Urinary tract infections are divided into upper urinary tract infections and lower urinary tract infections according to the site of infection; they can be divided into isolated or sporadic infections and recurrent infections according to the relationship between two infections, the latter of which can be divided into reinfection and bacterial persistence, which is also called recurrence; they can be divided into simple urinary tract infections, complicated urinary tract infections and urinary sepsis according to the state of the urinary tract at the time of the infection episode. Urinary tract infections are often found in women, especially in sexually active and postmenopausal women. Etiology More than 95% of urinary tract infections are caused by a single bacterium. In 90% of outpatients and 50% of inpatients, the pathogenic bacteria are Escherichia coli, and the serotypes of this bacterium can be up to 140 species, and the uropathogenic Escherichia coli is the same type as the Escherichia coli isolated from the patient’s feces, which is mostly seen in asymptomatic bacteriuria or uncomplicated uropathogenic infections; Aspergillus, Bacillus pneumoniae, Klebsiella pneumoniae, Pseudomonas aeruginosa, Streptococcus faecalis, etc. are seen in Candida albicans and new cryptococcal infections are seen in patients with diabetes mellitus, glucocorticoids and immunosuppressive drugs and after renal transplantation; Staphylococcus aureus is seen in skin trauma and drug addicts causing bacteremia and sepsis; viruses and mycoplasma infections are rare but tend to increase gradually in recent years. A variety of bacterial infections are seen in indwelling catheters, neurogenic bladder, stones, congenital malformations and vaginal, intestinal, urethral fistula, etc. Clinical manifestations 1, acute simple cystitis sudden onset, female patients onset is mostly associated with sexual activity. The main manifestations are bladder irritation signs, namely urinary frequency, urinary urgency, painful urination, discomfort in the bladder area or perineum and burning sensation in the urethra; urinary frequency varies in degree, and in severe cases, urge incontinence can occur; cloudy urine, white blood cells in the urine, common terminal hematuria, sometimes the whole hematuria, and even see blood clots discharge. There are usually no obvious symptoms of systemic infection, and the body temperature is normal or there is low fever. 2. Acute simple pyelonephritis (1) Urinary symptoms include bladder irritation such as urinary frequency, urgency, and painful urination; hematuria; lumbago on the affected side or bilaterally; significant pressure pain or percussion pain on the affected spinal rib angle; (2) Symptoms of systemic infection such as chills, high fever, headache, nausea, vomiting, loss of appetite, etc., often accompanied by elevated blood leukocyte count and increased hematocrit. 3, asymptomatic bacteriuria Asymptomatic bacteriuria is an insidious urinary tract infection, mostly seen in elderly women and women during pregnancy, patients do not have any symptoms of urinary tract infection, the incidence increases with age. 4.Complex urinary tract infection The clinical manifestations of complex urinary tract infection vary greatly and are often accompanied by other diseases that increase the risk of acquiring infection or treatment failure, which may or may not be accompanied by clinical symptoms (such as urinary frequency, urgency, painful urination, difficulty in urination, pain in the low back, pressure pain in the spinal rib angle, pain in the suprapubic area and fever). Complex urinary tract infections are often accompanied by other diseases, such as diabetes mellitus and renal failure; they also lead to more sequelae, the most serious and fatal conditions including urinary sepsis and renal failure, which can be classified as acute and chronic, reversible and irreversible, etc.