Renal

Question 1

Causes of type 2 RTA

Answer 1

= Defects in bicarb absorption
Tubular dysfunction such as Falconi syndrome: glycosuria, phosphaturia, aminoaciduria, hypouricemia, monoclonal gammopathies

Question 2

Type 2 RTA urine pH and ammonia

Answer 2

pH <5.5, ammonia normal (negative anion gap)

Question 3

Type 2 RTA serum bicarb and postassium

Answer 3

Hypokalaemia (bicarb + Na travel to distal tubule where Na is resorbed in exchange for K+), serum bicarb stabilises at 12-14

Question 4

Type 2 RTA treatment

Answer 4

**harder to treat, alkali replacement + thiazide diuretic (risk of alkali diuresis)

Question 5

Causes of type 1 RTA

Answer 5

= defects in hydrogen excretion
Sjogren syndrome, rheumatoid arthritis, tubulointerstitial disease (reflux uropathy, obstructive uropathy), medications (amphotericin B, lithium), dysproteinemias, Wilson’s disease, sickle cell disease, hypercalciuria

Question 6

Type 1 RTA urine pH, Ca, ammonia

Answer 6

pH >5.5, low urine ammonium -> urine anion gap positive, hypercalciuria (due to increased release of calcium and phosphate from bone to buffer of acid)

Question 7

Type 1 RTA serum bicarb, K+ and Phos

Answer 7

Normal anion gap metabolic acidosis with bicarb <10, hypokalaemia secondary to urine K+ wasting, hyperphosphatemia

Question 8

Type 1 RTA complications

Answer 8

Calcium phosphate stones (due to hypercalcemia and hypocitraturia - citrates usually form a soluble compound with calcium), nephrocalcinosis

Question 9

Type 1 RTA management

Answer 9

Bicarb tablets

Question 10

Type 4 RTA causes

Answer 10

= aldosterone deficiency or resistance

• Aldosterone deficiency: Addison’s disease, hyporeninemic hypoaldosteronism such as in diabetic nephropathy
• Aldosterone resistance: tubulointerstitial disease such as urinary obstruction, sickle cell disease, medullary cystic kidney disease, kidney transplant rejection
• Drug induced: ACEi, ARBs, heparin, COX2, calcineurin inhibitors

Question 11

Type 4 RTA urine pH, ammonia

Answer 11

pH <5.5, positive anion gap

Question 12

Type 4 RTA serum pH, K+

Answer 12

Hyperkalaemia, mild normal anion gap metabolic acidosis

Question 13

Type 4 RTA complications

Answer 13

Hypertension, fluid overload

Question 14

Type 4 RTA treatment

Answer 14

Fix underlying cause, thiazide or loop diuretics, fludrocortisones

Question 15

Indications for renal biopsy

Answer 15

Most important: active urinary sediment, heavy proteinuria, increasing serum creatinine with unclear aetiology
Other: exclude dual pathology, confirm diagnosis / prognosis / response to treatment

Question 16

What medications cause non-progressive raised creatinine

Answer 16

cimetidine, trimethroprim, cobistat, dolutegravir, bictegravir, rilpivirine