Renal - useful passmed facts

Question 1

Normal anion gap and what is the equation?

Answer 1

The anion gap is calculated by:

(sodium + potassium) - (bicarbonate + chloride)

A normal anion gap is 8-14 mmol/L

Question 2

Way to remember what the causes of raised and normal gap acidosis are

Answer 2

↑AG → when you have added some acid (lactate, ketones, urate, aspirin, methanol)
↔AG → ABCD: Addisons; Bicarb loss (GI, RTA); Chloride (e.g. saline); Drugs (acetazolamide)

high = stuff added (increased acid production or ingestion), low = stuff removed (decreased acid removal or loss of HCO3)

Question 3

Causes of raised anion gap metabolic acidosis MUDPILES

Answer 3

MUDPILES

Causes of raised anion gap metabolic acidosis:

Methanol
Uraemia
DKA (+ alcoholic ketoacidosis too)
Paracetamol/paraldehyde
Isoniazid
Lactate - shock, hypoxia
Ethanol/ethylene glycol
Salicylates

Question 4

Causes of normal anion gap acidosis

Answer 4

gastrointestinal bicarbonate loss: diarrhoea, ureterosigmoidostomy, fistula

renal tubular acidosis

drugs: e.g. acetazolamide

ammonium chloride injection

Addison’s disease

Question 5

When are hyaline casts seen in urine?

Answer 5

seen in normal urine

after exercise

during fever

with loop diuretics

Question 6

Which condition is raised urinary sodium seen in?

Answer 6

Occurs in Acute Tubular Necrosis

Question 7

Why are ACEi renoprotective in CKD?

Answer 7

‘ACE-is cause a significant, but predictable, drop in GFR by dilating the afferent arteriole. In CKD this reduces the Glomerular filtration pressure and therefore workload in the remaining nephrons, reducing the speed of decline in CKD. In AKI the glomerular filtration pressure and perfusion to the nephrons is probably already very low (that’s what caused the AKI), as such the additional drop caused by the ACE-i is not helpful, but harmful, as such, they should be TEMPORARILY stopped’

Question 8

What drug should all patients with CKD be started on?

Answer 8

All patients with chronic kidney disease should be started on a statin