What Is the Pathophysiology of Urinary Tract Infection?

Urinary tract infection

Urinary tract infection (UTI) refers to a pathogen that directly invades the urinary tract, grows and reproduces in the urine, and invades the urinary tract mucosa or tissue to cause damage. It is divided into pyelitis, cystitis, and urethritis according to the location of the pathogen. Pyelonephritis is also called upper urinary tract infection, and cystitis and urethritis are collectively called lower urinary tract infection. Because the infection in children is limited to a certain part of the urinary tract, and it is difficult to accurately locate it clinically, it is often referred to as UTI without distinction. It can be divided into symptomatic urinary tract infection (UTI) and asymptomatic bacteriuria according to the presence or absence of clinical symptoms.

Statistics of Urinary Tract Infection

Urinary tract infection According to a national survey in China in 1982, urinary tract infections accounted for 8.5% of the diseases in the system. In 1987, urine screening tests for children in 21 provinces and cities nationwide showed that UTI accounted for 12.5% of urinary attack in children. The incidence is generally higher than that of men, but it is higher in men than in women in newborns or early infancy.

Clinical symptoms of urinary tract infection

Acute infection of urinary tract infection

(1) Newborn to

Urinary tract infection Systemic symptoms are predominantly caused by bloodstream infections. Septicemia with jaundice, hidden bacterial urine, fever, hypothermia, pale skin, weight gain, milk rejection, diarrhea, lethargy, and convulsions.

(2) Infant and childhood, severe systemic symptoms, mainly abdominal pain, diarrhea, and vomiting. Crying and bad smell during urination can cause refractory diaper dermatitis due to frequent urination, and no enuresis occurs at night.

(3) In children, the infection of the lower urinary tract is mainly caused by bladder irritation, and the infection of the upper urinary tract is mainly fever, chills, low back pain, throbbing pain in the kidney area, tenderness of the rib and spine angle. Hemorrhagic cystitis caused by E. coli may have hematuria.

Recurrence and reinfection of urinary tract infections

Relapse means that the bacteriuria temporarily becomes negative after treatment, and the original pathogenic bacteria re-emerge again within a short period of time (<6 weeks) after stopping the drug, and the symptoms reappear. Reinfection means that an infection has been cured after treatment, and a long time (usually & gt; 6 weeks) after drug withdrawal is caused by another pathogenic bacteria invading the urinary tract.

Chronic infection of urinary tract infection

The course of disease is more than 6 months. Pyuria or bacteriuria can occur intermittently. Those with a long course of disease may have symptoms such as anemia, fatigue, and stunting.

Causes of Urinary Tract Infections

Any pathogenic bacteria can cause UTI, but most are Gram-negative bacilli, such as the colon

Urinary tract infection Bacteria, Paracoli, Proteus, Klebsiella, Pseudomonas aeruginosa, a few are Enterococcus and Staphylococcus. E. coli is the most common pathogenic bacteria in UI. About 60% -80%. Newborns with UTI for the first time, girls of all ages and boys under 1 year old, the main pathogenic bacteria is still Escherichia coli, while boys above 1 year old are mostly proteobacteria. For girls 10 to 16 years old, Staphylococcus albicans is also common, and Klebsiella and Enterococcus are more common in neonatal UTI.

Pathophysiology of urinary tract infection

The pathogenesis of UTI caused by bacteria is intricate and complicated, which is the result of interaction between host intrinsic factors and bacterial pathogens.

(I) Ways of infection

1.Bloodborne infections

Pathogens invading via blood-borne pathways are mainly golden yellow

Urinary tract infection staphylococcus.

Ascending infection

Pathogens go up from the urethral opening and enter the bladder, causing cystitis. Pathogens in the bladder migrate to the kidneys through the ureter and cause pyelonephritis, which is the most important way of UTI. The pathogenic bacteria that cause ascending infections are mainly E. coli, followed by Proteus or other enterobacteria, and bladder ureteral reflux (VUR) is often the direct channel for bacterial ascending infections.

Lymph infection and direct spread

Bacterial and pelvic infections in the colon can spread directly to the surrounding organs and tissues around the kidney through lymphatic infection of the kidney.

(II) Internal factors of the host

1. Changes in bacteria around the urethra and changes in urine characteristics have created conditions for the invasion and reproduction of pathogenic bacteria.

2. Bacteria adhere to urothelial cells (colonization), which is the first UTI caused by urinary tract proliferation.

Urinary system Conditions.

3. There is a defect in the production of secreted IgA in UTI patients, which reduces the concentration of secreted IgA in urine and increases the chance of UTI.

4. Congenital or acquired urinary tract malformations, increasing the risk of urinary tract infections.

5. Newborns and small infants have poor anti-infective ability and are susceptible to UTI. Diapers and urethral orifices are often contaminated with bacteria, and their local defense capabilities are poor, which can easily cause upward infection.

6. Diabetes, hypercalcemia, hypertension, chronic kidney disease, sickle cell anemia, and children with long-term application of glucocorticoids or immunosuppressants may have an increased incidence of UTI.

(Three) bacterial toxicity

Laboratory tests for urinary tract infections

1.Urine routine examination and urine cell count

(1) Routine urine examination: if the white blood cells in the clean middle-centrifugal sediment are> 10 / HPF, urinary tract infection can be suspected, and hematuria is also common. Patients with pyelonephritis have reduced specific gravity and osmotic pressure of intermediate proteinuria, leukocyte cast urine, and morning urine.

(2) Determination of urinary leukocyte excretion rate at 1 hour, white blood cell count> 30 × 104 / h is positive, urinary tract infection is suspected, <20 × 104 / h is negative, urinary tract infection can be excreted.

Urinary tract infection 2. Bacterial examination of urine culture

Urine bacterial culture and colony count are the main criteria for the diagnosis of urinary tract infection. Generally, it is considered that the number of colonies in the middle section of urine culture can be diagnosed 105 / ml, 104-105 / ml is suspicious, and <104 / ml is contaminated, but the analysis of the results should be based on the clinical and comprehensive evaluation of clinical and bacterial types of the sick child's gender and fertility. significance. Because one strand of Streptococcus contains 3 bacteria, it is generally considered that the number of colonies can be diagnosed between 103-104 / ml. Urine culture obtained through suprapubic bladder puncture has diagnostic significance as long as bacterial growth is found. As for girls with severe urinary tract irritation, if there are more white blood cells in the urine, the quantitative culture of urinary bacteria in the middle section is 102 / ml, and the pathogenic bacteria are E. coli or septic paracoccus, etc., which can also be diagnosed as UTI. Clinically suspected UTI and urine-negative bacteria culture negative, should be used for L-type bacteria and aerobic bacteria culture.

3.Urine direct smear method to find bacteria

Under the oil microscope, one bacterium can be found in each visual field, indicating that the bacterial count in the urine is above 105 / ml.

4. Nitrite test strip test (Griess test)

E. coli, Paracoli and Klebsiella were positive, gas-producing, deforming, pus aeruginosa and staphylococci were weakly positive, and Streptococcus faecalis and tuberculosis were negative. If morning urine is used, the positive rate can be increased.

5.Other

Such as urine sediment to find flash cells (gentian purple sand yellow staining) 20,000-40,000 / h can be diagnosed, newborn urinary tract infection blood culture can be positive.

Imaging examination of urinary tract infection

The purpose is to:

check for congenital or acquired deformities of the urinary system,

Understand the progress of chronic kidney damage or scar caused by missed diagnosis or inappropriate treatment,

Assist the diagnosis of upper urinary tract infection. Commonly used imaging examinations include B-mode ultrasound, intravenous pyelography plus tomography (to check the formation of renal scars), excretory urinary urography (to check VUR), dynamic, static radionuclide angiography, and CT scans.

Diagnosis and differential diagnosis of urinary tract infection

The symptoms of UTI in older children are similar to those of adults, and the symptoms of urinary tract irritation are obvious. If combined with laboratory tests, the diagnosis can be confirmed immediately. However, for infants and young children, especially newborns, due to the lack of obvious or absent-minded stimulus symptoms, their systemic performance is often prominent, which can easily lead to missed diagnosis. Therefore, it is necessary to repeatedly perform urine tests on fever mixed children with unknown etiology, and strive to perform incubation, colony count, and drug sensitivity tests before treatment with antibiotics. Those who have true bacterial urine, that is, the number of colonies in the clean mid-section quantitative culture 105ml or The diagnosis can be established by cocci 103 / ml or bacterial growth in the qualitative culture of suprapubic bladder puncture urine.

In addition to assessing the urinary system for bacterial infection, a complete UTI diagnosis should include the following:

(1) The infection is first infection, recurrence or re-infection;

(2) Determine the type of pathogenic bacteria and conduct drug sensitivity tests;

(3) No urinary tract malformations such as VUR, urinary tract obstruction, etc. If there is VUR, further understand the severity of "reflux" and the formation of kidney scars;

(4) Diagnosis of localization of infection, that is, upper urinary tract infection or lower urinary tract infection.

UTI needs to be distinguished from glomerulonephritis, renal tuberculosis, and acute urethral syndrome. The clinical manifestations of acute urethral syndrome are urinary tract irritation symptoms such as frequent urination, urgency, dysuria, and dysuria, but clean middle-stage urine culture has no bacterial growth or meaningless bacteriuria.

Acute UTI is treated with reasonable antibacterial treatment. Most symptoms disappear and are cured, but nearly 50% of patients can relapse or re-infect. Recurrent cases are often associated with urinary tract malformations, with VUR being the most common. VUR is closely related to kidney scars. The formation of kidney scars is the most important factor affecting the UTI prognosis of children. Kidney scars are most likely to form in school-age children, and progress is not obvious after 10 years of age. Once kidney scars cause hypertension, if it cannot be effectively controlled, Eventually progresses to chronic renal failure.

Urinary tract infection treatment plan

The purpose of treatment is to control symptoms, eliminate pathogens, remove predisposing factors, and prevent recurrence.

1.General processing

(1) Bed rest is needed during the acute phase. Children are encouraged to drink more water to increase urine output. Girls should also be mainly clean and hygienic.

(2) Encourage children to eat and provide enough calories, rich protein and vitamins to enhance the body's resistance.

(3) Symptomatic treatment: For children with high fever, headache, and low back pain, antipyretic pillows should be given to relieve symptoms. For those who have obvious symptoms of urinary tract irritation, they can be treated with anticholinergic drugs such as atropine and anisodamine or oral sodium bicarbonate. liquid. To reduce the symptoms of urinary tract irritation.

2.Antibacterial treatment

Principles for the selection of antibiotics: Infection site: For pyelonephritis, drugs with high blood concentration should be selected, and for cystitis, drugs with high urine concentration should be selected. Route of infection: For people with ascending infection, sulfa drugs are preferred. Such as fever and other systemic symptoms are obvious or a blood-borne infection, penicillins, aminoglycosides or cephalosporins are often used alone or in combination. According to the results of urine culture and drug sensitivity test, antibiotics were selected in combination with clinical efficacy. The drug should have a higher concentration in the kidney tissue, urine and blood. The selected drug has strong antibacterial ability, broad antibacterial spectrum, and it is best to use a powerful fungicide, and it is not easy for bacteria to produce drug-resistant strains. Drugs with little damage to renal function.

(1) Treatment of symptomatic UTI: For simple UTI, after urinary bacterial culture, compound sulfisoxazole (SMZCo) is the first choice, according to SMZ 50mg / (kg.d), TMP 10mg / (kg.d) ) Calculated, divided into two oral administrations for 7 to 10 days. After the urine bacterial culture results come out, antibacterial drugs are used for the drug sensitivity test results.

For children with upper urinary tract infection or urinary tract malformation, two antibacterial drugs are generally selected after bacterial culture. For newborns and infants, use ampicillin 75 ~ 100mg / (kg.d) intravenously and add cefotaxime sodium 50 ~ 100mg / (kg.d) intravenously for 10 ~ 14 days. After 1 year old, use ampicillin 100 ~ 200mg / (kg.d) Slow intravenous drip. The course of treatment is 10 to 14 days. Urine bacterial culture should be sent for 3 consecutive days after the start of treatment. If the urine culture is negative after 24 hours, it means that the drug used is effective, otherwise the drug is adjusted according to the results of the urine culture sensitivity test. Urine culture was performed one week after the drug was stopped.

(2) Treatment of asymptomatic bacteriuria: Simple asymptomatic bacteriuria generally does not require treatment. However, if patients with urinary tract obstruction, VUR or other urinary tract malformations, or previous infections that leave old scars on the kidneys, the above-mentioned antibacterial drugs should be actively selected for treatment. The course of treatment is 7 to 14 days, followed by prevention with small doses of antibacterial drugs until the urinary tract polarity is corrected.

(3) Treatment of recurrent UTI: There are no two types of recurrent UTI, namely relapse and reinfection. Relapse is caused by the original infection of the bacteria is not completely killed, the bacteria reproduced and reproduced in an appropriate environment, the majority of children with relapse occurred within 1 month after treatment. Redrying means that the last infection has been cured, and this time UTI was reinitiated by a different bacterium or strain. More work is more common in girls. Most often occur within 6 months after stopping the drug.

The treatment of recurrent UTI is treated with 2 kinds of antibacterial drugs after urinary drama culture. The course of treatment is 10-14 days, and then it is maintained with a small dose of medicine to prevent recurrence.

3. Actively correct urinary tract malformations

4.Local treatment of UTI

Intravesical fluid infusion is often used to treat patients with refractory chronic cystitis who have failed systemic administration.

Prevention of Urinary Tract Infections

1. Keep the vulva clean. (1) Baby girls should change diapers in time after urinating and washing the perineum and buttocks. The diapers used must be clean. Children after the age of l, both men and women, should wear concealed pants and do not sit on the ground to avoid vulvar and urethral infections. (2) Adults should wash the vulva once a day, change their underwear frequently, wipe the anus after stool, and avoid bringing anal dirt to the urethral opening from front to back. (3) Disable the sitting bath If you sit in the bathtub and take a bath, the sewage will easily infiltrate the urethra and cause infection. Because women's urethra is short and wide, the urethra is close to the vagina and anus, so special attention should be paid.

2. Pay attention to sexual hygiene. Causes of urinary tract infections, poor sexual hygiene habits are more common, the genital, vaginal, and urethral germs of a man and woman are easily transmitted to each other, and they are also easily infected. Therefore, before sexual life, external genitals should be washed. If contraceptives are used, they should be cleaned or disinfected. Before and after intercourse, you should urinate once. In addition, quit masturbation, especially using utensils to prevent urinary tract infections and injuries.

3. Prevent full urine. (1) When you have a urge to urinate, urinate in time, do not urinate, and empty your bladder every night before going to bed. (2) It is advisable for women who are pregnant for more than 5 months to sleep in the left and right sides to prevent the uterus from compressing the ureter and causing poor urine flow. (3) Actively treat diseases that cause urinary tract obstruction, such as urinary stones, tumors, benign prostatic hyperplasia, phimosis, renal ptosis, scarring, and congenital malformations of the urinary system.

4. Remove invasive bacteria. (1) Actively treat infectious diseases, such as tonsillitis, skin curtain swelling or trauma infection, cholecystitis, pelvic inflammatory disease, appendicitis, prostatitis, dental caries infection, sinusitis, etc., take a sufficient amount of medication, thoroughly clean, and prevent germs from passing through the bloodstream , Lymphatics, etc. enter the urinary system, while killing bacteria that have invaded the urinary tract. (2) Drink plenty of water, increase urine volume, make the urine continuously flush the urinary tract, expel bacteria and toxins as soon as possible, and keep the urinary tract clean.

5. Radical change prevention. (1) Thorough treatment: Patients who have been found to have urinary tract infections should take adequate medication within a sufficient course of treatment, and should not be taken lightly. Intermittent treatment or premature discontinuation of the drug may lead to chronic delay. Generally, after the symptoms completely disappear and the urine test returns to normal, the medication should be continued for 3 to 5 days, and the urine should be reviewed once a week after stopping the drug. If there are no abnormalities for more than 3 consecutive times, the basic cure can be considered. (2) Finding the chronic cause: chronic patients should look for the cause of unhealing, and see if there is a urinary tract obstruction or other infectious diseases, especially infectious diseases of the urethral opening; whether there are chronic consumables that cause the body's resistance to decrease Diseases such as diabetes, liver disease, tumors, tuberculosis, other kidney diseases, etc .; whether immunosuppressive drugs such as prednisone, Kunming mountain begonia, penicillamine and anti-tumor drugs are still being taken in the near future; whether the medication is illegal in violation of doctor's orders, etc. Wait. Then targeted prevention and (3) long-term follow-up observation: the complete cure of chronic urinary tract infections is a long-term matter, and follow-up observation should be performed. If the symptoms reappear within 6-9 weeks after discontinuation of the drug, it should be regarded as re-infection or recurrence of the original disease, and the drug should be continuously recruited for about six months. Urine should be rechecked monthly for half a year after discontinuation of the drug. Immediate treatment should be performed for signs of relapse to prevent the disease from evolving to the end and becoming uremia.

6. Suitable for movement. Strengthening physical exercise and physical fitness are important aspects of preventing urinary tract infections. Once infected, in the acute phase of fever and abnormal urine tests, you should rest in bed. During the recovery period, you must participate in moderate physical activities to avoid physical weakness and prolonged healing. The way you move can vary from person to person, but you should not be overly tired.

7. Food and Drug Prevention. (1) Fry or soak with plantain, dandelion, honeysuckle, wild ai, white grass root, etc., and often drink on behalf of tea. (2) 9 grams of loofah seeds, roasted and ground, and served with rice wine, once or twice a day. (3) Mung bean clothing or mung beans, boiled juice service (4) 60 grams of silver flower, add 120 grams of white sugar and fry, and drink frequently. Or honeysuckle 120 grams, decoction. (5) 15 grams of thistle, 15 grams of malan root, decoction. ^[1]