Renal Tubular Disorders — MCQs
In Bartter's syndrome there is a defect in
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 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 diabetic patient presents with hyperkalemia and urinary pH < 5.5. What is the MOST likely underlying cause?
Which of the following is a characteristic finding in distal RTA?
Among the following conditions, which is most likely to cause type 4 renal tubular acidosis?
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:
An infant presenting with failure to thrive, hypertension, metabolic acidosis, and hyperkalemia is most likely suffering from which condition?
Tyrosinemia Type I is caused due to deficiency of which enzyme?
Most common cause of persistent hypertension in a child with intrinsic renal disease is -
Renal Tubular Disorders Indian Medical PG Practice Questions and MCQs
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
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.
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
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.
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
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.
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
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].
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
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.
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
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.
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
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.
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)
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.
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
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.
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
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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