Daily Practice - Clinical Quiz #2

A 25-year-old primigravida at 20 weeks of gestation presents for a routine prenatal ultrasound. Her pregnancy has been uneventful, and she has no personal or family medical issues.

📋 Ultrasound Findings

The ultrasound shows multiple cysts with an absence of renal parenchyma at the site of the fetus’s right kidney, while the left kidney and amniotic fluid volume appear normal.

👉 Question: Fetal Anomaly

Which of the following best explains this finding?

A. Autosomal dominant hereditary condition

B. Congenital bifurcation of the ureteric bud

C. Failure of the metanephric mesenchyme to differentiate

D. Failure of the ureteric bud to develop

E. Autosomal recessive hereditary condition

Show Answer

✅ Correct Answer:

C. Failure of the metanephric mesenchyme to differentiate.

📚 Expert Detailed Answer and Rationale:

The ultrasound findings are classic for multicystic dysplastic kidney (MCDK), a non-hereditary congenital renal malformation. It is characterized by multiple non-communicating cysts and an absence of normal renal parenchyma.

C. ✅ Failure of the metanephric mesenchyme to differentiate – MCDK results from an abnormal interaction between the ureteric bud and the metanephric blastema during embryogenesis. This disrupts normal development and leads to the failure of the metanephric mesenchyme to form functional nephrons, resulting in a non-functional, cystic kidney.

A. & E. Autosomal dominant/recessive condition ❌ – These refer to Polycystic Kidney Disease (PKD). Autosomal Recessive PKD (ARPKD) typically presents with bilaterally enlarged, echogenic kidneys and oligohydramnios. Autosomal Dominant PKD (ADPKD) usually manifests later in adulthood. MCDK is a sporadic, non-hereditary condition.

B. Congenital bifurcation of the ureteric bud ❌ – This embryological anomaly leads to a duplicated collecting system (e.g., duplex kidney), not a dysplastic, non-functional kidney.

D. Failure of the ureteric bud to develop ❌ – Complete failure of the ureteric bud to develop results in renal agenesis, which is the complete absence of a kidney, rather than a multicystic kidney.

🧠 High-Yield Points:

• 💡 Pathogenesis: Maldevelopment of the ureteric bud–metanephric blastema interaction.
• 💡 Laterality: Usually unilateral. The contralateral kidney undergoes compensatory hypertrophy.
• 💡 Amniotic Fluid: Normal in unilateral cases because the contralateral kidney produces sufficient urine.
• 💡 Prognosis: Excellent with unilateral involvement. Typically requires only observation and follow-up.
• 💡 Associated Anomalies: Important to screen for contralateral anomalies like vesicoureteral reflux (VUR) or ureteropelvic junction (UPJ) obstruction.

📖 Read More on: Congenital Renal Anomalies

Hide Answer

💡 Clinical Challenge / Follow-Up:

Now, consider a different fetus where the ultrasound at 20 weeks shows bilaterally enlarged, echogenic (bright) kidneys and severe oligohydramnios (markedly reduced amniotic fluid).

Your Challenge:

1. What is the most likely diagnosis with these findings?
2. What is the inheritance pattern for this condition?

Show Answer

✅ Answer:

1. The diagnosis is now Autosomal Recessive Polycystic Kidney Disease (ARPKD). The bilateral, enlarged, echogenic kidneys and oligohydramnios are classic findings.
2. The inheritance pattern is autosomal recessive. This carries a 25% recurrence risk in future pregnancies.

Hide Answer

← Previous Post Next Post →

📱 Join our WhatsApp Channel 📱 Join our Telegram Channel