We report a case of right giant hydronephrosis. A 68-year-old man was admitted to our hospital with chief complaints of general fatigue, loss of appetite and a one-year history of progressive fullness on whole abdomen. Abdominal computed tomography scan exhibited a huge, homogeneous, low density mass originating from the right kidney. We performed right percutaneous nephrostomy and drained over 6,500 ml bloody fluid. Cytological examination of the drained fluid revealed atypical nuclear appearance defined as class III. Increased values of carbohydrate antigen 19-9 were observed both in the fluid as well as in the serum. We performed right nephrectomy. Macroscopic appearance of the resected kidney showed marked stenosis at the portion of ureteropelvic junction. Histological analysis of the stenotic portion demonstrated marked fibrosis without findings of malignancy.