In IVP, Adder head appearance is seen in:
Ureterocele is a cystic dilatation of the distal ureter. Cobra head or Adder head appearance is diagnostic of ureterocele. Spider leg appearance in polycystic kidney. Ref: Bailey & Love, 25th Edition, Page 1290
Polycystic kidney
Horse shoe kidney
Ureterocele
Hydronephrosis