DDX of abdominal mass in neonate – renal causes

Approach to DDX 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 venous flow on doppler US