Differential diagnosis of abdominal mass in neonate – renal causes

• Autosomal recessive polycystic kidney disease
• Mesoblastic nephroma
• Multicystic dysplastic kidney
• Renal vein thrombosis
• Ureteropelvic junction obstruction

Approach to differential diagnosis of renal causes of abdominal masses in neonates which accounts for ~ 50% of abdominal masses in neonates:

• The most common renal mass in the neonate is hydronephrosis which on US appears as multiple cysts of the same size which communicate
• The second most common renal mass in the neonate is multicystic dysplastic kidney which on US appears as multiple cysts of varying sizes which do not communicate
• The most common solid renal mass in the neonate is mesoblastic nephroma which is unilateral
• Autosomal recessive polycystic kidney disease on US appears as bilateral enlarged echogenic kidneys
• Renal vein thrombosis is usually a unilateral renal mass without renal vein flow on doppler US