Nephrology — MCQs

A 55-year-old man with type II diabetes mellitus, essential hypertension, and ischemic heart disease presents for a routine examination. Laboratory studies reveal a serum potassium of 6 mEq/L. He has no muscle weakness and no ECG changes apart from evidence of a prior inferior wall myocardial infarction. He has mild compensated metabolic acidosis with a normal serum anion gap. Urine examination shows significantly lower than expected potassium excretion despite an elevated serum potassium concentration. Which of the following is most likely to explain the hyperkalemia observed in this patient?

Q157Easy

All are features of Bartter syndrome, EXCEPT?

Q158Medium

Which investigation should be avoided in a proven case of renal papillary necrosis?

Q159Medium

Which of the following are indicators of a cardiorenal failure (CRF) in the context of acute renal failure (ARF)?

Q160Medium

Which of the following conditions is NOT associated with hypokalemia and hypertension?

Nephrology Indian Medical PG Practice Questions and MCQs

Question 151: Hypophosphatemia is seen in which of the following conditions?

A. Pseudohypoparathyroidism
B. Chronic renal failure
C. Rickets (Correct Answer)
D. Respiratory acidosis

Explanation: ### Explanation **Correct Answer: C. Rickets** **1. Why Rickets is the Correct Answer:** Rickets (specifically Vitamin D deficiency rickets) is characterized by a deficiency in Vitamin D, which leads to defective mineralisation of bone [1]. This deficiency leads to decreased intestinal absorption of calcium and phosphorus. The resulting low serum calcium triggers **Secondary Hyperparathyroidism**. Increased Parathyroid Hormone (PTH) levels act on the kidneys to increase phosphate excretion (phosphaturia) while attempting to normalize calcium [2]. This combination of decreased absorption and increased renal loss leads to significant **hypophosphatemia**. **2. Why the Other Options are Incorrect:** * **A. Pseudohypoparathyroidism:** This is a condition of end-organ resistance to PTH. Since PTH cannot act on the renal tubules to excrete phosphate, patients develop **hyperphosphatemia** and hypocalcemia. * **B. Chronic Renal Failure (CRF):** In CRF, the declining Glomerular Filtration Rate (GFR) leads to the retention of phosphate. This results in **hyperphosphatemia**, which is a hallmark of Chronic Kidney Disease-Mineral and Bone Disorder (CKD-MBD). * **C. Respiratory Acidosis:** Acidosis generally causes phosphate to shift from the intracellular to the extracellular compartment, potentially increasing serum phosphate. In contrast, **Respiratory Alkalosis** is a classic cause of hypophosphatemia due to an intracellular shift of phosphate [2]. **3. High-Yield Clinical Pearls for NEET-PG:** * **Intracellular Shift:** The most common cause of severe hypophosphatemia in hospitalized patients is **Refeeding Syndrome** (insulin-mediated shift). * **Fanconi Syndrome:** Always consider this if hypophosphatemia is associated with glycosuria, aminoaciduria, and type 2 RTA. * **FGF-23:** Remember that Fibroblast Growth Factor-23 is a potent phosphaturic hormone; its excess (as in Oncogenic Osteomalacia) leads to hypophosphatemia [2]. * **PTH Rule:** PTH is "Phosphate Trashing Hormone"—it lowers serum phosphate by inhibiting reabsorption in the proximal convoluted tubule [2].

Question 152: A normal-anion-gap metabolic acidosis occurs in which of the following conditions?

A. Diarrhoea (Correct Answer)
B. Diabetic ketoacidosis
C. Methyl alcohol poisoning
D. Acute renal failure

Explanation: **Explanation:** Metabolic acidosis is categorized based on the **Anion Gap (AG)**, calculated as: $Na^+ - (Cl^- + HCO_3^-)$. The normal range is 8–12 mEq/L. **1. Why Diarrhoea is Correct:** Diarrhoea is the most common cause of **Normal Anion Gap Metabolic Acidosis (NAGMA)**, also known as hyperchloremic metabolic acidosis [1]. In the lower GI tract, secretions are rich in bicarbonate ($HCO_3^-$). Massive loss of $HCO_3^-$ during diarrhoea leads to a compensatory increase in serum Chloride ($Cl^-$) to maintain electroneutrality [2]. Since the sum of $(Cl^- + HCO_3^-)$ remains relatively constant, the anion gap does not change. **2. Why Incorrect Options are Wrong:** Options B, C, and D are causes of **High Anion Gap Metabolic Acidosis (HAGMA)**. In these conditions, acidosis occurs due to the accumulation of unmeasured organic acids: * **Diabetic Ketoacidosis:** Accumulation of acetoacetate and beta-hydroxybutyrate [2]. * **Methyl Alcohol Poisoning:** Accumulation of formic acid. * **Acute Renal Failure:** Failure to excrete fixed acids (phosphates and sulfates). **3. NEET-PG High-Yield Pearls:** * **Mnemonic for NAGMA (USED CARP):** **U**reterosigmoidostomy, **S**aline infusion (large volume), **E**ndocrine (Addison’s), **D**iarrhoea, **C**arbonic anhydrase inhibitors (Acetazolamide), **A**mmonium chloride, **R**enal tubular acidosis (RTA), **P**ancreatic fistula [1]. * **Mnemonic for HAGMA (MUDPILES):** **M**ethanol, **U**remia, **D**KA, **P**araldehyde, **I**soniazid/Iron, **L**actic acidosis, **E**thylene glycol, **S**alicylates. * **Distinguishing RTA from Diarrhoea:** Use the **Urinary Anion Gap (UAG)**. UAG is negative in diarrhoea (normal renal response) and positive in RTA (impaired $H^+$ excretion).

Question 153: A patient with chronic renal failure on intermittent hemodialysis presents with anemia refractory to iron therapy. Which of the following additional drugs is indicated?

A. Cyanocobalamin
B. Folic acid
C. Pyridoxine
D. Erythropoietin (Correct Answer)

Explanation: The primary cause of anemia in Chronic Kidney Disease (CKD) is the **deficiency of Erythropoietin (EPO)**. [1] EPO is a glycoprotein hormone produced by the peritubular interstitial cells of the renal cortex. [1] In patients with chronic renal failure, the loss of functional renal parenchyma leads to inadequate EPO production, resulting in normocytic, normochromic anemia. **Why Erythropoietin is the correct answer:** In clinical practice, anemia of CKD is managed by first ensuring adequate iron stores (Transferrin saturation >30% and Ferritin >500 ng/mL). If the anemia remains **refractory to iron therapy**, the next step is the administration of **Erythropoiesis-Stimulating Agents (ESAs)** like Recombinant Human Erythropoietin or Darbepoetin alfa to stimulate red blood cell production in the bone marrow. [1] It is also important to note that anemia of chronic inflammation can be refractory to iron due to hepcidin upregulation. [2] **Analysis of Incorrect Options:** * **Cyanocobalamin (B12) & Folic Acid:** While water-soluble vitamins are lost during hemodialysis, they are rarely the primary cause of refractory anemia in CKD unless a specific nutritional deficiency is documented (megaloblastic anemia). * **Pyridoxine (B6):** Supplementation is often required in dialysis patients to prevent neuropathy or if they are on drugs like Isoniazid, but it is not the standard treatment for the primary anemia of renal failure. **High-Yield Clinical Pearls for NEET-PG:** * **Target Hemoglobin:** In CKD patients on EPO, the target Hb should be **10–11.5 g/dL**. Exceeding 13 g/dL increases the risk of stroke, venous thromboembolism, and hypertension. * **Most common cause of EPO resistance:** Iron deficiency. Always check iron status before escalating EPO dosage. * **Side Effect:** The most common side effect of EPO therapy is the **exacerbation of hypertension**.

Question 154: All of the following antibiotics are known to cause acute interstitial nephritis, except?

A. Erythromycin
B. Sulphonamides
C. Ciprofloxacin
D. Aminoglycosides (Correct Answer)

Explanation: **Explanation:** Acute Interstitial Nephritis (AIN) is a classic **Type IV hypersensitivity reaction** (delayed-type) occurring in the renal interstitium, most commonly triggered by drugs. **Why Aminoglycosides are the correct answer:** Aminoglycosides (e.g., Gentamicin, Amikacin) do not cause AIN. Instead, they are the classic cause of **Acute Tubular Necrosis (ATN)**. They cause direct dose-dependent toxicity to the proximal convoluted tubule cells. Clinically, this manifests as non-oliguric renal failure occurring 5–10 days after starting therapy, unlike the idiosyncratic, non-dose-dependent nature of AIN. **Why the other options are incorrect:** * **Sulphonamides:** These are among the most common triggers for drug-induced AIN. They can also cause crystalluria and obstructive uropathy. * **Ciprofloxacin:** Fluoroquinolones are well-documented causes of AIN. They may also present with granulomatous findings on renal biopsy. * **Erythromycin:** While less common than Penicillins or NSAIDs, Macrolides (including Erythromycin and Azithromycin) are recognized causes of drug-induced hypersensitivity AIN. **NEET-PG High-Yield Pearls:** 1. **Classic Triad of AIN:** Fever, Rash, and Arthralgia (present in only <10–15% of cases). 2. **Laboratory Hallmark:** **Eosinophiluria** (Hansel’s stain) and peripheral eosinophilia. 3. **Gold Standard Diagnosis:** Renal Biopsy (shows interstitial inflammatory infiltrate with eosinophils). 4. **Common Triggers (The 5 P's):** **P**ee (Diuretics), **P**ain-killers (NSAIDs), **P**enicillins/Cephalosporins, **P**PIs (Omeprazole), and **P**ifampicin (Rifampicin).

Question 155: Which drug is beneficial in managing chronic kidney disease?

A. Beta blocker
B. Amlodipine
C. ACE inhibitor (Correct Answer)
D. Telmisartan

Explanation: The primary goal in managing Chronic Kidney Disease (CKD) is to slow the progression of renal decline. **ACE inhibitors (ACEIs)** are the drugs of choice because they provide **renoprotection** beyond simple blood pressure control [1]. **Why ACE Inhibitors are correct:** ACE inhibitors (e.g., Enalapril, Ramipril) inhibit the conversion of Angiotensin I to Angiotensin II [2]. This leads to the **dilation of the efferent arteriole** in the glomerulus. By reducing the resistance at the exit of the glomerulus, they lower **intraglomerular capillary pressure**, which reduces proteinuria and slows the progression of diabetic and non-diabetic nephropathy [1]. **Analysis of Incorrect Options:** * **Beta-blockers (A):** While used for hypertension, they do not possess specific renoprotective properties or the ability to reduce proteinuria effectively. * **Amlodipine (B):** As a Dihydropyridine Calcium Channel Blocker (CCB), it primarily dilates the *afferent* arteriole [2]. This can sometimes increase intraglomerular pressure, making it less ideal as a first-line monotherapy for CKD compared to ACEIs. * **Telmisartan (D):** This is an Angiotensin Receptor Blocker (ARB). While ARBs are also highly beneficial and often used interchangeably with ACEIs [1], in the context of standard medical examinations and classic guidelines, **ACE inhibitors** are traditionally cited as the first-line gold standard for renoprotection. (Note: If both are options, ACEIs are often the preferred "textbook" answer unless the patient develops a cough [1]). **High-Yield Clinical Pearls for NEET-PG:** * **The "Creatinine Jump":** A rise in serum creatinine of up to 30% after starting an ACEI is acceptable and expected; the drug should only be stopped if the rise exceeds 30% or hyperkalemia becomes uncontrollable [2]. * **Contraindication:** ACEIs and ARBs are strictly contraindicated in **Bilateral Renal Artery Stenosis** and **Pregnancy** [2]. * **Dual Therapy:** Combining ACEIs and ARBs is generally avoided due to the increased risk of hyperkalemia and acute kidney injury without added benefit.

Question 156: A 55-year-old man with type II diabetes mellitus, essential hypertension, and ischemic heart disease presents for a routine examination. Laboratory studies reveal a serum potassium of 6 mEq/L. He has no muscle weakness and no ECG changes apart from evidence of a prior inferior wall myocardial infarction. He has mild compensated metabolic acidosis with a normal serum anion gap. Urine examination shows significantly lower than expected potassium excretion despite an elevated serum potassium concentration. Which of the following is most likely to explain the hyperkalemia observed in this patient?

A. Decreased insulin secretion
B. Decreased renin secretion (Correct Answer)
C. Increased blood glucose
D. Increased BNP secretion

Explanation: ### Explanation The patient presents with a classic triad of **Type 2 Diabetes Mellitus**, **hyperkalemia**, and **Normal Anion Gap Metabolic Acidosis (NAGMA)**. This clinical picture is highly suggestive of **Type 4 Renal Tubular Acidosis (RTA)**, also known as **Hyporeninemic Hypoaldosteronism**. **1. Why "Decreased renin secretion" is correct:** In long-standing diabetic patients, damage to the juxtaglomerular apparatus leads to **hyporeninemia**. Low renin results in low aldosterone levels. Since aldosterone is responsible for secreting $K^+$ and $H^+$ in the distal tubule (via the principal and alpha-intercalated cells), its deficiency leads to [1]: * **Hyperkalemia:** Reduced $K^+$ secretion. * **NAGMA:** Reduced $H^+$ secretion and impaired ammoniagenesis. The urine potassium excretion is inappropriately low because the "drive" (aldosterone) to excrete it is missing despite high serum levels [3]. **2. Why other options are incorrect:** * **A. Decreased insulin secretion:** While insulin deficiency can cause a shift of $K^+$ out of cells, it typically presents with acute hyperglycemia or DKA [2]. It does not explain the chronic NAGMA or the specific defect in urinary $K^+$ excretion seen here. * **C. Increased blood glucose:** Hyperglycemia causes hyperosmolality, which can pull $K^+$ out of cells (solvent drag). However, this is a transient shift and would not cause the persistent urinary excretion defect described. * **D. Increased BNP secretion:** BNP (Brain Natriuretic Peptide) actually *inhibits* renin and aldosterone, but its primary role is in heart failure volume regulation. It is not the primary pathological driver of hyperkalemia in diabetic nephropathy. ### Clinical Pearls for NEET-PG * **Type 4 RTA** is the only RTA characterized by **hyperkalemia**. * **Most common cause:** Diabetic Nephropathy. * **Commonly exacerbated by:** Drugs like ACE inhibitors, ARBs, or NSAIDs, which further suppress the renin-angiotensin-aldosterone system (RAAS) [1]. * **Diagnosis:** Low transtubular potassium gradient (TTKG) in the presence of hyperkalemia [4].

Question 157: All are features of Bartter syndrome, EXCEPT?

A. Polyuria
B. Metabolic alkalosis
C. Periodic paralysis
D. Hypertension (Correct Answer)

Explanation: **Explanation:** **Bartter syndrome** is a group of autosomal recessive disorders characterized by a defect in the thick ascending limb (TAL) of the loop of Henle. It mimics the chronic use of **Loop diuretics** (e.g., Furosemide) by inhibiting the **Na-K-2Cl (NKCC2) cotransporter**. 1. **Why Hypertension is the correct answer:** In Bartter syndrome, there is significant salt wasting. This leads to volume depletion, which triggers the **Renin-Angiotensin-Aldosterone System (RAAS)**. While aldosterone levels are high (secondary hyperaldosteronism), the patient remains **normotensive or hypotensive** due to the primary salt-wasting defect and increased prostaglandin production. Therefore, hypertension is *not* a feature. 2. **Analysis of incorrect options:** * **Polyuria:** Defective sodium reabsorption in the TAL disrupts the medullary osmotic gradient, impairing the kidney's ability to concentrate urine, leading to polyuria and polydipsia. * **Metabolic alkalosis:** Increased distal delivery of sodium and high aldosterone levels promote the secretion of H+ and K+ in the collecting duct, resulting in hypokalemic metabolic alkalosis. * **Periodic paralysis:** Severe hypokalemia (due to renal potassium wasting) can manifest clinically as muscle weakness or episodes of hypokalemic periodic paralysis. **Clinical Pearls for NEET-PG:** * **Bartter vs. Gitelman:** Bartter syndrome usually presents in infancy/childhood with hypercalciuria (stones). Gitelman syndrome (mimics Thiazides) presents in adolescence/adulthood with **hypocalciuria** and **hypomagnesemia**. * **Liddle Syndrome:** This is the "pseudo-aldosteronism" (gain of function in ENaC) which presents with **Hypertension**, hypokalemia, and metabolic alkalosis, but with *low* renin and *low* aldosterone. * **Treatment:** NSAIDs (to inhibit prostaglandins), potassium-sparing diuretics, and potassium supplementation.

Question 158: Which investigation should be avoided in a proven case of renal papillary necrosis?

A. Urine acidification test (Correct Answer)
B. Sickling test
C. TB-PCR-urine
D. Bacterial culture of urine

Explanation: **Explanation:** **Renal Papillary Necrosis (RPN)** is a clinicopathologic entity characterized by ischemic necrosis of the renal papillae. The correct answer is the **Urine Acidification Test** (using Ammonium Chloride) because RPN is a common cause of **Distal Renal Tubular Acidosis (Type 1 RTA)**. In RPN, the damaged collecting ducts and papillae lose their ability to secrete hydrogen ions. Performing an acid-loading test in a patient who already has a defect in acid excretion can precipitate severe, life-threatening systemic metabolic acidosis. Furthermore, the test is redundant since the diagnosis of RTA in the setting of RPN is usually clinical. **Analysis of Incorrect Options:** * **B. Sickling Test:** Sickle cell trait/disease is a major cause of RPN due to microvascular occlusion in the vasa recta. This test is often *indicated* to find the underlying etiology. * **C. TB-PCR-urine:** Genitourinary Tuberculosis is a classic cause of RPN ("sloughed papillae"). This is a diagnostic tool to identify the cause. * **D. Bacterial culture of urine:** Acute pyelonephritis (especially in diabetics) is a frequent trigger for RPN [1]. Cultures are essential for managing the associated infection [1]. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic for Causes (POSTCARDS):** **P**yelonephritis, **O**bstruction, **S**ickle cell, **T**uberculosis, **C**irrhosis, **A**nalgesics (NSAIDs), **R**enal vein thrombosis, **D**iabetes mellitus, **S**ystemic vasculitis. * **Classic Presentation:** Hematuria, flank pain (due to sloughed papillae causing ureteric colic), and recurrent UTIs. * **Radiology:** "Ring sign" on intravenous pyelography (IVP) represents a sloughed papilla surrounded by contrast. * **Most common cause overall:** Diabetes Mellitus. * **Most common cause of chronic RPN:** Analgesic nephropathy.

Question 159: Which of the following are indicators of a cardiorenal failure (CRF) in the context of acute renal failure (ARF)?

A. Anemia, small kidneys, creatinine > 7 mg% (Correct Answer)
B. Small kidneys, creatinine > 7 mg%, constrictive pericarditis
C. Creatinine > 7 mg%, constrictive pericarditis, peripheral neuropathy
D. Anemia, creatinine > 7 mg%, constrictive pericarditis

Explanation: ### Explanation The question focuses on differentiating **Chronic Kidney Disease (CKD)**—historically referred to in some contexts as Chronic Renal Failure (CRF)—from **Acute Kidney Injury (AKI/ARF)** [1]. In clinical practice, when a patient presents with elevated nitrogenous waste, these three indicators help confirm a chronic process [4]. #### 1. Why Option A is Correct The triad of **Anemia, Small Kidneys, and significantly elevated Creatinine** is classic for chronic pathology: * **Small Kidneys:** Normal kidney size is 9–12 cm. In CKD, progressive fibrosis and nephron loss lead to bilateral shrunken kidneys (<9 cm) on ultrasound. (Exceptions: Diabetes, Amyloidosis, PKD). * **Anemia:** CKD causes a deficiency in **Erythropoietin (EPO)** production by the peritubular interstitial cells, leading to normocytic normochromic anemia [2]. This is often associated with symptoms like pallor and tiredness [3]. * **Creatinine > 7 mg%:** While AKI can have high creatinine, comparing results to previous baselines is essential to establish chronicity [4]. #### 2. Why Other Options are Wrong * **Constrictive Pericarditis (Options B, C, D):** This is a chronic scarring of the pericardium often due to TB or idiopathic causes. While **Uremic Pericarditis** is a complication of renal failure, "Constrictive Pericarditis" is a specific structural heart diagnosis and not a standard diagnostic indicator of the chronicity of renal failure. * **Peripheral Neuropathy (Option C):** While uremic neuropathy occurs in end-stage renal disease, it is a subjective clinical finding and less definitive for diagnosing the state of renal failure compared to imaging (kidney size) and lab markers (hemoglobin). #### 3. NEET-PG High-Yield Pearls * **Best Imaging Modality:** Ultrasound is the first-line investigation to differentiate ARF from CKD by assessing kidney size and cortical echogenicity. * **Kidney Size Exception:** "Big Kidneys in CKD" (Mnemonic: **D**og **A**nd **P**ony **S**how) – **D**iabetes, **A**myloidosis, **P**olycystic Kidney Disease, **S**arcoidosis/HIV Nephropathy. * **Hypocalcemia/Hyperphosphatemia:** These are more characteristic of CKD due to failure of 1-alpha-hydroxylase (Vitamin D activation) and high phosphate levels [5].

Question 160: Which of the following conditions is NOT associated with hypokalemia and hypertension?

A. Liddle's syndrome
B. Conn's syndrome
C. Bartter's syndrome (Correct Answer)
D. Cushing's syndrome

Explanation: To approach questions regarding electrolyte imbalances and blood pressure, it is essential to categorize them based on the activity of the **Renin-Angiotensin-Aldosterone System (RAAS)**. [1] ### **Explanation** The combination of **hypertension and hypokalemia** typically indicates a state of mineralocorticoid excess (either primary or secondary). In these conditions, increased sodium reabsorption in the distal nephron leads to volume expansion (hypertension) and compensatory potassium wasting (hypokalemia). [1] **Bartter’s Syndrome (Correct Answer):** Bartter’s syndrome is a "salt-wasting" nephropathy caused by mutations in the thick ascending limb of the Loop of Henle (mimicking chronic loop diuretic use). Because the body is losing salt and water, there is chronic volume depletion. This triggers a **secondary increase in Renin and Aldosterone**, leading to hypokalemia and metabolic alkalosis, but the patient remains **normotensive or hypotensive**. ### **Analysis of Incorrect Options** * **Liddle’s Syndrome:** A genetic "gain-of-function" mutation of the ENaC channel. It mimics hyperaldosteronism (hypertension + hypokalemia) but presents with **low renin and low aldosterone**. [1] * **Conn’s Syndrome:** Primary hyperaldosteronism (usually an adrenal adenoma). Excess aldosterone causes sodium retention and potassium excretion, leading to **hypertension and hypokalemia**. [2] * **Cushing’s Syndrome:** High cortisol levels can overwhelm the 11β-HSD2 enzyme, allowing cortisol to bind to mineralocorticoid receptors, causing **hypertension and hypokalemia**. [2] ### **High-Yield Clinical Pearls for NEET-PG** * **Bartter vs. Gitelman:** Bartter’s mimics **Loop diuretics** (occurs in the Loop of Henle; associated with hypercalciuria). Gitelman’s mimics **Thiazides** (occurs in the Distal Tubule; associated with hypocalciuria). Both present with **low BP**. * **Liddle’s Treatment:** Amiloride or Triamterene (ENaC blockers). Spironolactone is ineffective because the defect is distal to the aldosterone receptor. * **Rule of Thumb:** If a patient has hypokalemia and metabolic alkalosis, check the BP. If BP is **high**, think Mineralocorticoid excess; if BP is **low/normal**, think Bartter/Gitelman or Diuretics.

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Nephrology — MCQs

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