Causes of UPJ Obstruction

Congenital

• Abnormality of collagen muscle causing stenosis at the UPJ
• High ureteral insertion
• Aberrant crossing renal vessels: arteries/vein at the renal hilum crossing anterior or posterior to the ureter can cause obstruction
• Failure of recanalization of the ureter (considered less likely)
• Presence of valves/kinks (considered less likely)

Acquired

• Vesicoureteral reflux
• Stricture or stenosis secondary to trauma, recurrent infection, instrumentation, calculi
• Neoplasm: benign (polyp) or malignant (transitional cell, squamous cell)

REFERENCES
Lawler LP, Jarret TW, Corl FM, Fishman EK. Adult ureteropelvic junction obstruction: insights with three-dimensional multi-detector row CT. Radiographics 2005;25:121-34.