Thank you for posting your query in healthcare magic.com... See hydronephrosis of kidney means dilatation of the renal pelvis...it can be due to obstruction of the ureter...also in obstruction in bladder and urethra it can happen...in that case there might be hydroureter also...there can be other causes like stricture or adhesions etc...see sometimes if it is minor, gets better on its own...but if its major or both sided, it can be of problem... I would suggest you to talk to your doctor and he/she would be able to tell better seeing the reports... Hope this was helpful... Regards