Congenital Anomalies of the Kidney — MCQs

10 questions

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

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

What should be done next in an 18-year-old girl with primary amenorrhea, a karyotype of 45,X0, and an infantile uterus on ultrasound?

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?

Baby born at 30 weeks to an 18-year-old primigravida weighing 2 kg, who died after 48 hours, with Apgar scores of 5 and 8 at 1 and 5 minutes, respectively. On autopsy, bilateral enlarged kidneys with multiple radially arranged cysts were found. Which of the following findings is expected to be associated with this?

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

An infant with severe dehydration secondary to diarrhea suddenly presents with flank mass and blood in urine. The most probable diagnosis is?

Unilateral renal agenesis is associated with:

Q10

A neonate presenting with ascites is diagnosed with urinary ascites. What is the most common cause?

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

Question 1: 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 2: 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 3: What should be done next in an 18-year-old girl with primary amenorrhea, a karyotype of 45,X0, and an infantile uterus on ultrasound?

A. Vaginoplasty
B. Clitoroplasty
C. B/L gonadectomy
D. Hormone therapy to induce puberty (Correct Answer)

Explanation: ***Hormone therapy to induce puberty*** - The patient has **Turner syndrome (45,X0)**, which causes **gonadal dysgenesis** and thus a lack of **estrogen** and **progesterone** production, leading to primary amenorrhea and an infantile uterus. - **Hormone replacement therapy** with estrogen and progestin is essential to induce secondary sexual characteristics, promote uterine development, and achieve cyclical bleeding, which mimics puberty. *Vaginoplasty* - **Vaginoplasty** is a surgical procedure to create or lengthen the vagina, typically considered for conditions like **Mayer-Rokitansky-Küster-Hauser syndrome** where the vagina is absent or underdeveloped but ovaries are functional. - This patient has an infantile uterus, not vaginal agenesis as the primary issue, and the underlying problem is **hormonal deficiency**, not a structural one that would be addressed by vaginoplasty first. *Clitoroplasty* - **Clitoroplasty** is a surgical procedure to reduce the size of an enlarged clitoris, usually performed in cases of **ambiguous genitalia** or **congenital adrenal hyperplasia**. - There is no indication of clitoromegaly or ambiguous genitalia in this patient's presentation; her primary issue is the absence of puberty. *B/L gonadectomy* - **Bilateral gonadectomy** is indicated in patients with **Y chromosome material** and **gonadal dysgenesis** (e.g., Swyer syndrome or mixed gonadal dysgenesis) due to the high risk of **gonadoblastoma**. - While this patient has **gonadal dysgenesis** associated with **Turner syndrome**, she lacks a **Y chromosome**, meaning the risk of malignant transformation in her streak gonads is low, and therefore prophylactic gonadectomy is not typically performed.

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: Baby born at 30 weeks to an 18-year-old primigravida weighing 2 kg, who died after 48 hours, with Apgar scores of 5 and 8 at 1 and 5 minutes, respectively. On autopsy, bilateral enlarged kidneys with multiple radially arranged cysts were found. Which of the following findings is expected to be associated with this?

A. Congenital absence of ureter
B. Hepatic cyst and fibrosis (Correct Answer)
C. Congenital brain malformation
D. Congenital anorectal malformation
E. Congenital cardiac malformation

Explanation: ***Hepatic cyst and fibrosis*** - The description of **bilateral enlarged kidneys with multiple radially arranged cysts** in a preterm infant is classic for **Autosomal Recessive Polycystic Kidney Disease (ARPKD)**. - **Hepatic cysts** and **congenital hepatic fibrosis** are highly characteristic extrarenal manifestations of ARPKD due to shared developmental origins of the kidney and liver bile ducts. - This is the most common and clinically significant association with ARPKD. *Congenital absence of ureter* - This condition is known as **renal agenesis** or **ureteral atresia**, which typically presents with absent or severely undeveloped kidneys, not enlarged cystic kidneys. - While it can lead to kidney failure, the anatomical findings described (enlarged, radially cystic kidneys) are inconsistent with a primary ureteral agenesis. *Congenital brain malformation* - While some genetic syndromes with renal involvement can have brain anomalies, **ARPKD** is not primarily associated with typical congenital brain malformations. - The primary systemic complications of ARPKD involve the **liver** and sometimes the **lungs** (due to oligohydramnios-induced pulmonary hypoplasia). *Congenital anorectal malformation* - This malformation is typically associated with various genetic syndromes or other developmental defects, but it is **not a characteristic finding** in ARPKD. - ARPKD's primary pathology is confined to the kidneys and liver. *Congenital cardiac malformation* - While cardiac anomalies are common congenital defects, they are **not specifically associated with ARPKD**. - ARPKD is primarily a disease of the kidneys and liver, with the main extrarenal manifestation being hepatic fibrosis and cysts.

Question 7: 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 8: An infant with severe dehydration secondary to diarrhea suddenly presents with flank mass and blood in urine. The most probable diagnosis is?

A. Renal vein thrombosis (Correct Answer)
B. Acute glomerulonephritis
C. Lipoid nephrosis
D. Pyelonephritis

Explanation: ***Renal vein thrombosis*** - **Dehydration**, especially in infants, is a significant risk factor for **renal vein thrombosis** due to increased blood viscosity and hypercoagulability - The sudden appearance of a **flank mass** (due to renal enlargement and hemorrhage) and **hematuria** (blood in urine) are classic signs of this condition - Classic triad includes flank mass, hematuria, and thrombocytopenia in the setting of predisposing factors like severe dehydration *Acute glomerulonephritis* - While it can cause hematuria, it typically presents with **edema**, **hypertension**, and **oliguria**, which are not mentioned in this scenario - A flank mass is not a typical presentation of acute glomerulonephritis - Usually follows streptococcal infection with latent period *Lipoid nephrosis* - This is a type of **nephrotic syndrome** characterized by **massive proteinuria**, edema, and normal renal function - Does not typically present with a flank mass or gross hematuria - More common presentation is generalized edema and frothy urine *Pyelonephritis* - This is a **bacterial infection of the kidney** that causes fever, flank pain, and dysuria - While it can cause microscopic hematuria, a sudden flank mass and gross hematuria are not typical presentations - Especially unlikely in the context of severe dehydration without signs of infection

Question 9: Unilateral renal agenesis is associated with:

A. Hiatus Hernia
B. Single umbilical artery (Correct Answer)
C. Hypogonadism
D. Polycystic disease of pancreas

Explanation: ***Single umbilical artery*** - **Unilateral renal agenesis** is often associated with other congenital anomalies, including the presence of a **single umbilical artery** (2-vessel cord instead of the normal 3-vessel cord). - Both conditions can be part of **VACTERL association** (Vertebral, Anorectal, Cardiac, Tracheo-Esophageal, Renal, and Limb anomalies). - The **single umbilical artery** is a marker for increased risk of **urogenital and cardiovascular malformations**, which fits with renal agenesis. - Found in approximately **7-10% of cases with renal anomalies**. *Hiatus Hernia* - A **hiatal hernia** is a condition where part of the stomach pushes up through the diaphragm. - Not a recognized or common association with **unilateral renal agenesis**. - While it can be congenital, it arises from different developmental pathways than renal agenesis. *Hypogonadism* - **Hypogonadism** involves reduced function of the gonads and is not directly associated with **renal agenesis**. - Renal agenesis results from problems with the **metanephric blastema** and **ureteric bud** development, not the reproductive axis. *Polycystic disease of pancreas* - **Polycystic disease of the pancreas** is an extremely rare condition and does not have a well-established association with **unilateral renal agenesis**. - This should not be confused with **polycystic kidney disease**, which is a completely different entity.

Question 10: A neonate presenting with ascites is diagnosed with urinary ascites. What is the most common cause?

A. Bilateral PUJ obstruction
B. Infant polycystic kidney disease
C. Posterior urethral valve (Correct Answer)
D. Meatal stenosis

Explanation: ***Posterior urethral valve*** - **Posterior urethral valve (PUV)** is the most common cause of **urinary tract obstruction** in male neonates, leading to severe bladder outflow obstruction, often resulting in **urinary ascites** due to urinary extravasation. - The obstruction causes high pressure in the bladder and urinary tract, which can lead to rupture of the urinary system (e.g., bladder, renal pelvis, ureters) and leakage of urine into the peritoneal cavity. *Bilateral PUJ obstruction* - While **pelvic-ureteric junction (PUJ) obstruction** can cause hydronephrosis, bilateral obstruction leading to urinary ascites is less common than PUV. - PUJ obstruction primarily affects the flow of urine from the kidney to the ureter, and although severe, is less likely to cause widespread urinary extravasation into the peritoneum compared to distal urethral obstruction. *Infant polycystic kidney disease* - **Infant polycystic kidney disease (ARPKD)** is characterized by enlarged kidneys with numerous cysts, leading to renal dysfunction and often pulmonary hypoplasia. - While ARPKD can cause significant renal pathology, it does not typically lead to urinary ascites through obstructive mechanisms; ascites, if present, is usually due to liver fibrosis or heart failure, not urinary obstruction. *Meatal stenosis* - **Meatal stenosis** is a narrowing of the urethral opening, which can cause urinary obstruction but is usually a less severe and more distal obstruction compared to PUV. - It might cause symptoms like a thin stream or dysuria but is rarely severe enough in neonates to cause back pressure leading to urinary extravasation and ascites.

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