Severe urinary tract infection is mainly caused by the presence of pathogenic bacteria in the body. A large number of pathogenic bacteria with strong virulence and low immune function will lead to urinary tract infection. After urinary tract infection occurs, if there is no timely treatment, or the body has diabetes, malnutrition, or there is obstruction in the urinary system, stones, or tumors, the infection will become progressively worse. The most common may be retrograde infection, hematogenous infection, lymphatic infection, etc. In case of severe urinary tract infection, blood culture and urine culture must be carried out to find out the pathogenic bacteria and select sensitive antibiotics for treatment. If the obstruction is caused, the obstruction should be relieved, nutrition should be increased, and sufficient water should be added.