Editing CUA: Antenatal hydronephrosis (2017) (section)

== Background ==

* '''<span style="color:#ff0000">Antenatal, also known as prental, hydronephrosis (ANH) is one of the most commonly detected ultrasound (US) findings, affecting 1‒5% of pregnancies'''
** The majority of ANH in the 3rd trimester is discovered due to US for maternal indications.
** The potential benefit of early detection of urinary tract dilation is to reduce renal damage due to treatment of obstruction and infection. Conversely, many of these antenatally detected cases spontaneously resolve with observation and consequently can be submitted to unnecessary investigations and continued medical follow-up.
* '''Hydronephrosis does not necessary imply urinary tract obstruction'''
** Hydronephrosis simply refers to dilation of the renal collecting system.
** Definition of congenital renal obstruction: impaired urinary drainage, which, if uncorrected, will limit the ultimate functional potential of the developing kidney.
*'''Post-natal resolution has been noted in 25‒50% of AHN cases.'''
** '''Of those persisting postnatally, the majority will be low-grade.'''
* '''An association between higher rates of post-natal pathology and severity of HN holds true for most HN diagnoses, with the exception of VUR. VUR rates among patients with mild, moderate, and severe prenatal HN are not significantly different.'''