Urinary tract infection (UTI), also known as bladder infection, refers to inflammation of the urinary tract caused by the invasion of pathogens into the mucous membranes or tissues of the urinary tract. According to the site of infection, UTI can be classified as upper UTI (pyelonephritis) and lower UTI (cystitis). Depending on the presence of underlying diseases, UTIs can also be categorized as complicated or uncomplicated.

Diagnosis of UTI:

1. Bacterial quantitative culture of midstream urine (with the requirement of urine staying in the bladder for 4-6 hours) with a bacterial count ≥105/mL.

2. Clean centrifuged midstream urine sediment with white blood cell count >10/HP and symptoms of UTI.

Differential diagnosis of upper and lower UTI:

1. Positive urine antibody-coated bacteria test results indicate pyelonephritis, while negative results are more likely to indicate cystitis.

2. Positive bacterial culture results in urine samples after bladder sterilization are indicative of pyelonephritis, while negative results are more indicative of cystitis.

Distinguishing acute and chronic pyelonephritis:

1. UTI history of over 1 year, poor response to antibiotic treatment, and multiple positive culture results are indicative of chronic pyelonephritis.

2. Persisting renal tubular dysfunction after treatment and confirmation of kidney changes on X-ray imaging are indicative of chronic pyelonephritis.

Urethral syndrome (urinary frequency-dysuria syndrome) should meet the following criteria:

1. Female patients with noticeable dysuria and urinary frequency, but without systemic symptoms such as fever or increased white blood cell count.

2. Multiple urine culture results with bacterial counts <105/mL.

3. Slight increase in white and red blood cells in urine, <10/HP.

Recurrence of UTI should meet the following criteria:

1. Recurrence of symptoms within 9 weeks after symptoms disappear and urine culture turns negative.

2. Bacterial count ≥105/mL with the same strain as the previous infection.

Reinfection of UTI should meet the following criteria:

1. Recurrence of symptoms after treatment, with a bacterial count ≥105/mL and a different strain (species) than the previous infection.