An obstruction anywhere along the urinary tract—from the kidneys, where urine is produced, to the urethra, through which urine leaves the body—can increase pressure inside the urinary tract and slow the flow of urine. An obstruction may occur suddenly or develop slowly over days, weeks, or even months. An obstruction may completely or only partially block part of the urinary tract.

Urinary tract obstruction can make the kidneys distend (dilate). Distention damages the kidneys. Although the kidneys can usually recover if the obstruction is relieved quickly, permanent damage may occur. Severe damage can result in loss of kidney function (kidney failure). Obstruction can also lead to stone formation and urinary tract infections. An infection may develop because bacteria that enter the urinary tract are not flushed out when the flow of urine is obstructed.

Last full review/revision August 2007 by Glenn M. Preminger, MD