Renal Tubular Disorders Indian Medical PG Practice Questions and MCQs
Practice Indian Medical PG questions for Renal Tubular Disorders. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Renal Tubular Disorders Indian Medical PG Question 1: In Bartter's syndrome there is a defect in
- A. Descending limb of LOH
- B. Thick ascending limb of LOH (Correct Answer)
- C. DCT
- D. PCT
Renal Tubular Disorders Explanation: ***Thick ascending limb of LOH***
- **Bartter's syndrome** is characterized by a genetic defect affecting the **Na-K-2Cl cotransporter (NKCC2)** located in the thick ascending limb of the loop of Henle.
- This defect impairs the reabsorption of sodium, potassium, and chloride ions, leading to significant **electrolyte imbalances** such as hypokalemia, metabolic alkalosis, and hyperreninemia.
*Descending limb of LOH*
- The descending limb is primarily permeable to **water** due to aquaporin channels, and impermeable to solutes.
- Defects in this segment are not typically associated with the electrolyte derangements seen in Bartter's syndrome.
*DCT*
- The **distal convoluted tubule (DCT)** is where fine-tuning of sodium and calcium reabsorption occurs, primarily through the Na-Cl cotransporter (NCC) and active calcium transport.
- Defects in the DCT are characteristic of **Gitelman's syndrome**, which has similar but generally milder symptoms compared to Bartter's syndrome.
*PCT*
- The **proximal convoluted tubule (PCT)** is responsible for the bulk reabsorption of filtered substances, including glucose, amino acids, bicarbonate, and about 65-70% of filtered sodium.
- While defects here can lead to various syndromes (e.g., Fanconi syndrome), they do not directly cause the specific electrolyte abnormalities seen in Bartter's syndrome.
Renal Tubular Disorders Indian Medical PG Question 2: A 1-month old baby present with frequent vomiting and failure to thrive. There are features of moderate dehydration. Blood sodium in 122 mEq/l and potassium is 6.1 mEq/l. The most likely diagnosis is?
- A. 11β-hydroxylase deficiency
- B. 21-hydroxylase deficiency (Correct Answer)
- C. Gitelman syndrome
- D. Bartter syndrome
Renal Tubular Disorders Explanation: ***21-hydroxylase deficiency***
- This condition presents in infancy with **salt-wasting adrenal crisis** due to impaired cortisol and aldosterone synthesis, leading to **hyponatremia**, **hyperkalemia**, **dehydration**, and **vomiting**.
- The deficiency in 21-hydroxylase blocks the synthesis of **aldosterone**, causing sodium loss and potassium retention, consistent with the electrolyte abnormalities.
*11β-hydroxylase deficiency*
- This deficiency causes an accumulation of **11-deoxycorticosterone (DOC)**, which has mineralocorticoid activity, leading to **hypertension** and **hypokalemia**, rather than hyponatremia and hyperkalemia.
- While it can cause virilization, the electrolyte imbalance is distinctly different from the case presented.
*Gitelman syndrome*
- This is a **renal tubulopathy** characterized by reabsorptive defects in the distal convoluted tubule, leading to **hypokalemia**, **metabolic alkalosis**, **hypomagnesemia**, and **hypocalciuria**.
- It would not typically present with severe hyponatremia or hyperkalemia in a neonate with salt wasting.
*Bartter syndrome*
- This is a **renal tubulopathy** affecting the thick ascending limb of the loop of Henle, resulting in significant salt loss, **hypokalemia**, **metabolic alkalosis**, and **hypercalciuria**.
- Like Gitelman syndrome, it is associated with hypokalemia, which contradicts the hyperkalemia seen in the patient.
Renal Tubular Disorders Indian Medical PG Question 3: A 10 year old boy is having polyuria, polydipsia, laboratory data showed (in mEq/lit) – Na+ 154, K+ 4.5, HCO3- 22, Serum osmolality – 295 mOsm/kg, Blood urea – 50 mg/dl, Urine specific gravity – 1.005. The likely diagnosis is –
- A. Barter's syndrome
- B. Recurrent UTI
- C. Diabetes insipidus (Correct Answer)
- D. Renal tubular acidosis
Renal Tubular Disorders Explanation: ***Diabetes insipidus***
- The classic presentation of **polyuria and polydipsia** with **hypernatremia (Na+ 154 mEq/L)** and **low urine specific gravity (1.005)** indicates inability to concentrate urine.
- The **serum osmolality of 295 mOsm/kg** (upper limit of normal) in the context of hypernatremia suggests inadequate water reabsorption, consistent with **diabetes insipidus (either central or nephrogenic)**.
- The dilute urine despite elevated serum sodium is pathognomonic for DI.
*Barter's syndrome*
- Characterized by **hypokalemic metabolic alkalosis**, increased renin and aldosterone, and normal to low blood pressure.
- The given laboratory values show **normal potassium (4.5 mEq/L)** and **normal bicarbonate (22 mEq/L)**, ruling out Barter's syndrome.
- Results from defects in the **Na-K-2Cl cotransporter** in the thick ascending limb of loop of Henle.
*Recurrent UTI*
- While UTIs may cause polyuria and polydipsia, they typically present with **dysuria, fever, urgency, and pyuria/bacteriuria**.
- UTIs do not cause **hypernatremia** or the specific pattern of dilute urine with elevated serum sodium.
- The clinical picture does not suggest infectious etiology.
*Renal tubular acidosis*
- RTA presents with **metabolic acidosis** (low bicarbonate, typically <15-18 mEq/L) with normal anion gap.
- The **normal bicarbonate level (22 mEq/L)** excludes RTA.
- Often associated with hypokalemia, growth retardation, and nephrocalcinosis in children.
Renal Tubular Disorders Indian Medical PG Question 4: A diabetic patient presents with hyperkalemia and urinary pH < 5.5. What is the MOST likely underlying cause?
- A. Uremia
- B. Primary hyperaldosteronism
- C. Type IV RTA (Correct Answer)
- D. Type I Renal tubular acidosis
Renal Tubular Disorders Explanation: ***Type IV RTA***
- Patients with **diabetes mellitus** frequently develop **hyporeninemic hypoaldosteronism**, leading to Type IV RTA [1].
- This condition is characterized by **hyperkalemia** and **acidosis** with a paradoxically low urinary pH (typically < 5.5).
*Uremia*
- **Uremia** can cause hyperkalemia and acidosis, but it is a broader term for severe kidney failure and not the most specific underlying cause for the given urinary findings.
- While patients with uremia can have aciduria, the combination of **diabetic hyperkalemia** and acid urine points more directly to a specific tubular defect.
*Primary hyperaldosteronism*
- **Primary hyperaldosteronism** is characterized by **hypertension**, **hypokalemia**, and metabolic alkalosis, which is the opposite of the patient's presentation [1].
- This condition involves excessive aldosterone production, leading to increased potassium excretion [1].
*Type I Renal tubular acidosis*
- **Type I RTA** (distal RTA) is characterized by the inability to acidify urine, resulting in a **urinary pH > 5.5** despite systemic acidosis [1].
- While it can cause hypokalemia (due to increased distal K+ secretion) and acidosis, the elevated urinary pH is a key differentiating factor from this patient's presentation [1].
Renal Tubular Disorders Indian Medical PG Question 5: Which of the following is a characteristic finding in distal RTA?
- A. Urine pH < 5.5
- B. Hypokalemia
- C. Hypercalciuria (Correct Answer)
- D. Nephrolithiasis
Renal Tubular Disorders Explanation: ***Hypercalciuria***
- **Hypercalciuria** is a characteristic finding in distal RTA (Type 1), leading to increased calcium in the urine.
- This occurs due to reduced **distal tubular reabsorption of calcium** and increased bone resorption from chronic acidosis.
*Urine pH < 5.5*
- In distal RTA, the kidneys are unable to acidify the urine properly, leading to a **urine pH > 5.5** [1].
- A urine pH < 5.5 would suggest a normal kidney response to systemic acidosis, ruling out distal RTA.
*Hypokalemia*
- While hypokalemia can occur in distal RTA, it is not always present and is not the most definitive characteristic finding.
- **Hypokalemia** is more characteristic of Type 1 RTA due to increased potassium excretion in an attempt to excrete H+ ions.
*Nephrolithiasis*
- **Nephrolithiasis** (kidney stones) is a common complication of distal RTA due to hypercalciuria and alkaline urine [2].
- However, hypercalciuria is the *reason* for the increased risk of nephrolithiasis, making it a more fundamental characteristic finding.
Renal Tubular Disorders Indian Medical PG Question 6: Among the following conditions, which is most likely to cause type 4 renal tubular acidosis?
- A. Chronic pyelonephritis
- B. Diabetic nephropathy (Correct Answer)
- C. Systemic lupus
- D. Multiple myeloma
Renal Tubular Disorders Explanation: ***Diabetic nephropathy***
- **Diabetic nephropathy** is a common cause of **type 4 renal tubular acidosis (RTA)** due to damage to the **juxtaglomerular apparatus** affecting **renin production** and subsequent aldosterone levels.
- The resulting **hypoaldosteronism** or **aldosterone resistance** [1] leads to impaired potassium and hydrogen secretion in the **distal tubules**, causing **hyperkalemia** and **metabolic acidosis**. [1]
*Chronic pyelonephritis*
- While chronic pyelonephritis can lead to **renal scarring** and **chronic kidney disease**, it typically does not directly cause type 4 RTA.
- It is more commonly associated with a variety of tubular defects, but not specifically the **hypoaldosteronism** characteristic of type 4 RTA unless severe general renal failure is present.
*Systemic lupus*
- **Systemic lupus erythematosus (SLE)** can cause **lupus nephritis**, leading to various forms of kidney damage, but it is more commonly associated with **type 1 (distal)** or **type 2 (proximal) RTA**, rather than type 4.
- Type 1 RTA in SLE is often due to an **autoimmune attack** on the **distal tubule's ability** to secrete hydrogen ions.
*Multiple myeloma*
- **Multiple myeloma** is known to cause **renal impairment** primarily through the deposition of **light chains** in the tubules, often leading to **proximal tubular dysfunction** (Fanconi syndrome) or **cast nephropathy**.
- This typically results in **type 2 RTA** (proximal RTA) characterized by impaired reabsorption of bicarbonate, amino acids, and phosphate, rather than the distal tubular and aldosterone-related issues seen in type 4 RTA.
Renal Tubular Disorders Indian Medical PG Question 7: An 8 years old child suffering from recurrent attacks of polyuria since childhood presents to the pediatrics OPD. On examination, the child has short stature. Vitals and B.P. are normal. S. Creatinine - 6 mg/dL, HCO3 - 16 meq/L, S Na+ - 134 meq/L. On USG, bilateral small kidneys are seen. Diagnosis is:
- A. Reflux nephropathy
- B. Medullary cystic kidney disease
- C. Nephronophthisis (Correct Answer)
- D. Polycystic kidney disease
Renal Tubular Disorders Explanation: ***Nephronophthisis***
- This condition presents with **recurrent polyuria** (due to **vasopressin resistance**), **short stature**, and progressive **renal failure** (elevated creatinine and low HCO3 indicating acidosis), which are all classic features of nephronophthisis.
- The finding of **bilateral small kidneys** on USG is consistent with nephronophthisis, as kidneys in this condition are typically small and echogenic due to interstitial fibrosis, despite sometimes having small cysts.
*Reflux nephropathy*
- While it can lead to **chronic kidney disease** and **short stature**, it is usually associated with a history of **recurrent urinary tract infections** and often presents with **renal scarring** and caliectasis, which are not mentioned.
- In reflux nephropathy, the kidneys may be asymmetrical or have focal scarring, rather than uniformly small, and polyuria is not a primary symptom.
*Medullary cystic kidney disease*
- This condition is also characterized by **polyuria**, **renal failure**, and **small kidneys**, but it typically manifests in **adulthood**.
- **Medullary cysts** are a prominent feature, but diagnosis is often later than early childhood.
*Polycystic kidney disease*
- **Autosomal dominant polycystic kidney disease (ADPKD)** usually presents in adulthood with **enlarged kidneys** and **hypertension**, not small kidneys and short stature in childhood.
- **Autosomal recessive polycystic kidney disease (ARPKD)** presents in infancy or early childhood with **enlarged, echogenic kidneys** with macroscopic or microscopic cysts, which contradicts the finding of small kidneys in this case.
Renal Tubular Disorders Indian Medical PG Question 8: An infant presenting with failure to thrive, hypertension, metabolic acidosis, and hyperkalemia is most likely suffering from which condition?
- A. Liddle's syndrome
- B. Bartter's syndrome
- C. Gittelman's syndrome
- D. Gordon syndrome (Correct Answer)
Renal Tubular Disorders Explanation: ***Gordon syndrome***
- **Gordon syndrome** (Pseudohypoaldosteronism Type II) is characterized by **hypertension**, **hyperkalemia**, and **metabolic acidosis**, which perfectly matches the clinical presentation in this infant.
- The underlying defect involves abnormal regulation of the **WNK kinase pathway**, leading to increased activity of the thiazide-sensitive Na-Cl cotransporter (NCC) in the distal convoluted tubule, resulting in increased sodium reabsorption and impaired potassium excretion.
- This causes **volume expansion** (leading to hypertension), **hyperkalemia** (due to reduced potassium secretion), and **metabolic acidosis** (due to impaired hydrogen ion secretion).
*Liddle's syndrome*
- This syndrome presents with **hypertension**, **hypokalemia**, and **metabolic alkalosis**, due to increased activity of the epithelial sodium channel (ENaC) in the collecting duct.
- The presence of **hyperkalemia** and **metabolic acidosis** rules out Liddle's syndrome.
*Bartter's syndrome*
- Characterized by **hypokalemia**, **metabolic alkalosis**, and **normal or low blood pressure**, due to impaired reabsorption in the thick ascending limb of the loop of Henle.
- The combination of **hypertension**, **hyperkalemia**, and **metabolic acidosis** is completely inconsistent with Bartter's syndrome.
*Gitelman's syndrome*
- This syndrome typically causes **hypokalemia**, **metabolic alkalosis**, **hypomagnesemia**, and **hypocalciuria**, due to a defect in the thiazide-sensitive NaCl cotransporter in the distal convoluted tubule.
- The infant's **hyperkalemia**, **hypertension**, and **metabolic acidosis** are completely inconsistent with Gitelman's syndrome.
Renal Tubular Disorders Indian Medical PG Question 9: Tyrosinemia Type I is caused due to deficiency of which enzyme?
- A. Homogentisate 1,2-dioxygenase
- B. Fumarylacetoacetate hydrolase (Correct Answer)
- C. Tyrosine aminotransferase
- D. 4-hydroxyphenylpyruvate dioxygenase
Renal Tubular Disorders Explanation: ***Fumarylacetoacetate hydrolase***
- **Tyrosinemia Type I**, also known as **hereditary tyrosinemia type 1 (HT1)**, is an **autosomal recessive** metabolic disorder caused by a deficiency of the enzyme **fumarylacetoacetate hydrolase (FAH)**.
- This enzyme is crucial for the final step in the **tyrosine degradation pathway**, leading to the accumulation of toxic metabolites like fumarylacetoacetate and succinylacetone.
*Tyrosine aminotransferase*
- Deficiency of **tyrosine aminotransferase** causes **Tyrosinemia Type II**, a distinct disorder from Type I.
- Type II tyrosinemia primarily affects the eyes and skin, presenting with **corneal ulcers** and painful **hyperkeratotic plaques**.
*Homogentisate 1,2-dioxygenase*
- Deficiency of **homogentisate 1,2-dioxygenase** leads to **alkaptonuria (black urine disease)**, a rare metabolic disorder.
- This condition involves the accumulation of **homogentisic acid**, which causes dark urine, **ochronosis** (bluish-black pigmentation of connective tissues), and severe arthropathy.
*4-hydroxyphenylpyruvate dioxygenase*
- Deficiency of **4-hydroxyphenylpyruvate dioxygenase** results in **Tyrosinemia Type III**, another rare form of tyrosinemia.
- This type is typically milder, often presenting with **neurological symptoms** such as intellectual disability and seizures, but without the severe liver and kidney damage seen in Type I.
Renal Tubular Disorders Indian Medical PG Question 10: Most common cause of persistent hypertension in a child with intrinsic renal disease is -
- A. CGN (Correct Answer)
- B. Obstructive uropathy
- C. Renal tumor
- D. Chronic Pyelonephritis
Renal Tubular Disorders Explanation: ***CGN***
- **Chronic glomerulonephritis (CGN)** is a leading cause of persistent hypertension in children with intrinsic renal disease due to widespread glomerular damage leading to **renin-angiotensin-aldosterone system** activation and fluid retention.
- The damaged kidneys are unable to filter waste and regulate blood pressure effectively, contributing to sustained hypertension.
*Chronic Pyelonephritis*
- While chronic pyelonephritis can cause hypertension, it is typically due to **scarring and inflammation** affecting renal function.
- However, it is not as common a cause of persistent hypertension as CGN in children with intrinsic renal disease.
*Obstructive uropathy*
- **Obstructive uropathy** is classified as a **post-renal (obstructive) disorder** rather than intrinsic renal disease, though it can lead to secondary renal parenchymal damage.
- It can cause hypertension through renal parenchymal damage and **renin release** due to increased pressure, but it is not a primary intrinsic renal disease.
*Renal tumor*
- **Renal tumors**, such as Wilms' tumor, can cause hypertension through **compression of renal arteries** or increased renin production.
- While a significant cause of hypertension, it is generally less common than CGN as a cause of persistent hypertension in children with *intrinsic renal disease* overall.
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