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
