Currently most pregnant women undergo one or two ultrasound scans during their pregnancy. When the fetus is scanned, kidneys and the urinary tracts are analyzed, In addition the volume of liquor (amniotic fluid) also helps to suspect kidney problems. Of late stretching of the kidney (Hydronephrosis) is detected very frequently.

During scanning of 100-200 pregnant ladies, one fetus is found to have this abnormality. This usually happens because of a blockage in the urinary tract. Before proceeding further it is essential to describe the normal arrangement of the kidneys.

In human body there are two kidneys, one on either side of belly. From each kidney urine drains out via a tube called ‘ureter’ into a common urinary bladder. The bladder is located in the lower most part of belly. Once enough urine accumulates, it empties via a tube called 'urethra'. Whenever there is a block in any of these tubes, kidney stretching results.