Ureteropelvic junction obstruction
Left loin pain
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- Left kidney shows small size (7.5 cm in bipolar dimension), decreased parenchymal thickness and markedly dilated, ballooned renal pelvis and calyces with abrupt termination at ureteropelvic junction. No intraluminal or mural cause for obstruction detected. Ureter is of normal caliber (chronic left UPJ obstruction).
- Delayed contrast excretion. No contrast seen in left ureter at excretory phase.
CT urography is the modality of choice for differentiating ureteropelvic junction obstruction from other causes of hydronephrosis and from parapelvic cysts. Excretion into the dilated calyces with a non-dilated ureter and abrupt transition at the ureteropelvic junction is characteristic. The kidney showed delayed contrast excretion due to obstruction. It may be congenital or secondary to other causes, such as inflammatory stricture, kink or a renal artery branch crossing the renal pelvis. It is a type of chronic hydronephrosis that leads to decreased parenchymal thickness and impaired function of the affected kidney.