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Urinary tract infection, pathology, cause

Cause of urinary tract infection:the cause of the disease More than 95% of urinary tract infections are caused by a single bacterium. About 90% 90% of the outpatient and inpatient, e. coli is the pathogenic bacteria, the fungus serotyping of up to 140...

Urinary tract infection, pathology, cause

Aug 14, 2017 by Kidney Disease Expert

(1) the cause of the disease

More than 95% of urinary tract infections are caused by a single bacterium. About 90% 90% of the outpatient and inpatient, e. coli is the pathogenic bacteria, the fungus serotyping of up to 140 kinds of type of e. coli urinary infection and separated from the patient fecal e. coli belong to the same kind of bacteria, see more at asymptomatic bacteriuria or uncomplicated urinary infection; Proteus, gas bacillus, white clay, klebsiella pneumoniae, pseudomonas aeruginosa, streptococcus faecalis in reinfection, urethral catheter, complications of urinary infection; White candida, new cryptococcal infection was found in diabetes and patients with glucocorticoids and immunosuppressive drugs and kidney transplantation; Staphylococcus aureus is seen in skin trauma and drug addiction and sepsis. Although the infection of the virus and mycoplasma is rare, there have been increasing trend in recent years. A variety of bacterial infections are found in the detention catheter, neurogenic bladder, stone, congenital malformation and vagina, intestinal and urethral fistula.

(2) pathogenesis

Urinary tract infection is caused by pathogenic bacteria invasion, and its pathogenesis is associated with pathogen infection, the ways and methods in pathogen invasion of infection can be pided into the following kinds.

Up to 95 percent of all urinary tract infections, which go up to the kidneys from the urethra through the bladder and ureter. Normally, there is a small amount of bacteria in the top 1 ~ 2cm of the urethral mouth, only when the body resists or the urethral mucosa is damaged, the bacteria can invade and reproduce. Flush urine, urine IgA, lysozyme, organic acids, mucosal integrity, bladder transitional epithelial secretion of adhesions (Muein) all can resist the invasion of pathogenic bacteria. Electron microscopy confirmed in recent years, there are a lot of e. coli surface P fimbriae, they can specifically recognize and combination in the corresponding receptors on the surface of the epithelial cells of the urinary tract, so that the bacteria closely attached on the urothelial cells, avoid being urine washed away. E. coli bacteria (O) antigen, flagella (H) antigen, capsular antigen (K), K of polysaccharide antigen can inhibit phagocyte bactericidal activity, is directly related with virulent. Proteus no pili and K antigens, which are not easily attached to the graft epithelium of the bladder, but can be attached to the squamous epithelial cells of the external genitalia. Urethral catheter, urinary stones, planer, tumor, prostate hypertrophy, congenital urinary tract malformation (including the wall within the ureter, bladder sphincter dysgenesis caused by bladder ureter reflux), neurons are ascending infection risk factors such as the bladder.

Blood line infection only accounts for less than 3% of urinary tract infections. The blood flow rate of the kidney is 20% to 25%, sepsis and bacteremia, and the bacteria in circulating blood easily reach the renal cortex. The use of diabetes, polycystic kidney, transplantation of kidney, urinary tract obstruction, renal vessel stenosis, analgesic or sulfonamide drugs has increased the vulnerability of kidney tissue. Common pathogenic bacteria are staphylococcus aureus, salmonella, pseudomonas and white candida infection opportunity is rare, directly by the lymphatic infection has not yet been confirmed.

Susceptibility factors

(1) urinary tract obstruction, urinary tract obstruction due to a variety of causes, such as renal and ureteral calculi, urethral stricture, urinary tract cancer, prostatic hypertrophy, etc all can cause urinary retention, the bacteria reproduce and infection. This disease can be caused by the stress of the urethral tube, the ptosis of the kidney or the water of the pelvis.

(2) urinary tract malformation or dysfunction, such as renal dysplasia, polycystic kidney, sponge, horseshoe kidney, double renal pelvis and double ureter malformations or huge ureter, etc., are easy to make local groups of bacteria resistance is reduced. Bladder ureteral reflux causes urine to flow from the bladder to the pelvis, thereby increasing the risk of disease. The function of urination of the neurocystic bladder is abnormal, resulting in urinary retention and bacterial infection.

(3) urethral intubation and equipment check: urethral catheterization, cystoscopy, urinary tract surgery can cause local mucosa damage, the former on the pathogenic bacteria of urethra into the bladder or urinary tract and cause infection. According to statistics, the incidence of persistent bacteriuria after a catheter is 1% ~ 2%. The incidence of persistent bacteriuria was more than 90 percent for more than four days, and the risk of severe pyelonephritis and gram-negative sepsis was significant.

(4) female urinary tract anatomy physiology characteristic: female urethral length only 3 ~ 5 cm, straight and wide, urethral sphincter weak, bacteria easy along the urethra to the bladder, urethral mouth and anus close at the same time, provide conditions for bacterial urinary tract. Local stimulus around the urethra, menses pudendum, vulnerable to bacterial contamination, vaginitis, cervicitis, such as disease of department of gynaecology, variation of sex hormone in pregnancy and postpartum sexual life, all can cause the vagina, the urethra mucous membrane changes for pathogenic bacteria invasion. As a result, the incidence of urinary tract infections among adult women is eight to ten times higher than that of men.

(5) the body's resistance to abate: systemic diseases such as diabetes, high blood pressure, chronic kidney disease, chronic diarrhea, long-term use of adrenal cortical hormone, etc to make the body resistance drops, the incidence of urinary tract infection increased obviously.

In short, the occurrence of urinary tract infections is a fairly complex process that can be summarized in the following steps:

The bacterial colonies with the P fungus fall around the gut and the urethral mouth and spread to the urethra.

In the urine, the bacteria are retrograde in the urinary tract and bind to the corresponding receptors of the epithelial cells of the urinary tract, and they reproduce locally and produce inflammation.

Through the turbulence of urine in urethral tubes, the bacteria carry on to the kidney, such as inflammation is not controlled in time, the kidney tissue is damaged, and finally the fibrosis occurs.

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