Work consistently and relentlessly
Have an extraordinary workload and …
Do so much more than most people know
Without kidney function, there is no survival … unless either dialysis or transplantation is undertaken
The anatomy and structure of the normal kidney is well described at
http://www.mythos.com/webmd/Content.aspx?P=KIDNEY
The functions of the normal kidney are well described at
http://vanderbiltowc.wellsource.com/dh/content.asp?ID=1077
Normal kidneys do many wonderful things. They:
Control the excretion of chemical wastes
Regulate body salt and body fluid
Control the volume of both the blood and tissue fluids
Control the blood pressure through renin and aldosterone production
Produce erythropoeitin and activate vitamin D from its inactive form
Control blood and bone calcium and phosphate levels
Regulate bone strength through controlling vitamin D
Control red blood cell production through erythropoeitin
Chronic kidney failure
Occurs when:
The anatomy and structure is damaged/lost
All or most of the normal functions are lost
When kidneys fail
The following two tables first compare normal kidneys to kidney failure then show the symptoms that result from kidney failure.
Read the left side of each table and compare with the right side.
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Normal Function
Excrete chemical wastes Regulate body salt and body fluid Control blood pressure Control body calcium and phosphate and regulate bone strength through vitamin D Control red blood cell production through erythropoeitin
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Kidney failure
Wastes build up and ‘poison’ the body Fluid retention occurs in the ankles and lungs Blood pressure rises Bone strength is slowly lost and blood vessels are damaged by calcium deposits Blood production falls, anaemia develops with less oxygen transport
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→ → |
→ |
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Kidney failure
Wastes build up and ‘poison’ the body Fluid retention occurs in the ankles and lungs Blood pressure rises Bone strength is slowly lost and blood vessels are damaged by calcium deposits Blood production falls, anaemia develops with less oxygen transport
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Symptoms
Cramps, itch, mental slowness, irritability Swollen legs and shortness of breath Headaches, dizziness Bone aches and pains and deteriorating blood circulation to the feet, legs and heart Shortness of breath, angina (chest pains), lethargy and fatigue
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How dialysis works
It may be useful to understand how dialysis works and I strongly recommend this easy guide to understanding dialysis …
Authored by A/Prof John Agar. Copyright © 2010
Nocturnal Haemodialysis Program
All rights reserved. Revised: March 14th 2010