Nephrology — MCQs

Nephrology Indian Medical PG Practice Questions and MCQs

Question 431: Which gene is most commonly mutated in autosomal dominant polycystic kidney disease (ADPKD)?

A. PKD1 (Correct Answer)
B. PKD2
C. NHPS1
D. HEF

Explanation: Explanation: Autosomal Dominant Polycystic Kidney Disease (ADPKD) is the most common inherited kidney disease [1]. It is characterized by the progressive development of numerous fluid-filled cysts in both kidneys, eventually leading to end-stage renal disease (ESRD). 1. Why PKD1 is correct: Approximately 85% of ADPKD cases are caused by mutations in the PKD1 gene, located on chromosome 16p13.3 [1]. This gene encodes the protein Polycystin-1, which is involved in cell-cell and cell-matrix interactions. Patients with PKD1 mutations typically present earlier and progress to ESRD at a younger age (mean age ~54 years) compared to PKD2 [1]. 2. Why other options are incorrect: * PKD2: Mutations in this gene (located on chromosome 4q21) account for the remaining ~15% of cases [1]. It encodes Polycystin-2. While clinically similar to PKD1, the disease course is generally milder and progresses to ESRD later in life (mean age ~74 years). * NPHS1: This gene encodes Nephrin and is mutated in Finnish-type Congenital Nephrotic Syndrome, not ADPKD. * HEF: This is not a recognized gene associated with polycystic kidney disease. High-Yield Clinical Pearls for NEET-PG: * Extra-renal manifestations: The most common is Liver cysts (Polycystic Liver Disease). The most serious is Berry aneurysms (Circle of Willis), which can lead to subarachnoid hemorrhage [1]. * Diagnosis: Ultrasonography is the primary screening tool; diagnostic criteria are based on the number of cysts relative to the patient's age [1]. * Treatment: Tolvaptan (a Vasopressin V2 receptor antagonist) is used to slow the progression of cyst growth and renal decline in high-risk patients. * Mnemonic: PKD1 is on Chromosome 16 (1+6=7; 16 is "sweet sixteen" and more common). PKD2 is on Chromosome 4.

Question 432: Which one of the following statements is FALSE regarding Dent's disease?

A. X-linked recessive disorder
B. Mutation in the sodium-potassium-chloride cotransporter (Correct Answer)
C. Hypercalciuria
D. Recurrent kidney stones

Explanation: **Explanation:** **Dent’s Disease** is a rare X-linked recessive proximal tubulopathy that belongs to the spectrum of **Fanconi Syndrome**. **Why Option B is the Correct (False) Statement:** The genetic hallmark of Dent’s disease is a mutation in the **CLCN5 gene**, which encodes the **ClC-5 chloride/proton antiporter**. This transporter is essential for the endocytosis of low-molecular-weight proteins in the proximal tubule. A mutation in the **sodium-potassium-chloride (NKCC2) cotransporter** actually causes **Bartter Syndrome (Type 1)**, not Dent’s disease. **Analysis of Other Options:** * **Option A (X-linked recessive):** This is true. Dent’s disease primarily affects males due to its X-linked inheritance pattern. * **Option C & D (Hypercalciuria and Recurrent Stones):** These are classic clinical features. The disease is characterized by the "classic triad": **Low-molecular-weight (LMW) proteinuria**, **hypercalciuria**, and at least one of the following: nephrocalcinosis, kidney stones (nephrolithiasis), or progressive renal failure. **High-Yield Clinical Pearls for NEET-PG:** * **LMW Proteinuria:** This is the most consistent finding (e.g., elevation of beta-2 microglobulin). * **Distinction from Lowe Syndrome:** Both are X-linked and cause Fanconi syndrome, but Lowe Syndrome (Oculocerebrorenal syndrome) also presents with congenital cataracts and intellectual disability. * **Treatment:** Focuses on preventing stones (hydration and thiazide diuretics) and managing chronic kidney disease progression. Avoid high doses of Vitamin D as it can worsen hypercalciuria [1].

Question 433: Salt-losing nephritis is a feature of which of the following conditions?

A. Interstitial nephritis (Correct Answer)
B. Renal amyloidosis
C. Lupus nephritis
D. Post-streptococcal glomerulonephritis

Explanation: **Explanation:** **Salt-losing nephritis** refers to a clinical syndrome where the kidneys are unable to conserve sodium despite low dietary intake, leading to hyponatremia, volume depletion, and hypotension. **Why Interstitial Nephritis is correct:** The primary site of sodium reabsorption is the renal tubules. In **Chronic Interstitial Nephritis (CIN)** and Medullary Cystic Disease, the structural damage occurs in the interstitium and the tubular basement membrane [1]. This disrupts the tubular transport mechanisms and the medullary concentration gradient. Consequently, the tubules become "blind" to aldosterone and fail to reabsorb sodium, leading to obligatory salt wasting. **Why the other options are incorrect:** * **Renal Amyloidosis:** Typically presents with nephrotic syndrome (massive proteinuria) due to glomerular deposition [2]. While it can involve the tubules, it is not a classic cause of salt-wasting. * **Lupus Nephritis:** This is primarily a glomerulonephritis (GN) characterized by immune complex deposition [4]. It usually presents with hypertension and sodium *retention* (edema) rather than salt wasting. * **Post-streptococcal Glomerulonephritis (PSGN):** An acute nephritic syndrome characterized by a decreased GFR, leading to salt and water retention, edema, and hypertension [3]. **High-Yield Clinical Pearls for NEET-PG:** * **Common causes of Salt-losing Nephritis:** Chronic pyelonephritis, Polycystic Kidney Disease (PKD), Medullary cystic disease, and Analgesic nephropathy. * **Differential Diagnosis:** Must be distinguished from **Addison’s Disease**. In salt-losing nephritis, ACTH and Cortisol levels are normal, but the kidney fails to respond to mineralocorticoids. * **Key Feature:** Patients require a high-salt diet to maintain fluid balance; restricting salt in these patients can lead to acute renal failure.

Question 434: RBC casts are typically found in which of the following conditions?

A. Diabetes Mellitus
B. Wegener's Granulomatosis (Correct Answer)
C. Systemic Exertional Exertion
D. Ankylosing Spondylitis

Explanation: The presence of **RBC casts** in urine is a pathognomonic marker of **Glomerulonephritis (GN)** or upper urinary tract bleeding. They form when red blood cells enter the renal tubule through a damaged basement membrane and are trapped within a matrix of Tamm-Horsfall protein [1]. **Why Wegener’s Granulomatosis is correct:** Wegener’s Granulomatosis (now known as Granulomatosis with Polyangiitis or GPA) is a small-vessel vasculitis [2]. It characteristically involves the kidneys, causing **Pauci-immune Crescentic Glomerulonephritis** [3]. This condition leads to severe glomerular capillary damage, allowing RBCs to leak into the tubules and form casts [1]. It is typically associated with **c-ANCA (PR3)** positivity. **Analysis of Incorrect Options:** * **A. Diabetes Mellitus:** Typically presents with proteinuria (micro/macroalbuminuria). While it causes glomerular damage, it usually presents with **waxy casts** or fatty casts (in nephrotic stages), not RBC casts, unless there is a superimposed inflammatory GN [1]. * **C. Systemic Exertional Exertion:** While extreme exercise can cause transient hematuria or hyaline casts, it does not typically produce RBC casts, which signify structural glomerular pathology [4]. * **D. Ankylosing Spondylitis:** This is a seronegative spondyloarthropathy. While it can rarely be associated with IgA Nephropathy or secondary Amyloidosis, it is not a primary or common cause of RBC casts. **NEET-PG High-Yield Pearls:** * **RBC Casts = Nephritic Syndrome** (e.g., PSGN, RPGN, Goodpasture’s, Lupus Nephritis) [1]. * **WBC Casts** = Acute Pyelonephritis or Tubulointerstitial Nephritis. * **Muddy Brown (Granular) Casts** = Acute Tubular Necrosis (ATN). * **Fatty Casts ("Maltese Cross")** = Nephrotic Syndrome. * **Broad/Waxy Casts** = Chronic Renal Failure (due to dilated tubules).

Question 435: At which stage of renal deterioration are the signs and symptoms of chronic renal failure (CRF) typically observed?

A. GFR 90 ml/min/1.73m 2
B. GFR 70 ml/min/1.73m 2
C. GFR 45 ml/min/1.73m 2 (Correct Answer)
D. GFR 80 ml/min/1.73m 2

Explanation: **Explanation:** Chronic Kidney Disease (CKD) is a progressive loss of renal function. The kidneys possess a significant **functional reserve**, meaning they can maintain homeostasis even when a large number of nephrons are lost [1]. 1. **Why Option C is Correct:** Clinical signs and symptoms of chronic renal failure (such as fatigue, anemia, nocturia, and mild electrolyte imbalances) typically do not manifest until the GFR falls below **50% of normal** (roughly <60 ml/min/1.73m²) [1]. Specifically, **Stage 3b CKD (GFR 30–44 ml/min/1.73m²)** is the threshold where metabolic changes become clinically evident. At a GFR of **45 ml/min**, the compensatory mechanisms of the remaining nephrons are overwhelmed, leading to the accumulation of nitrogenous waste (azotemia) and the onset of overt clinical symptoms [1]. 2. **Why Other Options are Incorrect:** * **Options A, B, and D (GFR 90, 80, and 70 ml/min):** These values represent Stage 1 or Stage 2 CKD. In these stages, patients are usually **asymptomatic**, as many diseases of the kidney are clinically silent in the early stages [1]. The remaining healthy nephrons undergo compensatory hypertrophy and hyperfiltration, maintaining normal excretory and endocrine functions. Diagnosis at these stages usually relies on markers of kidney damage (like albuminuria) rather than clinical symptoms. **High-Yield Clinical Pearls for NEET-PG:** * **Definition of CKD:** Evidence of kidney damage or GFR <60 ml/min/1.73m² for **≥3 months** [1]. * **First Clinical Sign:** Often **nocturia** (due to loss of concentrating ability) or **anemia** (due to decreased Erythropoietin) [1]. * **Most Common Cause:** Diabetes Mellitus (followed by Hypertension) [1]. * **Uremic Symptoms:** Usually appear when GFR drops below **15 ml/min** (Stage 5/ESRD), necessitating renal replacement therapy [1].

Question 436: Which of the following features favors prerenal azotemia over acute tubular necrosis (ATN)?

A. Urine osmolality > 500 mosmol/kg (Correct Answer)
B. Fractional excretion of sodium (FeNa) < 1%
C. Plasma urea/creatinine ratio > 20
D. Urine sodium < 10 mEq/L

Explanation: In **Prerenal Azotemia**, the kidneys are structurally intact but suffer from reduced perfusion. To compensate, the kidneys maximally reabsorb water and sodium, resulting in highly concentrated urine [1]. In contrast, **Acute Tubular Necrosis (ATN)** involves tubular damage, leading to a loss of concentrating ability and "salt-wasting." ### Why Option A is the Best Answer **Urine Osmolality > 500 mOsm/kg** is the most reliable indicator of intact tubular function. In prerenal states, high levels of ADH cause maximal water reabsorption, concentrating the urine. In ATN, the damaged tubules cannot maintain an osmotic gradient, resulting in isosthenuria (urine osmolality similar to plasma, usually <350 mOsm/kg). ### Analysis of Other Options While options B, C, and D are characteristic of prerenal azotemia, they are considered less definitive or "less favorable" in the context of this specific comparative question: * **FeNa < 1% (Option B):** Though a classic marker for prerenal states, it can be misleadingly low in early ATN (e.g., contrast-induced nephropathy or rhabdomyolysis). * **BUN/Creatinine Ratio > 20 (Option C):** This ratio increases in prerenal states due to enhanced proximal tubular reabsorption of urea. However, it can also be elevated in GI bleeds, steroid use, or high-protein diets, making it less specific for renal perfusion. * **Urine Sodium < 20 mEq/L (Option D):** Prerenal states typically show $U_{Na} < 20$ (not just <10). While <10 is suggestive, a high urine osmolality is a more physiologically robust indicator of tubular integrity. ### High-Yield Clinical Pearls for NEET-PG * **FeNa Calculation:** $(U_{Na} imes P_{Cr}) / (P_{Na} imes U_{Cr}) imes 100$. * **Exceptions to FeNa:** FeNa is unreliable if the patient is on **diuretics**. In such cases, use **Fractional Excretion of Urea (FeUrea < 35%)** to diagnose prerenal azotemia. * **Microscopy:** Prerenal azotemia shows **hyaline casts**, while ATN is characterized by **"muddy brown" granular casts" [1].

Question 437: Orthostatic proteinuria is defined as:

A. Proteinuria seen in the recumbent position
B. A benign condition (Correct Answer)
C. Associated with future risk of nephrotic syndrome
D. Excretion of > 300 mg of protein per day

Explanation: **Explanation:** **Orthostatic (Postural) Proteinuria** is a clinical entity characterized by the excretion of protein in the urine only when the patient is in an upright (orthostatic) position, while protein excretion remains normal when the patient is recumbent [1]. 1. **Why Option B is Correct:** Orthostatic proteinuria is considered a **benign condition** [1] with an excellent long-term prognosis. It is most commonly seen in adolescents and young adults (under age 30). It does not typically progress to chronic kidney disease or systemic illness, and in many cases, it resolves spontaneously as the patient ages. 2. **Why Other Options are Incorrect:** * **Option A:** Proteinuria is specifically **absent** in the recumbent position [1]. The diagnostic hallmark is a split urine collection showing normal protein levels in the overnight/supine sample. * **Option C:** It is **not** a precursor to nephrotic syndrome. It is a functional abnormality, likely due to hemodynamic changes or "nutcracker phenomenon" (compression of the left renal vein), rather than structural glomerular damage [1]. * **Option D:** Total 24-hour protein excretion in these patients is usually **less than 1 gram/day** (rarely exceeding 1.5g). While it is >150mg/day, the defining feature is the postural variation, not a specific threshold like 300mg. **High-Yield NEET-PG Pearls:** * **Diagnosis:** Requires a **Split Urine Collection**. The first morning void (representing the recumbent period) must be negative for protein, while daytime samples (ambulatory) show proteinuria [1]. * **Demographics:** Most common cause of isolated proteinuria in children and young adults. * **Management:** Reassurance and periodic monitoring. No aggressive treatment or renal biopsy is indicated unless protein levels exceed 1.5g/day or hematuria develops.

Question 438: What surgical procedure is most commonly associated with postoperative acute kidney injury?

A. Cardiac surgery with cardiopulmonary bypass (Correct Answer)
B. Neurosurgery
C. Transurethral resection of the prostate (TURP)
D. Carcinoma breast surgery

Explanation: **Explanation:** **1. Why Cardiac Surgery is Correct:** Cardiac surgery involving **cardiopulmonary bypass (CPB)** is the most common surgical cause of postoperative Acute Kidney Injury (AKI). The pathophysiology is multifactorial: * **Ischemia-Reperfusion Injury:** Non-pulsatile blood flow during bypass can lead to renal hypoperfusion. * **Inflammatory Response:** Contact of blood with the bypass circuit triggers a systemic inflammatory response syndrome (SIRS). * **Hemolysis:** Mechanical trauma to RBCs releases free hemoglobin, which is nephrotoxic. * **Oxidative Stress:** Reintroduction of oxygenated blood leads to the formation of reactive oxygen species (ROS) that damage tubular cells. **2. Analysis of Incorrect Options:** * **Neurosurgery:** While prolonged procedures carry a risk of dehydration or SIADH/Diabetes Insipidus, they are not inherently associated with high rates of AKI compared to cardiac procedures. * **TURP:** This is more commonly associated with **TURP Syndrome** (dilutional hyponatremia due to absorption of glycine/irrigation fluid) rather than primary AKI. * **Carcinoma Breast Surgery:** This is typically a superficial/soft tissue surgery with minimal hemodynamic instability or fluid shifts, making the risk of AKI very low. **3. High-Yield Clinical Pearls for NEET-PG:** * **Definition:** Post-cardiac surgery AKI is defined as an increase in serum creatinine by ≥0.3 mg/dL within 48 hours. * **Risk Factors:** Pre-existing CKD, advanced age, prolonged bypass time (>120 mins), and use of intra-aortic balloon pump (IABP). * **Prevention:** Maintaining adequate mean arterial pressure (MAP) and avoiding nephrotoxic drugs (NSAIDs, ACE inhibitors) perioperatively are the primary preventive strategies. * **Prognosis:** Even a minor rise in creatinine post-cardiac surgery is independently associated with increased 30-day mortality.

Question 439: Goodpasture's syndrome is characterized by:

A. Necrotizing hemorrhagic interstitial pneumonitis
B. Alveolitis
C. Patchy consolidation (Correct Answer)
D. Pulmonary edema

Explanation: **Explanation:** Goodpasture’s Syndrome (Anti-GBM disease) is an autoimmune disorder characterized by the presence of circulating antibodies against the **α3 chain of Type IV collagen** [2], found in the glomerular basement membrane [1] and pulmonary alveolar capillaries. **Why "Patchy Consolidation" is correct:** The hallmark pulmonary manifestation of Goodpasture’s syndrome is **diffuse alveolar hemorrhage (DAH)**. On a chest X-ray or CT scan, this intra-alveolar bleeding presents as **patchy or confluent areas of consolidation** (airspace opacities). These opacities are typically bilateral and perihilar, often sparing the costophrenic angles. Over time, as the blood is cleared, these may transition into ground-glass opacities. **Analysis of Incorrect Options:** * **A. Necrotizing hemorrhagic interstitial pneumonitis:** While the disease involves hemorrhage, it is primarily **alveolar**, not interstitial. The pathology shows intra-alveolar siderophages (hemosiderin-laden macrophages) rather than primary interstitial inflammation. * **B. Alveolitis:** This is a generic term for inflammation of the alveoli (common in extrinsic allergic alveolitis). In Goodpasture’s, the primary event is capillary basement membrane damage leading to hemorrhage, not a primary inflammatory alveolitis. * **C. Pulmonary edema:** While it may mimic the radiological appearance of DAH, pulmonary edema is caused by fluid overload or heart failure (hemodynamic), whereas Goodpasture’s is an autoimmune-mediated hemorrhagic process. **High-Yield Clinical Pearls for NEET-PG:** * **Triad:** Glomerulonephritis (RPGN), Pulmonary hemorrhage, and Anti-GBM antibodies [2]. * **Immunofluorescence:** Shows **Linear IgG deposits** along the basement membrane (Classic "Ribbon-like" appearance) [1]. * **Pulmonary Function Test:** Characteristically shows an **increased DLCO** (due to the presence of hemoglobin within the alveoli which binds CO). * **Treatment:** Plasmapheresis (to remove antibodies) + Corticosteroids + Cyclophosphamide [2]. * **Demographics:** Often affects young males (pulmonary-renal) or elderly females (renal-limited).

Question 440: Restless leg syndrome (RLS) is commonly seen in which of the following conditions?

A. Hypercalcemia
B. Hyperphosphatemia
C. Chronic renal failure (Correct Answer)
D. Hyperkalemia

Explanation: **Explanation:** **Restless Leg Syndrome (RLS)**, also known as Willis-Ekbom Disease, is a common neurological complication of **Chronic Renal Failure (CRF)** [1], particularly in patients with End-Stage Renal Disease (ESRD) on hemodialysis. [2] **Why Chronic Renal Failure is Correct:** The exact pathophysiology in CRF is multifactorial but is primarily linked to **iron deficiency** (common in uremia) and **dopaminergic dysfunction**. Iron is a necessary cofactor for tyrosine hydroxylase, the rate-limiting enzyme in dopamine synthesis. Uremic toxins and the associated anemia in CRF exacerbate these symptoms. RLS in these patients typically presents as an irresistible urge to move the legs, often accompanied by uncomfortable sensations that worsen at rest and during the night. [1] **Analysis of Incorrect Options:** * **A, B, and D (Hypercalcemia, Hyperphosphatemia, Hyperkalemia):** While these electrolyte imbalances are frequent complications of Chronic Renal Failure, they do not directly cause RLS. * **Hypercalcemia** typically presents with "stones, bones, abdominal groans, and psychic moans." * **Hyperphosphatemia** contributes to secondary hyperparathyroidism and pruritus. * **Hyperkalemia** is a medical emergency primarily affecting cardiac conduction. **High-Yield Clinical Pearls for NEET-PG:** * **First-line treatment for RLS in non-uremic patients:** Dopamine agonists (e.g., Pramipexole, Ropinirole). * **Treatment in CRF:** Management involves improving dialysis adequacy, correcting iron deficiency (target ferritin >100 ng/mL), and using Gabapentin or Pregabalin (often preferred over dopamine agonists in uremic RLS). * **Secondary causes of RLS:** Iron deficiency anemia (most common), Pregnancy, Diabetes Mellitus (peripheral neuropathy), and CRF. [1]

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Acute Kidney Injury

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Chronic Kidney Disease

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Glomerular Diseases

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Tubulointerstitial Diseases

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Nephrotic and Nephritic Syndromes

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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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Kidney in Systemic Diseases

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Kidney Stones and Obstructive Uropathy

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Hypertension in Kidney Disease

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Nephrology — MCQs

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