The urinary system of a dog is composed of the kidney, ureter, bladder and urethra. The most common one is lower urinary tract infection. Most lower urinary tract infections are accompanied by cystitis, while relatively less common ones are ureter and kidney infections, and kidney infections are also called "pyelonephritis".
When a dog is healthy, the urine in the bladder is usually sterile. When a urinary tract infection occurs, it means that the bacteria have entered the bladder from the urethra. The question is how the bacteria enter the bladder.
For this point, we have to talk about the urinary tract circulation of the dog. The dog's urine is excreted from the kidneys, stored in the bladder through the ureter, and then passes through the urethra to the external genitals, and finally excreted from the body through the external genitals. Although there are bacteria in the urethra and it is logically easy to get infected, the role of the autoimmune system prevents the rise of bacteria.
However, when dogs have stones or malnutrition, their immunity will be reduced and their blocking effect will be reduced accordingly. The bacteria enter the bladder from the urethra, and then the lower urinary tract infection occurs. If it is not discovered and treated in time, the bacteria are very likely to further rise and cause kidney infection.
In addition, some dogs will have abnormal lower urinary tract structure due to genetic problems, and this type of dog will be more likely to have lower urinary tract infection. Generally speaking, female dogs are more likely to suffer from lower urinary tract infection than male dogs, because female dogs peeing is a bacteria that will be more likely to be exposed to when squatting.