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Canadian Urological Association/Pediatric Urologists of Canada guideline on the investigation and management of antenatally detected hydronephrosis.

Prior to the advent of maternal ultrasonography in the 1980s, children with significant congenital hydronephrosis requiring surgery presented symptomatically with abdominal pain, urinary infection, hypertension, hematuria, or failure to thrive. Antenatal hydronephrosis (AHN) became one of the most commonly detected ultrasound (US) findings, affecting 1‒5% of pregnancies.1 The majority of AHN in the third trimester is discovered due to US for maternal indications. The benefits of this early detection of urinary tract dilation include a reduction in the renal damage due to obstruction and infection.2,3 On the other hand, many of these antenatally detected cases spontaneously resolve with observation and consequently can be submitted to unnecessary investigations and continued medical followup.4 The challenge to this day remains to predict which of these prenatally detected infants will require corrective surgery, prior to the development of symptoms or potentially irreversible renal damage, thus permitting a more tailored screening.