Editing CUA: Antenatal hydronephrosis (2017) (section)

==== Voiding cysto-urethrography (VCUG) [or nuclear cystography] ====
* '''Goal is to distinguish an obstructive cause of AHN from VUR''', not due to concern over UTI
** ≈'''16% of infants with ANH are found to have VUR, with 25% of such cases occurring in the non-dilated, contralateral renal unit.'''
* '''Nuclear cystography is more sensitive than VCUG for VUR with less radiation exposure'''

===== Indications =====
* '''<span style="color:#ff0000">The AUA guidelines on VUR similarly recommends that VCUG in the neonate with:'''
*# '''<span style="color:#ff0000">High-grade (SFU grade ≥3) hydronephrosis'''
*# '''<span style="color:#ff0000">Hydroureter'''
*# '''<span style="color:#ff0000">An abnormal bladder on ultrasound</span>''' (late-term prenatal or postnatal)
*# '''<span style="color:#ff0000">Develops a UTI on observation'''
* '''VCUG is not necessary in the evaluation of isolated LGHN (SFU 1‒2) with normal renal parenchyma and symmetric renal size'''
* '''<span style="color:#ff0000">Any infant with suspected bladder outlet obstruction (e.g., PUV) should have an urgent VCUG.''' 
**'''<span style="color:#ff0000">Findings associated with bladder outlet obstruction (7):'''
**# '''<span style="color:#ff0000">Dilated posterior urethra'''
**# '''<span style="color:#ff0000">Distended bladder'''
**# '''<span style="color:#ff0000">Thick or trabeculated bladder'''
**# '''<span style="color:#ff0000">History of oligohydramnios'''
**# '''<span style="color:#ff0000">Severe bilateral hydronephrosis'''
**# '''<span style="color:#ff0000">Increased renal cortical echogenicity''' (hyper-echogenicity)
**# '''<span style="color:#ff0000">Renal cortical cysts'''

===== Technique =====

*'''Steps by step'''
*# '''A scout view''' for assessment of spine anomalies, presence of significant constipation or urinary stones
*# '''Catheter is inserted'''
*#* '''A balloon catheter should not be used''', as the balloon can obscure the filling defect characteristic of a ureterocele.
*#* The amount of urine removed should be recorded and the urine sent for analysis and culture as indicated.
*#* The bladder should be gravity filled until the first void occurs, with recording of the bladder capacity.
*# '''Voiding views''' of the urethra with post-void views of the bladder.
*# '''Delayed imaging''' after the post-void image may be required if there is VUR into a dilated renal pelvis or ureter so as to assess for concomitant UPJO and UVJO
** '''A cyclical study with at least two fill and void cycles will increase the detection of VUR.'''
**#