Renal and acid-base disorders Flashcards
What do the kidneys produce that regulate blood cell count?
Erythropoeitin
What do the kidneys produce that affects Vit D synthesis?
1 alphahydroxylase (activates VitD)
How can kidney function be known?
How much fluid is being filtered? (GFR i.e how much fluid is it filtering per minute)
How leaky is the kidney?
How good is the kidney at clearing waste
How is GFR assessed?
Creatinine
What is the limitations of using creatinine clearance for understanding renal function?
It can not detect rapid, acute, injury to the kidney because creatinine levels take time to reflect changes in overall state of the kidneys.
Someone who has more muscle will produce more creatinine and elderly have higher creatinine clearance than younger people.
What are the 3 main functions of the kidney?
Excretory
Regulatory
Endocrine
What is GFR?
Amount of blood cleared through kidney per minute and this cna only be done through the kidney.
Formula for renal clearance
C = UV/P
C = clearance U = Urine concentration (mmol/L) V = Urine volume flow rate (ml/min) P = Plasma concentration (mmol/L)
How can GFR be estimated?
Creatinine
What affects renal clearance of creatinine clearance? How can this knowledge be used?
Meat intake
Muscle mass
Some drugs
(Muscle breakdown elevates creatinine levels)
Instead of looking at standard levels finding history of creatine level changes within a single individual is a good way of measuring its changes.
What is being done to measure changes in eGFR more accurately?
What are the limitation?
Being standardised for age, race, and sex.
Routinely reported with creatinine which is unreliable for short term changes.
Not reliable for extremes of body size/age or acute kidney to injury
Not validated in children or pregenancy
What is the Cockroft and Gault Creatinine Clearance?
A way to estimate GFR. 1.23(140-age) x Mass (kg) / pCreatining(umol/L)
In females x1.04
What is the Cockroft and Gault Creatine Clearance formula used for?
Drug dosing
What is Cr Clearance formula?
Cr Cl (ml/min/1.73m2) = U Cr x u Vol x 1.73 /P Cr x T x BSA
Creatine Clearance
Corrected for surface area (height and weight)
Reference intervals based on plasma and urine samples which makes it inaccurate due to inaccurate timing on samples.
What is the problem with using urea to estimate GFR?
Rate of production is not constant; 40 - 50% of urea is reabsorbed which makes it less useful as a measurement.
It is affected by Volume status/hydration protein intake tissue breakdown steroids GI haemorrhage Liver disease
How can tubular function be tested?
Blood gas
Plasma U + E’s
Urine volume
Urine pH, anion gap, Na, Cl, HCO3, aminoacids
How much protein gets into urine each day?
Normally only a small amount of protein gets into the urine (20 - 150mgs/day) This is predominantly albumin.
What are the mechanisms of proteinuria?
Glomerular
Tubular
Overflow (lots in the blood emptying into urine)
Benign
What happens to urine when it is high in protein?
Becomes frothy and bubbly
What is the cause of glomerular proteinuria?
Glomerulonephritis
Diabetes
What happens during glomerular proteinuria?
Loss of large proteins of increasing molecular weight starting with albumin.