20 MCQs on Renal Regulation of Electrolytes and Fluid Volume Control
Potassium Regulation MCQs
1. Which nephron segment is primarily responsible for potassium secretion?
- A) Proximal tubule
- B) Thin descending limb
- C) Thick ascending limb
- D) Distal convoluted tubule and collecting duct
- Answer: D) Distal convoluted tubule and collecting duct 1
2. Hypokalemia during continuous kidney replacement therapy (CKRT) is most effectively prevented by:
- A) Oral potassium supplements
- B) Using dialysate solutions with potassium concentration of 4 mEq/L
- C) Intravenous potassium supplementation
- D) Reducing dialysis time
- Answer: B) Using dialysate solutions with potassium concentration of 4 mEq/L 1
3. Which of the following is the major intracellular cation?
- A) Sodium
- B) Potassium
- C) Calcium
- D) Magnesium
- Answer: B) Potassium 1
4. The Na/K-ATPase activity that maintains intracellular potassium concentration can be impaired by:
- A) Excess dietary potassium
- B) Insufficient supplies of oxygen and energy
- C) Hyperkalemia
- D) Increased aldosterone
- Answer: B) Insufficient supplies of oxygen and energy 1
Calcium Regulation MCQs
5. What percentage of filtered calcium is reabsorbed in the proximal tubules?
- A) 20%
- B) 40%
- C) 60%
- D) 80%
- Answer: C) 60% 2
6. Which protein in the thick ascending limb is responsible for paracellular calcium reabsorption?
- A) TRPV5
- B) Calbindin-D28K
- C) Paracellin-1 (claudin-16)
- D) Calcium sensing receptor (CaSR)
- Answer: C) Paracellin-1 (claudin-16) 2
7. In the distal convoluted tubule, which protein serves as the main portal of entry for calcium reabsorption?
- A) NCX1
- B) TRPV5
- C) Plasma membrane Ca²⁺-ATPase
- D) Calbindin-D28K
- Answer: B) TRPV5 2
8. What is the normal plasma calcium concentration range?
- A) 6.5-8.5 mg/dL
- B) 8.5-10.5 mg/dL
- C) 10.5-12.5 mg/dL
- D) 12.5-14.5 mg/dL
- Answer: B) 8.5-10.5 mg/dL 2
Phosphate Regulation MCQs
9. What is the target serum phosphate level that should be maintained in acutely ill patients?
- A) >0.61 mmol/L
- B) >0.71 mmol/L
- C) >0.81 mmol/L
- D) >0.91 mmol/L
- Answer: C) >0.81 mmol/L 3
10. In patients with hypophosphatemia receiving continuous kidney replacement therapy, the preferred approach is:
- A) Intravenous phosphate supplementation
- B) Oral phosphate supplements
- C) Using dialysis solutions containing phosphate
- D) Reducing dialysis time
- Answer: C) Using dialysis solutions containing phosphate 3, 1
11. Phosphate deficiency can lead to:
- A) Decreased urinary magnesium excretion
- B) Increased urinary magnesium and calcium excretion
- C) Decreased urinary calcium excretion
- D) No effect on other electrolyte excretion
- Answer: B) Increased urinary magnesium and calcium excretion 4
12. In the theoretical model for phosphorus requirements in parenteral nutrition, which formula is used?
- A) P requirement = [calcium deposition/1.67] + [protein accretion*0.33]
- B) P requirement = [calcium deposition1.67] + [protein accretion0.33]
- C) P requirement = [calcium deposition/1.67] - [protein accretion*0.33]
- D) P requirement = [calcium deposition1.67] - [protein accretion0.33]
- Answer: A) P requirement = [calcium deposition/1.67] + [protein accretion*0.33] 1
Magnesium Regulation MCQs
13. What percentage of filtered magnesium is reabsorbed in the thick ascending limb of the loop of Henle?
- A) 20-30%
- B) 30-40%
- C) 50-60%
- D) 70-80%
- Answer: C) 50-60% 5
14. The target serum magnesium concentration that should be maintained in acutely ill patients is:
- A) ≥0.50 mmol/L
- B) ≥0.60 mmol/L
- C) ≥0.70 mmol/L
- D) ≥0.80 mmol/L
- Answer: C) ≥0.70 mmol/L 3
15. Which of the following increases the risk of hypomagnesemia during continuous kidney replacement therapy?
- A) Using high magnesium concentration dialysate
- B) Regional citrate anticoagulation
- C) Reducing dialysis time
- D) Using phosphate-containing solutions
- Answer: B) Regional citrate anticoagulation 3, 1
16. Magnesium reabsorption in the ascending limb of the loop of Henle is primarily:
- A) Active and transcellular
- B) Passive and paracellular
- C) Active and paracellular
- D) Passive and transcellular
- Answer: B) Passive and paracellular 6
Integration of Renal Mechanisms for Blood Volume and ECF Volume Control MCQs
17. Which of the following is NOT a strategy to manage hypertension in hemodialysis patients?
- A) Probing the prescribed target weight
- B) Increasing treatment time and/or frequency
- C) Decreasing interdialytic weight gain
- D) Increasing sodium intake
- Answer: D) Increasing sodium intake 1
18. In peritoneal dialysis patients, which of the following strategies can help maximize ultrafiltration for long dwells?
- A) Using lower tonicity glucose-based solutions
- B) Using icodextrin for long dwells
- C) Increasing dietary salt
- D) Avoiding diuretics in those with residual kidney function
- Answer: B) Using icodextrin for long dwells 1
19. The "strong ion difference" (SID) is an important concept in acid-base balance that involves which primary ions?
- A) Potassium and magnesium
- B) Calcium and phosphate
- C) Sodium and chloride
- D) Bicarbonate and hydrogen
- Answer: C) Sodium and chloride 1
20. In patients at risk of increased endogenous secretion of ADH, maintenance fluid therapy volume should be restricted to what percentage of the volume calculated by the Holliday and Segar formula?
- A) 40-55%
- B) 55-65%
- C) 65-80%
- D) 80-95%
- Answer: C) 65-80% 1