Lab 5: Biochemistry in renal disase (1) Flashcards
Consequences of renal disease (4)
- retention of waste products
- disorders in red cell production and vitamin D
- disorders in water balance/alterations in urine output
- disorders in electrolyte balance
What would presentation of renal disease depend on?
- cause
- glomerular/tubular dysfunction
- number of affected nephrons
What would the renal disease that affects glomerulus present with?
Glomerular renal disease:
A. Reduced filtration
- reduced urine volume (oliguria/anuria)
- increased plasma creatinine/urea
- hyperkalaemia
- hyperphosphataemia
- metabolic acidosis
B. Damage to golomerular membrane:
- proteinuria - large proteins
- haematuria
What would renal disease that affects tubules present with?
Tubular renal disease = reduced reabsorption:
- polyuria, low urine osmolarity -> kidney not able to reabsorb water
- metabolic acidosis -> kidney not able to reabsorb carbohydrate
- proteinuria -> molecules not being reabsorbed
- glycosuria
Hormonal changes related to late renal disease
- anaemia - due to decreased RBCs production
- hypocalcaemia - lack of active vitamin D (so reduced Ca++ reabsorption)
What’s uraemic syndrome ?
High level of waste product/ urea and creatinine
Symptoms of the uremic syndrome
Tests for glomerular function - what do we look at (in relation to kidney function)?
Test for glomerular function
- ability to remove waste products
- integrity of glomerular membrane and ability to prevent large particles entering the filtrate
Test for homronal function of the kidney - what do we look at (in terms of kidney function)?
- vitamin D
- erythropoietin
Test for tubular function of the kidney. What do we look at, in terms of functional kidney ability?
Tubular function:
- ability to adjust Na+/ K+, H+, water composition of a filtrate
- reabsorb small proteins, amino acids, glucose
What if GFR equivalent to?
GFR = clearance
Clearance = ability to remove waste products
What’s the clearance?
Clearance = ability to remove waste products
The volume of plasma that is filtered by the kidneys, and from which the substance is completely cleared per unit time
What are the criteria for an ideal marker for clearance = GFR?
No marker fulfils all these criteria
Formula for the clearance
Exogenous that can be used for assessment of GFR
Bolus injection - we time how long does it take to be cleared from the plasma
IV infusion -> and then we do clearance calculation
Urea use in the assessment of GFR
pros and cons
Creatinine use in assessment of GFR
pros and cons
Cystatin C as a marker used for GFR assessment
pros and cons
Cystatin C is not routinely used in GFR assessment
What’s needed to perform calculated GFR?
Clearance - blood and urine samples
(accurate 24 hour urine collection is needed)
How to collect 24 hr urine?
Day 1
- 8 am empty bladder (discard output)
- commence 24 hr urine collection
(all urine passed from now until 8 am next day must be collected in the container)
Day 2
- 8 am -> collect final urine output into the container
- collect blood sample with 24 hr period
Estimated (eGFR) vs calculated (GFR)
- Estimated - no need to do 24 hr urine collection (concentration of the plasma used as a marker)
- Calculated - 24 hr urine collection is needed
Formula used for calculations of eGFR
in adults
(although there are many other formulas that can be used)
Formula used for calculations of eGFR
in paediatrics
Tests/ Ix used for assessment of tubular function: the ability to excrete/retain water
- urine sodium, osmolarity and volume
compare with: serum sodium and osmolarity
Tests/ Ix used for assessment of tubular function: the ability to maintain acid-balance
- urine
- blood pH
- anion gap
- sodium bicarbonate
How to assess kidney ability to maintain electrolyte balance?
- serum sodium and potassium
- random urine sodium and potasium
How to assess kidney ability to reabsorb small proteins, amino acids and glucose?
- tubular proteinuria (different proteins/molecules)
- serum and urine amino acids
- urine glucose
Up to what glucose level would the glucose be reabsorbed by the kidney?
urine glucose -> renal threshold of 11 mmol/L
What do we measure (Ix) to check for the kidney ability to produce active vitamin D?
- serum adjusted calcium
- PTH
*if not enough vitamin D -> serum calcium will be low and PTH high (to keep calcium within normal range)
What do we measure (Ix) to check for the kidney ability to secrete erythropoietin?
- FBC -> look if there is any anaemia
- EPO
What criteria are there for a diagnosis of AKI?
Examples of pre-renal causes of AKI
Examples of intrinsic causes of AKI
Examples of post-renal causes of AKI
What (4) biochemical abnormalities does AKI present with?
- increased urea/creatinine
- hyponatraemia
- hyperkalaemia
- metabolic acidosis
Why hyperkalaemia is more dangerous in AKI than CKD?
A patient is used to high levels of potassium in CKD, whereas in AKI hyperkalaemia is rapid - body does not have time to get used to
What blood investigations do we do in AKI? (to identify the cause)
It’s more important to quickly identify a cause in AKI , so we can treat it quickly and prevent the progression of renal damage
What ‘imaging’ we do as Ix in cause of AKI?
It’s more important to quickly identify a cause in AKI , so we can treat it quickly and prevent the progression of renal damage
How to determine if it is pre-renal or intrinsic kidney injury?
Look at urea and creatinine
In pre- renal -> much higher increase in serum urea/creatinine
(because some urea is reabsorbed through tubule cells - so blood flow is slowed down, filter goes longer through the nephrone - more urea is reabsorbed)
