**4.5 Ureterovesical junction and upper tract dilation**

In general, ureterovesical junction obstruction caused by bladder remodelling in chronic urinary retention is a contributing mechanism for renal failure in BPH (Rule, Lieber et al. 2005). Upper tract dilation occurs as a consequence of a continuum bladder outlet obstruction and remodelling (detrusor hypertrophy and scarring) leading to anatomical ureterovesical junction obstruction (Jones, Ellis et al. 1991). Upper urinary tract dilation or hydronephrosis is consistent with chronic renal failure from obstructive uropathy. In men with BPH and increased serum creatinine, hydronephrosis is common (one third), and is found in 90% of men with BPH who are hospitalized for uremic symptoms (Sacks, Aparicio et al. 1989). In ultrasound evaluation it is common among patients with bilateral hydroureteronephrosis to observe compressing and thinning of renal cortex, with obvious impact in renal function. A history of enuresis, painless chronic retention, and palpable bladder should suggest a diagnosis of high pressure chronic retention with its attendant risk of hydroureteronephrosis (Sacks, Aparicio et al. 1989).
