Hydroureter could occur in a state where the whole ureter was remarkably expanded. The causes of occurrence are anatomi-cal urinary tract obstruction or vesicoureteral reflux, and it could occur unilaterally or bilaterally according to its reason. A 38-year-old man presented with left flank pain. Abdominal CT showed a severely atrophied left kidney and a large retroperi-toneal cyst near the left kidney. The pathologic finding showed that the cyst wall is composed of transitional epithelium, lamina propria, muscle, and adventitia, and final diagnosis was hydroureter. The unilateral marked hydroureter misdiagnosed as a retroperitoneal cyst was quite rare. We report on this rare case with literature.

• 김동현(조선대학교 의학전문대학원 내과학교실) | Dong Hyun Kim
• 신병철(조선대학교 의학전문대학원 내과학교실) | Byung Chul Shin
• 최남규(조선대학교 의학전문대학원 외과학 교실) | Nam Gyu Choi
• 홍란(조선대학교 의학전문대학원 병리학교실) | Ran Hong
• 김현리(조선대학교 의학전문대학원 내과학교실) | Hyun Lee Kim Corresponding author
• 정종훈(조선대학교 의학전문대학원 내과학교실) | Jong Hoon Chung