DefinitionChronic unilateral obstructive uropathy is a condition in which there is long-term blockage of one of the tubes (ureters) that drains urine from the kidneys.See also:Acute unilateral obstructive uropathyAcute bilateral obstructive uropathyChronic bilateral obstructive uropathyObstructive uropathyAlternative NamesUreteral obstruction - chronic; Obstructive uropathy - unilateral - chronicCauses, incidence, and risk factorsUnilateral obstructive uropathy usually occurs when ureteral or kidney stones block the flow of urine. Urine backs up and causes kidney swelling (hydronephrosis).Other causes include:Narrowing of the ureter that is present at birth (congenital), most commonly right below the kidney, a condition called ureteropelvic junction obstructionInjury to the ureter from pri