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Urinary and Genital Disorders (Children)

Dilation of kidneys



I am running 35 weeks of pregnancy and my baby was diagnosied with dilation of both kidneys. Right kidney 18-10 mm and left 13-5.5 mm. In the last two months, dilation of the right kidney increased 4mm in both dimensions, whereas left kidney only 1.5 mm. Kidneys are functioning well and other parameters of pregnancy are absolutely normal. What precautions should we take during the delivery? What special care and medical tests must we conduct for the newborn?


Unfortunately, a sonogram does not provide a specific diagnosis in this situation, in most cases. There are several possibilities: urinary reflux, obstructive hydronephrosis (at the level of the kidney), and non-obstructive hydronephrosis. Another possibility is posterior urethral valves, which is a serious condition, but which usually results in more severe hydronephrosis. I assume that the amniotic fluid volume is normal. Assuming that is the case, there is no need to schedule an early delivery. Following delivery, a careful physical exam is performed to be certain that no other abnormalities are present. In addition, blood tests to check on kidney function often, though not always, are performed. Next, a sonogram of the kidneys and bladder is done. Also, a voiding cystourethrogram is necessary, in which a small plastic catheter is inserted into the bladder and contrast is instilled, allowing visualization of the lower urinary tract. Sometimes the test shows urinary reflux, which is quite treatable. Generally, follow-up sonograms are necessary, and occasionally a kidney scan (nuclear medicine test) is necessary. If you are having a son, having a circumcision generally reduces the risk of developing a urinary tract infection.

Good luck with the delivery.

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Response by:

Jack S Elder, MD, FACS, FAAP Jack S Elder, MD, FACS, FAAP
Clinical Professor of Urology
School of Medicine
Case Western Reserve University