Ureteral obstruction :

Ureteral obstruction produces loss of renal function when there is only one renal unit and the ureter is obstructed or when obstruction is bilateral. Ureteral obstruction often is best identified by either intravenous pyelography (IVP) or retrograde pyelography, which allows one to identify the specific site of obstruction. Calculous disease is the most common cause of ureteral obstruction. Ureteral obstruction is not a surgical emergency that requires open surgical intervention, but it may be relieved by retrograde or antegrade passage of a double-J stent to bypass the obstruction, permitting orderly nonemergent identification of the cause of obstruction and selection of a treatment process.