Pediatric Ureteropelvic Junction Obstruction

Etiology: Intrinsic narrowing of ureter from abnormal smooth muscle or abnormal innervation or fibrous scar or extrinsic compression of ureter from a crossing blood vessel
Imaging:
— Pelvic and calyceal dilation of pelvis greater than calyces
— No ureteral dilation
— Visible focal narrowing at ureteropelvic junction
— Renal parenchymal thinning
Imaging MAG3 scan:
— Used for initial assessment and follow-up of function and drainage
— See delayed uptake and early central photophobia and poor drainage before and after lasix and minimal gravity drainage
DDX:
Complications: Predisposes to a relatively small renal trauma causing large renal injury
Treatment: May spontaneously improve or worsen
Clinical:
— Most common cause of antenatal hydronephrosis
— Most common cause of urinary tract obstruction in children
— Associated with contralateral multicystic dysplastic kidney
— Presentation: In younger children with more severe obstruction as congenital ureteropelvic junction obstruction, later in life with intermittent symptoms perhaps due to crossing vessel
— Can present as flank pain in teen after large fluid challenge or as large renal injury after minor blunt abdominal trauma

Radiology Cases of Ureteropelvic Junction Obstruction

US of ureteropelvic junction obstruction — Sagittal US of the right kidney (above) shows a single renal collecting system with no evidence of hydronephrosis. Sagittal US of the left kidney (below) show a single renal collecting system that has a moderate amount of hydronephrosis. The left renal pelvis is also moderately dilated. There was no left hydroureter.

Sagittal US of the left and right kidneys shows echogenic medullary pyramids bilaterally and mild right hydronephrosis.

US of ureteropelvic junction obstruction — Sagittal US of the right kidney (upper left) and left kidney (upper right) shows bilateral mild to moderate hydronephrosis. AP image from the excretory phase of an intravenous pyelogram shows bilateral moderately dilated renal collecting systems with normal appearing bilateral ureters.

IVP of ureteropelvic junction obstruction — 4 hour delayed image from an IVP exam shows an extremely dilated left renal collecting system. The left ureter is not seen.

Radiology Cases of Ureteropelvic Junction Obstruction Due to Retrocaval Ureter

IVP of retrocaval ureter — AP image from the excretory phase of a vintage intravenous pyelogram (left) shows a normal left renal collecting system and left ureter and an extremely dilated right renal collecting system. Magnified views of the right ureteropelvic junction (right above and right below) show a sharp kink at the right ureteropelvic junction.

Radiology Cases of Ureteropelvic Junction Obstruction Due to Crossing Vessel

IVP of ureteropelvic junction obstruction due to a crossing vessel — AP image from the excretory phase of an intravenous pyelogram (above) shows a normal left renal collecting system and a markedly dilated right renal collecting system. No contrast was seen in the right ureter. AP image from a retrograde pyelogram (below) shows a markedly dilated right renal collecting system and a narrowing and tortuosity to the proximal right ureter.

Radiology Cases of Ureteropelvic Junction Obstruction After Trauma

CT of hemorrhage into ureteropelvic junction obstruction after trauma — Coronal (above left) and sagittal (above right) CT with contrast of the abdomen show an extremely dilated right renal collecting system surrounded by an extremely thin rim of renal cortex. The axial image (below) shows high density material within the medial aspect of the renal collecting system.

CT of perirenal hematoma in a patient with a ureteropelvic junction obstruction — Axial CT without contrast of the abdomen (above) shows the unenhanced right kidney to have a low density dilated central collecting system and to be surrounded by a high density cresenteric fluid collection in the right perirenal space. Axial CT with contrast (below) better shows the low density dilated central collecting system and a decreased amount of enhancement in the right kidney when compared to the normal left kidney. The amount of enhancement in the right kidney is the same density as the right perirenal fluid collection.

Surgery Cases of Ureteropelvic Junction Obstruction

Surgery Cases of Ureteropelvic Junction Obstruction Due to Retrocaval Ureter

Surgery image of retrocaval ureter causing ureteropelvic junction obstruction — Surgical image (above) shows the decompressed distal right ureter (with the black loop around it) emerging from behind the inferior vena cava in the center of the image. The dilated proximal right ureter can be seen just to the right of the inferior vena cava at the top of the image. Post operative surgical image (below) shows the red vessel loops around the now decompressed proximal right ureter which has been transected and reanastomosed anterior to the inferior vena cava in the center of the image.

Gross Pathology Cases of Ureteropelvic Junction Obstruction

Gross Pathology Cases of Ureteropelvic Junction Obstruction Due to Pheochromocytoma

Gross pathology image of pheochromocytoma causing ureteropelvic junction obstruction — Sectioned gross pathological image shows an ovoid gray to tan mass surrounded by a thin fibrous capsule that is compressing the right ureter resulting in right hydroureteronephrosis.