Fact-sheet: Ureteropelvic junction obstruction
Updated on 09/02/2026 at 1:04 AM
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Definition
Ureteropelvic junction malformation with dilatation of the pyelocaliceal system.
Etiologies:
- Functional abnormalities: the most common. Aperistaltic segment of the ureteropelvic region (muscular thickening, atypical fiber orientation, etc.).
- Anatomic abnormalities: rarer.
Exceptional ureteral valve - Abnormally high insertion of the ureter on the renal pelvis
- Fibrous band or extrinsic adhesion
- Lower pole crossing vessels at the junction
- Other abnormalities.
Clinical features
More common in boys, detected at any age but classically in young adults.
Associated uropathies in 20% of cases.
Left Kidney > right.
Early detection on antenatal ultrasound.
Late detection: incidental or in the setting of urinary tract infection, abdominal mass, pain, hematuria...
Ultrasound
Suggests the diagnosis in the presence of pyelocaliceal dilatation without underlying ureteral dilatation.
Search for a polar vascular structure overlying the junction on color Doppler
CT
Reference examination. CT urography including an arterial phase (looking for a vascular etiology) and a delayed excretory phase.
Establishes the diagnosis: caliber discrepancy between the dilated renal pelvis and the narrow ureter.
Looks for an etiology.
Assesses renal functional impact.
Looks for associated abnormalities.
Detects complications: lithiasis, infection, urinoma, parenchymal destruction.
Preoperative work-up
MRI
In case of contraindication to CT urography.
Protocol:
Coronal T2 TSE +/- T2 HASTE (MR hydrography) sequences.
Axial T1 GE sequences
--> Injection of 20 mg furosemide just before
gadolinium injection.
Coronal and axial T1 GE FatSat sequences after
gadolinium injection at arterial, nephrographic, and
excretory (5 minutes) phases
Nuclear medicine
Mercaptoacetyltriglycine (MAG3) scintigraphy:
- essential in the preoperative work-up.
- assesses renal function, looks for obstruction.
Management
Surgery in case of complications (infectious, lithiasic), renal insufficiency, or obstructive symptoms:
- Pyeloplasty
- Endopyelotomy
- Simple dilatation
