Hi, you should see a urologist in situations as follows:
1. UTI not getting better after a course of antibiotics
2. Frequent UTI i.e. 3 attacks in a year or 2 attacks in 6 months
3. Flank or back pain with or without fever
4. Blood in the urine
5. If you have previous urinary stone diseases or you had surgery to your kidneys/ureters/bladder
6. If you have neurological problems such as spine problems, Parkinson's disease, stroke.
7. Males
In my opinion, young ladies usually will need to see a urologist for situations 1–4.
Hope this helps.