Question 1

 

Which acid–base abnormality is characteristic of renal tubular acidosis?

 

A. High anion gap metabolic acidosis

B. Normal anion gap metabolic acidosis

C. Metabolic alkalosis

D. Respiratory acidosis

E. Respiratory alkalosis

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Question 2

Which nephron segment is primarily affected in distal (Type 1) RTA?

 

A. Proximal tubule

B. Loop of Henle

C. Distal tubule/collecting duct

D. Glomerulus

E. Macula densa

 

Question 3

Which electrolyte abnormality is most commonly seen in Type 4 RTA?

 

A. Hypokalemia

B. Hyperkalemia

C. Hypernatremia

D. Hypocalcemia

E. Hypermagnesemia

 

Question 4

Which urine pH is typical in distal RTA despite systemic acidosis?

 

A. <4.5

B. <5.0

C. <5.5

D. >5.5

E. >7.0

 

Question 5

What defect occurs in proximal (Type 2) RTA?

 

A. Impaired bicarbonate reabsorption in proximal tubule

B. Decreased ammonium production

C. Failure of distal hydrogen secretion

D. Increased distal potassium secretion

E. Excess aldosterone production

 

Question 6

Which syndrome is associated with proximal RTA?

 

A. Goodpasture syndrome

B. Fanconi syndrome

C. Alport syndrome

D. Bartter syndrome

E. Gitelman syndrome

 

Question 7

Which complication is most associated with distal RTA?

 

A. Kidney stones

B. Pulmonary edema

C. Nephrotic syndrome

D. Hyperglycemia

E. Hypertension

 

Question 8

What mechanism causes hyperkalemia in Type 4 RTA?

 

A. Increased distal acid secretion

B. Aldosterone deficiency or resistance

C. Increased bicarbonate reabsorption

D. Increased ammonium excretion

E. Increased potassium secretion

 

Question 9

Which lab pattern suggests Type 1 RTA?

 

A. High urine pH and hypokalemia

B. Low urine pH and hyperkalemia

C. Low urine pH and hypokalemia

D. High urine pH and hyperkalemia

E. Normal urine pH

 

Question 10

Most common genetic cause of Type 2 RTA?

 

A. Autoimmune disease

B. Cystinosis

C. Wilson disease

D. Cystic fibrosis

E. PKD

 

Question 11

A 9‑year‑old boy has nephrocalcinosis, metabolic acidosis, urine pH 6.0, and hypokalemia. Diagnosis?

 

A. DKA

B. Type 2 RTA

C. Type 4 RTA

D. Lactic acidosis

E. Type 1 RTA

 

Question 12

A 12‑year‑old girl with Fanconi syndrome develops metabolic acidosis. Which type of RTA?

 

A. Type 1

B. Type 2

C. Type 3

D. Type 4

E. Mixed

 

Question 13

A patient with diabetic nephropathy develops hyperkalemia and mild metabolic acidosis. Diagnosis?

 

A. Distal RTA

B. Proximal RTA

C. Type 4 RTA

D. Lactic acidosis

E. Salicylate toxicity

 

Question 14

A child with metabolic acidosis has bicarbonate 16 and urine pH 5.0. Most consistent diagnosis?

 

A. Distal RTA

B. Proximal RTA

C. Type 4 RTA

D. Lactic acidosis

E. Respiratory acidosis

 

Question 15

A patient with RTA has severe hypokalemia and kidney stones. What is the underlying mechanism?

 

A. Increased bicarbonate reabsorption

B. Increased ammonium excretion

C. Increased aldosterone

D. Failure of distal acid secretion

E. Decreased chloride reabsorption

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Question 16

A 6-year-old boy is evaluated for poor growth and recurrent kidney stones. Laboratory studies show a normal anion gap metabolic acidosis, potassium of 3.0 mEq/L, and urine pH of 6.2 despite systemic acidemia. Renal ultrasound demonstrates medullary nephrocalcinosis. Which diagnosis best explains these findings?

​

A. Proximal RTA (Type 2)
B. Distal RTA (Type 1)
C. Type 4 RTA
D. Lactic acidosis
E. Chronic respiratory acidosis

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Question 17

A 10-year-old girl presents with fatigue and polyuria. Laboratory studies show metabolic acidosis with normal anion gap, potassium of 2.8 mEq/L, and urine pH of 5.0. Additional evaluation reveals glucosuria, aminoaciduria, and phosphaturia. Which condition is the most likely cause of her acid–base disorder?

​

A. Distal RTA (Type 1)
B. Proximal RTA (Type 2)
C. Type 4 RTA
D. Chronic kidney disease
E. Salicylate toxicity

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Question 18

A 15-year-old boy with type 1 diabetes and chronic kidney disease presents with fatigue and weakness. Laboratory testing reveals potassium 6.2 mEq/L, bicarbonate 18 mEq/L, and normal anion gap metabolic acidosis. Urine pH is <5.5. Which of the following best explains his acid–base disorder?

​

A. Distal RTA
B. Proximal RTA
C. Type 4 RTA due to hypoaldosteronism
D. Lactic acidosis
E. Diabetic ketoacidosis

 

Question 19

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A 7-year-old girl presents with growth failure and chronic metabolic acidosis. Potassium is 3.1 mEq/L, bicarbonate 14 mEq/L, and urine pH is 6.0. She has a history of sensorineural hearing loss. Which disorder is most consistent with these findings?

​

A. Distal RTA due to H⁺ secretion defect
B. Proximal RTA due to bicarbonate wasting
C. Type 4 RTA due to aldosterone deficiency
D. Renal failure–associated acidosis
E. Respiratory acidosis

 

Question 20

A 9-year-old boy presents with weakness and metabolic acidosis. His serum bicarbonate is 16 mEq/L, potassium 3.5 mEq/L, and urine pH 5.0. When bicarbonate is administered, the fractional excretion of bicarbonate rises significantly. Which diagnosis is most likely?

​

A. Distal RTA (Type 1)
B. Proximal RTA (Type 2)
C. Type 4 RTA
D. Lactic acidosis
E. Chronic respiratory acidosis

 

Question 21

A 13-year-old boy with a history of kidney transplantation presents for routine follow-up. His medications include tacrolimus and mycophenolate mofetil. Laboratory testing shows potassium 5.8 mEq/L, bicarbonate 19 mEq/L, and a normal anion gap metabolic acidosis. Urine pH is <5.5. Renal function is stable compared with previous visits.

Which of the following best explains this patient’s acid–base disorder?

​

A. Distal RTA due to impaired hydrogen secretion
B. Proximal RTA due to bicarbonate wasting
C. Type 4 RTA due to calcineurin inhibitor–induced hypoaldosteronism
D. Lactic acidosis due to tacrolimus toxicity
E. Chronic respiratory acidosis

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Answer Key

Question 1. B . RTA causes normal anion gap (hyperchloremic) metabolic acidosis.

 

Question 2. C. Distal RTA results from impaired hydrogen secretion in distal nephron.

 

Question 3. B, Type 4 RTA causes hyperkalemia due to aldosterone deficiency/resistance.

 

Question 4. D. Urine pH remains >5.5 despite systemic acidosis in distal RTA.

 

Question 5. A.Proximal RTA involves impaired bicarbonate reabsorption.

 

Question 6. B. Fanconi syndrome causes generalized proximal tubule dysfunction.

 

Question 7. A. Distal RTA commonly causes nephrolithiasis and nephrocalcinosis.

 

Question 8. E. Type 4 RTA occurs from reduced aldosterone activity.

 

Question 9. A. Distal RTA: alkaline urine with hypokalemia.

 

Question 10. B. Cystinosis is the most common genetic cause of Proximal RTA

 

Question 11. E. Nephrocalcinosis + high urine pH suggests distal RTA.

 

Question 12. B. Fanconi syndrome → proximal RTA.

 

Question 13. C . Hyperkalemia + diabetes → Type 4 RTA.

 

Question 14. B . Proximal RTA allows urine pH to fall once bicarbonate drops.

 

Question 15. D. Failure of distal acid secretion causes stones and hypokalemia.

 

Question 16. B — Distal RTA. Distal RTA presents with hypokalemia, urine pH >5.5, nephrocalcinosis, and kidney stones due to impaired distal hydrogen secretion.

 

Question 17. B. Proximal RTA. Fanconi syndrome causes generalized proximal tubular dysfunction with glucosuria, phosphaturia, aminoaciduria, and bicarbonate wasting.

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Question 18. C. Type 4 RTA Type 4 RTA is characterized by hyperkalemia and mild metabolic acidosis, most commonly due to hyporeninemic hypoaldosteronism in diabetes.

 

Question 19. A. Distal RTA.  Distal RTA may be associated with genetic defects affecting H⁺ secretion, sometimes linked with sensorineural hearing loss.

 

Question  20. B — Proximal RTA. Proximal RTA shows increased bicarbonate wasting, particularly after bicarbonate loading.

 

Question 21. C. Type 4 RTA due to calcineurin inhibitor–induced hypoaldosteronism

Tacrolimus and other calcineurin inhibitors can impair renin and aldosterone signaling, leading to hypoaldosteronism or aldosterone resistance. This results in Type 4 renal tubular acidosis, characterized by:

• Hyperkalemia

• Normal anion gap metabolic acidosis

• Urine pH typically <5.5

This complication is commonly seen in kidney transplant recipients treated with calcineurin inhibitors.