Which of the following is the most common renal cystic disease in infants is?
The multicystic dysplastic kidney is the commonest form of congenital cystic renal dysplasia and is due to complete ureteric obstruction in fetal life. The condition is usually unilateral; the bilateral disease is lethal.
Multicystic dysplastic kidney

The multicystic dysplastic kidney is a congenital condition in which the entire kidney is dysplastic with a preponderance of cysts.
The kidney is replaced by multiple cysts of varying sizes that do not communicate and no identifiable parenchyma is present.
Contralateral vesicouretral reflux is present in 15% cases.
Contralateral hydronephrosis is present in 5 - 10% cases.
It is the most common cause of an abdominal mass in a neonate. - Nelson
Polycystic kidney
Simple renal cyst
Unilateral renal dysplasia
Calyceal cyst