Nephrology Practice Questions

Q: According to the RIFLE criteria, what defines acute kidney injury?

Urine output 12 hours. The **RIFLE criteria** (Risk, Injury, Failure, Loss, and End-stage renal disease) were developed by the ADQI group to standardize the definition of Acute Kidney Injury (AKI). The classification is based on two parameters: Serum Creatinine (SCr)/GFR and Urine Output (UO). [1] ### **Explanation of the Correct Option** **Option B** is correct because, under the RIFLE criteria, the **"Injury"** stage is defined by: * **Creatinine:** 2-fold increase in SCr or GFR decrease > 50%. * **Urine Output:** 12 hours**. ### **Analysis of Incorrect Options** * **Option A:** 6 hours (not 8) defines the **"Risk"** stage. * **Option C:** 24 hours defines the **"Failure"** stage. * **Option D:** Anuria for **> 12 hours** also defines the **"Failure"** stage. ### **High-Yield NEET-PG Clinical Pearls** 1. **RIFLE vs. AKIN:** The AKIN (Acute Kidney Injury Network) criteria later modified this, defining AKI as a SCr increase of ≥ 0.3 mg/dL within 48 hours or a 1.5-fold increase from baseline. [1] 2. **The "L" and "E" in RIFLE:** * **Loss:** Persistent ARF = complete loss of kidney function > 4 weeks. * **ESRD:** End-stage renal disease > 3 months. 3. **Sensitivity:** The UO criteria are generally more sensitive but less specific than creatinine changes for early detection of AKI. 4. **KDIGO:** Currently, the KDIGO criteria are the most widely used in clinical practice, combining elements of both RIFLE and AKIN.

Q: Uremia occurs when total GFR is reduced by approximately what percentage?

50%. **Explanation:** **1. Why 50% is Correct:** Uremia is a clinical syndrome resulting from the accumulation of nitrogenous waste products (like urea and creatinine) that are normally excreted by the kidneys. The kidneys possess a significant "functional reserve." Clinical symptoms of uremia and significant elevations in serum BUN/Creatinine typically do not manifest until the total Glomerular Filtration Rate (GFR) falls below **50% of its normal value**. [1] At this threshold, the remaining nephrons can no longer compensate for the loss of function, leading to the systemic manifestations of renal failure. [1] **2. Analysis of Incorrect Options:** * **A (25%):** A reduction of only 25% (leaving 75% function) is well within the kidney's compensatory capacity. Patients remain asymptomatic, and serum markers often stay within normal limits. * **C (60%) & D (80%):** While uremia is certainly present at these levels of reduction, the question asks for the approximate point at which uremia *begins* to occur. By the time GFR is reduced by 80% (leaving only 20% function), the patient is in Stage 4 Chronic Kidney Disease (CKD) and is often symptomatic with overt complications. [1] **3. NEET-PG High-Yield Pearls:** * **Azotemia vs. Uremia:** Azotemia is the biochemical abnormality (elevated BUN/Cr), while Uremia is the clinical syndrome (symptoms like pericarditis, encephalopathy, and asterixis). [1] * **The "Creatinine Blind" Zone:** Serum creatinine may remain within the "normal" range (e.g., 1.0 mg/dL) even if GFR has dropped by 50%. This is why GFR is a more sensitive indicator of renal function than creatinine alone. * **Stages of CKD:** Remember the KDOQI classification; Stage 3 (GFR 30-59 mL/min) is often where systemic complications become clinically evident. [1]

Q: Nephrogenic diabetes insipidus is caused by all of the following except?

Hypocalcemia. Nephrogenic Diabetes Insipidus (NDI) occurs when the renal tubules are resistant to the action of Antidiuretic Hormone (ADH/Vasopressin), leading to an inability to concentrate urine [1]. **Why Hypocalcemia is the correct answer:** The correct answer is **Hypocalcemia** because it is actually **Hypercalcemia** that causes NDI. High serum calcium levels lead to the activation of calcium-sensing receptors in the thick ascending limb, which inhibits the accumulation of intracellular cAMP and interferes with the insertion of Aquaporin-2 channels in the collecting duct. This induces a state of ADH resistance. **Analysis of other options:** * **Lithium Toxicity:** This is the most common drug-induced cause of NDI. Lithium enters the principal cells through ENaC channels and interferes with the ADH-mediated signaling pathway. * **Amyloidosis:** This is an infiltrative disease. Deposition of amyloid proteins in the renal medulla disrupts the medullary osmotic gradient and damages the tubular response to ADH. * **Hypokalemia:** Low potassium levels cause downregulation of Aquaporin-2 channels and can lead to structural changes (vacuolization) in the proximal and distal tubules, resulting in ADH resistance. [1] **High-Yield Clinical Pearls for NEET-PG:** * **Electrolyte Mnemonic:** "High Ca, Low K" (Hypercalcemia and Hypokalemia) cause NDI. * **Drug of Choice:** For Lithium-induced NDI, **Amiloride** is preferred as it blocks the ENaC channels, preventing lithium entry into cells. * **General Treatment:** Thiazide diuretics (paradoxical effect) and NSAIDs (which inhibit prostaglandins that normally antagonize ADH). * **Congenital NDI:** Most commonly X-linked recessive (mutation in V2 receptor) or Autosomal recessive (mutation in Aquaporin-2) [1].

Q: Urine analysis of a patient with haematuria and hypercalciuria is most likely to reveal which of the following?

Isomorphic RBCs. ### Explanation The presence of **haematuria and hypercalciuria** in a patient typically points toward a **non-glomerular** cause of bleeding [1]. Hypercalciuria can cause irritation or micro-calculi formation in the renal pelvis or collecting system, leading to "urological" or extra-glomerular bleeding [2]. **1. Why Isomorphic RBCs is correct:** In extra-glomerular bleeding (e.g., stones, malignancy, or hypercalciuria-induced irritation), the red blood cells do not pass through the glomerular basement membrane [1]. Consequently, they maintain their normal size and biconcave shape. These are termed **isomorphic RBCs**. In contrast, glomerular bleeding causes RBCs to become "dysmorphic" (e.g., acanthocytes) due to mechanical trauma and osmotic shifts during their passage through the nephron. **2. Why other options are incorrect:** * **RBC Casts:** These are pathognomonic for **glomerular disease** (e.g., Glomerulonephritis). Casts form in the distal convoluted tubule when RBCs are trapped in a Tamm-Horsfall protein matrix. * **Nephrotic range proteinuria:** This indicates severe glomerular basement membrane damage (e.g., Minimal Change Disease, FSGS). Hypercalciuria-related haematuria is typically associated with minimal or no proteinuria [1]. * **Eosinophiluria:** This is a classic marker for **Acute Interstitial Nephritis (AIN)**, often drug-induced (e.g., NSAIDs, Penicillins), not hypercalciuria. **Clinical Pearls for NEET-PG:** * **Acanthocytes (G1 cells):** If >5% of total urinary RBCs are acanthocytes, it is highly specific for glomerular haematuria. * **Hypercalciuria:** Defined as >4 mg/kg/day of calcium excretion. It is the most common metabolic abnormality in children with unexplained isolated haematuria. * **Rule of Thumb:** Glomerular bleeding = Dysmorphic RBCs + RBC Casts + Significant Proteinuria. Extra-glomerular bleeding = Isomorphic RBCs + No Casts + Minimal Proteinuria [1].

Q: Microalbuminuria is defined as:

0.03-0.3 g of 24-hour urine albumin. **Explanation:** **Microalbuminuria** (now clinically referred to as **Moderately Increased Albuminuria**) is a critical marker for early-stage diabetic nephropathy and cardiovascular risk [1]. It represents a level of albumin excretion that is higher than normal but below the detection limit of a standard urine dipstick [1]. 1. **Why Option C is Correct:** The standard definition of microalbuminuria is an albumin excretion rate of **30–300 mg/day** (24-hour collection). Converting milligrams to grams, this equals **0.03–0.3 g of albumin**. It is essential to distinguish between *total protein* and *albumin*; microalbuminuria specifically measures the latter [3]. 2. **Analysis of Incorrect Options:** * **Option A (0.3–0.5 g protein):** This range exceeds the threshold for microalbuminuria and refers to "Macroalbuminuria" or overt proteinuria [3]. * **Option B (0.03–0.3 g protein):** This is incorrect because it specifies "protein." Total protein includes globulins and Tamm-Horsfall proteins; microalbuminuria is specific to albumin [2]. * **Option D (> 2.5 g protein):** This range approaches the **Nephrotic range proteinuria** (> 3.5 g/day), indicating severe glomerular damage. **High-Yield Clinical Pearls for NEET-PG:** * **Albumin-to-Creatinine Ratio (ACR):** In a spot urine sample, microalbuminuria is defined as an ACR of **30–300 mg/g**. * **Gold Standard:** The 24-hour urine collection remains the gold standard, but ACR is preferred for screening due to convenience. * **Clinical Significance:** It is the earliest clinical sign of diabetic nephropathy [3]. At this stage, the damage is potentially **reversible** with strict glycemic control and ACE inhibitors/ARBs. * **Diagnosis:** To confirm microalbuminuria, 2 out of 3 specimens collected over a 3-to-6-month period should be elevated (as transient elevation can occur due to exercise, fever, or CHF).

Q: Nephrocalcinosis is seen in all except:

Medullary cystic kidney disease. **Explanation:** Nephrocalcinosis refers to the generalized deposition of calcium salts within the renal parenchyma (medulla or cortex) [1]. To solve this question, one must distinguish between conditions that cause hypercalcemia/hypercalciuria and those that cause structural cysts. **Why Medullary Cystic Kidney Disease (MCKD) is the correct answer:** MCKD (now often classified under Autosomal Dominant Tubulointerstitial Kidney Disease) is characterized by the formation of cysts at the corticomedullary junction, tubular atrophy, and interstitial fibrosis [1]. While it involves the medulla, it **does not** typically lead to calcium deposition. In contrast, **Medullary Sponge Kidney** is a classic cause of nephrocalcinosis; students often confuse these two distinct entities [1]. **Analysis of Incorrect Options:** * **Sarcoidosis:** Causes increased production of 1,25-dihydroxyvitamin D by macrophages in granulomas, leading to hypercalcemia and hypercalciuria, which results in calcium deposition. * **Distal Renal Tubular Acidosis (Type 1 RTA):** This is the most common cause of medullary nephrocalcinosis [1]. The alkaline urine, hypocitraturia (citrate normally inhibits stone formation), and systemic acidosis leading to bone resorption create the perfect environment for calcium phosphate deposition. * **Milk Alkali Syndrome:** Excessive intake of calcium and absorbable alkali leads to hypercalcemia and metabolic alkalosis, directly causing metastatic calcification in the kidneys. **NEET-PG High-Yield Pearls:** * **Most common cause of Medullary Nephrocalcinosis:** Distal RTA (Type 1) [1]. * **Cortical Nephrocalcinosis:** Classically seen in Acute Tubular Necrosis (ATN), Chronic Glomerulonephritis, and Alport Syndrome [1]. * **Medullary Sponge Kidney vs. MCKD:** Remember, "Sponge" collects calcium (nephrocalcinosis), while "Cystic" (MCKD) leads to small kidneys and renal failure without calcification [1].

Q: Which of the following statements is NOT true about IgA nephropathy?

Absence of associated proteinuria is pathognomic.. **Explanation:** IgA Nephropathy (Berger’s Disease) is the most common primary glomerulonephritis worldwide. The correct answer is **D** because the statement is factually incorrect; proteinuria is a common feature of the disease and its presence (especially >1g/day) is a significant poor prognostic marker. There is no "pathognomonic" absence of proteinuria in this condition. [1] **Analysis of Options:** * **Option A:** This is **true**. Light microscopy typically shows mesangial hypercellularity and matrix expansion. These changes are often focal (involving some glomeruli) and segmental (involving parts of the glomerulus). [1] * **Option B:** This is **true**. Patients classically present with "synpharyngitic hematuria" (gross hematuria occurring concurrently with an upper respiratory infection) [1]. However, many patients are diagnosed via incidental microscopic hematuria found during routine screening. * **Option C:** This is **true**. Immunofluorescence (IF) is the gold standard for diagnosis, showing granular deposits of **IgA** (predominantly IgA1) in the mesangium [1]. These deposits are frequently accompanied by **C3 and IgG/IgM**. **NEET-PG High-Yield Pearls:** * **Pathogenesis:** Associated with "galactose-deficient IgA1" and the formation of anti-glycan antibodies. * **Clinical Presentation:** Synpharyngitic hematuria (short latent period of <2-3 days), unlike Post-Streptococcal Glomerulonephritis (PSGN), which has a longer latent period (1-3 weeks) [1]. * **Prognosis:** The **Oxford Classification (MEST-C score)** is used to predict clinical outcomes based on histology. * **Serum Complement:** Unlike PSGN or Lupus Nephritis, serum complement levels (C3, C4) are typically **normal** in IgA Nephropathy.

Question 1

A 32-year-old man complains of recurrent hematuria since his youth. The hematuria typically occurs following upper respiratory tract infections. Vital signs are normal. Urinalysis shows proteinuria, hematuria, and a few red blood cell casts. Laboratory studies disclose normal levels of BUN and creatinine. The ANA and ANCA tests are negative. Which of the following is the most likely diagnosis?

Accepted Answer

Berger disease (IgA nephropathy)

Answer

Amyloid nephropathy

Answer

Hereditary nephritis (Alport syndrome)

Answer

Membranous glomerulopathy

Question 2

According to the RIFLE criteria, what defines acute kidney injury?

Accepted Answer

Urine output < 0.5 ml/kg/h for > 12 hours

Answer

Urine output < 0.5 ml/kg/h for > 8 hours

Answer

Urine output < 0.3 ml/kg/h for > 24 hours

Answer

Anuria for > 12 hours

Question 3

Which of the following findings is NOT associated with Adult Polycystic Kidney Disease?

Accepted Answer

Tricuspid valve prolapse

Answer

Autosomal dominant inheritance

Answer

Mutations affecting cell-cell-matrix interaction

Answer

Intracranial berry aneurysm

Question 4

What is the treatment of choice in acute hyperkalemia that is life-threatening to cardiac myocytes?

Accepted Answer

Infusion of calcium gluconate

Answer

Oral resins

Answer

Intravenous infusion of insulin

Answer

Beta-blockers

Question 5

Uremia occurs when total GFR is reduced by approximately what percentage?

Accepted Answer

50%

Answer

25%

Answer

60%

Answer

80%

Question 6

Nephrogenic diabetes insipidus is caused by all of the following except?

Accepted Answer

Hypocalcemia

Answer

Toxicity of lithium

Answer

Amyloidosis

Answer

Hypokalemia

Question 7

Urine analysis of a patient with haematuria and hypercalciuria is most likely to reveal which of the following?

Accepted Answer

Isomorphic RBCs

Answer

RBC casts

Answer

Nephrotic range proteinuria

Answer

Eosinophilluria

Question 8

Microalbuminuria is defined as:

Accepted Answer

0.03-0.3 g of 24-hour urine albumin

Answer

0.3-0.5 g of 24-hour urine protein

Answer

0.03-0.3 g of 24-hour urine protein

Answer

> 2.5 g of 24-hour urine protein

Question 9

Nephrocalcinosis is seen in all except:

Accepted Answer

Medullary cystic kidney disease

Answer

Sarcoidosis

Answer

Distal renal tubular acidosis

Answer

Milk alkali syndrome

Question 10

Which of the following statements is NOT true about IgA nephropathy?

Accepted Answer

Absence of associated proteinuria is pathognomic.

Answer

The pathological changes are proliferative and usually confined to mesangial cells; usually focal and segmental.

Answer

Hematuria may be gross or microscopic.

Answer

On immunofluorescence, deposits contain IgA and IgG.

Nephrology — MCQs

Nephrology — MCQs

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