How can urinary retention lead to obstructive uropathy?
Normal patients should have the ability to void at least 80% of their bladder volume, with a postvoid residual of less than 50 mL.
In the setting of bladder outlet obstruction (BOO) or poor bladder contractility, the efficiency of bladder emptying may decrease and residual urine may increase.
An elevated postvoid residual is associated with increased risk of infection and can lead to a distended and a hypotonic bladder.
If high (typically >40 cm H 2 O) intravesical pressures develop due to excessive bladder volumes and/or poor bladder compliance, urine can reflux up the ureters and cause hydroureteronephrosis and obstructive nephropathy.