Complex sentence: Urine cultures are typically negative for infection, yet it is not unusual for patients to believe that they have had infections for years rather than IC, because the symptoms of an infection are nearly identical to the symptoms of IC.
Split into simpler sentences: Urine cultures are typically negative for infection, yet it is not unusual for patients to believe that they have had infections for years rather than IC. Because the symptoms of an infection are nearly identical to the symptoms of IC.