Editing Ureteropelvic Junction Obstruction (section)

==Etiology==

=== Classification ===
*'''<span style="color:#ff0000">Congenital/primary vs. acquired/secondary</span> or intrinsic vs. extrinsic'''
**'''<span style="color:#ff0000">Most cases are congenital</span>''', but may only become clinically apparent much later in life
***'''UPJO in neonates is most frequently found as a result of maternal-fetal ultrasound'''
****Many newborns diagnosed with hydronephrosis on ultrasound are subsequently found to have UPJO

==== Congenital ====

* '''<span style="color:#0000ff">SHAVA (5)</span>'''
#'''<span style="color:#ff0000">True ureteral </span><span style="color:#0000ff">S</span><span style="color:#ff0000">tricture</span>'''
#'''<span style="color:#0000ff">H</span><span style="color:#ff0000">igh insertion</span> found more frequently in the presence of renal ectopia or fusion anomalies'''
#'''<span style="color:#0000ff">A</span><span style="color:#ff0000">berrant vessels</span> (controversy persists). Regardless, the presence of crossing vessels has a detrimental effect on the success rates of endopyelotomy'''
#'''<span style="color:#ff0000">Kinks or </span><span style="color:#0000ff">V</span><span style="color:#ff0000">alves</span>''' produced by infoldings of the ureteral mucosa and muscularis
#'''<span style="color:#0000ff">A</span><span style="color:#ff0000">peristaltic segment</span>'''

* '''UPJO in newborns and infants is most often caused by an ''intrinsic'' narrowing'''
** '''The ureteral segment has an interruption in the development of the circular musculature of the UPJ''' and an alteration in collagen fibers in and around the muscular cells. This results in a narrowed segment of the UPJ with '''functional discontinuity of the muscular contractions and ultimately to insufficient emptying of the renal pelvis'''
* '''UPJO in childhood and adolescence is often extrinsic narrowing caused by an accessory vessel to the lower pole of the kidney''' giving rise to flank pain, nausea, and vomiting.
**'''Extrinsic obstruction seen in association with a lower pole vessel''' (aberrant, accessory, or early branching) '''that passes anteriorly to the UPJ or proximal ureter and contributes to mechanical obstruction'''
* '''Congenital renal malformations commonly associated with UPJO (8):'''
*# '''Contralateral UPJO (most common anomaly)'''
*# '''Renal dysplasia'''
*# '''Multicystic dysplastic kidneys'''
*# '''Renal agenesis'''
*# '''Horseshoe kidneys'''
*# '''VUR'''
*# '''Ectopic kidney'''
*# '''Duplex kidney'''

==== Acquired ====

* '''<span style="color:#0000ff">CRIIBS (5)</span>'''
#'''<span style="color:#0000ff">C</span><span style="color:#ff0000">ancer</span>'''
#'''<span style="color:#ff0000">Vesicoureteral </span><span style="color:#0000ff">R</span><span style="color:#ff0000">eflux</span>'''<span style="color:#0000ff">;</span> can lead to upper tract dilation with subsequent elongation, tortuosity, and kinking or narrowing of the UPJ
#'''<span style="color:#ff0000">Post-</span><span style="color:#0000ff">I</span><span style="color:#ff0000">nflammatory or postoperative scarring or <span style="color:#0000ff">I</span><span style="color:#ff0000">schemia</span>'''
#'''<span style="color:#0000ff">B</span><span style="color:#ff0000">enign lesion (e.g. fibroepithelial polyps)</span>'''
#'''<span style="color:#0000ff">S</span><span style="color:#ff0000">tones</span>'''

=== Intermittent UPJO ===

* '''Dietl's crisis is intermittent abdominal pain associated with nausea and vomiting following an episode of high fluid intake.'''
*Although a renal scan with Lasix is used in an attempt to prompt the crisis, it may on occasion be falsely negative.
*In these patients, it is best to repeat a renal ultrasound at the time of pain and compare this to a baseline renal ultrasound taken when the patient was asymptomatic. If increased hydronephrosis at the time of symptoms is present, it is diagnostic and the pyeloplasty will be curative.