Bacteria in urine may be caused by pyelonephritis, and may also be caused by contaminated urine specimen, urethritis, cystitis and other factors. 1. Pyelonephritis: the presence of bacteria in the urine may be related to pyelonephritis, which is usually accompanied by fever, chills, fatigue, frequent urination, pain in urination, lumbago and other symptoms, and there may be white blood cells and red blood cells in the urine. 2. Urine specimen contamination: urine specimen is contaminated during the urine test, which can also lead to the presence of bacteria in the urine, but the patient does not have any clinical symptoms, and the urine routine can be normalized. 3. Urethritis, cystitis: with other urinary tract infections, it is also easy to make the presence of bacteria in the urine, such as urethritis or cystitis, usually accompanied by pain in urination, frequent urination, urinary urgency, urinary symptoms. There are other reasons why there are bacteria in the urine, if accompanied by other obvious symptoms, should be timely to the regular hospital, to do further examination, to clarify the type of disease and the severity of the disease, and then follow the doctor’s instructions for targeted treatment.