Thanks for sharing your concern with us.
The mild fullness of the upper one third ureter
is suggestive of partial block somewhere in the ureter. The most common cause of it at your age is going to be stone in the ureter.
You should get yourself further investigated with NCCT KUB (Non contrast enhanced Ct scan
of the kidney-ureter-bladder reion) and see a urologist
. Most of the patients with ureteric stones can be managed with medications. Post NCCT KUB you should start yourself on medications under the guidance of urologist. The treatment shall include alpha blockers and calcium channel blockers besides analgesics,
Let me know if you have any other questions.