Children's urinary tract infection

　　1. Reasons why children are prone to urinary tract infections:

　　(1) Physiological characteristics:Because infants use diapers, the urethral opening is often contaminated with feces, plus poor local defense ability, it is easy to cause ascending infection, and girls with short urethra are even more so. Infants have poor antibacterial ability and are prone to bacteremia, which can lead to下行 infection.

　　(2) Congenital malformation and urinary tract obstruction:The former is more common in children than in adults, such as narrowing of the renal pelvis and ureteral junction, hydronephrosis, posterior urethral valve, and polycystic kidney can all lead to poor drainage and secondary infection. In addition, obstruction can also be caused by neurogenic bladder, stones, tumors, etc. In the Loop Medical Center, those with urethral anomalies can account for 25% to 50% of urinary tract infections.

　　(3) Vesicoureteral urine reflux (abbreviated as urine reflux):Common in the infantile period. Abroad, it is introduced that 35% to 60% of children under 10 years of age with urinary tract infection have vesicoureteral reflux, but the number of cases reported in China is very few, and further observation is needed. Under normal circumstances, the ureter runs through part of the bladder wall. When the bladder is full of urine and during urination, the bladder wall compresses this part of the ureter to close it, so that urine cannot reflux. In the infantile period, due to the short ureter running through the bladder wall, many children do not close completely during urination, resulting in reflux. Bacteria can cause infection by ascending with the reflux. The harm of vesicoureteral reflux lies in causing reflux nephropathy and kidney scar formation, which often occurs in children under 5 years old. The degree of reflux is proportional to the kidney scar. Mild reflux can disappear with age, but severe reflux often requires surgical correction. Therefore, it is of great significance to determine whether there is reflux in children with urinary tract infection for the purpose of diagnosis and treatment guidance.

　　2. Pathogenic bacteria 80% to 90% are pathogenic from enteric bacteria:In the primary primary urinary tract infection cases, the most common is Escherichia coli, followed by Proteus, Klebsiella, and Paracoccus, etc. A few are Streptococcus faecalis and Staphylococcus aureus, etc., occasionally caused by viruses, mycoplasma, or fungi. More than 90% of the Escherichia coli isolated from children with acute pyelonephritis are P-fimbriae strains, and it is believed that the adhesiveness of P-fimbriae (P-fimbriae) is the cause of the upward spread of microorganisms. Incomplete treatment or those with urinary tract structural abnormalities are more likely to produce drug resistance, leading to recurrent infections, persistent and chronic. Sometimes, due to the action of antibiotics, bacteria produce mutations, cell membrane rupture, and cannot maintain the original state, but can still survive in the hypertonic renal medulla environment. If medication is stopped too early, the bacteria can recover to its original state and cause disease. Moreover, this bacterium does not grow on general culture media but only on hypertonic, nutrient-rich culture media, so for chronic pyelonephritis, when clinical symptoms do not improve after treatment and urine culture is repeatedly negative, high osmotic culture should be performed at the same time to clarify the pathogen.

　　3. Infection pathways.① Ascending infection is more common in girls; ② Hematogenous infection often occurs in newborns and infants, commonly seen in the course of scabies, pneumonia, and sepsis; ③ A few can be caused by direct involvement of the lymphatic pathway and adjacent organs or tissues; ④ Urinary tract instrument examination can also be a route of infection.

　　1. Pyonephrosis of the kidney Pyonephrosis, also known as pyonephrosis, refers to the extensive destruction of renal parenchyma caused by suppurative infection, forming a pus cavity.It is more common in infectious hydronephrosis, renal calculi, and pyelonephritis, especially when accompanied by obstructive urinary tract lesions, making it more likely to occur. The main clinical manifestations are chronic pyuria and systemic consumption symptoms, such as fatigue, weakness, weight loss, malnutrition, anemia, and fever. Sometimes, due to the extreme narrowness or complete obstruction of the pelviureteral junction, there may be no urinary system symptoms in the later stage, and the main manifestation is a lumbar mass. However, a careful history can reveal a past history of urinary tract infection. Intravenous pyelography shows loss of renal function on the affected side, and ultrasonic examination can detect cystic masses. After treatment with antibiotics and blood transfusions to improve the general condition, nephrectomy can be performed. Due to severe adhesion and scar formation around the kidney, general nephrectomy may encounter great difficulties and may require subcapsular nephrectomy.

　　2、肾周炎肾周炎(perinnephritis)又称肾周脓肿，在儿科虽不多见，但各年龄均可发病。感染的部位在肾周围的脂肪组织，多为单侧性。病原菌常为金黄色葡萄球菌，由它处病灶通过血流、淋巴而达肾周围，尤以皮肤感染常为原发病灶，亦可由肾实质感染直接播及肾周围组织。症状轻征不一，重者起病即有高热、寒战、恶心、呕吐、腰痛及上腹痛，有时疼痛可牵及腹壁或下肢。病变刺激腰大肌，引起腰大肌痉挛而使髋关节屈曲，因而下肢不能伸直。血白细胞增高，而尿常规检查往往正常。当本病与肾盂炎同时存在时，还会有尿频及脓尿等症状。

　　B型超声波检查对诊断帮助较大、X线检查虽不能决定诊断，但有很大帮助。肾和腰大肌影像不清、脊柱向患侧弯曲，在呼吸时作肾盂造影可见肾脏固定不动。治疗主要为抗菌药物配合局部热敷或药敷及液体补充等，如有脓形成，经穿刺证实后可切开引流。

　　1、急忙尿路感染是指病程在6个月内者。症状因年龄及感染累及部位而异。年长儿与成人相似，年龄越小全身症状越明显，局部排尿刺激症状多较轻或易被忽视。

　　(1)新生儿期：多由血行感染所致。症状轻重不等，以全身症状为主，如发热、吃奶差、苍白、呕吐、腹泻、腹胀等非特异性表现。多数小儿可有生长发育停滞、体重增长缓慢。部分病儿可有抽风、嗜睡，有时可见黄疸。但一般局部排尿症状多不明显，因此要提高对本病的警惕，对原因不明的发热应及早作尿常规检查及悄、血培养以明确诊断。

　　(2)婴幼儿期：仍以全身症状为主，如发热、轻咳、反复腹泻等。尿频、尿急、尿痛等排尿症状随年龄增长逐渐明显。排尿时哭闹，悄频或有顽固性尿布疹应想到本病。偶可出现黄疸。

　　(3)儿童期：下尿路感染时多仅表现为尿频、尿急、尿痛等尿路刺激症状，有时可有终末血尿及遗尿，而全身症状多不明显。但上尿路感染时全身症状多较明显，表现为发热、寒战、全身不适、可伴腰痛及肾区扣击痛。同时可伴有排尿刺激症状。部分病人可有血尿，但蛋白尿及水肿多不明显。一般不影响肾功能。如治疗不彻底或反复发作或有尿路梗阻、畸形等其它因素者可转为慢性。

　　2. Chronic urinary tract infection refers to a course of 6 months or more, with a prolonged illness.The severity of symptoms varies, ranging from no obvious symptoms to renal failure (first appearing as impaired concentrating function). Recurrent episodes may manifest as intermittent fever, lumbago, fatigue, weight loss, progressive anemia, and so on. Local lower urinary tract irritation symptoms may be absent or intermittent. Pyuria and hematuria may be present or not obvious. Children often have urinary reflux or congenital urinary tract structural abnormalities. B-ultrasound examination or intravenous pyelography may show renal scars. Early correction can reduce renal damage.

　　Acute urinary tract infection can usually be rapidly recovered with reasonable antibacterial treatment, but half of the patients may have recurrence or reinfection. In chronic cases, 1/4 can be cured, and some patients may develop renal insufficiency for many years, especially in those with congenital urinary tract abnormalities or urinary tract obstruction. If not corrected in time, the prognosis is poor.

　　1. Urine samples should be collected after washing the vulva and then rinsed with 1:1000 fen洁尔灭. Leave the midstream urine for testing. This method is simple and easy to perform, and is currently the most commonly used method for urine collection. For infants, a sterile plastic bag can be fixed to the vulva to collect urine, but if no urine flow is collected within 30 minutes, it should be disinfected again. Catheterization carries the risk of introducing bacteria, and it is generally best to avoid it. Suprapubic bladder puncture is reliable because it is performed under completely sterile conditions, and can be used for midstream urine or catheterized results that are suspicious. This method is simple and safe, and blood in urine within 24 hours after surgery is only 0.6%.

　　2. If the leukocyte count in the clean midstream urine sediment is greater than 5/HP, it should be considered a possible urinary tract infection. If leukocytes are aggregated in clumps or if there are leukocyte casts and proteinuria, the diagnostic value is even greater. The latter two can indicate kidney involvement, but the detection of leukocytes alone is still not sufficient to diagnose upper urinary tract infection.

　　3. Urine culture and colony counting are important diagnostic criteria for this disease. Although the normal bladder is free of bacteria, there may be contamination with foreign bacteria during urination. In healthy children, 60% to 70% of midstream urine cultures may show bacterial growth, and 38% of catheterized cultures may have bacteria, but the colonies are relatively few. Therefore, relying solely on the presence or absence of bacterial growth as a diagnostic criterion often leads to errors, and it is necessary to perform colony counting simultaneously. A colony count of 100,000/ml or more can be diagnosed as urinary tract infection, 1 to 100,000/ml may be suspected, and less than 10,000/ml is usually contamination. Girls whose second urine culture colonies are all above 100,000/ml and are of the same strain can be diagnosed more reliably. Boys should consider the diagnosis of pyuria if the urine sample is uncontaminated and the colony count is above 10,000/ml. Fresh urine is important for culture, and if immediate culture is not possible, it should be placed in a 4℃ refrigerator immediately.

　　4. Direct smear of urine to find bacteria: Use one drop of mixed fresh urine, place it on a glass slide, dry it, and stain it with methylene blue or Gram stain. If more than one cell can be found under the oil lens, it indicates that the bacteria in the urine are above 100,000/ml. This method is simple and rapid, has certain reliability, and is significant for diagnosis.

　　5. The auxiliary examination of bacteriuria commonly used includes nitrate reduction test, which can be used as a screening test for the disease, with a positive rate of 80% to 90%. This method is simple, reliable, and has no false positives, but may be negative if there is a lack of nitrates in the urine; with large diuresis or the use of antibiotics.

Urine tract infections are often due to poor gasification of the bladder, resulting in damp-heat, or due to blood stasis, etc., and can be eaten more. clear heat and promote diuresisfoods such as loofah,. Mung beanFu Ling, raw licorice can clear heat, and can be used in combination. Strengthen physical exercise in daily life, prevent colds, and reduce the chance of infection. Maintain a cheerful spirit. When Qi and blood are smooth, all diseases will stay away from you..

　　The key to the treatment of this disease lies in actively controlling infection, preventing recurrence, eliminating precipitating factors, correcting congenital or acquired urinary tract structural abnormalities, and preventing renal damage.

　　1. General treatment for acute infections should include bed rest, increased fluid intake, frequent urination to reduce the time bacteria stay in the bladder. Girls should pay attention to the cleanliness of the vulva and actively treat pinworms.

　　2. Antimicrobial therapy should be early and aggressive. Drug selection is generally based on:

      ① Infection site: For pyelonephritis, drugs with high blood concentrations should be chosen, while for lower urinary tract infections, drugs with high urine concentrations such as furan or sulfonamides should be chosen;

　　② Urine culture and drug sensitivity results;

　　③ Drugs with minimal renal damage. Acute primary infections are treated with the following drugs, with symptoms improving and bacteriuria disappearing within 2 to 3 days. If symptoms do not improve or bacteriuria persists after 2 to 3 days of treatment, it often indicates that the bacteria may be resistant to the drug, and an early adjustment should be made. Combination of two drugs may be used if necessary.

　　(1) Sulfonamide drugs: Due to their strong antibacterial effect on most Escherichia coli, high solubility in urine, and low resistance, they are inexpensive and often the first choice for initial infections. The common preparation is sulfamethoxazole (SME), which is often combined with the synergist trimethoprim (TMP) (i.e., co-trimoxazole SMZco). The dosage is 50 mg/(kg·d) taken twice a day. The general course of treatment is 1 to 2 weeks. To prevent crystallization in the urine, adequate fluid intake is recommended, and caution should be exercised in cases of renal insufficiency.

　　(2) Pipemidic acid (PPA): Effective for urinary tract infections caused by Escherichia coli due to its high excretion rate in urine, resulting in significant efficacy. Suitable for various types of urinary tract infections. Dosage is 30 to 50 mg/(kg·d), taken orally in 3 to 4 divided doses. Side effects are rare, with mild stomach discomfort possible. Caution should be exercised in children.

　　(3) Furazolidone: Has a wide range of antibacterial activity, has a significant effect on Escherichia coli, and is not easy to develop drug resistance. The dose is 8～10mg/(kg·d), taken orally in 3 divided doses. It is prone to gastrointestinal reactions and is recommended to be taken after meals. It can also be used in combination with TMP. It is more suitable to choose furazolidone for persistent infections that require continuous treatment for 3 to 4 months.

　　(4) Norfloxacin; It is a fully synthetic broad-spectrum antibacterial drug of the quinolone class, with strong antibacterial activity against Gram-negative and Gram-positive bacteria. The dose is 5～10mg/(kg·d), taken orally in 3～4 divided doses. Due to its strong antibacterial activity, long-term use can lead to dysbacteriosis, and attention should be paid when using it. Generally not used in children.

　　(5) Ampicillin,先锋霉素：Both are broad-spectrum antibiotics with good antibacterial activity and are often used for the treatment of urinary tract infections. Kanamycin and gentamicin have good antibacterial activity, but due to their nephrotoxicity and adverse effects on hearing, they should be used with caution.

　　3. Treatment course During acute infection, if the selected antibiotic is sensitive to bacteria, a general 10-day course of treatment can control the infection in the vast majority of patients, and a 5-day course may be sufficient if there is no fever. Regular follow-up should be conducted annually or longer after recovery. Because most recurrences are caused by reinfection, it is not recommended to use long-term therapy for all patients. Specific recommendations are as follows:

      ① For those who do not frequently relapse, acute treatment should be given after recurrence;

　　② For those who recurrently relapse, after controlling the acute symptoms, one can take a small dose (1/3 to 1/4 of the therapeutic dose) of SMZco, furazolidone, pipemidic acid, or norfloxacin before going to bed each night, and the course of treatment can last for 3 to 6 months. For those with repeated infections or renal parenchymal damage, the course of treatment can be extended to 1 to 2 years. To prevent the development of drug-resistant strains, combined medication or alternating medication can be used, that is, each drug is used for 2 to 3 weeks and then rotated, in order to improve the efficacy.

　　4. Approximately half of children with urinary tract infections associated with various etiologies can be actively treated for urinary tract structural abnormalities. Especially in chronic or recurrent urinary tract infections, urinary tract structural abnormalities are often present at the same time, and it is necessary to actively search for and treat them as soon as possible to prevent renal parenchymal damage.