To diagnose interstitial cystitis, does the patient have to have pain in urethra or pain when peeing? or can the pain just be pelvic/vaginal?

All of the above: Ic can manifest in different ways for each person. Most common symptoms are burning/discomfort with urination (dysuria) and feeling that you need to use the restroom urgently (urgency). Diagnosis is made based on symptoms, but sometimes cystoscopy is also needed (camera to look inside bladder).

Bladder pain.: Interstitial cystitis also called painful bladder syndrome is a very common condition. The most common symptom is pain in the bladder and surrounding structures. Many people also experience frequent urination, strong urge to urinate, symptoms that worsen during your period and painful intercourse.