Severe right sided hydronephrosis, with a transition point at the pelviureteric
junction is grossly stable. There is cortical atrophy consistent with long
stranding obstruction with marked right sided perinephric fat stranding which
has progressed since prior studies suggesting either urine leak or fat
stranding secondary to superadded right sided upper renal tract infection. There
are no calculi detected. The fat stranding extends into the right
retroperitoneum inferiorly with no peripherally enhancing collection or
abdominal free fluid.
Conclusion: Severe right sided hydronephrosis with a transition point at the pelviureteric junction consistent with long standing pelviureteric obstruction. Perinephric fat stranding on the right with associated right sided upper renal tract urothelial thickening and hyperenhancement is most in keeping with superadded infection. Urine leak due to perforation is a less likely cause of the progression of fat stranding.