Nephrology Practice Questions

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

Diarrhoea. **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).

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

Erythropoietin. 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**.

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

Aminoglycosides. **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).

Q: All are features of Bartter syndrome, EXCEPT?

Hypertension. **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.

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

Urine acidification test. **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 1

Hypophosphatemia is seen in which of the following conditions?

Accepted Answer

Rickets

Answer

Pseudohypoparathyroidism

Answer

Chronic renal failure

Answer

Respiratory acidosis

Question 2

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

Accepted Answer

Diarrhoea

Answer

Diabetic ketoacidosis

Answer

Methyl alcohol poisoning

Answer

Acute renal failure

Question 3

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

Accepted Answer

Erythropoietin

Answer

Cyanocobalamin

Answer

Folic acid

Answer

Pyridoxine

Question 4

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

Accepted Answer

Aminoglycosides

Answer

Erythromycin

Answer

Sulphonamides

Answer

Ciprofloxacin

Question 5

Which drug is beneficial in managing chronic kidney disease?

Accepted Answer

ACE inhibitor

Answer

Beta blocker

Answer

Amlodipine

Answer

Telmisartan

Question 6

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?

Accepted Answer

Decreased renin secretion

Answer

Decreased insulin secretion

Answer

Increased blood glucose

Answer

Increased BNP secretion

Question 7

All are features of Bartter syndrome, EXCEPT?

Accepted Answer

Hypertension

Answer

Polyuria

Answer

Metabolic alkalosis

Answer

Periodic paralysis

Question 8

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

Accepted Answer

Urine acidification test

Answer

Sickling test

Answer

TB-PCR-urine

Answer

Bacterial culture of urine

Question 9

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

Accepted Answer

Anemia, small kidneys, creatinine > 7 mg%

Answer

Small kidneys, creatinine > 7 mg%, constrictive pericarditis

Answer

Creatinine > 7 mg%, constrictive pericarditis, peripheral neuropathy

Answer

Anemia, creatinine > 7 mg%, constrictive pericarditis

Question 10

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

Accepted Answer

Bartter's syndrome

Answer

Liddle's syndrome

Answer

Conn's syndrome

Answer

Cushing's syndrome

Nephrology — MCQs

Nephrology — MCQs

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