Role of kidneys in acid-base balance MCQs With Answer

Role of kidneys in acid-base balance MCQs With Answer

The kidneys play a central role in acid-base balance by reabsorbing filtered bicarbonate, generating new bicarbonate, and excreting acid as ammonium and titratable acids. For B.Pharm students, understanding renal regulation mechanisms, carbonic anhydrase function, tubular H+ secretion, ammoniagenesis, and renal tubular acidosis (RTA) is essential for pharmacotherapy and drug safety. Key terms include renal compensation, bicarbonate reclamation, distal and proximal tubular processes, aldosterone effects, and anion gap metabolic acidosis. This focused MCQ set reinforces physiology, pathophysiology, and drug interactions relevant to renal acid-base control. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. Which renal process is primarily responsible for reclaiming the majority of filtered bicarbonate?

• Distal tubule H+ secretion by alpha-intercalated cells
• Proximal tubule reabsorption via Na+/H+ exchanger and carbonic anhydrase
• Collecting duct ammonium excretion
• Loop of Henle passive bicarbonate diffusion

Correct Answer: Proximal tubule reabsorption via Na+/H+ exchanger and carbonic anhydrase

Q2. Which enzyme catalyzes the reversible hydration of CO2, facilitating bicarbonate reclamation in renal tubules?

• Adenylate cyclase
• Carbonic anhydrase
• Renin
• Glutaminase

Correct Answer: Carbonic anhydrase

Q3. Ammoniagenesis in the proximal tubule primarily uses which amino acid as substrate?

• Alanine
• Glutamine
• Glycine
• Leucine

Correct Answer: Glutamine

Strong note: ensure each question starts bold. Continue.

Q4. The major urinary form in which the kidney excretes acid generated from metabolism is:

• Free hydrogen ions (H+)
• Ammonium (NH4+)
• Sodium bicarbonate
• Chloride ions

Correct Answer: Ammonium (NH4+)

Q5. Titratable acidity in urine mainly reflects H+ buffered by which substance?

• Ammonia
• Phosphate
• Bicarbonate
• Sulfate

Correct Answer: Phosphate

Q6. In metabolic acidosis, renal compensation over days involves which change?

• Decreased ammoniagenesis
• Increased bicarbonate excretion
• Increased NH4+ excretion and new bicarbonate generation
• Immediate hyperventilation

Correct Answer: Increased NH4+ excretion and new bicarbonate generation

Q7. Which cell type in the collecting duct secretes H+ via H+-ATPase during acid secretion?

• Principal cells
• Alpha-intercalated cells
• Beta-intercalated cells
• Macula densa cells

Correct Answer: Alpha-intercalated cells

Q8. Beta-intercalated cells in the collecting duct are primarily involved in:

• Bicarbonate secretion into urine during alkalosis
• Ammonium production
• Water reabsorption via aquaporin-2
• Active sodium secretion

Correct Answer: Bicarbonate secretion into urine during alkalosis

Q9. Renal tubular acidosis (RTA) type 1 (distal) is characterized by:

• Impaired NH4+ production in proximal tubule
• Defective distal H+ secretion leading to urine pH >5.5
• Proximal bicarbonate wasting with low urine pH
• Hyperaldosteronism with hypokalemia and metabolic alkalosis

Correct Answer: Defective distal H+ secretion leading to urine pH >5.5

Q10. Which of the following drugs can cause proximal (type 2) RTA by inhibiting carbonic anhydrase?

• Spironolactone
• Acetazolamide
• Amiloride
• Furosemide

Correct Answer: Acetazolamide

Q11. The Henderson-Hasselbalch equation relates which two major components of acid-base balance?

• Sodium and potassium concentrations
• pH, bicarbonate (HCO3-) and partial pressure of CO2 (pCO2)
• Urine pH and urine bicarbonate
• Ammonium and phosphate concentrations

Correct Answer: pH, bicarbonate (HCO3-) and partial pressure of CO2 (pCO2)

Q12. The kidney’s response to chronic respiratory acidosis includes:

• Rapid decrease in bicarbonate generation
• Increased bicarbonate reabsorption and new bicarbonate generation
• No change because compensation is only respiratory
• Increased renal HCO3- excretion

Correct Answer: Increased bicarbonate reabsorption and new bicarbonate generation

Q13. An increased anion gap metabolic acidosis suggests accumulation of:

• HCO3-
• Unmeasured anions like lactate or ketoacids
• Chloride
• Albumin only

Correct Answer: Unmeasured anions like lactate or ketoacids

Q14. Urine anion gap (UAG) helps estimate renal NH4+ excretion. A strongly negative UAG indicates:

• Low NH4+ excretion (renal cause)
• High NH4+ excretion (extra-renal cause for acidosis)
• Hyperaldosteronism
• Diuretic use

Correct Answer: High NH4+ excretion (extra-renal cause for acidosis)

Q15. Which hormone increases H+ secretion by stimulating H+-ATPase and promotes potassium excretion, linking K+ and H+ handling?

• Aldosterone
• Antidiuretic hormone
• Thyroxine
• Parathyroid hormone

Correct Answer: Aldosterone

Q16. In hypokalemia, renal acid-base handling shifts leading to:

• Decreased ammoniagenesis and metabolic alkalosis
• Increased ammoniagenesis and metabolic acidosis
• Increased bicarbonate excretion causing acidosis
• No change in acid-base status

Correct Answer: Increased ammoniagenesis and metabolic alkalosis

Q17. Diuretics like loop and thiazides can cause metabolic alkalosis mainly by:

• Increasing renal HCO3- synthesis
• Promoting volume contraction and secondary aldosterone activation
• Inhibiting carbonic anhydrase in proximal tubule
• Blocking H+-ATPase in collecting duct

Correct Answer: Promoting volume contraction and secondary aldosterone activation

Q18. Which laboratory finding is most consistent with renal metabolic acidosis due to impaired NH4+ excretion?

• Low anion gap and negative urine anion gap
• Normal anion gap and positive urine anion gap
• High HCO3- and low pCO2
• Metabolic alkalosis and hypokalemia

Correct Answer: Normal anion gap and positive urine anion gap

Q19. Which drug class inhibits angiotensin II formation and can reduce proximal bicarbonate reabsorption indirectly?

• Beta blockers
• ACE inhibitors
• Calcium channel blockers
• Loop diuretics

Correct Answer: ACE inhibitors

Q20. Chronic kidney disease (CKD) often leads to metabolic acidosis because of:

• Excessive bicarbonate production
• Reduced ammoniagenesis and decreased acid excretion
• Increased distal H+ secretion
• Overactivity of carbonic anhydrase

Correct Answer: Reduced ammoniagenesis and decreased acid excretion

Q21. Which of the following best describes the kidney’s role in compensating for metabolic alkalosis?

• Increase NH4+ excretion and generate bicarbonate
• Decrease H+ secretion and increase bicarbonate excretion
• Increase proximal bicarbonate reabsorption
• Stimulate respiratory rate to retain CO2

Correct Answer: Decrease H+ secretion and increase bicarbonate excretion

Q22. A patient on spironolactone would be expected to have which effect on renal acid-base handling?

• Increased H+ secretion and metabolic alkalosis
• Decreased H+ secretion and tendency toward metabolic acidosis or hyperkalemia
• Inhibition of carbonic anhydrase and proximal RTA
• Increased ammoniagenesis

Correct Answer: Decreased H+ secretion and tendency toward metabolic acidosis or hyperkalemia

Q23. Which buffer system is most important for immediate defense against pH changes in renal tubular fluid?

• Protein buffers
• Phosphate buffer system
• Bicarbonate buffer system only in blood
• Hemoglobin buffer

Correct Answer: Phosphate buffer system

Q24. In metabolic acidosis, urinary pH is expected to be low. Which condition would instead produce an inappropriately high urine pH?

• Proximal RTA (type 2)
• Distal RTA (type 1)
• Excess dietary protein
• Respiratory alkalosis

Correct Answer: Distal RTA (type 1)

Q25. Which diagnostic test best distinguishes between renal and extra-renal causes of normal anion gap metabolic acidosis?

• Serum lactate level
• Urine anion gap
• Serum bicarbonate alone
• Arterial oxygen tension

Correct Answer: Urine anion gap

Q26. Carbonic anhydrase inhibitors cause bicarbonaturia by acting primarily on which nephron segment?

• Distal tubule
• Proximal tubule
• Collecting duct
• Loop of Henle

Correct Answer: Proximal tubule

Q27. Which change is characteristic of respiratory acidosis with renal compensation?

• Rapid decrease in bicarbonate within minutes
• Gradual increase in plasma bicarbonate over days
• Decreased urinary ammonium excretion
• Immediate increase in ventilation

Correct Answer: Gradual increase in plasma bicarbonate over days

Q28. The primary determinant of extracellular fluid pH is the ratio of:

• H+ to OH- concentrations
• HCO3- to pCO2
• Na+ to K+
• Cl- to HCO3-

Correct Answer: HCO3- to pCO2

Q29. Which of the following increases renal NH4+ trapping in the collecting duct?

• High urine pH
• Low urine pH due to H+ secretion
• Inhibition of carbonic anhydrase
• Administration of loop diuretics

Correct Answer: Low urine pH due to H+ secretion

Q30. Which electrolyte disturbance commonly accompanies distal RTA (type 1)?

• Hyperkalemia
• Hypokalemia
• Hypernatremia
• Hypercalcemia

Correct Answer: Hypokalemia

Q31. Which statement about renal handling of bicarbonate after a single dose of acetazolamide is true?

• It increases bicarbonate reabsorption
• It causes bicarbonate diuresis leading to metabolic acidosis
• It causes metabolic alkalosis chronically
• It increases distal H+ secretion

Correct Answer: It causes bicarbonate diuresis leading to metabolic acidosis

Q32. In evaluating metabolic acidosis, delta gap (∆AG/∆HCO3-) helps assess:

• Presence of mixed acid-base disorders
• Renal concentrating ability
• Degree of respiratory compensation
• Urinary phosphate excretion

Correct Answer: Presence of mixed acid-base disorders

Q33. Which of the following drugs can reduce ammoniagenesis and worsen acidosis in CKD?

• Loop diuretics
• ACE inhibitors
• Thiazide diuretics
• Carbonic anhydrase inhibitors

Correct Answer: ACE inhibitors

Q34. A patient with diabetic ketoacidosis has metabolic acidosis with an increased anion gap. Renal compensation will primarily involve:

• Immediate respiratory correction only
• Increased NH4+ excretion and new bicarbonate formation over days
• Decreased H+ secretion
• Increased urine bicarbonate loss

Correct Answer: Increased NH4+ excretion and new bicarbonate formation over days

Q35. Which renal transport defect underlies type 4 RTA?

• Defective proximal bicarbonate reclamation
• Aldosterone deficiency or resistance leading to impaired distal Na+ reabsorption and H+ secretion
• Defective HCO3- secretion by beta-intercalated cells
• Excess distal H+ secretion

Correct Answer: Aldosterone deficiency or resistance leading to impaired distal Na+ reabsorption and H+ secretion

Q36. In metabolic alkalosis due to vomiting, renal compensation is blunted when:

• There is contraction alkalosis with low aldosterone
• Hypokalemia is present causing sustained H+ secretion
• Kidney function is normal
• Urine chloride is high

Correct Answer: Hypokalemia is present causing sustained H+ secretion

Q37. Which parameter directly measures respiratory contribution to acid-base status?

• Serum bicarbonate
• Arterial pCO2
• Serum lactate
• Urinary ammonium

Correct Answer: Arterial pCO2

Q38. The term “new bicarbonate generation” by kidneys refers to:

• Reabsorption of filtered bicarbonate
• Synthesis of bicarbonate via metabolism of glutamine and excretion of NH4+
• Loss of bicarbonate in stool
• Respiratory compensation

Correct Answer: Synthesis of bicarbonate via metabolism of glutamine and excretion of NH4+

Q39. Which of the following increases renal HCO3- reclamation in the proximal tubule?

• Acidosis with upregulation of carbonic anhydrase and transporters
• Acetazolamide therapy
• Volume expansion with isotonic saline
• Alkalosis

Correct Answer: Acidosis with upregulation of carbonic anhydrase and transporters

Q40. Which urinary finding supports a diagnosis of distal RTA rather than proximal RTA?

• Low urinary bicarbonate excretion during systemic alkalemia
• Urine pH >5.5 despite systemic acidosis
• Massive bicarbonate wasting with urine pH <5.5
• Negative urine anion gap

Correct Answer: Urine pH >5.5 despite systemic acidosis

Q41. Which medication can cause type 4 RTA by inducing hyperkalemia?

• Spironolactone
• Acetazolamide
• Furosemide
• Hydrochlorothiazide

Correct Answer: Spironolactone

Q42. An elevated urine titratable acidity indicates:

• Increased H+ excretion buffered by urinary phosphate
• Decreased ability to excrete acid
• Primary respiratory alkalosis
• Impaired ammoniagenesis

Correct Answer: Increased H+ excretion buffered by urinary phosphate

Q43. Which scenario increases the anion gap?’

• Hyperchloremic metabolic acidosis from diarrhea
• Lactic acidosis from shock
• Respiratory alkalosis
• Volume contraction alkalosis

Correct Answer: Lactic acidosis from shock

Q44. Which transport mechanism facilitates H+ secretion in proximal tubule cells?

• Na+/K+ ATPase on apical membrane
• Na+/H+ exchanger (NHE3) on apical membrane
• ENaC on apical membrane
• HCO3-/Cl- exchanger on apical membrane

Correct Answer: Na+/H+ exchanger (NHE3) on apical membrane

Q45. Which of these laboratory patterns is typical of metabolic alkalosis with chloride depletion?

• Low urine chloride, high bicarbonate, hypokalemia
• High urine chloride, low bicarbonate, hyperkalemia
• Normal urine chloride, low sodium, hyponatremia
• High urine bicarbonate and hypernatremia

Correct Answer: Low urine chloride, high bicarbonate, hypokalemia

Q46. Which of the following increases renal acid excretion capacity chronically?

• Chronic metabolic alkalosis
• Chronic metabolic acidosis with upregulation of ammoniagenesis
• Acute respiratory acidosis
• High protein diet without renal adaptation

Correct Answer: Chronic metabolic acidosis with upregulation of ammoniagenesis

Q47. NSAIDs can affect renal acid-base balance by:

• Increasing ammoniagenesis
• Inhibiting prostaglandin synthesis, reducing renin and aldosterone, potentially causing hyperkalemia and type 4 RTA
• Stimulating carbonic anhydrase in proximal tubule
• Directly activating H+-ATPase in collecting duct

Correct Answer: Inhibiting prostaglandin synthesis, reducing renin and aldosterone, potentially causing hyperkalemia and type 4 RTA

Q48. In a patient with metabolic acidosis and normal anion gap, which cause is least likely?

• Diarrhea
• Renal tubular acidosis
• Uremia with decreased acid excretion
• Lactic acidosis

Correct Answer: Lactic acidosis

Q49. Which physiological change in the kidney facilitates increased H+ secretion during hypokalemia?

• Decreased H+-ATPase expression in intercalated cells
• Intracellular acidosis in tubular cells promoting NH4+ production
• Reduced ammoniagenesis
• Increased distal chloride delivery

Correct Answer: Intracellular acidosis in tubular cells promoting NH4+ production

Q50. For a B.Pharm student, understanding renal acid-base mechanisms is essential primarily because:

• It’s only important for diagnostic imaging
• Drugs can alter renal acid-base handling affecting efficacy and safety
• Kidneys do not significantly affect drug pharmacokinetics
• Only respiratory system manages acid-base balance

Correct Answer: Drugs can alter renal acid-base handling affecting efficacy and safety

G S Sachin

I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.

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