Metabolic 2: Renal function tests Flashcards
describe the hierarchy of renal function tests from inaccurate to most accurate
s-Urea
24 h Creatinine Clearance
s-Creatinine
eGFR estimated from s-Creatinine
(EPI or MDRD or Cockcroft-Gault- formulas)
Direct GFR measurement used for research
what type of imbalance is there of K+ in DKA and why?
Decreased renal excretion
Shift of intracellular potassium
- due to insulin lack
- acidosis
- tissue catabolism
Total body potassium lower
how do you calculate the anion gap?
AG = (Na+ + K+)–(Cl– + HCO3–)
what should you review in an AKI?
Probably dehydrated – fluid saline Review drugs: ACEI/ARB, NSAID, Diuretics BP Monitor urine output Saline + insulin Monitor Na, K, HCO3, eGFR, glucose
what are some complications of an AKI?
Volume overload, raised K+, H+, PO4,
Initial assessment:
Volume status: possible dehydration
how is proteinuria identified?
Urine dipstick
Quantitative measurement of urine albumin excretion Usually as ACR: Albumin Creatinine Ratio
what is the major clinical manifestation of diabetic nephropathy?
Major clinical manifestation is albuminuria
what are the key factors of nephrotic syndrome?
Heavy albuminuria ACR >250 mg/mmol ACR > 70 mg/mmol = 1g protein/ 24h (protein excretion > 3.5g/24h) Low serum albumin < 30g/L Peripheral oedema Low oncotic pressure Kidney sodium retention Also frequently observed: Hyperlipidemia Thrombotic disease
explain the metabolism of protein and urea’s origin
Protein ∝ Amino acids ∝ Urea
Alanine Urea + Pruvate Aspatate Urea + Oxalo-acetate Glucose
explain the origin of creatinine
Muscle mass ∝ Creatine ∝ Creatinine
Creatine + ATP Creatine~P + ADP
Constant decay
Creatinine
List the different kidney stone types
Calcium oxalate - mc Calcium phosphate Uric acid Ammonium – infection Cysteine – inborn error Xanthine – very rare – inborn error
what causes calcium stones?
Calcium
Primary hyperparathyroidism
Renal tubular acidosis - distal
High sodium intake
what casues oxalate stones?
Low calcium/high oxalate diet
Low urine citrate
what causes uric acid stones?
- high purine diet
- Alcohol. Obesity, drugs
what investigations would you carry out for a kidney stone?
Fluid intake especially Hot environment
Radiology – residual stones, nephrocalcinosis
Urine culture
Urine pH
Serum sodium, potassium, chloride, bicarbonate, creatinine, calcium, albumin, phosphate, alkaline phosphatase, uric acid, vitamin D, PTH,
what is the treatment of RTA?
Rx: potassium citrate
correct acidosis, potassium
how is acid base balance maintained?
lungs via removal of CO2
kidneys via reabsoprtion of Hco3 and excretion of H+
what is the extracellular buffers?
bicarbonate and albumin
what are the intracellular buffers?
Hb and muscle protein
what is the main extracellular cation?
Na+
what is the main intracellular cation?
K+
what are the causes of met acidosis ?
increase H+ = ketoacidosis, lactic, ehtelyen glycol
Decreased excretion: RTA, kidney failure/ AKI
Bicarb loss = diarrhoea, RTA
hypercholremic acidosis
what causes a met acidosis with raised anion gap?
DKA
AKI
Lactic acidosis
what causes a met acidosis with normal anion gap?
RTA
GIT diarrhoea
Ureterostomy
what are the findings in vomiting
low Cl alkalosis with low K+ raised Cr high urine osmolality urea high due to dehydration
what causes a met alkalosis ?
loss of H+: vomiting, gastric aspiration
loss in the kidney: diuretics, Cushing’s, aldosteronism
whta causes resp acidosis
neuromuscular disease
resp depression
what causes a resp alkalosis
anaemia, hpyoxia, altitude, over ventilation such as emotional
what influences potassium levels?
AKI, Met acidosis, aldosterone,
what influences sodium levels?
water retention, AKI, polydipsia, high glucose (artefact), aldosterone
