Kidney failure and replacement Flashcards
What are the 4 main functions of the kidneys?
Regulating fluid compartment volumes (ECF, ICF, Na+ and H2O)
Electrolyte balance (K+ and pH)
Excretion of metabolic wastes (urea and loads of others)
Hormones (EPO and vit D)
What are the 4 different consequences of kidney failure?
Oedema (fluid compartment volumes)
Hyperkalaemia (electrolyte balance)
Vomiting and drowsiness (excretion of metabolic wastes)
Anaemia and bone weakness (hormones)
What is the main measure of kidney function?
Glomerular filtration rate (GFR)- amount of filtrate produced by kidneys
What is normal GFR?
90-120ml/min
How do you determine GFR?
Creatinine
What is creatinine?
Small molecule so it filters very easily so the amount that is in the filtrate is the same as the amount of creatinine in the blood and isn’t reabsorbed so creatinine clearance rate isn’t similar to GFR
What are benefits of creatinine?
It is cheap and widely available
What is inulin used for?
A method of accurately measuring GFR
Why is the normal range for the relationship between creatinine and GFR not a good concept?
The relationship between the two is non-linear so you can lose a lot of kidney function (go from GFR of 120 to 60) without much of a change in serum creatinine so not sensitive to early changes in kidney function
Also lots of other factors affect creatinine clearance- age, ethnicity and muscle mass
What are the two main formulae used to interpret changes in serum creatinine?
Cockcroft-Gault
MDRD
These adjust the measurement of GFR based on other factors (gender, weight and race)
What symptoms occur with gradually decreasing kidney function?
Fluid retention (first to happen)
Anaemia and bone disease
Electrolyte abnormalities
Uraemia
What are the differences between acute and chronic renal failure?
Acute: Hyperkalaemia and vomiting/drowsiness
Chronic: Oedema and anaemia/bone weakness
What are the three different types of renal failure?
Pre-renal
Renal
Post-renal
What causes pre-renal failure?
Associated with diseases where the perfusion through the kindest is low. Causes include hypovolaemia and heart failure
What are the features of pre-renal failure?
Usually obvious why they’ve got it
Always oliguric
What are the causes of intrinsic renal failure?
Acute tubular necrosis- usually gets better by itself
Nephritis
Chronic renal failure
What are the two main groups of ATN?
Ischaemic and toxic
What does ATN often result from?
ATN often results from a pre-renal or post-renal kind of renal failure- so once you’ve corrected the problem, it may take time to get better because ATN has to resolve
What is important about nephritis?
There is a type of intrinsic renal failure that doesn’t get better by itself