Congenital Anomalies of the Kidney — MCQs

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Congenital Anomalies of the Kidney — MCQs

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A renal mass seen on prenatal check-up is most probably:

All of the following are true about childhood polycystic kidney disease, except –

Which of the following is NOT a recognized cause of renal agenesis?

A 22-year-old primigravida visits ANC OPD with 20 weeks POG. On examination uterine height reveals a 16-week size. USG shows reduced liquor. What will be the diagnosis?

A 3 week old child presents with an abdominal mass. What is the most common congenital renal cystic abnormality causing this presentation?

Which of the following is the most common renal cystic disease in infants?

Autosomal recessive Polycystic kidneys - all are true except -

The Finnish type of congenital nephrotic syndrome occurs due to gene mutation affecting the following protein –

Alport syndrome is noted because of a defect in what type of collagen?

Q10

Which of the following can be a cause of Oligohydramnios?

Congenital Anomalies of the Kidney Indian Medical PG Practice Questions and MCQs

Question 1: A renal mass seen on prenatal check-up is most probably:

A. Neuroblastoma
B. Wilms' tumor
C. Mesoblastic nephroma (Correct Answer)
D. Renal sarcoma

Explanation: ***Mesoblastic nephroma*** - This is the most common **congenital renal tumor** and is often detected antenatally or in the **neonatal period**. - It is typically a **benign tumor** that presents as a solid, well-circumscribed renal mass. *Neuroblastoma* - While it can present as an abdominal mass in infants, **neuroblastoma** usually arises from adrenal glands or sympathetic ganglia, not primarily the kidney itself. - It often shows features of calcification and can be associated with elevated **catecholamines**. *Wilms' tumor* - **Wilms' tumor** is the most common childhood renal malignancy, but it is typically diagnosed in older infants and young children (peak incidence at 2-3 years), less commonly detected definitively on prenatal check-ups. - Prenatal detection of **Wilms' tumor** is rare, and it usually grows rapidly postnatally. *Renal sarcoma* - **Renal sarcoma** is an extremely rare primary renal tumor in children, making it a much less likely diagnosis than mesoblastic nephroma for a prenatal renal mass. - These tumors tend to be aggressive but are statistically much less common in the prenatal period.

Question 2: All of the following are true about childhood polycystic kidney disease, except –

A. Renal cyst present at birth
B. Hepatic fibrosis
C. Pulmonary hypoplasia
D. Autosomal dominant (Correct Answer)

Explanation: ***Autosomal dominant*** - Childhood polycystic kidney disease (CPKD) refers to **autosomal recessive polycystic kidney disease (ARPKD)**, which is inherited in an **autosomal recessive pattern**. - The autosomal dominant form, **autosomal dominant polycystic kidney disease (ADPKD)**, typically presents in adulthood, though it can rarely manifest in childhood. *Renal cyst present at birth* - In **ARPKD**, renal cysts are often present and detectable **at birth** or even prenatally, leading to significantly enlarged kidneys. - These cysts result from malformations of the **collecting ducts**, which are crucial for kidney function. *Hepatic fibrosis* - **Congenital hepatic fibrosis** is a common and serious extra-renal manifestation of **ARPKD**. - This hepatic involvement can lead to **portal hypertension** and associated complications. *Pulmonary hypoplasia* - Severe **oligohydramnios** due to poor fetal kidney function in **ARPKD** can result in **pulmonary hypoplasia**. - This underdeveloped lung tissue is a major cause of mortality in affected neonates.

Question 3: Which of the following is NOT a recognized cause of renal agenesis?

A. Failure of fusion of ureteric bud with metanephros
B. Defective development of nephric tissue
C. Failure of ascent of primitive cells (Correct Answer)
D. None of the above

Explanation: Failure of ascent of primitive cells - **Renal agenesis** involves the complete absence of a kidney(s), primarily due to early developmental failures. - While issues with cell migration are important in **kidney development**, the *failure of ascent of primitive cells* is not a direct or recognized primary cause of renal agenesis itself; rather, it relates more to aspects of kidney migration or positional anomalies, not complete absence of the organ. *Defective development of nephric tissue* - If the **nephric tissue** (metanephric mesenchyme) fails to develop properly, it cannot interact with the ureteric bud to form a kidney. - This lack of proper development is a direct cause of **renal agenesis**. *Failure of fusion of ureteric bud with metanephros* - The **ureteric bud** induces the differentiation of the metanephros into the various components of the kidney. - If this crucial **fusion and interaction** do not occur, the kidney will not form, leading to renal agenesis.

Question 4: A 22-year-old primigravida visits ANC OPD with 20 weeks POG. On examination uterine height reveals a 16-week size. USG shows reduced liquor. What will be the diagnosis?

A. Bilateral renal agenesis (Correct Answer)
B. Bartter’s syndrome
C. Liddle syndrome
D. Fetal anemia

Explanation: ***Renal agenesis*** - **Bilateral renal agenesis** leads to **oligohydramnios** because the fetal kidneys are the primary producers of amniotic fluid after 16 weeks of gestation. - The reduced amniotic fluid (liquor) is consistent with the decreased uterine size (16-week size at 20 weeks POG) and is a hallmark of this condition, often resulting in **Potter sequence**. *Bartter’s syndrome* - This is a rare, inherited renal tubulopathy characterized by significant electrolyte disturbances (hypokalemia, metabolic alkalosis, hypercalciuria) due to impaired ion transport. - While it affects kidney function, it does not typically cause severe **oligohydramnios** or **renal agenesis** and would not explain the small uterine size in this scenario. *Liddle syndrome* - This is a rare genetic disorder characterized by early-onset hypertension, hypokalemia, and metabolic alkalosis, due to constitutive activation of the epithelial sodium channel (ENaC) in the collecting ducts. - It does not involve structural kidney abnormalities or significantly impact amniotic fluid volume during pregnancy to cause the described findings. *Fetal anemia* - Fetal anemia can lead to complications such as **hydrops fetalis**, which would typically cause **polyhydramnios** or a uterine size larger than expected due to fluid accumulation, not oligohydramnios or a smaller uterine size. - Reduced liquor and a small uterine size are not characteristic presentations of fetal anemia.

Question 5: A 3 week old child presents with an abdominal mass. What is the most common congenital renal cystic abnormality causing this presentation?

A. Distended bladder
B. Wilms tumor
C. Neuroblastoma
D. Multicystic dysplastic kidney (Correct Answer)

Explanation: ***Multicystic dysplastic kidney*** - This is the **most common cause of an abdominal mass detected in the neonatal period** due to its congenital nature. - It results from abnormal renal development in utero, leading to multiple non-communicating cysts and virtually no functioning renal tissue. *Distended bladder* - While a distended bladder can present as an abdominal mass in an infant, especially with **posterior urethral valves**, it is typically symptomatic with difficulty urinating or urinary tract infections. - It is not the most common overall cause of an abdominal mass at this age. *Wilms tumor* - **Wilms tumor**, originating from the kidney, is the **most common renal malignancy in children**, but it typically presents in toddlers (2-5 years of age) rather than at 3 weeks old. - Presentation at 3 weeks would be exceptionally rare, as it is an embryonal tumor that grows over time. *Neuroblastoma* - **Neuroblastoma** is a common extracranial solid tumor in infancy, often originating in the adrenal gland or sympathetic chain. - However, it is generally outranked by multicystic dysplastic kidney as the *most common* cause of an abdominal mass this early in life, and it can present with various systemic symptoms depending on tumor location and metastasis.

Question 6: Which of the following is the most common renal cystic disease in infants?

A. Polycystic kidney
B. Simple renal cyst
C. Unilateral renal dysplasia (Correct Answer)
D. Calyceal cyst

Explanation: ***Unilateral renal dysplasia*** - This condition is also known as **multicystic dysplastic kidney (MCDK)** and is the **most common renal cystic disease** diagnosed in infants, often prenatally. - It results from abnormal kidney development where the normal renal parenchyma is replaced by multiple **non-communicating cysts** and undifferentiated tissue. *Polycystic kidney* - **Autosomal dominant polycystic kidney disease (ADPKD)** typically presents later in life, often in adulthood, and is rarely symptomatic in infants. - **Autosomal recessive polycystic kidney disease (ARPKD)** can present in infants but is less common than MCDK and usually involves bilateral, uniformly enlarged kidneys with numerous small cysts. *Simple renal cyst* - **Simple renal cysts** are rare in infants and usually benign, often idiopathic, and are generally single and small. - They are much less common than MCDK as a cause of significant neonatal renal cystic disease. *Calyceal cyst* - A **calyceal cyst** is a rare, usually solitary, simple cyst that arises from a calyx and is typically an incidental finding. - It does not represent a widespread renal cystic disease and is much less common than **multicystic dysplastic kidney** in infants.

Question 7: Autosomal recessive Polycystic kidneys - all are true except -

A. Defective gene is PKHD1
B. Both kidneys show innumerable cysts
C. USG shows salt and pepper appearance (Correct Answer)
D. Seen in adults

Explanation: ***USG shows salt and pepper appearance*** - The **"salt and pepper" appearance** on imaging is characteristic of **autosomal dominant polycystic kidney disease (ADPKD)** due to multiple renal cysts of varying sizes and associated vascular calcifications, not autosomal recessive polycystic kidney disease (ARPKD). - ARPKD typically presents with **enlarged, hyperechoic kidneys** with loss of corticomedullary differentiation on ultrasound due to numerous small cysts. *Defective gene is PKHD1* - The dysfunctional gene in **autosomal recessive polycystic kidney disease (ARPKD)** is indeed **PKHD1**, located on chromosome 6. - This gene encodes for **fibrocystin/polyductin**, a protein primarily found in renal and biliary epithelial cells, whose mutation leads to cyst formation. *Both kidneys show innumerable cysts* - ARPKD is characterized by **bilateral involvement** with diffuse dilation of the collecting ducts, leading to innumerable small cysts in both kidneys. - These cysts cause significant **renal enlargement** and can lead to severe renal dysfunction. *Seen in adults* - **Autosomal recessive polycystic kidney disease (ARPKD)** typically manifests in **infancy or childhood**, often prenatally or neonatally. - While some milder forms may present later in childhood, it is **not generally seen in adults**; adult-onset polycystic kidney disease is usually autosomal dominant (ADPKD) [1].

Question 8: The Finnish type of congenital nephrotic syndrome occurs due to gene mutation affecting the following protein –

A. Nephrin (Correct Answer)
B. Alpha–actinin
C. Podocin
D. CD2-associated protein

Explanation: The Finnish type of congenital nephrotic syndrome occurs due to gene mutation affecting the following protein – ***Nephrin*** * The **Finnish type congenital nephrotic syndrome (CNF)** is specifically caused by mutations in the *NPHS1* gene, which codes for the protein **nephrin**. * **Nephrin** is a crucial component of the **slit diaphragm** in podocytes, essential for maintaining the glomerular filtration barrier and preventing protein loss [1]. *Alpha–actinin* * **Alpha-actinin** is a protein that anchors actin filaments to various membrane structures, including the podocyte cytoskeleton. * Mutations in genes encoding alpha-actinin (e.g., *ACTN4*) are associated with some forms of **focal segmental glomerulosclerosis (FSGS)**, but not specifically the Finnish type CNF [1]. *CD2 activated protein* * **CD2-associated protein (CD2AP)** is another important podocyte protein involved in anchoring the slit diaphragm to the actin cytoskeleton [1]. * Mutations in the *CD2AP* gene can cause some forms of **steroid-resistant nephrotic syndrome** and FSGS, but not the Finnish type CNF. *Podocin* * **Podocin** is a lipid raft-associated protein in podocytes, encoded by the *NPHS2* gene, crucial for stabilizing nephrin and forming the slit diaphragm [1]. * Mutations in *NPHS2* (leading to podocin dysfunction) are a common cause of **steroid-resistant nephrotic syndrome** in childhood, but not the Finnish type congenital nephrotic syndrome. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Kidney, pp. 923-924.

Question 9: Alport syndrome is noted because of a defect in what type of collagen?

A. Collagen type I
B. Collagen type III
C. Collagen type VII
D. Collagen type IV (Correct Answer)

Explanation: ***Collagen type IV*** - Alport syndrome is primarily caused by mutations in genes encoding the **alpha chains of type IV collagen**, specifically COL4A3, COL4A4, and COL4A5 genes [1]. - This **type IV collagen** is a major component of the **glomerular basement membrane (GBM)** in the kidneys, leading to its characteristic pathology [1]. *Collagen type I* - Defects in **collagen type I** are primarily associated with **osteogenesis imperfecta**, a condition characterized by brittle bones. - It is the most abundant collagen in the body, found in **skin, tendons, and bone**, but not the primary collagen affected in Alport syndrome. *Collagen type III* - Mutations in **collagen type III** are linked to **Ehlers-Danlos syndrome type IV**, also known as the vascular type, which causes fragile blood vessels and organs [2]. - This type of collagen is prevalent in **hollow organs** and **blood vessels**, and its defect does not explain Alport syndrome's renal, ocular, and auditory features. *Collagen type VII* - Defects in **collagen type VII** are responsible for **dystrophic epidermolysis bullosa**, a severe blistering skin disorder. - This collagen forms **anchoring fibrils** that connect the epidermis to the dermis, and its involvement is distinct from Alport syndrome. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Kidney, pp. 929-930. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Genetic Disorders, pp. 154-155.

Question 10: Which of the following can be a cause of Oligohydramnios?

A. Macrosomia
B. Multiparity
C. Renal agenesis (Correct Answer)
D. Twins

Explanation: ***Renal agenesis*** - **Fetal urine production** is the primary source of **amniotic fluid** in the latter half of pregnancy, so **bilateral renal agenesis** prevents this production. - Oligohydramnios due to renal agenesis is often associated with **Potter sequence**, characterized by facial anomalies, limb deformities, and pulmonary hypoplasia due to prolonged severe oligohydramnios. *Macrosomia* - **Macrosomia** (large baby) is not a cause of oligohydramnios; a larger fetus does not directly reduce amniotic fluid volume. - In fact, conditions like **gestational diabetes** which can cause macrosomia, are often associated with **polyhydramnios** (excess amniotic fluid) due to increased fetal urination. *Multiparity* - **Multiparity** (having had multiple previous pregnancies) is not directly associated with oligohydramnios. - While it can be a risk factor for certain pregnancy complications, it does not physiologically lead to reduced amniotic fluid. *Twins* - A multifetal pregnancy, such as **twins**, can sometimes be associated with complications like **twin-to-twin transfusion syndrome**, where one twin might develop oligohydramnios and the other polyhydramnios. - However, the presence of twins itself does not intrinsically cause oligohydramnios; it is a potential complication of specific twin types or their pathologies rather than a direct cause.

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