Nephrology Practice Questions

Q: The neonatal kidney achieves concentrating ability equivalent to an adult's kidney by which age?

One year of age. **Explanation:** The renal system undergoes significant maturation during the first year of life. At birth, the neonatal kidney is physiologically immature, characterized by a low Glomerular Filtration Rate (GFR) and a limited ability to concentrate urine. **Why Option A is Correct:** The maximum concentrating capacity of a neonate is approximately **700 mOsm/L**, whereas an adult can concentrate urine up to **1200–1400 mOsm/L**. This limitation is due to shorter Loops of Henle, lower urea concentration in the renal medulla, and a relative insensitivity of the distal tubules to Antidiuretic Hormone (ADH). By **one year of age**, the anatomical and functional maturation of the nephrons allows the infant to achieve adult-level concentrating ability. **Analysis of Incorrect Options:** * **Option B (18 months):** While some complex tubular functions continue to refine, the primary milestone for concentrating ability is reached by 12 months. * **Option C (3 to 6 months):** Although GFR increases rapidly during this period (reaching near-adult levels relative to surface area by 6–12 months), the concentrating mechanism lags behind and is not yet at adult capacity. * **Option D (Just before puberty):** This is far too late; renal function is essentially mature long before middle childhood. **High-Yield Clinical Pearls for NEET-PG:** * **GFR Maturation:** GFR reaches adult levels (adjusted for surface area) by **2 years of age**. * **Acidification:** The ability to acidify urine reaches adult levels by the end of the **first month**. * **Clinical Implication:** Because infants cannot concentrate urine effectively, they are at a significantly higher risk of **hypernatremic dehydration** during episodes of diarrhea or poor fluid intake.

Q: A child with recurrent urinary tract infections is most likely to show which of the following conditions?

Vesicoureteric reflux. **Explanation:** **Vesicoureteric Reflux (VUR)** is the most common underlying anatomical abnormality found in children with recurrent urinary tract infections (UTIs). It involves the retrograde flow of urine from the bladder into the ureter and kidney due to an incompetent vesicoureteric junction. This stasis of urine acts as a reservoir for bacterial growth, leading to recurrent episodes of cystitis and, more critically, pyelonephritis. **Analysis of Options:** * **Vesicoureteric Reflux (Correct):** It is present in approximately 30-40% of children presenting with their first febrile UTI. Long-term consequences include renal scarring (reflux nephropathy) and hypertension. * **Posterior Urethral Valves (PUV):** While a common cause of obstructive uropathy and UTIs in *male infants*, it is less frequent overall compared to VUR and typically presents with a poor urinary stream and a palpable bladder. * **Neurogenic Bladder:** This leads to UTIs due to incomplete emptying (stasis), but it is usually associated with overt spinal cord defects (e.g., myelomeningocele) rather than being the primary cause in a general pediatric population. * **Renal and Ureteric Calculi:** These are relatively rare in the pediatric age group compared to adults and are usually secondary to metabolic disorders or anatomical stasis. **Clinical Pearls for NEET-PG:** * **Gold Standard Investigation:** Voiding Cystourethrogram (VCUG) is the investigation of choice to diagnose and grade VUR. * **Initial Screening:** Ultrasound is often the first step, but a normal USG does *not* rule out VUR. * **Management:** Low-grade VUR (Grades I-II) often resolves spontaneously; high-grade VUR (Grades IV-V) may require surgical reimplantation (e.g., Cohen’s procedure). * **DMSA Scan:** This is the most sensitive test for detecting **renal scarring** following recurrent UTIs.

Q: What is the formula for calculating GFR?

GFR (ml/minute per 1.73 m2) = k x height / serum creatinine. The correct answer is **Option A**. In pediatric medicine, the standard method for estimating the Glomerular Filtration Rate (eGFR) is the **Schwartz Formula**. ### **Why Option A is Correct** The Schwartz Formula is based on the physiological principle that creatinine production is proportional to muscle mass, which in children is directly related to their **height (length)**. * **Formula:** $eGFR = \frac{k \times \text{Height (cm)}}{\text{Serum Creatinine (mg/dL)}}$ * **The Constant (k):** This represents the creatinine excretion per unit of body size. It varies with age (e.g., 0.45 for infants, 0.413 in the updated "Bedside Schwartz" formula). ### **Why Other Options are Incorrect** * **Option B & C:** Weight is not used in the pediatric eGFR formula because weight fluctuates significantly with fluid status (edema) and nutrition, making it an unreliable surrogate for muscle mass compared to height. * **Option D:** This suggests an inverse relationship between height and GFR, which is mathematically incorrect. As a child grows taller and gains muscle mass, their creatinine production increases; therefore, height must be in the numerator to balance the equation. ### **High-Yield Clinical Pearls for NEET-PG** 1. **Bedside Schwartz Formula:** The most commonly used updated constant is **0.413**. It is used for children aged 1 to 16 years. 2. **Units:** Always remember height is measured in **centimeters (cm)** and serum creatinine in **mg/dL**. 3. **Cystatin C:** In children with abnormal muscle mass (e.g., neuromuscular wasting), Serum Cystatin C is a more accurate marker than creatinine as it is independent of muscle bulk. 4. **Gold Standard:** While Schwartz is used clinically, the gold standard for measuring GFR remains **Inulin clearance** (though rarely used in routine practice).

Q: Post-streptococcal glomerulonephritis in children is diagnosed by?

Mild proteinuria, hematuria, high ASO titer. **Explanation:** Post-streptococcal glomerulonephritis (PSGN) is a classic example of **Nephritic Syndrome**, occurring typically 1–3 weeks after a Group A Beta-hemolytic Streptococcal infection (pharyngitis or impetigo) [1]. **1. Why Option C is Correct:** * **Hematuria:** This is the hallmark of nephritic syndrome, often presenting as "cola-colored" or smoky urine due to glomerular capillary damage. [1] * **Mild Proteinuria:** Unlike nephrotic syndrome, proteinuria in PSGN is usually sub-nephrotic (<3.5 g/day), often described as "mild to moderate." * **High ASO Titer:** Evidence of a recent streptococcal infection is essential for diagnosis. Anti-streptolysin O (ASO) titers are elevated in 90% of cases following pharyngitis (Anti-DNAse B is more sensitive for skin infections). **2. Why Other Options are Incorrect:** * **Options A & B (Heavy Proteinuria):** Heavy (nephrotic-range) proteinuria and high cholesterol are characteristic of **Nephrotic Syndrome** (e.g., Minimal Change Disease), not PSGN. [1] * **Options B & D (Low/Normal ASO):** PSGN is an immune-mediated sequela of a specific bacterial infection; therefore, streptococcal antibodies (ASO, Anti-DNAse B, or Streptozyme) must be elevated to confirm the etiology. [1] **3. High-Yield Clinical Pearls for NEET-PG:** * **Complement Levels:** Characterized by **low C3** levels (due to consumption via the alternative pathway). C3 levels typically return to normal within 6–8 weeks. * **Light Microscopy:** Shows "Starry sky" appearance or diffuse proliferative glomerulonephritis with enlarged, hypercellular glomeruli. [1] * **Electron Microscopy:** Pathognomonic **"Sub-epithelial humps"** (immune complex deposits). [1] * **Immunofluorescence:** "Lumpy-bumpy" or granular deposits of IgG and C3. [1] **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Kidney, pp. 914-916.

Q: A 12-year-old boy presented with severe vomiting and diarrhea. He was brought to the hospital due to severe oliguria. He was given IV fluids and furosemide without any diuresis. Blood biochemistry revealed: Urea 120 mg% and serum creatinine 4 mg%. What is the most likely diagnosis?

Hemolytic uremic syndrome. ### Explanation The correct diagnosis is **Hemolytic Uremic Syndrome (HUS)**. **Why it is correct:** The clinical triad of HUS consists of **Microangiopathic Hemolytic Anemia (MAHA), Thrombocytopenia, and Acute Kidney Injury (AKI)** [1], [2]. In children, the most common form is "D+ HUS" (Diarrhea-associated), typically caused by Shiga toxin-producing *E. coli* (O157:H7) [1]. The patient’s history of severe diarrhea followed by oliguria and significantly elevated nitrogenous waste (Urea 120, Creatinine 4) is a classic presentation [2]. The **failure to respond to IV fluids and furosemide** indicates established intrinsic renal damage (thrombotic microangiopathy), which is characteristic of HUS rather than simple dehydration [1]. **Why incorrect options are wrong:** * **Prerenal Azotemia:** While diarrhea causes dehydration, prerenal AKI should respond to aggressive fluid resuscitation with an increase in urine output. The lack of diuresis here points toward intrinsic damage. * **Acute Tubular Necrosis (ATN):** While ATN can follow severe dehydration, the specific prodrome of diarrhea in a pediatric patient strongly favors HUS. In exams, "diarrhea + renal failure" in a child is HUS until proven otherwise. * **Acute Glomerulonephritis (AGN):** AGN typically presents with hematuria (cola-colored urine), hypertension, and edema, usually following a respiratory or skin infection (e.g., PSGN), not a diarrheal illness. **Clinical Pearls for NEET-PG:** * **Most common cause of AKI in children:** HUS. * **Pathogenesis:** Shiga toxin causes endothelial injury, leading to platelet microthrombi in the glomerular capillaries [1]. * **Peripheral Smear:** Look for **Schistocytes** (fragmented RBCs) [1]. * **Management:** Primarily supportive (dialysis if needed). Antibiotics and anti-motility agents are generally avoided as they may worsen toxin release.

Q: A 4-month-old infant with a urinary tract infection (UTI) was treated for 14 days with IV cefotaxime. What is the next step in management?

Ultrasound (USG) only. ### Explanation The management of a first-time febrile Urinary Tract Infection (UTI) in infants and children has evolved to minimize invasive procedures. According to the **AAP (American Academy of Pediatrics)** and **Indian Society of Pediatric Nephrology (ISPN)** guidelines, the primary goal after the first UTI is to screen for structural abnormalities. **1. Why Option A is Correct:** **Ultrasound (USG) KUB** is the recommended first-line investigation for all infants (2 months to 2 years) after their first febrile UTI. It is non-invasive and effective at detecting structural anomalies like hydronephrosis, renal agenesis, or duplication. In this 4-month-old, USG is the immediate next step to screen for any gross anatomical defects. **2. Why Other Options are Incorrect:** * **Option B (USG + MCU):** A Micturating Cystourethrogram (MCU/VCUG) is no longer routine after the *first* UTI unless the USG shows hydronephrosis, scarring, or other suspicious findings. It is also indicated if the UTI is "atypical" (e.g., non-E. coli organism, septicemia) or "recurrent." * **Option C & D (DMSA):** A DMSA scan is used to detect acute pyelonephritis or permanent renal scarring. While highly sensitive, it is not a routine immediate investigation after a first UTI unless the clinical course is complicated or the USG is abnormal. **Clinical Pearls for NEET-PG:** * **MCU Timing:** If indicated, MCU should be performed after the infection has subsided (usually 2–4 weeks later) to avoid false positives due to infection-induced reflux. * **DMSA Timing:** To detect permanent scarring, DMSA should be performed **6 months** after the acute infection. * **Prophylaxis:** Routine antibiotic prophylaxis is generally not recommended after the first UTI unless high-grade Vesicoureteral Reflux (VUR) is diagnosed. * **Gold Standard for VUR:** MCU remains the gold standard for diagnosing and grading VUR.

Q: A child presented with frothy urine, massive proteinuria, and edema. Urine examination revealed no RBCs, no WBCs, no casts, and no crystals. There is no prior episode of similar presentation. What is your diagnosis?

Minimal change disease. ### Explanation The clinical presentation of **frothy urine** (indicating significant proteinuria), **massive proteinuria**, and **edema** defines **Nephrotic Syndrome**. **1. Why Minimal Change Disease (MCD) is correct:** MCD is the most common cause of nephrotic syndrome in children (approx. 80% of cases). The hallmark of MCD is **"pure" nephrotic syndrome**, meaning it presents with massive proteinuria but lacks features of "nephritic" involvement. The absence of RBCs (hematuria), WBCs, and casts in the urine sediment is highly characteristic. In MCD, light microscopy shows normal glomeruli, but electron microscopy reveals **effacement of podocyte foot processes**. **2. Why other options are incorrect:** * **IgA Nephropathy:** This is a **nephritic** syndrome. It typically presents with recurrent episodes of gross or microscopic hematuria (RBCs in urine), often following an upper respiratory tract infection. * **Membranous Glomerulonephritis (MGN):** While it causes nephrotic syndrome, it is rare in children and more common in adults. It is often associated with secondary causes like Hepatitis B or SLE. * **Membranoproliferative Glomerulonephritis (MPGN):** This typically presents with a **mixed nephrotic-nephritic picture**, meaning urine would likely show hematuria and casts, along with low complement (C3) levels. **Clinical Pearls for NEET-PG:** * **Most common cause** of Nephrotic Syndrome in children: MCD. * **Selective Proteinuria:** MCD is characterized by the loss of albumin only (due to loss of polyanionic charge on the basement membrane). * **Treatment of Choice:** Corticosteroids (Prednisolone) are the first-line therapy; MCD is highly steroid-responsive. * **Diagnosis:** In children, a renal biopsy is usually **not** required initially if the presentation is classic; it is reserved for steroid-resistant cases.

Q: Physical examination of a neonate reveals a distended bladder and palpable kidneys. The infant produces a weak urinary stream. A voiding cystourethrogram is shown. He appears to be otherwise normal. Which of the following is the most likely diagnosis?

Posterior urethral valve. ***Posterior urethral valve*** - **Voiding cystourethrogram** shows **dilated posterior urethra** with **keyhole sign** and **trabeculated bladder**, pathognomonic for posterior urethral valves in male neonates. - Clinical presentation of **distended bladder**, **palpable kidneys**, and **weak urinary stream** is classic for **infravesical obstruction** caused by posterior urethral valves. *Ureteropelvic junction obstruction* - Would cause **hydronephrosis** but **normal bladder** appearance on imaging, not the distended bladder seen here. - Typically presents with **flank pain** or **palpable flank mass**, not bladder distension or weak urinary stream. *Prune belly syndrome* - Characterized by **absent abdominal wall musculature**, **cryptorchidism**, and **urinary tract abnormalities** - not just isolated urinary symptoms. - VCUG would show **tortuous, dilated ureters** and **large bladder**, but without the **keyhole sign** of posterior urethra dilation. *Duplication of the collecting system* - Usually **asymptomatic** in neonates or presents with **recurrent UTIs**, not bladder distension or weak stream. - VCUG would demonstrate **duplicated collecting systems** with possible **vesicoureteral reflux**, not posterior urethral dilation.

Q: A 5-year-old child develops the sudden onset of bloody diarrhea, vomiting of blood, hematuria, and renal failure following a flulike gastrointestinal illness. The blood urea nitrogen (BUN) level is markedly increased, but fibrin degradation products and blood clotting times are within normal limits. A peripheral blood smear reveals poikilocytes, schistocytes, and a decrease in the number of platelets. No fever or neurologic symptoms are present. What is the best diagnosis for this patient?

Hemolytic-uremic syndrome (HUS). ### Explanation The clinical presentation describes the classic triad of **Hemolytic-Uremic Syndrome (HUS)**: Microangiopathic hemolytic anemia (MAHA), thrombocytopenia, and acute kidney injury (AKI). **1. Why HUS is the Correct Answer:** HUS typically follows a prodromal gastrointestinal illness (often caused by Shiga toxin-producing *E. coli* O157:H7). The toxin causes endothelial damage in the renal microvasculature, leading to platelet activation and microthrombi formation. As RBCs pass through these partially occluded vessels, they are mechanically shredded, resulting in **schistocytes** (fragmented cells) and **poikilocytes**. The consumption of platelets leads to thrombocytopenia, while the localized thrombi in the kidney cause renal failure (elevated BUN/Creatinine) and hematuria. **2. Why the Other Options are Incorrect:** * **DIC:** While DIC also features schistocytes and low platelets, it is characterized by **abnormal coagulation profiles** (prolonged PT/aPTT) and elevated Fibrin Degradation Products (FDPs). In this case, clotting times and FDPs are normal, ruling out DIC. * **TTP:** TTP shares the features of HUS but is more common in adults and typically presents with a **pentad** that includes fever and prominent **neurologic symptoms**, both of which are absent here. * **ITP:** ITP presents with isolated thrombocytopenia. It does not cause schistocytes, hemolytic anemia, or renal failure. **3. NEET-PG High-Yield Pearls:** * **Most common cause of AKI in children:** HUS. * **Classic Triad:** Hemolytic anemia (Coombs negative) + Thrombocytopenia + Renal failure. * **Key Lab Finding:** Normal PT/aPTT (distinguishes HUS from DIC). * **Management:** Primarily supportive (fluid/electrolyte balance, dialysis if needed). **Antibiotics and anti-motility agents are contraindicated** as they may increase toxin release and worsen the condition.

Question 1

The neonatal kidney achieves concentrating ability equivalent to an adult's kidney by which age?

Accepted Answer

One year of age

Answer

Eighteen months of age

Answer

Three to six months of age

Answer

Just before puberty

Question 2

A child with recurrent urinary tract infections is most likely to show which of the following conditions?

Accepted Answer

Vesicoureteric reflux

Answer

Posterior urethral valves

Answer

Neurogenic bladder

Answer

Renal and ureteric calculi

Question 3

What is the formula for calculating GFR?

Accepted Answer

GFR (ml/minute per 1.73 m2) = k x height / serum creatinine

Answer

GFR (ml/minute per 1.73 m2) = k x weight / serum creatinine

Answer

GFR (ml/minute per 1.73 m2) = k / (weight x creatinine)

Answer

GFR (ml/minute per 1.73 m2) = k / (height x creatinine)

Question 4

Post-streptococcal glomerulonephritis in children is diagnosed by?

Accepted Answer

Mild proteinuria, hematuria, high ASO titer

Answer

Heavy proteinuria, high cholesterol, high ASO titer

Answer

Heavy proteinuria, hematuria, low ASO titer

Answer

Mild proteinuria, high cholesterol, normal ASO titer

Question 5

A 12-year-old boy presented with severe vomiting and diarrhea. He was brought to the hospital due to severe oliguria. He was given IV fluids and furosemide without any diuresis. Blood biochemistry revealed: Urea 120 mg% and serum creatinine 4 mg%. What is the most likely diagnosis?

Accepted Answer

Hemolytic uremic syndrome

Answer

Prerenal azotemia

Answer

Acute glomerulonephritis

Answer

Acute tubular necrosis

Question 6

A 4-month-old infant with a urinary tract infection (UTI) was treated for 14 days with IV cefotaxime. What is the next step in management?

Accepted Answer

Ultrasound (USG) only

Answer

Ultrasound (USG) + MCU

Answer

Ultrasound (USG) + DMSA

Answer

Ultrasound (USG) + MCU + DMSA

Question 7

A child presented with frothy urine, massive proteinuria, and edema. Urine examination revealed no RBCs, no WBCs, no casts, and no crystals. There is no prior episode of similar presentation. What is your diagnosis?

Accepted Answer

Minimal change disease

Answer

IgA nephropathy

Answer

Membranous glomerulonephritis

Answer

MPGN

Question 8

In Lowe syndrome, all of the following are seen except?

Accepted Answer

Hypotonia

Answer

Undescended testes in males

Answer

Cataract

Answer

Low IQ

Question 9

Physical examination of a neonate reveals a distended bladder and palpable kidneys. The infant produces a weak urinary stream. A voiding cystourethrogram is shown. He appears to be otherwise normal. Which of the following is the most likely diagnosis?

Accepted Answer

Posterior urethral valve

Answer

Ureteropelvic junction obstruction

Answer

Prune belly syndrome

Answer

Duplication of the collecting system

Question 10

A 5-year-old child develops the sudden onset of bloody diarrhea, vomiting of blood, hematuria, and renal failure following a flulike gastrointestinal illness. The blood urea nitrogen (BUN) level is markedly increased, but fibrin degradation products and blood clotting times are within normal limits. A peripheral blood smear reveals poikilocytes, schistocytes, and a decrease in the number of platelets. No fever or neurologic symptoms are present. What is the best diagnosis for this patient?

Accepted Answer

Hemolytic-uremic syndrome (HUS)

Answer

Autoimmune thrombocytopenic purpura (ITP)

Answer

Disseminated intravascular coagulopathy (DIC)

Answer

Thrombotic thrombocytopenic purpura (TTP)

Nephrology — MCQs

Nephrology — MCQs

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