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Multicystic Dysplastic Kidney (MCDK) is a congenital, non-hereditary renal malformation characterized by a non-functioning kidney replaced by multiple non-communicating cysts of variable size with absence of normal renal parenchyma.
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It results from abnormal metanephric differentiation due to early urinary tract obstruction or ureteral atresia.
| Feature | Description |
|---|---|
| Pathogenesis | Abnormal interaction between ureteric bud and metanephric blastema → improper nephron formation |
| Cause | Thought to be due to early in utero obstruction of the ureter (e.g., ureteral atresia or stenosis) |
| Laterality | • Unilateral (most common) |
| • Bilateral (rare, lethal due to anuria and pulmonary hypoplasia) | |
| Syndromic associations | May occur in syndromes like Meckel–Gruber, Trisomy 13/18, Branchio-oto-renal syndrome |
Gross and microscopic features:
| Feature | Description |
|---|---|
| Macroscopic | Multiple non-communicating cysts with no identifiable renal pelvis or calyces |
| Microscopic | Immature ducts, cartilage, fibrous stroma; absence of functioning nephrons |
Prenatal Imaging Findings
| Finding | Description |
|---|---|
| Enlarged kidney | Multicystic appearance with variable-sized cysts |
| No identifiable renal pelvis/sinus | No central echo complex |
| Non-communicating cysts | Unlike hydronephrosis where cysts (calyces) communicate |
| Increased echogenicity | Of intervening stroma |
| Unilateral MCDK | Contralateral kidney often hypertrophied |
| Bilateral MCDK | Absent bladder, oligohydramnios, lethal |
Multicystic dysplastic kidney in a fetus at 20 weeks of gestational age. a Prenatal sagittal US image shows multiple anechoic non-communicating cysts of different sizes replacing the left kidney (arrows). b, c Coronal (b) and sagittal (c) fetal steady-state free precession (SSFP) MR images of the same fetus demonstrate multiple bright T2-weighted cysts replacing the left kidney (solid arrow). No normal renal parenchyma is observed. Note the enlargement of the anteroposterior dimension of the abdomen by the multicystic dysplastic kidney (open arrow)
Meyers, M.L., Treece, A.L., Brown, B.P. et al. Imaging of fetal cystic kidney disease: multicystic dysplastic kidney versus renal cystic dysplasia. Pediatr Radiol 50, 1921–1933 (2020). https://doi.org/10.1007/s00247-020-04755-5
Postnatal US findings:
| Parameter | Description |
|---|---|
| Affected kidney | Multicystic, non-functioning, often involutes over time |
| Contralateral kidney | May be normal or show compensatory hypertrophy or associated anomalies |
| Bladder | Present and normally visualized in unilateral cases |
| Condition | Key Differences |
|---|---|
| Hydronephrosis | Central pelvis visible; communicating cystic dilations |
| Multilocular cystic nephroma | Well-encapsulated, rare in neonates |
| Autosomal recessive polycystic kidney disease (ARPKD) | Bilateral; enlarged echogenic kidneys with tiny cysts |
| Cystic renal tumors | Wilm’s tumor, mesoblastic nephroma – often solid/cystic with vascularity |
Associated anomalies:
| System | Examples |
|---|---|
| Urinary tract | Vesicoureteral reflux (VUR), UPJ obstruction, contralateral renal agenesis |
| Reproductive tract (in females) | Müllerian anomalies |
| Genetic syndromes | Meckel–Gruber, branchio-oto-renal, Trisomy 13 |