Ureteropelvic junction (UPJ) obstruction describes a restriction of urine flow from the kidney into the ureter (the tube that drains urine into the bladder) that results in dilation of the renal pelvis.
UPJ obstruction is often present at birth, but occasionally does not present until adulthood. UPJ obstruction may cause intermittent flank pain or be totally asymptomatic.
Causes and Risk Factors
The cause of a UPJ obstruction is usually congenital (you are born with it) due to a narrowing of the ureter or due to extrinsic compression from an abnormal blood vessel. Other less common causes that occur later in life include inflammation, kidney stones, or rarely tumors.
When to Speak with a Urologist about UPJ Obstruction
You should talk to a Urologist about UPJ obstruction if you have intermittent flank pain and imaging shows a dilated kidney without evidence of kidney stones.
What to Expect when Seeking Treatment
In addition to a history and physical examination, initial assessment includes urine testing to check for blood and infection as well as blood work to measure kidney function. A complete imaging evaluation with CT or MR urogram is necessary to delineate the anatomy and identify potential causes. Further imaging with a nuclear medicine renal scan is necessary to confirm the presence of obstruction as well as to determine the degree of obstruction and how well each of your kidneys are functioning. Urine cytology may be sent if there is a concern for a tumor causing the obstruction.
Observation is a reasonable management strategy if you are not having symptoms. But surgical intervention would be indicated in the setting of pain, renal functional impairment, recurrent stones, or recurrent urinary tract infections.
Removal of the entire kidney would be recommended in the setting of extremely poor function of the affected kidney. Assuming sufficient function however, there are several possible surgical interventions to treat UPJ obstruction.
Ureteral stent placement placed through a small camera in the bladder can help drain urine from the kidney with a temporary internal tube from the kidney to the bladder.
Endopyelotomy involves passing a device up the ureter to cut open or balloon dilate the narrowed area without external incisions. Endopyelotomy success rates are around 70% overall though only around 40% in the setting of a crossing blood vessel.
The most definitive surgical repair is performed through several small incisions and called robot-assisted dismembered pyeloplasty that involves detaching the ureter from the renal pelvis, rerouting it around a crossing blood vessel, and creating a new widened connection. Pyeloplasty success rates are around 95%.