Nephrology — MCQs

Nephrology Indian Medical PG Practice Questions and MCQs

Question 11: Fractional excretion of sodium < 1 is seen in which of the following conditions?

A. Pre-renal azotemia (Correct Answer)
B. Acute tubular necrosis
C. Acute ureteral obstruction
D. Interstitial nephritis

Explanation: ### Explanation **Fractional Excretion of Sodium (FeNa)** is a critical diagnostic tool used to differentiate between causes of acute kidney injury (AKI) [1]. It measures the percentage of sodium filtered by the kidney that is actually excreted in the urine. #### 1. Why Pre-renal Azotemia is Correct In **Pre-renal azotemia**, the primary pathology is renal hypoperfusion (e.g., dehydration, heart failure, or hemorrhage). Because the renal tubules remain structurally intact and functional, they respond physiologically to decreased perfusion by activating the Renin-Angiotensin-Aldosterone System (RAAS). This leads to **maximal reabsorption of sodium and water** to restore intravascular volume. Consequently, very little sodium is excreted in the urine, resulting in a **FeNa < 1%**. #### 2. Why the Other Options are Incorrect * **Acute Tubular Necrosis (ATN):** This is an intrinsic renal injury where the tubular epithelial cells are damaged. The "sick" tubules lose their ability to reabsorb sodium. Therefore, sodium is lost in the urine, leading to a **FeNa > 2%**. * **Interstitial Nephritis:** This is an intrinsic inflammatory process [1]. Like ATN, the tubular dysfunction prevents efficient sodium reabsorption, typically resulting in a **FeNa > 1%**. * **Acute Ureteral Obstruction:** This is a post-renal cause [1]. While early obstruction can sometimes mimic pre-renal values, established obstruction causes pressure-induced tubular damage, leading to impaired sodium handling and a **FeNa > 1%**. #### 3. Clinical Pearls for NEET-PG * **Formula:** $FeNa = \frac{(Urine\ Na \times Plasma\ Creatinine)}{(Plasma\ Na \times Urine\ Creatinine)} \times 100$ * **Exceptions to FeNa < 1%:** While usually indicating pre-renal states, FeNa < 1% can also be seen in **Contrast-induced nephropathy**, **Acute Glomerulonephritis**, and **Myoglobinuric AKI** (Rhabdomyolysis). * **Diuretics:** FeNa is unreliable if the patient is on diuretics (which force sodium excretion). In such cases, **Fractional Excretion of Urea (FeUrea) < 35%** is a more accurate marker for pre-renal azotemia. * **Urine Osmolality:** In pre-renal states, urine is highly concentrated (>500 mOsm/kg), whereas in ATN, it is dilute/isosthenuric (~300 mOsm/kg).

Question 12: Hyperchloremic metabolic acidosis is seen in all EXCEPT?

A. Renal tubular acidosis type 1
B. Diarrhea
C. Uremia
D. Gitelman syndrome (Correct Answer)

Explanation: The core concept tested here is the differentiation between **Normal Anion Gap Metabolic Acidosis (NAGMA)** and **Metabolic Alkalosis**. **Why Gitelman Syndrome is the correct answer:** Gitelman syndrome is a salt-wasting tubulopathy caused by a defect in the thiazide-sensitive NaCl cotransporter in the distal convoluted tubule. It presents with **Metabolic Alkalosis** (not acidosis), hypokalemia, and hypomagnesemia [1]. Because it causes alkalosis, it cannot be the cause of hyperchloremic metabolic acidosis. **Analysis of incorrect options (Causes of NAGMA):** * **Renal Tubular Acidosis (RTA) Type 1:** RTAs are classic causes of NAGMA [2]. In Type 1 (Distal RTA), there is a failure to secrete H+ ions. To maintain electrical neutrality, the kidney retains Chloride, leading to hyperchloremia. * **Diarrhea:** This is the most common gastrointestinal cause of NAGMA. Loss of bicarbonate-rich intestinal fluids leads to a relative increase in serum Chloride to balance the loss of HCO3-. * **Uremia:** While advanced chronic kidney disease (CKD) typically causes a High Anion Gap Metabolic Acidosis (HAGMA) due to phosphate/sulfate retention, **early-stage renal failure (uremia)** often presents as a hyperchloremic NAGMA before the anion gap widens. **NEET-PG High-Yield Pearls:** 1. **NAGMA Formula:** Remember the mnemonic **USED CARP** (Ureterosigmoidostomy, Small bowel fistula, Extra-chloride, Diarrhea, Carbonic anhydrase inhibitors, RTA, Pancreatic fistula). 2. **Gitelman vs. Bartter:** Gitelman presents in older children/adults with **hypocalciuria**, whereas Bartter presents in infancy with **hypercalciuria**. Both cause metabolic alkalosis [1]. 3. **Anion Gap:** Always calculate the Anion Gap ($Na - [Cl + HCO3]$). If it is normal (8–12 mEq/L) in the presence of acidosis, it is Hyperchloremic Metabolic Acidosis [2].

Question 13: All are features of Rapidly progressive glomerulonephritis (RPGN) except?

A. Rapid recovery (Correct Answer)
B. Crescent formation
C. Hypertension
D. Non-selective proteinuria

Explanation: **Explanation:** Rapidly Progressive Glomerulonephritis (RPGN) is a clinical syndrome characterized by a rapid and progressive loss of renal function, typically leading to end-stage renal disease (ESRD) within weeks to months if left untreated [3]. **Why "Rapid recovery" is the correct answer:** RPGN is defined by its aggressive nature. Without aggressive immunosuppressive therapy (such as pulse steroids, cyclophosphamide, or plasmapheresis), it does **not** recover rapidly; instead, it leads to irreversible renal failure [3]. Recovery is often incomplete even with treatment, making "Rapid recovery" the false statement. **Analysis of incorrect options:** * **Crescent formation:** This is the hallmark pathological feature of RPGN [1], [2]. Crescents form due to the proliferation of parietal epithelial cells and the infiltration of monocytes into Bowman’s space following glomerular capillary wall rupture [2]. * **Hypertension:** As a form of nephritic syndrome, RPGN involves fluid retention and activation of the renin-angiotensin system, leading to hypertension and edema [2]. * **Non-selective proteinuria:** Damage to the glomerular filtration barrier allows proteins of various molecular weights to leak into the urine [2]. While usually not in the nephrotic range, the proteinuria is non-selective [3]. **High-Yield Clinical Pearls for NEET-PG:** * **Classification:** RPGN is divided into three types [1]: * **Type I:** Anti-GBM disease (e.g., Goodpasture syndrome) – Linear IgG deposits [1], [3]. * **Type II:** Immune-complex mediated (e.g., PSGN, SLE) – Granular deposits [1], [3]. * **Type III:** Pauci-immune (e.g., Wegener’s/GPA, Microscopic polyangiitis) – ANCA associated [3]. * **Histology:** Diagnosis requires >50% of glomeruli to show crescent formation on light microscopy [1]. * **Urinalysis:** Characterized by "active sediment" (RBC casts and dysmorphic RBCs).

Question 14: Nephrocalcinosis is seen in which of the following conditions?

A. Hypoparathyroidism
B. Medullary sponge kidney (Correct Answer)
C. Diabetes Mellitus
D. All of the above

Explanation: **Explanation:** Nephrocalcinosis refers to the generalized deposition of calcium salts (calcium oxalate or calcium phosphate) within the renal parenchyma [3]. It is typically classified into medullary (most common) and cortical types [3]. **1. Why Medullary Sponge Kidney (MSK) is Correct:** MSK is a congenital disorder characterized by cystic dilatation of the collecting ducts [1]. This leads to urinary stasis and localized hypercalciuria within the dilated ducts, creating an ideal environment for the formation of calcium phosphate or calcium oxalate stones [1]. Consequently, MSK is one of the most common causes of **medullary nephrocalcinosis**. **2. Why the Other Options are Incorrect:** * **Hypoparathyroidism:** This condition is characterized by *low* serum calcium levels [4]. Nephrocalcinosis is associated with **Hyperparathyroidism** (due to hypercalcemia and hypercalciuria) [3]. * **Diabetes Mellitus:** While DM is a leading cause of chronic kidney disease and papillary necrosis, it does not typically cause the parenchymal calcium deposition seen in nephrocalcinosis. **3. High-Yield Clinical Pearls for NEET-PG:** * **Medullary Nephrocalcinosis (Common Causes):** Remember the mnemonic **"R-A-M"**: **R**enal Tubular Acidosis (Type 1/Distal), **A**ntacids (Milk-alkali syndrome), and **M**edullary Sponge Kidney [3]. Hyperparathyroidism and Sarcoidosis are also major causes [2], [3]. * **Cortical Nephrocalcinosis (Rare):** Classically seen in **Acute Tubular Necrosis (ATN)**, Chronic Glomerulonephritis, and **Ethylene Glycol poisoning**. It may occur in areas of cortical necrosis [3]. * **Radiology:** On X-ray or CT, MSK presents with a characteristic "bouquet of flowers" or "paintbrush" appearance due to contrast filling the dilated ducts [1].

Question 15: All of the following may be associated with massive proteinuria EXCEPT?

A. Amyloidosis
B. Renal vein thrombosis
C. Polycystic kidneys
D. Polyarteritis nodosa (Correct Answer)

Explanation: Massive proteinuria (nephrotic-range proteinuria, typically >3.5 g/day) occurs due to significant damage to the glomerular filtration barrier (podocytes or basement membrane) [2]. **Why Polyarteritis Nodosa (PAN) is the correct answer:** PAN is a systemic necrotizing vasculitis that primarily affects **medium-sized arteries**. In the kidneys, it involves the renal arteries and their branches (interlobar and arcuate arteries), leading to microaneurysms, ischemia, and infarction. Crucially, PAN **spares the glomeruli** (it is a non-glomerular disease). Therefore, it typically presents with hypertension and hematuria, but **not** massive proteinuria [3]. **Analysis of Incorrect Options:** * **Amyloidosis:** This is a classic cause of nephrotic syndrome. Deposition of amyloid fibrils in the glomerular basement membrane disrupts the filtration barrier, leading to some of the highest levels of proteinuria seen in clinical practice [4]. * **Renal Vein Thrombosis (RVT):** RVT is both a cause and a consequence of nephrotic syndrome. While it is most commonly associated with Membranous Nephropathy, the resulting venous congestion can exacerbate glomerular damage and proteinuria. * **Polycystic Kidneys (ADPKD):** While mild-to-moderate proteinuria is more common, massive proteinuria can occur in advanced stages due to secondary focal segmental glomerulosclerosis (FSGS) caused by hyperfiltration in the remaining nephrons [1]. **NEET-PG High-Yield Pearls:** * **PAN Rule of Thumb:** PAN is "Glomerulonephritis-negative." If a vasculitis involves the glomerulus (causing RPGN or massive proteinuria), think of Small Vessel Vasculitis (e.g., GPA, MPA) instead [3]. * **PAN & Hepatitis B:** Approximately 10-30% of PAN cases are associated with Hepatitis B surface antigenemia. * **Diagnosis:** The gold standard for PAN is a biopsy or visceral angiography showing "string of pearls" microaneurysms.

Question 16: Which of the following is used for staging of Chronic Kidney Disease (CKD)?

A. Estimated Glomerular Filtration Rate (e-GFR) and serum creatinine
B. Estimated Glomerular Filtration Rate (e-GFR) and serum albumin
C. Estimated Glomerular Filtration Rate (e-GFR) and urine output
D. Estimated Glomerular Filtration Rate (e-GFR) and albuminuria (Correct Answer)

Explanation: **Explanation:** The staging of Chronic Kidney Disease (CKD) is based on the **KDIGO (Kidney Disease: Improving Global Outcomes)** classification system, which utilizes two primary parameters: **e-GFR (G-stage)** and **Albuminuria (A-stage)** [1]. This is often referred to as the "CGA" classification (Cause, GFR, and Albuminuria). 1. **Why Option D is correct:** CKD is defined as abnormalities of kidney structure or function present for >3 months [1]. While e-GFR measures the filtration capacity (Stages G1–G5), albuminuria (measured via Urine Albumin-to-Creatinine Ratio - UACR) is a sensitive marker of kidney damage and a potent predictor of cardiovascular risk and progression to End-Stage Renal Disease (ESRD) [1]. Even if e-GFR is normal (>90 ml/min), a patient can be diagnosed with CKD if persistent albuminuria is present. 2. **Why other options are incorrect:** * **Option A:** Serum creatinine is used to *calculate* e-GFR (via formulas like CKD-EPI), but it is not a staging criterion on its own due to variations based on muscle mass and age [1]. * **Option B:** Serum albumin reflects nutritional status or systemic inflammation; it is not used for CKD staging. * **Option C:** Urine output is a criterion for **AKIs (Acute Kidney Injury)** via the RIFLE, AKIN, or KDIGO criteria, but it is not used for staging chronic disease. **High-Yield Clinical Pearls for NEET-PG:** * **CKD Definition:** e-GFR <60 ml/min/1.73m² or markers of kidney damage (like Albuminuria ≥30 mg/24h) for **>3 months** [1]. * **Formula of Choice:** The **CKD-EPI formula** is currently preferred over MDRD for estimating GFR. * **Albuminuria Categories:** A1 (<30 mg/g), A2 (30–300 mg/g - formerly "microalbuminuria"), and A3 (>300 mg/g - "macroalbuminuria") [1]. * **Most common cause of CKD:** Diabetes Mellitus (followed by Hypertension) [1].

Question 17: Systemic eosinophilia with renal failure is found in all of the following except:

A. Drug-induced interstitial nephritis
B. Chronic interstitial nephritis (Correct Answer)
C. Atherosclerotic renal failure
D. Polyarteritis nodosa

Explanation: ### Explanation The presence of **systemic eosinophilia** in the context of renal failure is a significant diagnostic clue pointing toward hypersensitivity, embolic, or vasculitic processes. **Why Chronic Interstitial Nephritis (CIN) is the correct answer:** Chronic Interstitial Nephritis is characterized by progressive interstitial fibrosis and tubular atrophy [2]. Unlike the acute form, the inflammatory infiltrate in CIN is predominantly mononuclear (lymphocytes and macrophages) rather than eosinophilic. Because it is a chronic, scarring process rather than an active hypersensitivity reaction, it is **not** associated with systemic eosinophilia or eosinophiluria. **Analysis of Incorrect Options:** * **Drug-induced Acute Interstitial Nephritis (AIN):** This is a classic Type IV hypersensitivity reaction. Systemic eosinophilia is seen in approximately 30–50% of cases, often accompanied by a skin rash and fever [3]. * **Atherosclerotic Renal Failure (Atheroembolic Disease):** Following vascular procedures, cholesterol crystals can dislodge and cause distal ischemia [1]. This triggers a systemic inflammatory response, and **eosinophilia** is a hallmark laboratory finding in about 60–80% of these patients [1]. * **Polyarteritis Nodosa (PAN):** As a systemic necrotizing vasculitis, PAN (especially when associated with certain triggers or overlapping with eosinophilic granulomatosis with polyangiitis) can present with significant peripheral eosinophilia and multi-organ failure, including the kidneys [3]. **NEET-PG High-Yield Pearls:** 1. **Hansel’s Stain:** The preferred stain to detect eosinophils in urine (more sensitive than Wright’s stain). 2. **Triad of AIN:** Fever, rash, and arthralgia (though all three are present in <10% of patients). 3. **Atheroembolic Clue:** Look for "blue toe syndrome" or livedo reticularis following a cardiac catheterization in a patient with rising creatinine and eosinophilia [1].

Question 18: A 25-year-old man presents with renal failure. His uncle died of renal failure 3 years ago. On slit lamp examination, keratoconus is present. What is the most likely diagnosis?

A. Autosomal Dominant Polycystic Kidney Disease (ADPCKD)
B. Autosomal Recessive Polycystic Kidney Disease (ARPCKD)
C. Alport syndrome (Correct Answer)
D. Denys-Drash syndrome

Explanation: **Explanation:** The clinical triad of **hereditary renal failure**, a positive **family history**, and specific **ocular abnormalities** (like keratoconus) is classic for **Alport Syndrome** [1]. **1. Why Alport Syndrome is correct:** Alport syndrome is caused by mutations in the genes encoding the **alpha chains of Type IV collagen** (COL4A3, COL4A4, COL4A5) [1]. Since Type IV collagen is a structural component of basement membranes, its defect affects: * **Kidneys:** Leads to progressive glomerulonephritis and renal failure. * **Eyes:** Causes **Anterior Lenticonus** (pathognomonic), **Keratoconus**, and maculopathy. * **Ears:** Results in Sensorineural Hearing Loss (SNHL). The mention of the uncle's death suggests an X-linked dominant inheritance pattern (the most common form), though autosomal forms exist. **2. Why other options are incorrect:** * **ADPCKD:** While it causes renal failure and has a strong family history, it typically presents in the 4th-5th decade and is associated with extra-renal manifestations like hepatic cysts and berry aneurysms, not keratoconus [2]. * **ARPCKD:** Usually presents in infancy or childhood with bilateral flank masses and pulmonary hypoplasia; it is associated with congenital hepatic fibrosis, not ocular defects. * **Denys-Drash Syndrome:** Characterized by the triad of Wilms tumor, pseudohermaphroditism, and early-onset nephropathy. It does not feature a family history of renal failure or keratoconus. **Clinical Pearls for NEET-PG:** * **Pathognomonic Eye Sign:** Anterior Lenticonus (conical protrusion of the lens). * **Electron Microscopy (EM):** Shows a characteristic **"Basket-weave appearance"** due to irregular thinning and thickening of the Glomerular Basement Membrane (GBM) [1]. * **Inheritance:** 80% are X-linked Dominant (mutations in *COL4A5*). * **Rule of thumb:** If a young male has hematuria, hearing loss, and eye signs—think Alport Syndrome.

Question 19: T.T.K.G >8 is seen in all except?

A. Diabetes mellitus
B. Acute glomerulonephritis
C. Adrenocortical insufficiency
D. Cushing syndrome (Correct Answer)

Explanation: **Transtubular Potassium Gradient (TTKG)** is a clinical tool used to estimate the conservation or excretion of potassium by the cortical collecting duct. It reflects the activity of **Aldosterone** [1]. ### **Understanding the Concept** The formula for TTKG is: $TTKG = rac{[K^+]_{urine} imes [Osm]_{plasma}}{[K^+]_{plasma} imes [Osm]_{urine}}$ * **TTKG > 8:** Indicates that Aldosterone is present and active (the kidney is actively secreting potassium). * **TTKG < 3:** Indicates a lack of Aldosterone or resistance to its action (the kidney is failing to secrete potassium). ### **Explanation of Options** * **Cushing Syndrome (Correct Answer):** In Cushing syndrome, there is an excess of glucocorticoids (Cortisol). Cortisol has inherent mineralocorticoid activity and can bind to aldosterone receptors [3]. This leads to **increased potassium secretion**, resulting in a **TTKG > 8**. Therefore, it is *not* an exception. * *Note:* The question asks for "all except," but based on physiological principles, Cushing syndrome actually *causes* a high TTKG. If the question implies a state where TTKG is typically low, Cushing is the outlier because it represents a hyper-mineralocorticoid state. * **Diabetes Mellitus:** Often associated with Hyporeninemic Hypoaldosteronism (Type 4 RTA). This leads to low aldosterone levels and a **TTKG < 3**. * **Adrenocortical Insufficiency (Addison’s):** Characterized by primary aldosterone deficiency [2]. Without aldosterone, the kidneys cannot secrete potassium, resulting in a **TTKG < 3**. * **Acute Glomerulonephritis:** Can lead to a state of "pseudohypoaldosteronism" or decreased distal delivery of sodium, often resulting in a low TTKG during hyperkalemic phases. ### **High-Yield Clinical Pearls for NEET-PG** 1. **Prerequisite for TTKG:** The urine must be hypertonic to plasma (Urine Osm > Plasma Osm) and urine $Na^+$ should be $>25 \text{ mmol/L}$. 2. **Hyperkalemia + TTKG < 3:** Suggests Hypoaldosteronism (Addison's, ACE inhibitors, or Type 4 RTA) [1]. 3. **Hypokalemia + TTKG > 8:** Suggests excessive renal loss (Conn’s syndrome, Cushing syndrome, or Diuretics) [2]. 4. **Key Rule:** TTKG is the "Aldosterone Bioassay" at the bedside.

Question 20: What is the best initial test for determining the stage of renal insufficiency?

A. Serum creatinine (Correct Answer)
B. Creatinine clearance
C. Glomerular filtration rate
D. Serum urea

Explanation: **Explanation:** **1. Why Serum Creatinine is the Correct Answer:** Serum creatinine is considered the **best initial test** because it is simple, inexpensive, and widely available [1]. In clinical practice, the staging of Chronic Kidney Disease (CKD) is primarily based on the **Estimated Glomerular Filtration Rate (eGFR)**, which is calculated using formulas (like MDRD or CKD-EPI) that rely predominantly on the **serum creatinine** value [1]. It serves as the fundamental baseline biomarker for assessing renal function in an initial workup. **2. Analysis of Incorrect Options:** * **Creatinine Clearance (CrCl):** While more accurate than serum creatinine alone, it requires a cumbersome **24-hour urine collection**, making it impractical as an "initial" test [2]. It is usually reserved for specific scenarios like pregnancy, extremes of body size, or prior to dosing highly toxic drugs. * **Glomerular Filtration Rate (GFR):** This is the "Gold Standard" for determining the *actual* stage of renal insufficiency [2]. However, true GFR measurement requires the infusion of exogenous markers like **Inulin** (the physiological gold standard) or radioisotopes (Iothalamate) [1]. These are complex and expensive, hence not the "initial" test. * **Serum Urea:** This is an unreliable marker for staging because levels are significantly influenced by non-renal factors such as high-protein diet, GI bleed, dehydration, and steroid use. **3. Clinical Pearls for NEET-PG:** * **Gold Standard for GFR:** Inulin clearance [2]. * **Most accurate formula for eGFR:** CKD-EPI (preferred over MDRD) [1]. * **Creatinine Lag:** Serum creatinine may not rise until **50% of nephron function** is lost, making it a late marker in acute settings but the standard for staging chronic insufficiency. * **Cockcroft-Gault Formula:** Used for drug dosing; it incorporates Age, Weight, and Serum Creatinine.

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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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