Pelviureteric 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 the pelviureteric junction. No intraluminal or mural cause for obstruction detected. The left ureter is of normal caliber. Delayed contrast excretion at the left pelvicalyceal system and no contrast reaches left ureter at the excretory phase.
The radiological features likely represent chronic left pelviureteric junction obstruction. In this case, there is branching of the left renal artery at the pelviureteric junction wrapping it horizontally that might be a probable etiology.
CT urography is the modality of choice for differentiating pelviureteric 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 pelviureteric junction is characteristic. The kidney showed delayed contrast excretion due to obstruction.
Pelviureteric junction obstruction may be congenital or secondary to inflammatory stricture, kink or a renal artery branch crossing the renal pelvis. If untreated, it results in chronic hydronephrosis that leads to decreased parenchymal thickness and impaired function of the affected kidney.