Ureteropelvic junction obstruction (UPJO) is an obstruction of the urinary tract at the outlet to the kidney. It is most commonly seen in children congenitally (they are born with it), however it may be acquired or only first recognized in adulthood. In many patients, there is an aberrant blood vessel crossing at the junction which is at the root of the problem. In others, the junction between the ureter and the renal pelvis is intrinsically too narrow. Usually UPJO is a unilateral problem, however, both kidneys may have UPJO.
Some patients are entirely without symptoms. Others develop back pain, flank pain, or abdominal pain. The pain may be exacerbated when challenged with large quantities of fluid. The obstruction may cause stones to form in the kidney, or for the kidney to loose function over time.
The diagnosis is made by various imaging studies. A CAT scan or ultrasound, and occasionally intravenous pyelography identifies the problem. The problem is quantified by a nuclear medicine renal scan (MAG III with Lasix) – this test describes how much function each of the kidneys contribute to overall kidney function, and shows how much time it takes for urine to transit out of the renal pelvis.
Indications for treatment may include the following:
- Proportionate kidney function is reduced
- Transit time of urine out of the kidney is prolonged
- Pain is relieved by temporary stenting of the ureter