Genitourinary Radiology > Collecting System > Ureters > Dilatation


The most important cause of ureteral dilatation that needs to be ruled out is obstruction due to neoplasm. This is almost always transitional cell carcinoma and rarely metastatic disease or squamous cell carcinoma. The most common cause is urinary stones.

Ureteral dilatation may be divided in two ways: unilateral vs. bilateral and lower ureter vs. upper ureter. Bilateral causes include bladder outlet obstruction, bladder neoplasma, bladder inflammation, prune-belly syndrome, diabetes insipidus, polydipsia, primary megaureter, and reflux. Unilateral causes include vesicoureteral reflux and primary megaureter.

Processes that involve the lower ureteral segment include primary megaureter and vesicoureteral reflux (grade 1); if only the upper ureter is involved, common causes include retrocaval or retroiliac ureter, enlarged uterus, and postpartum ectasia.

Gray scale ultrasound of right kidney shows mild hydronephrosis with fluid filled and dilated calyces (c) connecting to distended infundibuli (arrow) and dilated renal pelves (p).

Gray scale ultrasound of left kidney in a different patient shows mild hydronephrosis similar to the patient at left. The patient presented with left flank pain. The ultrasound technologist was able to follow the dilated ureter down to the level of the insertion of the ureter into the bladder revealing an obstructing stone at the UPJ.

Gray scale ultrasound of the bladder in a patient with a stone in the distal left ureterovesicular junction (UVJ).  Arrow shows stone.

Close up of the stone seen in the same patient as image to the left.  Note the dilated left distal ureter (arrow) caused by obstruction from the UVJ stone.  

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