Nephrology Practice Questions

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: 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.

Q: Which of the following conditions is characterized by these ECG changes?

Hyperkalemia. ***Hyperkalemia*** - Classic ECG changes include **peaked T waves**, **widened QRS complexes**, and **flattened or absent P waves** as potassium levels rise. - Severe hyperkalemia can progress to a **sine wave pattern** on ECG, which is a life-threatening arrhythmia requiring immediate treatment. *Hyponatremia* - **Sodium imbalances** do not produce characteristic or specific ECG changes. - Clinical manifestations are primarily **neurological** (confusion, seizures) rather than cardiac rhythm disturbances. *Hypernatremia* - Like hyponatremia, **elevated sodium levels** do not cause distinctive ECG abnormalities. - Symptoms are mainly **neurological** (altered mental status, hyperreflexia) due to cellular dehydration. *Hypokalemia* - ECG changes include **flattened T waves**, **prominent U waves**, and **ST depression** - opposite to hyperkalemia findings. - May also cause **prolonged QT interval** and increased risk of **torsades de pointes** arrhythmia.

Q: Which of the following is a common feature of Gitelman syndrome?

Metabolic alkalosis. **Explanation:** **Gitelman syndrome** is an autosomal recessive salt-wasting tubulopathy caused by a loss-of-function mutation in the **SLC12A3 gene**, which encodes the **thiazide-sensitive sodium-chloride (Na-Cl) cotransporter** in the distal convoluted tubule (DCT). 1. **Why Metabolic Alkalosis is Correct:** The defect in the Na-Cl cotransporter leads to increased delivery of sodium and water to the collecting duct. This stimulates the Renin-Angiotensin-Aldosterone System (RAAS). Aldosterone promotes sodium reabsorption in exchange for potassium and **hydrogen ions (H+)** in the intercalated cells. The excessive loss of H+ ions results in **hypokalemic metabolic alkalosis**, mimicking the chronic use of thiazide diuretics. 2. **Analysis of Incorrect Options:** * **A. Hyperkalemia:** Incorrect. Increased distal delivery of sodium and high aldosterone levels lead to significant potassium wasting, resulting in **hypokalemia**. * **C. Hypermagnesemia:** Incorrect. Gitelman syndrome is uniquely characterized by profound **hypomagnesemia** due to magnesium wasting in the DCT. * **D. High calcium excretion:** Incorrect. Unlike Bartter syndrome (which presents with hypercalciuria), Gitelman syndrome is characterized by **hypocalciuria** (low urinary calcium). This occurs because the reduced intracellular sodium in the DCT cells enhances the activity of the basolateral Na/Ca exchanger, promoting calcium reabsorption. **NEET-PG High-Yield Pearls:** * **Gitelman vs. Bartter:** Gitelman presents later (adolescence/adulthood) and features **hypocalciuria** and **hypomagnesemia**. Bartter presents earlier (infancy) with **hypercalciuria** (mimicking loop diuretics). * **Mnemonic:** **G**itelman = **G**radual (late onset) + **G**ood (low) urinary calcium. * **Clinical Presentation:** Patients often present with muscle cramps, fatigue, and salt craving.

Q: What is the most common organism isolated in emphysematous pyelonephritis?

Escherichia coli. **Explanation:** **Emphysematous Pyelonephritis (EPN)** is a severe, necrotizing infection of the renal parenchyma characterized by the presence of gas within the kidney or perinephric space. It is a urological emergency, predominantly seen in patients with uncontrolled diabetes mellitus (approx. 90% of cases) or urinary tract obstruction. [1] **Why Escherichia coli is correct:** * **E. coli** is the most common organism isolated, accounting for approximately **60-70%** of cases. [1] * **Pathophysiology:** In diabetic patients, high tissue glucose levels provide a substrate for facultative anaerobes like *E. coli*. These bacteria undergo mixed-acid fermentation, producing carbon dioxide ($CO_2$) and hydrogen ($H_2$) gas, which accumulates in the renal tissues. **Why other options are incorrect:** * **Klebsiella pneumoniae:** This is the second most common cause (approx. 10-20%). While it also performs fermentation leading to gas production, its prevalence is significantly lower than *E. coli*. * **Proteus mirabilis:** Though associated with staghorn calculi and urease-producing infections, it is a rare cause of EPN compared to the coliforms. * **Pseudomonas aeruginosa:** This is an uncommon isolate in EPN, usually seen in healthcare-associated infections or post-instrumentation, but it is not the primary causative agent. **High-Yield Clinical Pearls for NEET-PG:** * **Risk Factors:** Diabetes Mellitus (most common) and Female gender. [1] * **Diagnosis:** **NCCT Abdomen** is the gold standard (shows gas in the renal parenchyma). * **Management:** Medical management with IV antibiotics and percutaneous drainage (PCD) is the first line. Emergency nephrectomy is reserved for patients who fail conservative therapy. * **Classification:** Often classified using the **Wan et al.** or **Huang and Tseng** criteria based on CT findings.

Question 1

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

Accepted Answer

Aminoglycosides

Answer

Erythromycin

Answer

Sulphonamides

Answer

Ciprofloxacin

Question 2

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 3

Increased anion gap acidosis is seen in which of the following conditions?

Accepted Answer

Diabetic ketoacidosis (DKA), Alcoholic ketoacidosis (AKA), Renal tubular acidosis (RTA), Alcoholic fatty liver disease (AFLD)

Answer

Renal tubular acidosis (RTA), Alcoholic fatty liver disease (AFLD), Organic aciduria

Answer

Alcoholic fatty liver disease (AFLD), Organic aciduria, Diarrhoea

Answer

Diabetic ketoacidosis (DKA), Alcoholic fatty liver disease (AFLD), Diarrhoea

Question 4

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 5

Which of the following conditions is characterized by these ECG changes?

Accepted Answer

Hyperkalemia

Answer

Hyponatremia

Answer

Hypernatremia

Answer

Hypokalemia

Question 6

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

Question 7

In which one of the following conditions is a renal biopsy contraindicated?

Accepted Answer

Uncontrolled hypertension

Answer

Acute renal failure

Answer

Nephrotic syndrome

Answer

Isolated hematuria

Question 8

Which of the following is a common feature of Gitelman syndrome?

Accepted Answer

Metabolic alkalosis

Answer

Hyperkalemia

Answer

Hypermagnesemia

Answer

High calcium excretion

Question 9

Pre-renal azotemia is associated with which of the following characteristic features?

Accepted Answer

Urinary sodium < 10 mmol/L

Answer

Renal failure index > 1

Answer

Urine osmolality < 500 mOsm/kg

Answer

Urinary creatinine/plasma creatinine ratio < 20

Question 10

What is the most common organism isolated in emphysematous pyelonephritis?

Accepted Answer

Escherichia coli

Answer

Proteus

Answer

Pseudomonas

Answer

Klebsiella

Nephrology — MCQs

Nephrology — MCQs

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