Metabolic 2: Renal function tests, acid base & metabolism & renal stones Flashcards
Glomerular filtration rate
Most frequent test of kidney function
Based on serum-creatinine
- poor sensitivity for minor kidney damage
- starts to rise: 50% glomeruli lost
- marker of progressive kidney damage
Hyperkalaemia
Decreased renal excretion
Shift of intracellular potassium
- due to lack of insulin
- acidosis
- tissue catabolism
Total body potassium lower
Potassium influences
Decreased renal excretion
Re-distribution
- metabolic acidosis
- extracellular H+ exchanged for intracellular K+
- tissue catabolism
Serum K+ is high but total body K+ is low
Anion gap
(Na+ + K+) - (Cl- + HCO3-)
Consider unmeasured anions
- ketones
- lactate
- ethylene glycol
- salicylate
Sodium influences
Water retention
- acute kidney injury
Excessive water intake
- polydipsia
Artefactual
- high glucose
Artefact: high glucose
AKI
Urgent patient review
GFR maybe compromised: low BP, shock
- decreased blood flow to kidneys
Consider
- obstruction, hydration, infection
- drugs: ACEi/ARBs, NSAIDs, diuretics
Waste products accumulate: creatinine, urea, acid
Complications of AKI
Volume overload, raised K+, H+, PO4
Initial assessment
- volume status: possible dehydration, CHF
- s-K, HCO3, PO4, calcium, albumin
- s-uric acid, magnesium
- FBC
Glomerular disease manifestation
- asymptomatic urinary abnormalities
- acute kidney injury
- end stage kidney disease
Glomerular disease
Glomerular basement membrane
Barrier to the passage of macromolecules
- both size and charge selective
Clinical manifestations
- hematuria and/or albuminuria/proteinuria
- kidney insufficiency
- hypertension
- oedema
Albuminuria- proteinuria
Change in clinical use from proteinuria to albuminuria
Urine albumin measurements improved
Urine protein measurements more variable
Urine dipstick
Diabetic nephropathy- albuminuria
Major clinical manifestation is albuminuria
- predicts high risk for future nephropathy
Diabetic microvascular disease
- nephropathy, retinopathy, neuropathy
Risk factors: hypertension etc
Nephrotic syndrome
Urine albumin loss
- low serum albumin
Low oncotic pressure stimulates
- liver albumin synthesis
- also lipoprotein synthesis
- hypercholesterolaemia and hypertriglyceridaemia
Creatine kinase
Levels related to muscle mass
Women < men
Children < adults
Black africans greater muscle mass
After physical exertion
- increase: slight- moderate
- if raised, repeat after 3 days with no exertion
DKA, low eGFR, AKI
Probably dehydrated- fluid saline
Review drugs: ACEi/ARBs, NSAIDs, diuretics
BP
Monitor urine output
Saline and insulin
Monitor Na, K, HCO3, eGFR, glucose
Types of kidney stones
80% are composed of calcium salts
Calcium oxalate
Calcium phosphate
Uric acid
Ammonium- infection
Cysteine- inborn error
Xanthine- very rare- inborn error
