Kidney Dysplasia

The kidneys are a pair of bean-shaped organs that filter fluid and wastes from the blood to form urine. Urine flows from the kidneys to the bladder through tubes called ureters. Kidney dysplasia is a condition that can occur in babies while they are growing in the womb. Other terms that health care providers and scientists use to describe this condition are renal dysplasia and multicystic dysplastic kidney (MCDK).

In kidney dysplasia, the internal structures of one or both of the baby's kidneys do not develop normally. Fluid-filled sacs called cysts replace normal kidney tissue. Kidney dysplasia usually happens in only one kidney. A baby with one working kidney can grow normally and has few, if any, health problems. Babies with kidney dysplasia affecting both kidneys generally do not survive pregnancy, and those who do survive need dialysis and kidney transplant very early in life.

Ureters are tubes that grow into the kidneys and branch out to form a network of tubules that will collect urine when the fetus is developing in the womb. In kidney dysplasia, the tubules fail to branch out completely. The urine that would normally flow through small tubules has nowhere to go, so it collects inside the affected kidney and forms cysts.

Source: MedicineNet.com
http://www.medicinenet.com/kidney_dysplasia/article.htm