BI Causes: Porsche 911: 911 Sale - Version - BI Causes: Porsche 911: 911 Sale: Bladder Infection or Cystitis is basically an infection that happens within the bladder, which is part of the urinary tract. Within the Urinary Tract, they are several organs that if infected would constitute urinary tract infection (UTI) or bladder infection, these organs are as follows: Read about the causes of Bladder Infection and how to treat it.