For urinary tract infections, we need to know the specific routes of infection. If the routes of infection are not known, then treatment is actually very slow and there may be incurable consequences, resulting in an increased chance of recurrence. The following is a look at the four main ways to cause urinary tract infections. 1, upstream infection The pathogenic bacteria from the urethra upstream, into the bladder and cause infection, and then from the bladder through the ureter up to the kidneys and cause pyelonephritis. This is the main invasive route for bladder and kidney infections. The female urethra is short and straight, about 2 to 4 cm long, and close to the vagina and rectum, which is easily contaminated. Bacteria are more likely to be carried into the bladder during sexual intercourse, so urinary tract infections are far more common in women than in men. There are different amounts of bacteria residing in the front urethra at 3-4 cm in healthy men and in the distal 1 cm of the female urethra. The vast majority of urinary tract infections in women are caused by fecal flora that travels up the urethra from the perineum. In general, there is often a large number of fecal flora colonizing the vestibule of the urethra, and bacterial colonization of the vestibule of the urethra creates the conditions for urinary tract infections. 2, hematogenous infection Bacteremia or sepsis produced by the formation of bacterial foci of infection in any part of the body, if the bacteria are virulent and the number of bacteria is high, coupled with defective kidney tissue, it is easy to cause pyelonephritis. The main causative organism is often Staphylococcus aureus. 3. Lymphatic infections Bacteria in the colon can be spread to the kidney via the lymphatic vessels. In pelvic infections, bacteria can spread to the bladder or kidney via the periureteral lymphatics. However, urinary tract infections through the lymphatic route are less common. 4. Direct spread of infection from adjacent tissues This mode of infection is very rare. For example, appendicitis abscesses and pelvic infections can occasionally spread directly to the urinary tract. The mechanism of infection is not yet very clear, it is believed that bacteria into the bladder, Escherichia coli, Bacillus deformans can be combined with their umbrella and the receptors on the bladder mucosa, adhere to the bladder wall to grow and multiply, causing cystitis, this phenomenon of bacterial adhesion is an important part of causing urinary tract infections. Post-cystitis can affect the function of the ureter and its orifice in the bladder wall segment, leading to vesicoureteral reflux, causing the infected urine to flow back up. Endotoxin from bacteria can significantly decrease ureteral peristalsis, causing urine depression and increased pressure in the ureter, creating a physiological obstruction, all of which contribute to the development of pyelonephritis.