Nephrology — MCQs

A 6-year-old child has been drinking more water and urinating more frequently for the past 7 months. Physical examination reveals dehydration. Urinalysis findings include a pH of 6.5, specific gravity of 1.010, and no protein, blood, glucose, or ketones. There are no WBCs, RBCs, or casts. Serum electrolytes show Na+, 152 mmol/L; K+, 4.6 mmol/L; Cl-, 120 mmol/L; HCO3-, 21 mmol/L; urea nitrogen, 29 mg/dL; and creatinine, 3.2 mg/dL. An ultrasound scan shows bilaterally small kidneys with barely visible medullary cysts concentrated at the corticomedullary junction. Which of the following genes is most likely mutated in this child?

Q27Easy

Nocturnal enuresis is the occurrence of involuntary voiding at night in a child older than which age?

Q28Easy

What is the incidence of liver cysts in childhood polycystic kidney disease?

Q29Easy

Nocturnal enuresis may be considered normal up to what age?

Q30Medium

Which is a reliable marker for estimating glomerular filtration rate (GFR) in children?

Nephrology Indian Medical PG Practice Questions and MCQs

Question 21: Which of the following is NOT a cause of Type 2 renal tubular acidosis?

A. Cystinosis
B. Lowe syndrome
C. Essential fructosuria (Correct Answer)
D. Galactosemia

Explanation: **Explanation:** **Type 2 Renal Tubular Acidosis (Proximal RTA)** is characterized by a defect in the proximal tubule's ability to reabsorb filtered bicarbonate ($HCO_3^-$). This often occurs as part of **Fanconi Syndrome**, a generalized dysfunction of the proximal tubule. **Why Essential Fructosuria is the Correct Answer:** Essential fructosuria is a benign, asymptomatic autosomal recessive condition caused by a deficiency of the enzyme **fructokinase**. Since fructose is not converted to fructose-1-phosphate, it does not accumulate in toxic amounts in the renal cells; it is simply excreted in the urine. Therefore, it does **not** cause renal tubular damage or RTA. **Analysis of Incorrect Options (Causes of Type 2 RTA):** * **Cystinosis:** The most common inherited cause of Fanconi syndrome in children. Intracellular accumulation of cystine crystals damages proximal tubular cells. * **Lowe Syndrome (Oculocerebrorenal syndrome):** An X-linked recessive disorder characterized by cataracts, intellectual disability, and proximal tubular dysfunction (Fanconi syndrome). * **Galactosemia:** Deficiency of Galactose-1-phosphate uridyltransferase (GALT) leads to the accumulation of galactose-1-phosphate, which is toxic to the renal proximal tubules, leading to Type 2 RTA. * *Note: **Hereditary Fructose Intolerance (HFI)** (aldolase B deficiency) does cause Type 2 RTA, unlike Essential Fructosuria.* **High-Yield Clinical Pearls for NEET-PG:** 1. **Type 2 RTA** is associated with **hypokalemia** and a **low transtubular potassium gradient (TTKG)**. 2. **Fanconi Syndrome Pentad:** Phosphaturia, Glycosuria (with normal blood glucose), Aminoaciduria, Uricosuria, and Tubular Proteinuria. 3. **Urine pH:** In Type 2 RTA, urine pH can be **< 5.5** (acidic) once the blood bicarbonate level drops below the lowered renal threshold. 4. **Bone Disease:** Chronic phosphate wasting in Type 2 RTA leads to **Rickets** in children and **Osteomalacia** in adults.

Question 22: What is the most reliable method for obtaining a urine specimen?

A. Urethral catheterization
B. Catheter aspiration
C. Midstream voiding
D. Suprapubic aspiration (Correct Answer)

Explanation: **Explanation:** In pediatric nephrology, the "gold standard" for obtaining a sterile urine specimen is **Suprapubic Aspiration (SPA)**. **1. Why Suprapubic Aspiration is the Correct Answer:** SPA involves the direct needle aspiration of urine from the bladder through the abdominal wall. Because the needle bypasses the urethra and the perineum—areas heavily colonized with commensal flora—any bacterial growth obtained via SPA is considered clinically significant (even if the colony count is <10³ CFU/mL). It is the most reliable method because it carries the lowest risk of contamination. **2. Analysis of Incorrect Options:** * **Urethral Catheterization:** While more reliable than a voided sample, it still carries a risk of introducing bacteria from the distal urethra into the specimen, leading to potential false positives. * **Midstream Voiding:** This is the standard for toilet-trained children but is highly susceptible to contamination from skin and preputial flora. In non-toilet-trained infants, "bag specimens" are notorious for high false-positive rates (up to 70%). * **Catheter Aspiration:** This typically refers to taking a sample from an indwelling catheter, which is discouraged due to the rapid formation of biofilms and high colonization rates. **3. NEET-PG High-Yield Pearls:** * **Gold Standard:** SPA is the most accurate method for diagnosing UTI in neonates and young infants. * **Diagnostic Threshold:** For SPA, **any** number of gram-negative bacilli or >several hundred gram-positive cocci is diagnostic of a UTI. * **Clinical Practice:** While SPA is the most reliable, **Urethral Catheterization** is the most common "sterile" method used in emergency departments due to its higher success rate compared to SPA (which requires a full bladder). * **Bag Collection:** Never use a bag specimen for a urine *culture*; it is only useful for *screening* (if the urinalysis is negative, it helps rule out UTI).

Question 23: Which of the following is a renal cause of acute renal failure in children?

A. Minimal change disease
B. Renal amyloidosis
C. Pre-eclampsia
D. Hemolytic uremic syndrome (Correct Answer)

Explanation: **Explanation:** Acute Kidney Injury (AKI) in children is classified into three categories: Pre-renal (hypoperfusion), Intrinsic/Renal (parenchymal damage), and Post-renal (obstructive). **Hemolytic Uremic Syndrome (HUS)** is the most common **intrinsic renal cause** of acute renal failure in children. It is characterized by the triad of microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury. The pathophysiology involves Shiga toxin-induced endothelial injury in the glomerular capillaries, leading to microthrombi formation, which directly damages the renal parenchyma. **Analysis of Incorrect Options:** * **Minimal Change Disease (MCD):** While it is the most common cause of Nephrotic Syndrome in children, it typically presents with massive proteinuria and edema rather than acute renal failure. AKI in MCD is rare and usually secondary to severe hypovolemia (pre-renal). * **Renal Amyloidosis:** This is a chronic systemic disease resulting in chronic kidney disease (CKD) rather than acute failure. It is also extremely rare in the pediatric age group. * **Pre-eclampsia:** This is a multisystem disorder of pregnancy. While it can cause renal dysfunction in the mother, it is not a cause of pediatric renal failure. **High-Yield Clinical Pearls for NEET-PG:** * **Most common cause of AKI in children:** Pre-renal (due to gastroenteritis/dehydration). * **Most common intrinsic renal cause of AKI in children:** HUS (specifically D+ HUS caused by *E. coli* O157:H7). * **HUS Triad:** Microangiopathic Hemolytic Anemia (Schistocytes on smear) + Thrombocytopenia + AKI. * **Management Tip:** Antibiotics and anti-motility agents are contraindicated in Shiga-toxin HUS as they may worsen toxin release.

Question 24: A 4-year-old child presented with generalized edema and ascites. There was no hypertension or hematuria. Renal function tests were normal. Urinalysis revealed massive proteinuria. What is the most probable underlying cause?

A. Membranous glomerulonephritis
B. Minimal change disease (Correct Answer)
C. Post-streptococcal glomerulonephritis
D. IgA nephropathy

Explanation: ### Explanation The clinical presentation of generalized edema, ascites, and massive proteinuria in a preschool-aged child, in the absence of hypertension, hematuria, or renal insufficiency, is the classic description of **Nephrotic Syndrome**. **Why Minimal Change Disease (MCD) is correct:** MCD is the most common cause of primary nephrotic syndrome in children (accounting for ~80% of cases under the age of 6). It is characterized by "selective" proteinuria (mainly albumin) due to the loss of the glomerular polyanion charge. On light microscopy, the glomeruli appear normal (hence "minimal change"), but electron microscopy reveals characteristic **effacement of podocyte foot processes**. It typically responds very well to corticosteroid therapy. **Why the other options are incorrect:** * **Post-streptococcal Glomerulonephritis (PSGN):** This is a **Nephritic Syndrome**. It typically presents with the triad of hematuria (cola-colored urine), hypertension, and edema, often following a throat or skin infection. * **Membranous Glomerulonephritis:** This is the most common cause of nephrotic syndrome in **adults**, not young children. In children, it is rare and often secondary to systemic diseases like Hepatitis B or SLE. * **IgA Nephropathy:** This is the most common cause of glomerulonephritis worldwide and typically presents as **recurrent gross hematuria** following an upper respiratory tract infection (synpharyngitic hematuria). **High-Yield Clinical Pearls for NEET-PG:** * **Age Factor:** MCD is most common between 2–6 years of age. * **Diagnosis:** In children with classic features of MCD, a renal biopsy is **not** initially required; a trial of steroids (Prednisolone) is the standard first step. * **Biopsy Indications:** Biopsy is indicated if the child is <1 year or >12 years old, has persistent hypertension, gross hematuria, low C3 levels, or is steroid-resistant. * **Most common complication:** Infections (especially Spontaneous Bacterial Peritonitis due to *S. pneumoniae*) due to loss of immunoglobulins in urine.

Question 25: What is the drug of choice for a child with a first episode of nephrotic syndrome?

A. Cyclophosphamide
B. Prednisolone (Correct Answer)
C. Mycophenolate
D. Cyclosporine

Explanation: **Explanation:** The management of Nephrotic Syndrome in children is a high-yield topic for NEET-PG. The primary pathology in most children (approx. 80-90%) is **Minimal Change Disease (MCD)**, which is highly steroid-sensitive. **1. Why Prednisolone is the Correct Answer:** Oral **Prednisolone** is the gold standard and first-line therapy for the initial episode of idiopathic nephrotic syndrome. The standard ISPN (Indian Society of Pediatric Nephrology) protocol for the first episode involves a total of 12 weeks of therapy: * **Initial Phase:** 2 mg/kg/day (max 60 mg) for 6 weeks. * **Maintenance Phase:** 1.5 mg/kg (max 40 mg) on alternate days for the next 6 weeks. The goal is to induce remission (uphill protein-to-creatinine ratio < 0.2 or dipstick trace/nil for 3 consecutive days). **2. Why Other Options are Incorrect:** * **Cyclophosphamide (A):** This is an alkylating agent used as a "steroid-sparing" drug. It is indicated for **frequent relapsers** or steroid-dependent cases, not for the first episode. * **Mycophenolate Mofetil (C):** Used as a second-line steroid-sparing agent in children who show toxicity to steroids or cyclophosphamide. * **Cyclosporine (D):** A Calcineurin inhibitor (CNI) reserved for **Steroid-Resistant Nephrotic Syndrome (SRNS)**. **Clinical Pearls for NEET-PG:** * **Definition of Remission:** Urinary protein excretion < 4 mg/m²/hr or dipstick Nil/Trace for 3 consecutive days. * **Steroid Resistance:** Failure to achieve remission after 4 weeks of daily prednisolone therapy. * **Most Common Complication:** Infections (specifically Spontaneous Bacterial Peritonitis caused by *S. pneumoniae*). * **Vaccination:** Live vaccines (OPV, MMR, Varicella) are **contraindicated** while the child is on high-dose steroids.

Question 26: A 6-year-old child has been drinking more water and urinating more frequently for the past 7 months. Physical examination reveals dehydration. Urinalysis findings include a pH of 6.5, specific gravity of 1.010, and no protein, blood, glucose, or ketones. There are no WBCs, RBCs, or casts. Serum electrolytes show Na+, 152 mmol/L; K+, 4.6 mmol/L; Cl-, 120 mmol/L; HCO3-, 21 mmol/L; urea nitrogen, 29 mg/dL; and creatinine, 3.2 mg/dL. An ultrasound scan shows bilaterally small kidneys with barely visible medullary cysts concentrated at the corticomedullary junction. Which of the following genes is most likely mutated in this child?

A. MCKD1
B. NPHP1 (Correct Answer)
C. PKD1
D. PKHD1

Explanation: **Explanation:** The clinical presentation of polyuria, polydipsia, and progressive renal failure in a child, combined with ultrasound findings of **small kidneys and medullary cysts**, is classic for **Nephronophthisis (NPH)**. **1. Why NPHP1 is correct:** Nephronophthisis is an autosomal recessive ciliopathy and the most common genetic cause of end-stage renal disease (ESRD) in children. The hallmark features include a defect in urinary concentrating ability (leading to polyuria/polydipsia) and tubulointerstitial fibrosis. Unlike Polycystic Kidney Disease (PKD), the kidneys in NPH are **shrunken/small**, and cysts are typically located at the **corticomedullary junction**. **NPHP1** (encoding the protein Nephrocystin-1) is the most frequently mutated gene in this condition. **2. Why other options are incorrect:** * **MCKD1 (ADTKD):** Medullary Cystic Kidney Disease (now called Autosomal Dominant Tubulointerstitial Kidney Disease) presents similarly but occurs in **adults** (3rd–5th decade) and follows an autosomal dominant inheritance. * **PKD1:** Mutations cause Autosomal Dominant Polycystic Kidney Disease (ADPKD). This presents with **bilaterally enlarged kidneys** and multiple large cortical cysts, usually manifesting in adulthood. * **PKHD1:** Mutations cause Autosomal Recessive Polycystic Kidney Disease (ARPKD). This presents in **neonates/infants** with massive nephromegaly and is associated with congenital hepatic fibrosis. **Clinical Pearls for NEET-PG:** * **Triad of NPH:** Polyuria, growth retardation, and progressive renal failure with "bland" urinary sediment. * **Imaging Gold Standard:** Small, echogenic kidneys with loss of corticomedullary differentiation; cysts are a late finding. * **Extra-renal associations:** Senior-Løken syndrome (NPH + Retinitis Pigmentosa) and Joubert syndrome (NPH + Cerebellar ataxia).

Question 27: Nocturnal enuresis is the occurrence of involuntary voiding at night in a child older than which age?

A. 2 1/2 years
B. 3 1/2 years
C. 4 years
D. 5 years (Correct Answer)

Explanation: **Explanation:** **1. Why 5 years is the correct answer:** According to the DSM-5 and the International Children’s Continence Society (ICCS), **nocturnal enuresis** is defined as involuntary voiding of urine during sleep in children aged **5 years or older**. This age threshold is chosen because, by age 5, approximately 90-95% of children have achieved mature bladder control and are developmentally expected to remain dry at night. Diagnosis before this age is considered clinically premature as the neuromuscular maturation of the bladder is often still ongoing. **2. Why the other options are incorrect:** * **A & B (2 ½ and 3 ½ years):** At these ages, the lack of nocturnal bladder control is considered a normal developmental stage. Daytime continence is usually achieved by age 2–3, but nighttime dryness typically follows months or years later. * **C (4 years):** While many children are dry by age 4, it is still within the range of normal physiological variation. A diagnosis of enuresis is deferred until age 5 to avoid unnecessary medicalization of a developmental lag. **3. NEET-PG High-Yield Pearls:** * **Primary vs. Secondary:** Primary enuresis occurs in a child who has never been dry for >6 months. Secondary enuresis occurs after a period of dryness of at least 6 months (often triggered by stress, UTI, or DM). * **Epidemiology:** It is more common in boys. There is a strong genetic component (77% risk if both parents were affected). * **Management:** * **First-line:** Behavioral modification (fluid restriction before bed, "lifting," and bladder training). * **Most effective long-term:** Enuresis/Bed-wetting alarms (Conditioning therapy). * **Pharmacotherapy:** **Desmopressin (DDAVP)** is the drug of choice for rapid symptomatic relief (e.g., for camps). Imipramine (TCA) is used as a last resort due to cardiotoxicity.

Question 28: What is the incidence of liver cysts in childhood polycystic kidney disease?

A. 5%
B. 10%
C. 18%
D. 50% (Correct Answer)

Explanation: **Explanation:** **Autosomal Dominant Polycystic Kidney Disease (ADPKD)**, often referred to as "adult-type," can manifest in childhood. While the primary pathology involves the formation of renal cysts, it is a multisystem disorder. **1. Why 50% is Correct:** In children diagnosed with ADPKD, the liver is the most common extrarenal site of cyst formation. While these cysts are rare in infants, their prevalence increases significantly with age. By the time children with ADPKD reach late adolescence, approximately **50%** will have detectable liver cysts on high-resolution ultrasonography. Unlike the renal cysts, liver cysts in ADPKD rarely lead to hepatic failure, as they arise from the biliary epithelium rather than hepatocytes. **2. Analysis of Incorrect Options:** * **5%, 10%, and 18%:** These percentages are too low for the pediatric/adolescent population. While the incidence starts near 0% in newborns, it climbs steadily throughout childhood. By adulthood, the incidence of liver cysts in ADPKD patients exceeds 70-90%. **3. High-Yield Clinical Pearls for NEET-PG:** * **Genetics:** ADPKD is most commonly due to mutations in **PKD1** (Chromosome 16) or **PKD2** (Chromosome 4). PKD1 is associated with more severe disease and earlier onset. * **ADPKD vs. ARPKD:** Do not confuse this with Autosomal Recessive Polycystic Kidney Disease (ARPKD). In **ARPKD**, the liver involvement is **Congenital Hepatic Fibrosis** (biliary dysgenesis), not discrete macrocysts. * **Extrarenal Manifestations:** Apart from liver cysts, watch for **Berry aneurysms** (Circle of Willis), pancreatic cysts, and Mitral Valve Prolapse (MVP). * **Hypertension:** This is often the earliest clinical sign of ADPKD in children, even before a significant decline in GFR.

Question 29: Nocturnal enuresis may be considered normal up to what age?

A. 3 years
B. 4 years
C. 5 years
D. 6 years (Correct Answer)

Explanation: **Explanation:** The correct answer is **6 years**. Nocturnal enuresis is defined as the involuntary voiding of urine during sleep in a child who is old enough to have attained bladder control. **1. Why 6 years is correct:** Bladder control is a developmental milestone achieved through the maturation of the central nervous system and the bladder-brain feedback loop. While most children achieve daytime dryness by age 4, nocturnal (nighttime) dryness takes longer. According to standard pediatric guidelines (and frequently tested in NEET-PG based on Indian clinical standards), nocturnal enuresis is considered a clinical concern only if it persists beyond the **5th birthday**. Therefore, it is considered **normal up to the age of 5 or 6 years**. Many textbooks specifically cite 6 years as the threshold for initiating formal evaluation or intervention. **2. Why other options are incorrect:** * **3 & 4 years:** At these ages, the neuromuscular coordination required to inhibit bladder contractions during sleep is still developing. Bedwetting is statistically common and developmentally appropriate. * **5 years:** While the DSM-5 uses 5 years as a diagnostic cutoff, clinical practice often allows for "normal" variation up to age 6, especially in boys, before labeling it a pathology requiring treatment. **High-Yield Clinical Pearls for NEET-PG:** * **Primary vs. Secondary:** Primary enuresis means the child has never been dry for >6 months. Secondary enuresis occurs after a period of dryness (often due to stress or UTI). * **Most Common Cause:** Developmental delay in bladder control (not psychological). * **Treatment of Choice:** * **Initial:** Behavioral modification (fluid restriction, bladder training). * **Most Effective Long-term:** Enuresis Alarm (Conditioning therapy). * **Drug of Choice:** Desmopressin (ADH analogue) – provides rapid but temporary relief. * **Gender:** It is more common in boys.

Question 30: Which is a reliable marker for estimating glomerular filtration rate (GFR) in children?

A. Serum creatinine
B. Inulin
C. Beta 2 microglobulin
D. Cystatin (Correct Answer)

Explanation: **Explanation:** **Cystatin C** is considered a highly reliable marker for estimating GFR in children because its production rate is constant across all ages. Unlike creatinine, Cystatin C is a low-molecular-weight protein produced by all nucleated cells at a steady rate. It is freely filtered by the glomerulus and is not affected by muscle mass, gender, or inflammatory states, making it particularly useful in pediatric patients with varying body compositions or muscle-wasting conditions. **Analysis of Incorrect Options:** * **Serum Creatinine:** While commonly used, it is unreliable in children because levels depend heavily on **muscle mass**, which changes significantly with age and growth. It also undergoes tubular secretion, leading to an overestimation of GFR. * **Inulin:** This is the **Gold Standard** for measuring GFR because it is neither secreted nor reabsorbed. However, it is not a "marker" used in routine clinical practice because it requires continuous intravenous infusion and timed urine collection, making it impractical. * **Beta 2 Microglobulin:** While it filters through the glomerulus, its levels are significantly affected by malignancies and inflammatory conditions, making it less specific for GFR estimation than Cystatin C. **High-Yield Clinical Pearls for NEET-PG:** * **Schwartz Formula:** The most common clinical method to estimate GFR in children: $eGFR = (k \times \text{Height in cm}) / \text{Serum Creatinine}$. * **Best Endogenous Marker:** Cystatin C. * **Best Exogenous/Gold Standard:** Inulin clearance. * **Radioisotope of choice:** Tc-99m DTPA is commonly used for GFR estimation in clinical scans.

Practice by Chapter

Urinary Tract Infections

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Vesicoureteral Reflux

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Glomerulonephritis

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Nephrotic Syndrome

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Acute Kidney Injury

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Chronic Kidney Disease

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Renal Tubular Disorders

Practice Questions

Congenital Anomalies of the Kidney

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Hydronephrosis

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Hypertension in Children

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Hemolytic Uremic Syndrome

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Renal Replacement Therapy in Children

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Nephrology — MCQs

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