In certain populations, such as the elderly, symptoms may be less specific and include depressed mental status and failure to thrive, or there may be no symptoms at all. Children less than 2-years-old may also have nonlocalizing symptoms. These differences likely reflect an inability to mount an efficient immune response.

Because urethritis can sometimes mimic the symptoms of cystitis, patients should be evaluated for possible gonorrhea or Chlamydia urethritis, as well as for bacterial vaginitis or genital herpes. In addition, the differential must include the numerous causes of nonbacterial cystitis. For example, trauma may cause bladder inflammation and is often seen in women after forceful sexual intercourse. Interstitial cystitis (also known as bladder pain syndrome) may also be associated with cystitis-like symptoms. Hemorrhagic cystitis is most commonly seen in patients undergoing cyclophosphamide treatment but can also result from adenovirus infection, especially in children. Finally, radiation therapy can cause cystitis secondary to scarring.