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Urinary and Genital Disorders (Children)

Bilateral Calyceal



At 23 weeks the ultrasound showed "bilateral calyceal renal size of 5 - 6 mm". The amniotic fluid volume is normal and the second trimester prenatal screening results were normal/negative. What does "bilateral calyceal renal size of 5 - 6 mm" mean; and how serious is this? Does this mean my baby may have genetic abnormalities?


Having some degree of renal pelvic dilation is very common in unborn babies, and affects as many as 1 in 50 to 1 in 100. The degree of enlargement of dilation is mild, and probably not significant. However, following delivery, it is important to obtain a follow-up sonogram, ideally after 48 to 72 hours, to be certain that the kidneys are normal. Often this finding results from a mild kink in the upper ureter, but in some cases it results from severe urinary backflow from the bladder to the kidneys. In the majority of cases the swelling resolves and there is no need for exploration or surgery to repair an obstructed ureter.

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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