Urinary tract infection in children

Introduction to urinary tract infection in children Urinary tract infection (UTI), referred to as urinary sensation, refers to the invasion of the urinary system by pathogenic microorganisms, which multiply in the urine and invade the urinary tract mucosa or tissue to cause an inflammatory reaction. Divided into the urinary tract and lower urinary tract infection The former refers to pyelonephritis, and the latter refers to cystitis and urethritis. The upper urinary tract infection is more harmful, with the highest incidence of infants and young children. Repeated infection can form renal scars, and severe cases can cause secondary hypertension and chronic renal failure. basic knowledge Sickness ratio: 1%-3% Susceptible people: young children Mode of infection: non-infectious Complications: sepsis, children with high fever, hypertension, chronic renal failure

Causes of urinary tract infection in children

Bacterial infection (30%):

Escherichia coli accounts for 75% to 90%, followed by Klebsiella pneumoniae, Proteus, Aeromonas and Alcaligenes. In recent years, the proportion of Gram-positive cocci is increased, such as Streptococcus mutans and Staphylococcus, operated by instruments. The bacteria that induce urinary sensation may be intestinal bacteria and Pseudomonas aeruginosa. The urinary sensation may be more than one in the urinary tract obstruction, structural abnormalities, urinary calculi, vesicoureteral reflux and neurogenic bladder. Mixed infection of bacteria,

Virus infection (30%):

When the body's immunity declines poorly, some viral families cause infections, especially adenoviruses can cause hemorrhagic cystitis.

Fungal infections (25%):

May be secondary to diabetes in the treatment of indwelling catheterization, immunodeficiency disease or steroids, broad-spectrum antibiotics or other immunosuppressive agents.

Pathogenesis

Mainly through the ascending and bloodstream infections, direct invasion of adjacent organ infections is rare, and the normal urinary tract has anti-infective effects through the following mechanisms:

1 regular urination to wash the bacteria out of the urethra;

2 urine has IgA, lysozyme, organic acid and other antibacterial substances;

3 Secretory IgA produced by the mucosa of the urinary tract and adhesion molecules secreted by the epithelial cells of the bladder mucosa can effectively reduce the adhesion of bacteria, so only when the cause exists, it is the cause of urinary sensation.

Ascending infection

Normal pediatric urethra has a little bacteria. When the body's resistance is reduced or the urethral mucosa is damaged, the bacteria can invade or rise along the urethra to cause bladder, renal pelvis and renal interstitial infection. Normal ureteral peristalsis can inject urine into the bladder, and the girl's urethra is short. There are more opportunities for ascending infection than boys. Infants with diapers and vulva are easily contaminated by feces. This is one of the reasons why infants and young children are prone to ascending infections. The following factors can promote ascending infections:

(1) Pediatric anatomy and physiology characteristics: Pediatric ureter is long and curved, the wall muscle muscle elastic fiber is incomplete, the creeping power is weak, easy to expand, and the urine flow is not smooth.

(2) vesico-ureteral reflux (VUR): ureteral abdominal segment, pelvic segment and bladder segment, normal ureter enters the bladder at an obtuse angle, inward, downward into the bladder wall with a certain degree of slope and length The ureteral bladder junction is composed of a muscle fascia sheath. The ureteral bladder opening is obliquely fissure-like and acts as a valve. When the ureter enters the bladder, the angle changes, the stroke in the bladder wall is too short, and the number of annular and longitudinal muscle fibers at the end of the ureter Congenital anomalies with abnormal distribution or ureteral bladder opening, and neurogenic bladder caused by spinal meningocele can cause ureteral bladder reflux, immature ipsilateral urethral nerve development in infancy, during bladder filling and urination Detrusor hyperfunction, so that the intravesical pressure increased, changing the anatomical relationship between the bladder wall and the ureter junction also caused VUR, but for the temporary, urinary reflux is divided into 5:

Level 1I: reflux is only seen in the ureter,

Grade 2II: reflux to the renal pelvis, renal pelvis,

Grade 3III: mild to moderate dilatation and distortion of the ureter, moderate dilatation of the renal pelvis, no dull or mild dullness of the ureter,

Grade 4IV: Moderate expansion of the ureter, the dome of the dome disappears completely.

5V grade: significant expansion and distortion of the ureter, significant expansion of the renal pelvis and renal pelvis, most of the renal pelvis does not see nipple pressure, the harm of urine reflux is that it can cause recurrent urinary sensation caused by renal scar, and, above the level III urine The flow may also cause intrarenal reflux and renal interstitial damage due to excessive pressure in the renal pelvis, and both may cause chronic renal failure at the same time or separately.

(3) Other congenital malformations and urinary tract obstruction: such as stenosis of the ureter and ureteral junction, hydronephrosis, posterior urethral valve, polycystic kidney disease, etc. can cause poor drainage and secondary infection, in addition, can also be caused by a neurogenic bladder, Stones, tumors, etc. cause obstruction.

(4) Pathogenic bacteria: The pathogenicity of pathogenic bacteria is also the main factor affecting urine sensation. Taking Escherichia coli as an example, its bacterial antigen and capsular antigen K are necessary conditions for determining the pathogenicity of Escherichia coli urinary tract. In addition, there are many P-pilus on the surface of Escherichia coli, which can express adhesin and can specifically bind to specific receptors on the surface of urinary tract epithelial cells, so that the cells adhere closely to the urinary tract epithelium and avoid being washed by urine. , can be caused by local reproduction to cause ascending infection.

2. Blood infection

In the case of bacteremia caused by sepsis or other lesions, bacteria enter the renal cortex and renal pelvis through the bloodstream, causing urinary sensation, and blood infections are more common in newborns.

Pediatric urinary tract infection prevention

Emphasize the importance of urinary screening, timely detection of patients, and timely treatment. Develop a good habit of drinking more water, do not urinate, and keep the genitals clean. Strictly grasp the indications for insertion of the catheter, and try to avoid urinary tract examination. For patients with frequent recurrent urinary tract infections, a thorough examination should be performed to make a diagnostic evaluation, except for urinary tract obstruction and vesicoureteral reflux.

Pediatric urinary tract infection complications Complications sepsis children with hyperthermia hypertension chronic renal failure

Can cause febrile seizures, sepsis, repeated infections can cause chronic hypertension and chronic renal failure. Complications of urinary tract infections are renal papillary necrosis, peri-renal inflammation and peri-renal abscess, infectious kidney stones and Gram-negative bacilli sepsis.

Symptoms of urinary tract infection in children Common symptoms Urinary urinary frequency repeated infections chills High fever urinary incontinence Convulsions Kidney area Sickness Pain Elevation fast sepsis

Due to age and urinary sensation, there are three main manifestations: pyelonephritis, cystitis and asymptomatic bacteriuria.

1. Pyelonephritis: Infants and young children account for the majority, with systemic infection symptoms as the main performance, often more than 38.5 °C fever, high fever can have convulsions or chills, but also general malaise, wilting, pale complexion, vomiting, nausea , diarrhea, older children report flank or low back pain, kidney area sputum pain, neonatal manifestations such as sepsis, weight loss, feeding difficulties, jaundice, irritability, fever or body temperature does not rise.

2. Cystitis: mostly elderly girls, frequent urination, urgency, difficulty urinating, urinary incontinence, lower abdominal discomfort, pain in the suprapubic area, symptoms of urinary incontinence, sometimes odor in the urine, genital eczema, cystitis generally not Causes fever.

3. Asymptomatic bacteriuria: Asymptomatic bacteriuria refers to urine culture in children, but no clinical symptoms of any infection, almost all girls, but if not treated may develop symptomatic urinary tract infection, patients with more infections Or the clinical symptoms of urinary tract stimulation, combined with urine routine, urine culture colony count can make a diagnosis.

Pediatric urinary tract infection check

Blood test

Acute pyelonephritis often has a significant increase in the total number of white blood cells and neutrophils, an increase in erythrocyte sedimentation rate, C-reactive protein > 20 mg / L, the above experimental indicators are more normal in cystitis.

2. Urine routine examination

In the middle of urinary centrifuge examination, white blood cells 5 / Hp suggest urinary tract infection, if you see white blood cell cast, suggest pyelonephritis, renal papillary or cystitis can have obvious hematuria, severe urinary tract inflammation, there may be transient protein Urine, some sick children may have hematuria or terminal hematuria.

3. Bacteriological examination

Urine culture is an important evidence for the diagnosis. It is required to do before the application of antibiotics. Do not drink more water before urinating. In the process of urine retention, it should be strictly operated according to routine operation to avoid urine pollution. Urine culture can be contaminated by bacteria in the anterior urethra and urethra. Therefore, it is necessary to do clean middle-stage urine culture and colony count before treatment. If the colony count is 100,000/ml, it has diagnostic significance, and 10,000-100,000/ml is suspicious, but there are patients with urinary tract irritation. Urinary white blood cells are significantly increased, urine culture colony counts of 1000 to 10,000 / ml should also consider the diagnosis of urinary sensation, in addition, some Gram-positive cocci, such as Streptococcus mutans, slow division, such as 1000 / ml can also be diagnosed Urinary sensation, for infants and newborns, as well as children who have difficulty urinating and have difficulty in urinary bladder, can perform pubic bladder puncture culture. Positive culture has diagnostic significance. If urine for bacteria culture cannot be submitted in time, it should be temporarily Put it in the refrigerator at 4 °C, otherwise it will affect the result. There is fever and urine induction at the same time to do blood culture. A large amount of diuretic or antibacterial therapy has been applied, which will affect the results of urine culture. If the urine culture is positive, the drug should be tested for drug sensitivity. Guide treatment.

4. Urine direct smear to find bacteria

Use a drop of evenly fresh urine to dry on a glass slide, stain with methylene blue or gram, and see 1 bacteria per field in high magnification or oil mirror, indicating that the count of urine colonies is >100,000/ml, according to Gram staining and bacterial morphology of urinary sediment smear can be used as a reference for drug treatment.

5. bacteriuria auxiliary examination

Urine nitrite reduction test can be used as screening test, the positive rate can reach 80%.

6. Other inspections

Other laboratory indicators of tubular damage, urinary 2-mG, increased urinary N-acetyl--D-glucosidase (NAG), and decreased osmolality suggest pyelonephritis.

7.B-ultrasound

It can detect the abnormal structure of the urinary system and the function of bladder excretion, and whether there are stones, obstruction, residual urine and other causes of infection.

8. X-ray inspection

Intravenous pyelography can show whether the urinary system has congenital malformations (such as heavy kidney, polycystic kidney disease, etc.), hydronephrosis and its extent, understanding the size of the kidney, and whether there is evidence of chronic inflammation and renal scarring such as renal pelvis and renal pelvis deformation. The first urinary induction at the age of 5 was performed for excretory cystography to detect urinary tract stenosis and posterior urethral valve.

9. Nuclide check

Renal static imaging with 99mTc-Dimercaptosuceine acid (DMSA) can be used as a reliable indicator for the diagnosis of upper urinary tract infection. The sensitivity and specificity for the detection of pyelonephritis are above 90%. In the pyelonephritis, the outline of the kidney is normal. Due to the inflammatory cell infiltration of the renal parenchyma, renal interstitial edema, and necrosis of the renal tubular cells, the DMSA is reduced, resulting in a sparse area of the isotope distribution of the lesion. When the inflammation is dissipated, the sparse area can disappear. In chronic pyelonephritis and renal scar formation, the DMSA in the lesion is less ingested, and the kidney shape can be reduced due to scar contraction or a wedge-shaped defect area.

Diagnosis and diagnosis of urinary tract infection in children

Diagnostic points

1. Clean mid-stage urine test: white blood cells 5 / Hp in the microscopic examination, or have urinary symptoms.

2. Mid-stage urine culture: colony count 100,000/ml.

3. If there is no one, the middle part of the urine culture should be done again. The same bacteria is still 100,000/ml, which can be diagnosed. It can be called asymptomatic bacteriuria. According to the leukocytic tube type, the total number of white blood cells and neutrophils are increased. Increased erythrocyte sedimentation rate, elevated C-reactive protein, suggesting pyelonephritis, imaging DMSA examination, confirming the presence of pyelonephritis, and understanding the extent and extent of inflammation. Patients with upper urinary tract infection should also have a urinary system B-ultrasound, <5 years old The child should be treated with excretory cystography (2 to 3 weeks after urinary sensation control) to understand the presence or absence of UVR or urinary tract urinary tract urinary tract sensation, without urinary tract structure and/or dysfunction. It is a simple urinary sensation; the urinary sensation with structural and/or dysfunction is a complex urinary sensation, which is prone to recurrence or repeated infection, resulting in the consequences of hypertension and chronic renal failure.

Differential diagnosis

Infants and young children with acute pyelonephritis often have symptoms of acute infection and poisoning, but lack special symptoms of urinary system. Therefore, in the diagnosis of febrile diseases, the possibility of urinary sensation should be guarded, and attention should be paid to the identification of acute infections in other systems. Acute pyelonephritis may be associated with sepsis, especially in neonates and those with obstructive nephropathy. Therefore, patients with obvious symptoms of infection and blood leukocytes 20×109/L25×109/L should be cultured. In addition to urinary sensation, there may be temporary leukocytosis in the course of acute glomerulonephritis, but hematuria, edema and hypertension; acute interstitial nephritis and lupus nephritis also have leukocyteuria, which should be combined with clinical symptoms and related examinations. For differential diagnosis, no effect on general antibacterial therapy and urinary tract culture without multiple bacterial growth, should be combined with chest X-ray, OT test, urine sediment to find acid-fast bacilli, tuberculosis culture and intravenous pyelography, etc. except for urinary tuberculosis , tsutsugamushi disease and children without good health care, phimosis, perineal inflammation may also have frequent urination, urgency symptoms, but urinary white blood cells are normal or only slightly increased, Culture results do not meet the sense of urine, after deworming, care and strengthen the vulva local treatment can relieve symptoms and do not need an oral antibiotic.

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