<s>[INST] Where do UTIs start? [/INST] Most UTIs start in the lower urinary tract. Bacteria enter through the urethra and spread upward to the bladder. This can cause cystitis, a bladder infection. In some cases, an infection of the urethra called urethritis can develop at the same time. Source: ACOG. Link: https://www.acog.org/womens-health/faqs/urinary-tract-infections. Field: Urology. Disease: Urinary Tract Infection  </s>