Hello Good evening,Frequent UTI
is common in females due to various anatomical and physiological reasons.
Since you have not mentioned age of your mother, So it is little bit difficult to reach exact reason but in USG(ultrasound) there is dilation in calyx, so probably there is an obstruction in urinary tract
either it is in ureter or urinary bladder
Obstruction can be of any type like minor ureteric stone or scaring or stricture in the ureter or urethra, dehydration
is a add on reason to these.
So please ask mother to do followings:
do not hold urine for long due to any reason.
take antibiotics as prescribed by physicianurologist
plan for invasive cystoscopy if needed.