How does multicystic kidney dysplasia differ from polycystic kidney disease?

At birth,not heredit: The former is a congenital but not hereditary disease involving usually one kidney forming a mass of cysts without functioning kidney tissue. Found with prenatal ultrasound. Kidney shrinks and the other kidney assumes its work. The most common form of PKD which is hereditary results in increasing cyst number and size over many years. Other organs have cysts and kidneys fail over many years.