Urea and Electrolytes

Question 1

when is urea raised

Answer 1

dehydration, gi bleed, increased protein breakdown (surgery, trauma infection, malignancy), high protein intake, drugs

Question 2

when is urea decreased

Answer 2

in malnutrtion, liver disease and pregnancy

Question 3

acute kidney injury diagnosis definition

Answer 3

a rise in serum creatinine >50% from baseline or urine output <0.5ml/kg/h for 6 hrs (oliguria)

Question 4

what is creatinine blood conc specific for

Answer 4

determining kidney injury

Question 5

pre renal causes of AKI

Answer 5

causes of reduced renal perfusion –> hypovolaemia, haemorrhage, sepsis, renovascular disease

Question 6

intrinsic causes of AKI

Answer 6

acute tubular necrosis (ATN)(ischaemic or nephrotoxic), acute interstitial nephritis, acute glomerulonephritis

Question 7

post renal causes of AKI

Answer 7

urinary tract obstruction (stones, stricture, prostate, tumour, blood clot)

Question 8

how to investigate pre renal causes of AKI

Answer 8

fluid volume assessment

renal artery doppler (if suspected renovascular disease)

Question 9

how to investigate intrinsic renal failure

Answer 9

urine dipstick –> will show haematuria and proteinuria in glomerulonephritis
in acute tubular necrosis –> urine is usually bland/
urine protein-creatinine ratio to quantify and monitor proteinuria

Question 10

when is a renal biopsy done

Answer 10

if unexplained AKI, glomerulonephritis is suspected, positive nephritis screen, persistent ATN

Question 11

how to investigate post renal failure

Answer 11

renal tract ultrasound –> will show dilated renal calcyces

Question 12

chronic kidney disease definition

Answer 12

presence of marker of kidney damage (proteinuria) or GFR less than 60ml/min for >3 months

Question 13

most common causes of CKD

Answer 13

diabetes (secondary to glomerular disease),
chronic hypertension,
chronic glomerulonephritis diseases (vasculitides)
others - drugs, PKD

Question 14

when to dialyse (AEIOU)

Answer 14

Acidosis
Electrolyte abnormalities - hyper- kalaemia, atraemia and calcaemia 
Intoxicants (methanol, lithium)
Overload - acute pulm oedema
Uraemia

Question 15

when is regular dialysis required in chronic renal failure

Answer 15

when GFR is <15ml/min

Question 16

causes of hypovolaemic hyponatremia (sodium lost so water follows)

Answer 16

if urinary Na+ >30 –> sodium is lost from kidneys = diuretics, addisons disease, kidney injury or osmotic diuresis
if urinary Na+ is <30 –> sodium lost elsewhere = diarrhoea/vomitting, fistula, burns

Question 17

causes of euvolaemic hyponatremia (water is gained so it dilutes blood)

Answer 17

if urinary Na+ >30 AND urinary osm >100 –> from kidneys = SIADH, hypothyroidism, glucocorticoid insufficiency
if urinary Na+<30 or urinary osm<100 –> from elsewhere = drank too much water

Question 18

causes of oedematous hyponatraemia

Answer 18

low Na+ is caused by excess ADH release secondary to intravascular fluid depletion (due to extravasation). = congestive heart failure, hypoalbuminaemia (nephrotic syn or cirrhosis)

Question 19

causes of normovolaemic hypernatraemia

Answer 19

iatrogenic - excess IV crystalloids, sodium containing drugs

Question 20

causes of hypovolaemic hypernatraemia

Answer 20

producing small vols of conc urine –> fluid loss (diarrhoea/vom, burns)
not producing small vols of conc urine (abnormal response) –> diabetes insipidus or osmotic diuresis (DKA)

Question 21

causes of hypokalaemia (3 mechanisms)

Answer 21

increased renal excretion, increased cellular intake, other K+ loss (diarrhoea/vom)

Question 22

why would the kidneys excrete more K+

Answer 22

diuretics, endocrine (steroids, Cushings disease, Conns syndrome), renal tubular acidosis, hypomagnesaemia

Question 23

why would there be increased K+ cellular intake

Answer 23

salbutamol, insulin, alkalosis

Question 24

causes of hyperkalaemia (3 mechanisms)

Answer 24

reduced renal excretion, excess K+ load or increased cellular release

Question 25

why would there be reduced renal excretion of K+

Answer 25

acute/chronic kidney injury, drugs (potassium sparing diuretics, acei, nsaids), addisons disease

Question 26

why would there be excess K+ load

Answer 26

iatrogenic, massive blood transfusion

Question 27

why would there be increased extracellular release of K+

Answer 27

acidosis, tissue breakdown (rhabdomyolysis, haemolysis)

Question 28

causes of hypocalcaemia (3 mechanisms)

Answer 28

increased renal excretion, PTH related, increased depostion/reduced uptake

Question 29

causes of increased renal excretion of calcium

Answer 29

drugs (loop diuretics), chronic kidney disease, rhabdomyolysis/tumour

Question 30

causes of pth related hypocalcaemia

Answer 30

hypoparathyroidism, hypomagnesaemia, psuedohypoparathyroidism, cincalcet

Question 31

causes of increased depostion/reduced uptake of calcium

Answer 31

bisphosphonates and vit d deficicnecy

Question 32

causes of hypercalcaemia (4 mechanisms)

Answer 32

decreased renal excretion, increased release from bones excess pth, excess vit d intake

Question 33

causes of decreased renal excretion of calcium

Answer 33

drugs -thiazide diuretics

Question 34

causes of increased release of calcium from bone

Answer 34

bone metastasis (increased ALP), myeloma (normal ALP), sarcoidosis, thyrotoxicosis

Question 35

causes of excess pth that causes hypercalcaemia

Answer 35

primary or tertiary hyperparathyroidism,

Question 36

causes of hypomagnesemia

Answer 36

excess loss - diuretics, severe diarrhoea, DKA
poor nutrition/alcoholism
most is in bone so tends to reduce if Ca or K are low

Question 37

causes of hypophosphatemia

Answer 37

vit d deficiency, refeeding syndrome, primary hyperparathyroidism, poor nutrition/alcoholism