Renal excretory function

Question 1

How is GFR calculated?

Answer 1

([urine]/[plasma]) x flow/volume per minute of urine

Question 2

What is the MDRD equation? What is required in order to calculate the value?

Answer 2

• estimation of GFR
• requirements:
  1. creatinine
  2. age
  3. gender
  4. ethnicity

Question 3

In which situations would eGFR under/overestimate true GFR?

Answer 3

Underestimates:
- muscular individuals - will have a naturally higher serum creatinine

Overestimates:
- malnourished individuals have reduced serum creatinin

Question 4

What condition arises from a defect in the apical Na/cysteine co-transporter in the proximal tubule?

Answer 4

Cystinuria (autosomal recessive condition)

Question 5

What condition arises from a defect in the apical Na/glucose co-transporter in the proximal tubule?

Answer 5

Renal glycosuria

Question 6

What condition arises from a defect in the basolateral Na/HCO3- co-transporter in the proximal tubule?

Answer 6

Proximal renal tubular acidosis –> type 2 RTA = Fanconi syndrome

Question 7

What condition arises from a defect in the apical Na+/K+/2Cl- co-transporter in the loop of Henlé?

Answer 7

Type 1 Bartter syndrome

• mimics the effects of frusemide
• results in hypokalaemia, metabolic acidosis, hypocalcaemia, hypomagnesaemia

Question 8

What condition arises from a defect in the apical Na+/Cl- co-transporter in the distal tubule?

Answer 8

Gitelmann’s syndrome

• mimics effects of thiazide use
• results in hypokalaemia, metabolic alkalosis, hypomagnesaemia, hypercalcaemia

Question 9

What transporter/cotransporter is inhibited by loop diuretics?

Answer 9

Na+/K+/2Cl- cotransporter

Question 10

What transporter/cotransporter is inhibited by thiazide-like diuretics?

Answer 10

Na+/Cl- cotransporter

Question 11

What is the result of a deficit of ADH secretion?

Answer 11

Copious dilute urine –> occur in diabetes insipidus