Nephrology Practice Questions

Q: The captopril test is used as a diagnostic test for?

Renovascular hypertension. The **Captopril Test** (specifically the Captopril Renography or Captopril-enhanced DTPA/MAG3 scan) is a classic diagnostic tool for **Renovascular Hypertension (RVH)**, most commonly caused by renal artery stenosis [1], [2]. **1. Why Renovascular Hypertension is correct:** In renal artery stenosis, the affected kidney experiences decreased perfusion pressure [1]. To maintain the Glomerular Filtration Rate (GFR), the kidney activates the Renin-Angiotensin-Aldosterone System (RAAS). Angiotensin II causes **vasoconstriction of the efferent arteriole**, which maintains intraglomerular pressure. When Captopril (an ACE inhibitor) is administered, it blocks the formation of Angiotensin II. This leads to **efferent arteriolar vasodilation**, causing a sharp drop in intraglomerular pressure and a significant **reduction in GFR** in the stenotic kidney. This functional drop is captured via radionuclide imaging (MAG3), confirming the diagnosis [2]. **2. Why other options are incorrect:** * **Postural Hypotension:** Diagnosed via the "Tilt Table Test" or by measuring blood pressure changes upon standing. * **Acute Congestive Heart Failure:** Diagnosed clinically and via NT-proBNP levels and Echocardiography. While ACE inhibitors are used for treatment, they are not used as a diagnostic "test." * **Myocardial Infarction:** Diagnosed via ECG changes and cardiac biomarkers (Troponin I/T) [3]. **High-Yield Clinical Pearls for NEET-PG:** * **Gold Standard Diagnosis:** Renal Angiography remains the gold standard for RVH. * **Screening:** Duplex Doppler or CT/MR Angiography are now more commonly used than the Captopril test in modern practice [1], [4]. * **Clinical Clue:** Suspect RVH if a patient develops an acute rise in serum creatinine (>30%) after starting an ACE inhibitor or ARB. * **Physical Sign:** A continuous abdominal bruit is highly suggestive of renal artery stenosis [1].

Q: What is the typical blood flow rate used in a hemodialysis machine?

300-500 ml/min. **Explanation:** In hemodialysis, the **Blood Flow Rate (Qb)** is a critical determinant of solute clearance (Kt/V). To achieve adequate removal of urea and creatinine within a standard 3-to-4-hour session, a flow rate of **300–500 ml/min** is required [1]. This range is optimized to maximize the concentration gradient across the dialyzer membrane while remaining within the physiological limits of a well-functioning arteriovenous fistula (AVF) or graft. **Analysis of Options:** * **Option A (100-200 ml/min):** This rate is too slow for efficient adult dialysis. It is typically only used during the initiation of the very first dialysis session to prevent **Dialysis Disequilibrium Syndrome (DDS)** or in pediatric cases. * **Option C & D (700-1000+ ml/min):** These rates are physiologically unsustainable for most vascular accesses. High flow rates exceeding 600 ml/min significantly increase the risk of high-output cardiac failure and can cause excessive turbulence, leading to hemolysis or access stenosis. **NEET-PG High-Yield Pearls:** 1. **Dialysate Flow Rate (Qd):** Usually maintained at **500–800 ml/min** (typically 1.5 to 2 times the blood flow rate) to maintain a steep diffusion gradient. 2. **Vascular Access:** The "Gold Standard" is the **Brescia-Cimino fistula** (Radio-cephalic) [1]. 3. **Rule of 6s:** A mature fistula should have a diameter >6mm, be 600ml/min. 4. **Dialysis Disequilibrium Syndrome:** Caused by rapid removal of urea from the blood, leading to cerebral edema. Prevented by using lower blood flow rates (Option A) in the initial session.

Q: What is the treatment for lithium-induced diabetes insipidus?

Amiloride. Lithium-induced Diabetes Insipidus (DI) is the most common cause of drug-induced **Nephrogenic Diabetes Insipidus**. **Why Amiloride is the Correct Answer:** Lithium enters the principal cells of the collecting duct through **ENaC (Epithelial Sodium Channels)**. Once inside, lithium inhibits glycogen synthase kinase-3β (GSK-3β), which interferes with the action of ADH (Vasopressin) on its V2 receptors. This prevents the insertion of Aquaporin-2 channels, leading to polyuria. **Amiloride** is a potassium-sparing diuretic that specifically **blocks ENaC**. By blocking these channels, amiloride prevents lithium from entering the principal cells, thereby restoring the kidney's sensitivity to ADH and reducing polyuria. **Analysis of Incorrect Options:** * **A. Vasopressin:** This is the treatment for *Central* DI [1]. In lithium-induced DI, the kidneys are resistant to vasopressin; therefore, giving more will not resolve the issue [1]. * **B. Mineralocorticoid antagonist (e.g., Spironolactone):** These act on the aldosterone receptor but do not specifically block the entry of lithium through ENaC as effectively as amiloride. * **D. Loop diuretic (e.g., Furosemide):** These inhibit the Na-K-2Cl symporter in the Loop of Henle and would actually worsen dehydration and polyuria. **High-Yield Clinical Pearls for NEET-PG:** 1. **First-line management:** If possible, discontinue lithium. If lithium must be continued (e.g., for bipolar stability), **Amiloride** is the drug of choice. 2. **Thiazide Diuretics:** Paradoxically, Thiazides can also be used in Nephrogenic DI. They cause mild volume depletion, which increases proximal tubule reabsorption of water, reducing the volume delivered to the distal nephron. 3. **Monitoring:** Always monitor serum lithium levels, as diuretics can alter lithium clearance and potentially lead to toxicity.

Q: A 19-year-old man presents to the emergency department with symptoms of malaise, nausea, and decreased urine output. He was previously well, and his physical examination is normal except for an elevated jugular venous pressure (JVP) and a pericardial rub. His electrolytes reveal acute kidney injury (AKI). Which of the following findings on the urinalysis is most likely in keeping with acute glomerulonephritis (GN)?

Erythrocyte casts. ### Explanation **Correct Answer: D. Erythrocyte casts** The presence of **erythrocyte (red blood cell) casts** is the pathognomonic hallmark of **acute glomerulonephritis (GN)** [1]. In GN, the glomerular filtration barrier is damaged, allowing RBCs to leak into the nephron [2]. As these cells pass through the distal convoluted tubule and collecting duct, they are trapped within a matrix of Tamm-Horsfall mucoprotein, forming a cylindrical cast. Finding RBC casts definitively localizes the source of hematuria to the renal parenchyma (glomerulus) rather than the lower urinary tract [1]. **Analysis of Incorrect Options:** * **A. Proteinuria:** While common in GN, proteinuria is non-specific [2]. It can occur in nephrotic syndrome, tubular diseases, or even functional states like heavy exercise or fever. * **B. White blood cell (WBC) casts:** These are characteristic of **acute pyelonephritis** or **acute tubulointerstitial nephritis (AIN)** [3]. They indicate inflammation or infection within the kidney interstitium. * **C. Granular casts:** Often described as "muddy brown" casts, these are the hallmark of **Acute Tubular Necrosis (ATN)**. They represent degenerated tubular epithelial cells. **Clinical Pearls for NEET-PG:** * **Dysmorphic RBCs (Acanthocytes):** Along with RBC casts, these are highly suggestive of glomerular bleeding. * **Clinical Context:** In this 19-year-old patient, the combination of AKI, elevated JVP, and a pericardial rub suggests **uremic pericarditis**—a medical emergency requiring urgent dialysis [4]. * **Nephritic Syndrome Triad:** Hematuria (RBC casts), Hypertension, and Azotemia (AKI) [5]. * **High-Yield Association:** If a young male presents with hemoptysis and RBC casts, consider **Goodpasture Syndrome** (Anti-GBM disease) [3].

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.

Question 1

Which intervention should be planned for a patient with renal calculi?

Accepted Answer

Strain all urine

Answer

Maintain bed rest

Answer

Increase dietary purines

Answer

Restrict fluids

Question 2

Which of the following is seen in nephrotic syndrome?

Accepted Answer

Low lipid

Answer

Low serum calcium

Answer

Raised AT-III

Answer

Platelet activation

Question 3

Low and fixed specific gravity of urine is seen in which of the following conditions?

Accepted Answer

Chronic renal failure

Answer

Diabetes mellitus

Answer

Diabetes insipidus

Answer

Acute glomerulonephritis

Question 4

The captopril test is used as a diagnostic test for?

Accepted Answer

Renovascular hypertension

Answer

Postural hypotension

Answer

Acute congestive heart failure

Answer

Myocardial infarction

Question 5

What is the typical blood flow rate used in a hemodialysis machine?

Accepted Answer

300-500 ml/min

Answer

100-200 ml/min

Answer

700-800 ml/min

Answer

>1000 ml/min

Question 6

A 32-year-old man presents with a serum sodium of 125 mEq/L. On examination, his blood pressure is 110/70 mmHg and pulse is 110/min. When sitting up, he feels lightheaded with a drop in blood pressure. His urine sodium is 5 mEq/L and urine osmolality is 800 mOsm/kg. What is the most likely diagnosis for this patient's hyponatremia?

Accepted Answer

Extrarenal sodium and fluid losses

Answer

Congestive heart failure (CHF)

Answer

Syndrome of Inappropriate Antidiuretic Hormone secretion (SIADH)

Answer

Polydipsia

Question 7

What is the treatment for lithium-induced diabetes insipidus?

Accepted Answer

Amiloride

Answer

Vasopressin

Answer

Mineralocorticoid antagonist

Answer

Loop diuretic

Question 8

A 19-year-old man presents to the emergency department with symptoms of malaise, nausea, and decreased urine output. He was previously well, and his physical examination is normal except for an elevated jugular venous pressure (JVP) and a pericardial rub. His electrolytes reveal acute kidney injury (AKI). Which of the following findings on the urinalysis is most likely in keeping with acute glomerulonephritis (GN)?

Accepted Answer

Erythrocyte casts

Answer

Proteinuria

Answer

White blood cell casts

Answer

Granular casts

Question 9

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 10

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

Nephrology — MCQs

Nephrology — MCQs

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