Hi
Hydronephrosis can be due to obstruction in
kidney tube or due to reflux of urine back towards kidney
Obstruction if mild or moderate can be observed, if severe needs to be operated. In children an EC scan is done to know kidney function.
Reflux if severe also needs to be treated with reflux injection or surgery.
Mcug differentiates the two.
Fever can occur after mcug. If it persists, get a urine culture done and consult your doctor.