Ureteropelvic junction obstruction

Etiology
- Congenital
  - Intrinsic: malformation of the smooth muscle of a ureteral segment and consecutive impairment of peristalsis (functional stenosis)
  - Extrinsic: aberrant renal pole artery causing proximal ureteral obstruction
- Acquired: factors causing ureteral obstruction
Clinical features
- Newborns and infants
  - Palpable upper abdominal mass
  - Failure to thrive
  - Recurrent pyelonephritis
- Children and adults
  - Flank pain or upper abdominal pain that may be triggered or worsened during states of increased diuresis (e.g., after caffeine or alcohol consumption).
  - Nausea/vomiting
  - Recurrent pyelonephritis
  - Hematuria
Diagnostics
- Ultrasound
  - In industrialized countries, most cases of congenital ureteropelvic junction obstruction are diagnosed antenatally with hydronephrosis on prenatal ultrasound.
- IV urography
Treatment
- Observation: asymptomatic, mild cases
- Surgery
  - Symptomatic patients or those with > 40% loss of renal function