Nephrology — MCQs

Nephrology Indian Medical PG Practice Questions and MCQs

Question 591: RBC casts in the microscopic examination of urine are an indicator of which of the following conditions?

A. Acute glomerulonephritis (Correct Answer)
B. Acute pyelonephritis
C. Chronic glomerulonephritis
D. Nephrotic syndrome

Explanation: ### Explanation **1. Why Acute Glomerulonephritis (AGN) is Correct:** RBC casts are the hallmark of **glomerular bleeding** [3]. In AGN, the glomerular filtration barrier is damaged (due to inflammation), allowing Red Blood Cells (RBCs) to leak into the nephron [3]. As these cells pass through the distal convoluted tubule and collecting duct, they are trapped within a matrix of **Tamm-Horsfall protein** (uromodulin). The cylindrical shape of the tubule molds them into "casts." Their presence definitively localizes the source of hematuria to the renal parenchyma (specifically the glomeruli) rather than the lower urinary tract [1]. **2. Why the Other Options are Incorrect:** * **B. Acute Pyelonephritis:** This is an upper urinary tract infection characterized by **WBC casts** (leukocyte casts) and bacteria, indicating tubulointerstitial inflammation. * **C. Chronic Glomerulonephritis:** While RBCs may be seen, the characteristic finding in chronic renal failure is **Broad, Waxy casts**, which result from the compensatory dilation of remaining functional nephrons. * **D. Nephrotic Syndrome:** This is characterized by massive proteinuria [3]. The classic microscopic findings are **Fatty casts**, "Maltese cross" appearance under polarized light, and oval fat bodies. **3. NEET-PG High-Yield Pearls:** * **RBC Casts:** Pathognomonic for Glomerulonephritis (e.g., PSGN, IgA Nephropathy, RPGN) [3]. * **WBC Casts:** Pathognomonic for Pyelonephritis or Acute Interstitial Nephritis (AIN). * **Eosinophiluria:** Highly suggestive of Drug-induced AIN [4]. * **Muddy Brown (Granular) Casts:** Pathognomonic for Acute Tubular Necrosis (ATN). * **Hyaline Casts:** Can be normal (seen in dehydration or after intense exercise). * **Dysmorphic RBCs (Acanthocytes):** Like RBC casts, these indicate a glomerular origin of hematuria [2].

Question 592: Anuria is defined as passing less than _____ ml of urine per day?

A. 400ml
B. 3000ml
C. 100ml (Correct Answer)
D. 1000ml

Explanation: ### Explanation **Correct Option: C (100 ml)** **Medical Concept:** In clinical nephrology, **Anuria** is defined as a urine output of **less than 100 ml in 24 hours**. It represents a near-complete cessation of urine production and is a medical emergency [1]. It is most commonly associated with total urinary tract obstruction, severe acute tubular necrosis (ATN), or catastrophic vascular events (e.g., bilateral renal artery occlusion or cortical necrosis). **Analysis of Incorrect Options:** * **A. 400 ml:** This is the threshold for **Oliguria**. Oliguria is defined as urine output **<400 ml/day** (or <0.5 ml/kg/hr in adults) [1]. This volume is significant because it is the minimum amount of urine required to excrete the daily solute load (approx. 600 mOsm) under maximal urinary concentration. * **B. 3000 ml:** This threshold (specifically >3 L/day) defines **Polyuria**. It is seen in conditions like Diabetes Mellitus, Diabetes Insipidus, or the diuretic phase of ATN. * **D. 1000 ml:** This is within the range of normal daily urine output (typically 800–2000 ml/day depending on fluid intake). **High-Yield Clinical Pearls for NEET-PG:** * **Azotemia:** Biochemical abnormality (elevated BUN/Creatinine) without clinical symptoms. * **Uremia:** The clinical syndrome resulting from renal failure (pericarditis, encephalopathy, asterixis). * **Sudden Anuria:** Always rule out **Post-renal obstruction** (e.g., stones, prostatic hypertrophy) first using bedside ultrasound [1]. * **Non-oliguric AKI:** Urine output remains >400 ml/day despite rising creatinine; often seen in aminoglycoside toxicity or contrast-induced nephropathy.

Question 593: All of the following are true about ischemia-associated kidney injury, EXCEPT:

A. Healthy kidneys account for 10% of total oxygen consumption.
B. The renal medulla is the most hypoxic region of the body.
C. Ischemia associated with rhabdomyolysis is more dangerous.
D. Healthy kidneys receive 30% of the cardiac output. (Correct Answer)

Explanation: ### Explanation **1. Why Option D is the Correct Answer (The Exception):** In a healthy adult, the kidneys receive approximately **20–25% of the total cardiac output**, not 30%. This high blood flow (roughly 1.1 L/min) is not required for the metabolic needs of the tissue itself, but rather to maintain a high Glomerular Filtration Rate (GFR) for effective waste excretion and electrolyte balance. **2. Analysis of Other Options:** * **Option A (Oxygen Consumption):** The kidneys are highly metabolic organs, accounting for about **7–10% of total body oxygen consumption**. Most of this energy is consumed by the Na+/K+-ATPase pumps in the proximal tubule and thick ascending limb for active solute reabsorption. * **Option B (Medullary Hypoxia):** Despite high total blood flow, the **renal medulla** receives only about 10% of renal blood flow [1]. Due to the countercurrent exchange system and high metabolic demand for sodium reabsorption, the partial pressure of oxygen ($PO_2$) in the medulla is as low as 10–20 mmHg, making it the **most physiologically hypoxic region** in the body and highly susceptible to ischemic Acute Tubular Necrosis (ATN). * **Option C (Rhabdomyolysis):** Ischemia in rhabdomyolysis is particularly dangerous because it is multifactorial. It involves **intrarenal vasoconstriction** (ischemia), direct **myoglobin toxicity**, and **intratubular cast formation**, which synergistically worsen kidney injury compared to simple hypovolemic ischemia. **3. NEET-PG High-Yield Pearls:** * **Vulnerable Segments:** The **S3 segment of the proximal tubule** and the **medullary thick ascending limb (mTAL)** are the most sensitive to ischemic injury due to their high metabolic activity and location in the hypoxic medulla. * **Autoregulation:** Renal blood flow is autoregulated between a Mean Arterial Pressure (MAP) of **80–180 mmHg** [2]. * **Fractional Excretion of Sodium (FeNa):** In ischemic ATN, FeNa is typically **>2%**, whereas in pre-renal azotemia, it is **<1%**.

Question 594: All of the following are causes of Renal Vein Thrombosis, EXCEPT?

A. Membranous Nephropathy
B. Membranoproliferative glomerulonephritis
C. Lupus Nephritis
D. Post streptococcal Glomerulonephritis (Correct Answer)

Explanation: **Explanation:** Renal Vein Thrombosis (RVT) is a common complication of **Nephrotic Syndrome**. The hypercoagulable state in nephrotic syndrome occurs due to the urinary loss of anticoagulant factors (Antithrombin III, Protein C, and S) and a compensatory increase in procoagulant factors (Fibrinogen) by the liver. **Why Post-streptococcal Glomerulonephritis (PSGN) is the correct answer:** PSGN is a classic example of **Nephritic Syndrome**, characterized by hematuria, hypertension, and oliguria [1]. Unlike nephrotic syndrome, the degree of proteinuria in PSGN is usually sub-nephrotic. Therefore, the profound loss of anticoagulants required to trigger RVT is typically absent in PSGN. **Analysis of other options:** * **Membranous Nephropathy (MN):** This is the **most common** cause of RVT among all glomerulopathies [1]. Up to 30-50% of patients with MN may develop RVT. * **Membranoproliferative Glomerulonephritis (MPGN):** This condition frequently presents with nephrotic-range proteinuria and is a well-recognized risk factor for thromboembolic complications. * **Lupus Nephritis (LN):** Specifically Class V (Membranous) Lupus Nephritis carries a high risk of RVT. Additionally, the presence of Antiphospholipid antibodies in SLE patients further increases the write of thrombosis. **High-Yield Clinical Pearls for NEET-PG:** * **Most common cause of RVT:** Membranous Nephropathy [1]. * **Clinical Presentation:** Acute RVT presents with flank pain, hematuria, and an enlarged kidney; chronic RVT is often asymptomatic. * **Diagnosis:** Gold standard is Renal Venography, but **CT Angiography** or Doppler Ultrasound are the preferred initial investigations. * **Left vs. Right:** The left renal vein is more commonly involved due to its longer course and anatomical considerations.

Question 595: In hyponatremia associated with renal failure, what is the target serum sodium level?

A. 120 mEq/L (Correct Answer)
B. 125 mEq/L
C. 130 mEq/L
D. 135 mEq/L

Explanation: In the context of renal failure (especially Acute Kidney Injury or End-Stage Renal Disease), hyponatremia is primarily a result of **dilutional hyponatremia** due to the kidney's inability to excrete free water [1]. The management goal in these patients is not to normalize the sodium level to 135–145 mEq/L, but rather to raise it just enough to prevent life-threatening neurological complications (like cerebral edema or seizures). [1] **Why 120 mEq/L is the correct answer:** In renal failure patients, the target serum sodium is generally set at **120 mEq/L**. This level is considered a "safe threshold" that mitigates the immediate risk of severe neurological symptoms while avoiding the dangers of aggressive over-correction. Since these patients often have fluid overload, the primary treatment is **fluid restriction** rather than saline infusion. [1] **Analysis of Incorrect Options:** * **B (125 mEq/L) & C (130 mEq/L):** While these levels are safer than profound hyponatremia, they are not the specific initial targets defined for renal failure management. Aiming for these higher levels too quickly increases the risk of fluid overload and hypertension in an already oliguric patient. * **D (135 mEq/L):** This is the lower limit of the normal range. Rapidly correcting to this level carries a high risk of **Osmotic Demyelination Syndrome (ODS)**, formerly known as Central Pontine Myelinolysis. [1] **High-Yield Clinical Pearls for NEET-PG:** * **Correction Rate:** Never exceed a correction rate of **8–10 mEq/L in 24 hours** to prevent ODS. [1] * **Treatment of Choice:** In renal failure with hyponatremia, the mainstay of treatment is **strict fluid restriction** (usually 500 mL + previous day's urine output). [1] * **Symptomatic Hyponatremia:** If the patient has seizures, 3% hypertonic saline is used, but only to raise sodium by 4–6 mEq/L rapidly, then slowing down.

Question 596: What is the earliest clinical indicator of sodium loss?

A. Altered sensorium (Correct Answer)
B. Reduced skin turgor
C. Arrhythmia
D. Orthostatic hypertension

Explanation: **Explanation:** The correct answer is **Altered sensorium**. **Why it is correct:** Sodium is the primary determinant of serum osmolality [1]. When sodium is lost (Hyponatremia), the extracellular fluid (ECF) becomes hypotonic relative to the intracellular fluid (ICF). To maintain osmotic equilibrium, water shifts from the ECF into the cells via osmosis. The brain is particularly sensitive to this process; as water moves into brain cells, it leads to **cerebral edema**. Because the skull is a rigid structure, even minor swelling increases intracranial pressure, manifesting early as subtle changes in sensorium, headache, lethargy, or confusion. **Why the other options are incorrect:** * **Reduced skin turgor:** This is a sign of **volume depletion** (dehydration), not specifically sodium loss [1]. While often seen together, skin turgor is an unreliable indicator in the elderly and occurs after significant fluid loss. * **Arrhythmia:** This is more characteristic of **potassium** (Hyperkalemia/Hypokalemia) or **calcium** imbalances [1]. Sodium levels do not typically trigger arrhythmias unless extreme. * **Orthostatic hypotension (not hypertension):** Orthostatic changes are signs of intravascular volume depletion. Note that the option says "hypertension," which is clinically incorrect in the context of fluid/sodium loss. **High-Yield NEET-PG Pearls:** * **Normal Serum Sodium:** 135–145 mEq/L. * **Most common electrolyte abnormality** in hospitalized patients: Hyponatremia. * **Clinical Pearl:** The severity of symptoms depends more on the **rate of fall** of sodium rather than the absolute value. * **Danger Zone:** Rapid correction of chronic hyponatremia can lead to **Osmotic Demyelination Syndrome** (Central Pontine Myelinolysis) [1]. Rule of thumb: Do not exceed 8–10 mEq/L in 24 hours [1].

Question 597: All of the following are components of nephrotic syndrome except?

A. Edema
B. Hypercoagulability
C. Hypocholesterolemia (Correct Answer)
D. Infection

Explanation: **Explanation:** Nephrotic syndrome is a clinical triad of heavy proteinuria (>3.5 g/day), hypoalbuminemia (<3 g/dL), and edema [3]. The correct answer is **Hypocholesterolemia** because nephrotic syndrome is actually characterized by **Hyperlipidemia** (specifically hypercholesterolemia). [1] **Why Hypocholesterolemia is the correct answer (The "Except"):** In nephrotic syndrome, the liver increases the synthesis of lipoproteins (LDL and VLDL) to compensate for low oncotic pressure caused by albumin loss. Additionally, there is decreased clearance of lipids due to reduced activity of lipoprotein lipase. This leads to elevated serum cholesterol and triglycerides, not low levels. **Analysis of other options:** * **Edema:** This is a hallmark feature. Decreased plasma oncotic pressure (due to hypoalbuminemia) leads to fluid shifting into the interstitium. This triggers the RAA system, causing sodium and water retention, further worsening the edema [3]. * **Hypercoagulability:** Patients are at high risk for venous thromboembolism (specifically Renal Vein Thrombosis). This occurs due to the urinary loss of Antithrombin III, Protein C, and S, alongside increased hepatic synthesis of clotting factors and increased platelet aggregation. * **Infection:** Patients are prone to infections (particularly *S. pneumoniae*) due to the urinary loss of Immunoglobulins (IgG) and complement factors (Factor B). **High-Yield Clinical Pearls for NEET-PG:** * **Most common cause in children:** Minimal Change Disease [2]. * **Most common cause in adults:** Focal Segmental Glomerulosclerosis (FSGS) [1]. * **Urinary finding:** "Maltese cross" appearance under polarized microscopy due to oval fat bodies (lipiduria) [1]. * **Complication:** Renal Vein Thrombosis is most commonly associated with Membranous Nephropathy [4].

Question 598: An elderly male presents with one episode of gross hematuria. Which of the following investigations is NOT recommended for investigating this patient?

A. Cystoscopy
B. Urine microscopy for malignant cells
C. Urine tumor markers (Correct Answer)
D. Intravenous pyelogram

Explanation: The primary goal in evaluating an elderly patient with gross hematuria is to rule out malignancy, specifically **Urothelial Carcinoma** (Bladder Cancer) or **Renal Cell Carcinoma**. [1] **Why Option C is the Correct Answer (NOT recommended):** While several urine tumor markers (e.g., NMP22, BTA stat) exist, they are **not recommended** for the initial diagnostic workup of hematuria according to AUA and EAU guidelines. They lack the necessary sensitivity and specificity to replace gold-standard investigations and often yield false positives in the presence of stones, infection, or inflammation. **Why the other options are wrong (Recommended investigations):** * **Cystoscopy (A):** This is the gold standard for evaluating the lower urinary tract. It is mandatory in patients >35 years with gross hematuria to visualize bladder tumors that imaging might miss. * **Urine microscopy for malignant cells (B):** Urine cytology has high specificity for detecting high-grade urothelial carcinoma and CIS (Carcinoma in situ). [1] * **Intravenous Pyelogram (D):** Historically, IVP was the standard for imaging the upper tract (ureters and renal pelvis). While largely replaced by **CT Urography** in modern practice, it remains a valid classical investigation for upper tract morphology in exams. **Clinical Pearls for NEET-PG:** * **Rule of Thumb:** Any painless gross hematuria in an elderly patient is **Bladder Cancer** until proven otherwise. [1] * **Initial Investigation of Choice:** Ultrasonography (KUB) is often the first step, but **CT Urography** is the most sensitive imaging for the upper tract. [2] * **Most common cause of hematuria (overall):** Urinary Tract Infection (UTI). * **Most common cause of hematuria (elderly):** Bladder malignancy or BPH.

Question 599: Which acid-base disturbance is associated with Chronic Renal Failure (CRF)?

A. Respiratory acidosis
B. Respiratory alkalosis
C. Metabolic acidosis (Correct Answer)
D. Metabolic alkalosis

Explanation: **Explanation:** In Chronic Renal Failure (CRF), the kidneys lose their ability to maintain acid-base homeostasis due to a progressive decline in the number of functioning nephrons [3]. The development of **Metabolic Acidosis** in CRF occurs via three primary mechanisms: 1. **Reduced Ammonia Production:** The remaining nephrons cannot produce enough ammonia ($NH_3$) to buffer and excrete hydrogen ions ($H^+$). 2. **Failure to Reabsorb Bicarbonate:** There is a decreased capacity to reclaim filtered $HCO_3^-$. 3. **Retention of Organic Acids:** As the GFR drops below 20–25 mL/min, the kidney fails to excrete "fixed" metabolic acids (sulfates, phosphates, and organic anions), leading to a **High Anion Gap Metabolic Acidosis (HAGMA)**. **Why the other options are incorrect:** * **Respiratory Acidosis/Alkalosis:** These are primary disorders of ventilation ($CO_2$ retention or washout) [2]. While CRF patients may show respiratory compensation (Kussmaul breathing), the primary pathology is metabolic, not respiratory. * **Metabolic Alkalosis:** This involves a loss of $H^+$ (e.g., vomiting) or gain of $HCO_3^-$. In CRF, the body is unable to excrete acid, making alkalosis highly unlikely unless there is an external factor like aggressive diuretic use or massive vomiting. **High-Yield Pearls for NEET-PG:** * **Early CRF:** Often presents as **Normal Anion Gap Metabolic Acidosis (NAGMA)** due to impaired ammonia excretion. * **Advanced CRF (Stage 4-5):** Typically presents as **High Anion Gap Metabolic Acidosis (HAGMA)** due to phosphate and sulfate retention. * **Clinical Sign:** Look for **Kussmaul’s respiration** (deep, sighing breaths) as a compensatory mechanism to blow off $CO_2$ and raise pH [1].

Question 600: Which of the following is NOT a variable used in the Modification of Diet in Renal Disease (MDRD) formula?

A. Age
B. Gender
C. Race
D. Weight (Correct Answer)

Explanation: The **Modification of Diet in Renal Disease (MDRD)** formula is a widely used equation for estimating the Glomerular Filtration Rate (eGFR) [1]. It was developed to provide a more accurate assessment of kidney function than serum creatinine alone, as creatinine levels are influenced by muscle mass and metabolism. ### Why Weight is the Correct Answer Unlike the older **Cockcroft-Gault formula**, which explicitly requires the patient's **weight** (and is used primarily for drug dosing), the MDRD formula does **not** include weight. The MDRD equation was mathematically derived to adjust for body surface area (BSA) automatically, normalizing the result to $1.73\ m^2 [1]$. Therefore, weight is not a variable in the calculation. ### Why Other Options are Incorrect The 4-variable MDRD formula (the most commonly used version) requires the following parameters: * **Age (A):** GFR naturally declines with age; hence it is a critical variable. * **Gender (B):** Women generally have lower muscle mass than men, leading to lower baseline creatinine for the same GFR. * **Race (C):** The original formula included a correction factor for African Americans (1.212) due to higher average muscle mass (Note: Modern guidelines are moving away from race-based corrections, but for exam purposes, it remains a historical component of the formula). * **Serum Creatinine:** The primary biochemical marker used. ### High-Yield Clinical Pearls for NEET-PG * **Cockcroft-Gault Formula:** Variables include Age, Sex, Weight, and Serum Creatinine. (Memory aid: **W**eight is in **C**ockcroft, not MDRD). * **CKD-EPI:** Currently preferred over MDRD in clinical practice as it is more accurate at higher GFR levels (>60 mL/min). * **Limitations:** MDRD is less accurate in patients with extreme body sizes (morbid obesity or malnutrition), pregnancy, or rapidly changing kidney function (acute kidney injury).

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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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