Nephrology — MCQs

Nephrology Indian Medical PG Practice Questions and MCQs

Question 141: Which of the following is the commonest cause of salt-wasting nephropathy?

A. Analgesic (NSAID) misuse (Correct Answer)
B. Amyloidosis
C. Grommets disease
D. Systemic Lupus Erythematosus (SLE)

Explanation: ### Explanation **Salt-wasting nephropathy** refers to a group of renal disorders where the kidney fails to reabsorb sodium despite normal adrenal function, leading to hyponatremia and volume depletion. [1] **Why Analgesic Misuse is Correct:** The primary site for sodium reabsorption is the renal tubule. [1] Salt-wasting occurs predominantly in **Tubulointerstitial Diseases**. Chronic misuse of NSAIDs or analgesics leads to **Analgesic Nephropathy**, characterized by chronic interstitial nephritis and papillary necrosis. The damage to the medullary interstitium and distal tubules impairs the sodium-reabsorbing capacity and the counter-current mechanism, making it the most common clinical cause of salt-wasting among the given options. **Analysis of Incorrect Options:** * **Amyloidosis:** Primarily affects the glomerulus (causing nephrotic syndrome). [2] While it can involve the interstitium in advanced stages, it is not the classic or most common cause of salt-wasting. * **Grommets Disease:** This is a distracter term (Grommets are ventilation tubes used in the ear for Otitis Media with Effusion) and is not a recognized renal pathology. * **Systemic Lupus Erythematosus (SLE):** While SLE (Lupus Nephritis) can involve the tubules, it typically presents as a **Glomerulonephritis** (proteinuria, hematuria, and hypertension) rather than a primary salt-wasting tubulopathy. **NEET-PG High-Yield Pearls:** * **Common Causes of Salt-Wasting:** Chronic Pyelonephritis, Medullary Cystic Disease, Polycystic Kidney Disease (PKD), and Analgesic Nephropathy. * **Clinical Presentation:** Patients often present with "normotensive" or hypotensive states despite renal failure, polyuria, and a craving for salt. * **Distinction:** Do not confuse salt-wasting nephropathy with Addison’s disease; in nephropathy, aldosterone levels are usually elevated (secondary hyperaldosteronism) as the body attempts to compensate for renal sodium loss. [1]

Question 142: What is the most specific marker of renal function?

A. Creatinine clearance
B. Insulin clearance
C. Blood urea
D. Serum creatinine (Correct Answer)

Explanation: The correct answer is **Serum Creatinine**. In the context of routine clinical practice and NEET-PG examinations, serum creatinine is considered the most specific marker for assessing renal function because its production is relatively constant and its excretion is primarily through glomerular filtration [1]. **Why Serum Creatinine is the Correct Answer:** Creatinine is an endogenous breakdown product of creatine phosphate in muscle. Its production rate is constant and proportional to muscle mass [1]. Unlike urea, it is not significantly affected by diet or hydration. While it is slightly secreted by the tubules (leading to a minor overestimation of GFR), it remains the most reliable and specific "single-sample" marker for monitoring stable renal function [2]. **Analysis of Incorrect Options:** * **A. Creatinine Clearance:** While it provides an estimate of GFR, it requires a 24-hour urine collection, which is prone to collection errors. It is often considered more *sensitive* than serum creatinine for early renal impairment but less *specific* as a standalone marker due to increased tubular secretion at low GFR [2]. * **B. Inulin Clearance:** This is the **Gold Standard** for measuring GFR because inulin is freely filtered and neither reabsorbed nor secreted [1], [2]. However, it is an exogenous substance requiring continuous infusion, making it a research tool rather than a routine clinical marker. * **C. Blood Urea:** This is a poor marker of renal function because it is non-specific [4]. Urea levels are significantly influenced by high-protein diets, GI bleeds, dehydration (pre-renal azotemia), and catabolic states (fever/steroids). **High-Yield Clinical Pearls for NEET-PG:** * **Gold Standard for GFR:** Inulin Clearance [1], [2]. * **Most common marker used in practice:** Serum Creatinine [1], [4]. * **Earliest marker of Diabetic Nephropathy:** Microalbuminuria (30–300 mg/day) [3]. * **Cockcroft-Gault Formula:** Used to estimate creatinine clearance; it factors in age, weight, and sex. * **Note:** Serum creatinine may not rise above the normal range until GFR has fallen by approximately 50%, representing a "blind zone" in early renal disease.

Question 143: A patient presents with acute renal failure (ARF) and complete anuria. An ultrasound shows normal findings. What is the next appropriate investigation?

A. Intravenous pyelography (IVP)
B. Antegrade pyelography
C. Retrograde pyelography
D. Radio renogram (Correct Answer)

Explanation: ### Explanation In a patient with **Acute Renal Failure (ARF) and complete anuria** where the ultrasound is normal, the primary diagnostic goal is to differentiate between **acute tubular necrosis (ATN)** and **acute cortical necrosis** or a vascular catastrophe (like bilateral renal artery occlusion). **Why Radio Renogram is the correct answer:** A **Radioisotope Renogram (DTPA or MAG3 scan)** is the investigation of choice to assess renal perfusion and functional integrity in anuric patients [1]. If the scan shows good perfusion but no excretion, it suggests ATN. If there is a complete absence of perfusion (the "rim sign" or "black hole" appearance), it points toward bilateral cortical necrosis or vascular obstruction. It is non-invasive and does not require iodinated contrast, making it safe in ARF. **Analysis of Incorrect Options:** * **A. Intravenous Pyelography (IVP):** Absolutely contraindicated in ARF. The iodinated contrast is nephrotoxic and will not be excreted by a non-functioning kidney, providing no diagnostic value while potentially worsening the renal failure. * **B. Antegrade Pyelography:** This involves percutaneous needle entry into the renal pelvis. It is usually reserved for cases where ultrasound shows hydronephrosis (obstructive uropathy) but a retrograde approach is not possible. * **C. Retrograde Pyelography:** This is used to rule out mechanical obstruction in the ureters. While it can be used in anuria, it is an invasive procedure. Since the ultrasound is normal (no hydronephrosis), a functional study like a renogram is preferred first to assess perfusion. **Clinical Pearls for NEET-PG:** * **Definition of Anuria:** Urine output <50 ml/day [1]. * **Most common cause of ARF with Anuria:** Obstructive uropathy (must be ruled out by USG first) [2]. * **Normal USG + Anuria:** Think of Acute Cortical Necrosis, Bilateral Renal Artery Embolism, or severe ATN. * **Gold Standard for Cortical Necrosis:** Renal Biopsy (shows coagulative necrosis), but **Radio Renogram** is the initial functional imaging of choice.

Question 144: Which of the following has no role in the treatment of dangerous hyperkalemia?

A. Intravenous calcium chloride
B. Salbutamol
C. Hemodialysis
D. Intravenous sodium bicarbonate (Correct Answer)

Explanation: In the management of life-threatening hyperkalemia, the goal is to stabilize the myocardium, shift potassium intracellularly, and enhance elimination [1]. **Explanation of the Correct Answer:** **D. Intravenous Sodium Bicarbonate:** Current clinical guidelines (such as AHA and KDIGO) state that sodium bicarbonate has **no role** in the acute, emergency management of hyperkalemia, especially when used as a monotherapy. It does not lower potassium levels rapidly or reliably in patients without metabolic acidosis. While it may be used in cases of severe pre-existing metabolic acidosis (pH < 7.2), it is no longer considered a first-line treatment for "dangerous" hyperkalemia. **Why the other options are wrong (They ARE used):** * **A. Intravenous Calcium Chloride/Gluconate:** This is the first step in treatment [1]. It **stabilizes the cardiac membrane** by antagonizing the effects of potassium on the resting membrane potential, preventing arrhythmias. It does *not* lower serum potassium. * **B. Salbutamol:** This is a $\beta_2$-agonist that stimulates the Na+/K+-ATPase pump, causing an **intracellular shift** of potassium. It is a rapid-acting temporizing measure. * **C. Hemodialysis:** This is the **most definitive and effective** method for potassium removal, especially in patients with renal failure or those refractory to medical therapy. **High-Yield Clinical Pearls for NEET-PG:** * **The "Rule of 10":** Calcium gluconate (10 ml of 10% solution) is preferred over Calcium chloride because it is less caustic to peripheral veins [1]. * **Insulin-Glucose:** 10 units of IV regular insulin with 50g of 25-50% Dextrose is the most reliable method to shift potassium intracellularly. * **ECG Changes:** The earliest sign is **Tall Tented T-waves**, followed by PR prolongation, loss of P-waves, and finally the **Sine Wave pattern**, which precedes cardiac arrest.

Question 145: Which of the following is NOT a cause of rapidly progressive glomerulonephritis?

A. Systemic Lupus Erythematosus (SLE)
B. Polyarteritis nodosa
C. Post-streptococcal glomerulonephritis
D. Rheumatoid arthritis (Correct Answer)

Explanation: Rapidly Progressive Glomerulonephritis (RPGN) is a clinical syndrome characterized by a rapid decline in GFR (usually >50% within weeks to months) and the histological hallmark of **crescent formation** in the majority of glomeruli [1]. **Explanation of the Correct Answer:** * **Option D (Rheumatoid Arthritis):** While RA is a systemic inflammatory disease, it is **not** a recognized cause of RPGN. Renal involvement in RA is typically due to secondary amyloidosis (AA type), membranous nephropathy (often drug-induced by gold or penicillamine), or analgesic nephropathy. It does not typically manifest as a crescentic, rapidly declining glomerulonephritis. **Explanation of Incorrect Options:** * **Option A (SLE):** Lupus Nephritis (specifically Class IV - Diffuse Proliferative GN) is a classic cause of **Type II (Immune-complex mediated) RPGN** [1]. * **Option B (Polyarteritis nodosa):** Although classic PAN involves medium-sized vessels and often spares the glomueruli, it is frequently grouped with systemic vasculitides that cause **Type III (Pauci-immune) RPGN** [1]. Note: Microscopic Polyangiitis (MPA) is a more common cause of RPGN than classic PAN. * **Option C (PSGN):** While most cases of PSGN resolve spontaneously, a small percentage (approx. 1-3%) can progress to a "crescentic" phase, leading to RPGN [1]. **High-Yield Clinical Pearls for NEET-PG:** * **Classification of RPGN:** 1. **Type I (Anti-GBM):** Goodpasture syndrome (Linear IgG deposits) [1]. 2. **Type II (Immune Complex):** SLE, PSGN, IgA Nephropathy, Henoch-Schönlein Purpura (Lumpy-bumpy/Granular deposits) [1]. 3. **Type III (Pauci-immune):** Wegener’s (GPA), Microscopic Polyangiitis, Churg-Strauss (ANCA associated; little to no immune deposits) [1]. * **Histology:** The "crescents" are formed by the proliferation of **parietal epithelial cells** and the migration of monocytes/macrophages into Bowman’s space.

Question 146: A 68-year-old man weighing 60 kg has a plasma creatinine of 3 mg/dL. What is his estimated creatinine clearance?

A. 10 mL/min
B. 20 mL/min (Correct Answer)
C. 30 mL/min
D. 40 mL/min

Explanation: To calculate the estimated Creatinine Clearance (eCrCl) in a clinical setting, the **Cockcroft-Gault formula** is the gold standard for exam purposes. ### **Calculation using Cockcroft-Gault Formula:** The formula is: $\text{CrCl (mL/min)} = \frac{(140 - \text{Age}) \times \text{Weight (kg)}}{72 \times \text{Plasma Creatinine (mg/dL)}}$ *Note: For females, multiply the result by 0.85.* **Plugging in the values:** $\text{CrCl} = \frac{(140 - 68) \times 60}{72 \times 3}$ $\text{CrCl} = \frac{72 \times 60}{72 \times 3}$ $\text{CrCl} = \frac{60}{3} = \mathbf{20 \text{ mL/min}}$ ### **Analysis of Options:** * **Option B (20 mL/min):** This is the correct value derived from the standard formula. * **Options A, C, and D:** These are incorrect as they do not align with the mathematical calculation. A common error is forgetting to include the "72" constant or miscalculating the age factor (140 - 68 = 72). ### **NEET-PG High-Yield Pearls:** 1. **Formula Variables:** Remember that CrCl is **directly proportional** to body weight and **inversely proportional** to age and serum creatinine. 2. **Gender Adjustment:** Always check the gender in the clinical vignette. If this patient were female, the answer would be $20 \times 0.85 = 17 \text{ mL/min}$. 3. **Limitations:** The Cockcroft-Gault formula overestimates GFR because creatinine is not only filtered by the glomerulus but also secreted by the proximal tubules [1]. 4. **CKD Staging:** A CrCl of 20 mL/min places this patient in **Stage 4 Chronic Kidney Disease** (Severely decreased GFR: 15–29 mL/min).

Question 147: Which of the following is NOT typically seen in cystitis?

A. Fever (Correct Answer)
B. Hematuria
C. Dysuria
D. Nocturia

Explanation: **Explanation:** The clinical differentiation between **Lower Urinary Tract Infection (Cystitis)** and **Upper Urinary Tract Infection (Pyelonephritis)** is a high-yield concept for NEET-PG. **1. Why Fever is the Correct Answer:** Cystitis is a localized mucosal inflammation of the bladder. It is typically **afebrile** because the infection is confined to the bladder surface and does not involve the renal parenchyma or systemic circulation. The presence of high-grade fever, chills, and rigors strongly suggests that the infection has ascended to the kidneys (Acute Pyelonephritis) or has resulted in bacteremia [1]. [2] **2. Analysis of Incorrect Options:** * **Dysuria (Option C):** This is the hallmark symptom of cystitis, caused by the irritation of the urethral and bladder mucosal lining during micturition. * **Nocturia (Option D) and Frequency:** Inflammation of the bladder wall (detrusor muscle) leads to decreased bladder capacity and increased irritability, resulting in the frequent urge to void during the day and night. * **Hematuria (Option B):** Gross or microscopic hematuria occurs due to the friability of the inflamed bladder mucosa [3]. When present with dysuria, it is often termed "hemorrhagic cystitis." **Clinical Pearls for NEET-PG:** * **The "Triad" of Cystitis:** Dysuria, Frequency, and Urgency. * **Pyelonephritis Indicators:** Fever, flank pain (CVA tenderness), and nausea/vomiting [2]. * **Most Common Pathogen:** *E. coli* remains the leading cause of both cystitis and pyelonephritis [2]. * **Sterile Pyuria:** If a patient has symptoms of cystitis but negative routine cultures, consider *Chlamydia trachomatis* or *Neisseria gonorrhoeae* [1].

Question 148: All of the following factors are associated with adverse prognosis and high risk of renal progression in Lupus Nephritis, EXCEPT:

A. High levels of Anti-ds DNA
B. Persistent proteinuria (nephrotic range > 3 gm/day)
C. Hypocomplementenemia
D. Anti-LA (SSB) (Correct Answer)

Explanation: **Explanation:** In Systemic Lupus Erythematosus (SLE), renal involvement is a major determinant of morbidity and mortality. Identifying markers of poor renal prognosis is crucial for aggressive management. **Why Anti-La (SSB) is the correct answer:** Anti-La (SSB) and Anti-Ro (SSA) antibodies are classically associated with **Sjögren’s syndrome** [1] and **Neonatal Lupus** (congenital heart block). In the context of SLE, they are often associated with a *lower* risk of developing severe nephritis. Therefore, they are not markers of adverse renal prognosis or progression. **Analysis of Incorrect Options (Markers of Poor Prognosis):** * **High levels of Anti-dsDNA:** There is a strong correlation between rising titers of Anti-dsDNA and the development of lupus nephritis (especially Class III and IV). It reflects active disease and a higher risk of renal flares. * **Persistent Nephrotic-range Proteinuria:** Proteinuria >3 g/day is a significant clinical predictor of progression to End-Stage Renal Disease (ESRD). Failure to achieve a "renal response" (reduction in proteinuria) within 6–12 months of therapy indicates a poor long-term prognosis. * **Hypocomplementemia (Low C3, C4):** Low complement levels indicate active classical pathway activation and immune complex deposition in the glomeruli. Persistent hypocomplementemia is a hallmark of active lupus nephritis and predicts poor renal outcomes. **NEET-PG High-Yield Pearls:** * **Most common cause of death in SLE:** Renal failure (early years) and Cardiovascular disease (late years). * **Most sensitive antibody for SLE:** ANA (95-98%) [1]. * **Most specific antibodies for SLE:** Anti-dsDNA and Anti-Smith (Anti-Sm) [1]. * **Histopathology:** Class IV (Diffuse Proliferative Lupus Nephritis) is the most common and most severe form. * **Other poor prognostic factors:** Elevated serum creatinine at presentation, male gender, African American ethnicity, and high Chronicity Index on renal biopsy.

Question 149: Hereditary nephritis is seen in:

A. Analgesic nephropathy
B. Balkan nephropathy
C. Alport syndrome (Correct Answer)
D. Eosinophilic nephritis

Explanation: **Explanation:** **Alport Syndrome** is the correct answer as it is a classic example of **hereditary nephritis** [1]. It is primarily an X-linked dominant disorder (85% of cases) caused by mutations in the genes encoding the **alpha-chains of Type IV collagen** (specifically COL4A3, COL4A4, and COL4A5) [1]. Type IV collagen is a structural component of the basement membranes in the kidney, ears, and eyes. Clinically, it presents with a triad of progressive hematuria (leading to ESRD), sensorineural hearing loss, and ocular abnormalities (e.g., anterior lenticonus). **Analysis of Incorrect Options:** * **Analgesic Nephropathy:** This is an **acquired** chronic interstitial nephritis caused by the long-term overuse of pain medications (e.g., phenacetin, NSAIDs). It is characterized by renal papillary necrosis. * **Balkan Nephropathy:** This is an **environmentally induced** chronic tubulointerstitial nephritis found in the Danube River basin [3]. It is linked to the ingestion of **aristolochic acid** from seeds of the *Aristolochia clematitis* plant [3]. * **Eosinophilic Nephritis:** This is typically a manifestation of **Acute Interstitial Nephritis (AIN)**, most commonly a hypersensitivity reaction to drugs (e.g., NSAIDs, antibiotics like Penicillin). It is an immunologic, not hereditary, condition. **High-Yield Clinical Pearls for NEET-PG:** * **Electron Microscopy (EM) Finding:** The pathognomonic feature of Alport Syndrome is the **"Basket-weave appearance"** (irregular thickening, thinning, and splitting of the Glomerular Basement Membrane) [1]. * **Thin Basement Membrane Disease (TBMD):** Also known as Benign Familial Hematuria; it is a differential for Alport but has a much better prognosis. * **Goodpasture Syndrome vs. Alport:** While both involve Type IV collagen, Goodpasture is an *autoimmune* attack against the alpha-3 chain [2], whereas Alport is a *genetic* defect [1].

Question 150: A female patient presents with an upper respiratory tract infection. Two days later, she develops hematuria. What is the probable diagnosis?

A. IgA nephropathy (Correct Answer)
B. Wegener's granulomatosis
C. Henoch-Schonlein purpura
D. Poststreptococcal glomerulonephritis

Explanation: ### Explanation **Correct Answer: A. IgA nephropathy** The clinical hallmark of **IgA nephropathy (Berger’s disease)** is **synpharyngitic hematuria** [1]. This refers to the onset of gross hematuria occurring simultaneously or within 1–3 days of an upper respiratory tract infection (URTI) [1]. The underlying mechanism involves the overproduction of galactose-deficient IgA1 in response to mucosal triggers, which forms immune complexes that deposit in the glomerular mesangium, causing inflammation [1]. **Why the other options are incorrect:** * **Poststreptococcal glomerulonephritis (PSGN):** This is the most common differential. However, PSGN has a **latent period** of 1–3 weeks after a sore throat (pharyngitis) or 3–6 weeks after a skin infection (impetigo). It is associated with low C3 complement levels, whereas IgA nephropathy typically has normal complement levels. * **Henoch-Schönlein Purpura (HSP):** While HSP shares the same pathology as IgA nephropathy (IgA vasculitis), it is a systemic disease. Diagnosis requires extra-renal manifestations like palpable purpura (usually on lower limbs), arthralgia, and abdominal pain. * **Wegener’s Granulomatosis (GPA):** This is a small-vessel vasculitis characterized by involving the upper/lower respiratory tract (sinusitis, lung nodules) and kidneys (RPGN). It is associated with c-ANCA (PR3) positivity and does not typically present as immediate post-URTI hematuria. **High-Yield Clinical Pearls for NEET-PG:** * **Most common** cause of primary glomerulonephritis worldwide. * **Complement levels:** Characteristically **normal** (unlike PSGN, Lupus, or MPGN). * **Prognostic Marker:** Persistent proteinuria (>1g/day) is the most important predictor of progression to ESRD. * **Association:** Frequently associated with Celiac disease and Liver cirrhosis (decreased clearance of IgA complexes).

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Glomerular Diseases

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Urinary Tract Infections

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Renal Replacement Therapy

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Fluid and Electrolyte Disorders

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Acid-Base Disorders

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Nephrology — MCQs

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