Neonatal urinary tract infection

Introduction to neonatal urinary tract infections Urinary system infection (newborn) refers to the increase of white blood cells or pus cells in bacteriuria or urine caused by certain bacterial infections. Bacteria can be infected by blood circulation or directly invade the urinary tract, including pyelonephritis, cystitis and urethra. Inflammation, because the infection is difficult to be confined to a certain part of the urinary tract, clinically unable to locate, collectively known as urinary tract infection. The presence of urinary tract infections often suggests whether we have a potential urinary tract malformation (ureteral fistula, ureteropelvic junction obstruction), vesicoureteral reflux or functional bladder abnormalities. basic knowledge The proportion of the disease: the incidence rate of 0.01% - 0.04% of the newborn Susceptible people: children Mode of infection: non-infectious Complications: jaundice

Causes of neonatal urinary tract infection

Blood infection (20%):

The most common route for neonatal urinary tract infections is common in septicemia, purulent meningitis, pneumonia, impetigo, etc., and is associated with lower immune function in neonates.

Upstream infection (15%):

Neonatal urinary tract is characterized by a wide pelvis and ureter, dysplasia of the ureteral wall muscles and elastic fibers, large curvature, easy to be pressed and twisted, easy to have urinary retention and poor drainage and infection; neonatal bladder-ureteral connection The function of the valve is weak. When the filling pressure of the bladder is increased, the urine is easy to flow upwards and the infection is urinary. The urethra of the newborn baby girl is only 1cm long (sexual maturity is 3~5cm), and the external mouth is exposed and close to the anus. There are many opportunities for ascending infection. Although the urethra is longer in newborn male infants, the urine in the bladder is not easy to empty every time the urine is urinated. Especially in children with phimosis, the accumulation of dirt is also prone to ascending infection. The above characteristics are all prone to infection. the elements of.

Lymphatic infection (15%):

There is a lymphatic pathway between the intestines and the kidneys and the urinary tract. Intestinal infections in the newborn, especially Escherichia coli enteritis and Salmonella typhimurium enteritis, are prone to urinary tract infections.

Direct infection (20%):

Less common, but adjacent organs or tissues have suppurative infections, such as suppurative peritonitis, peri-renal abscess, etc., can directly affect the urinary tract infection.

Pathogenesis

1. Factors that are susceptible to urinary tract infection in newborns

(1) Physiological characteristics: Due to the use of diapers, the urethral opening is susceptible to infection by feces; the neonatal antibacterial ability is poor, and it is easy to suffer from sepsis, which causes bacterial blood to spread. In addition, some children have surface proteins produced by the bladder mucosa. The high affinity of the receptors with antigens on the bacterial cell wall makes these children more susceptible to urinary tract infections.

(2) congenital deformity and urinary obstruction: ureteral pelvic stenosis, posterior urethral valve, ureteral cyst or ectopic ureter, can cause poor drainage and secondary infection.

(3) vesicoureteric reflux: Under normal circumstances, when the urine in the bladder is filled and urinated, it can compress the ureter that walks in the bladder wall, so that the closed urine can not be refluxed. In the neonatal period, Due to the short ureter that walks in the bladder wall, the ureter is closed and regurged when urinating. When there is vesicoureteral reflux, pyelitis is easy to occur.

2. Pathogens: Most of the pathogens are Gram-negative bacteria, the bacteria are highly toxic and the bacteria produce pili, so that they can adhere to the urethra, move upwards, easily spread the pathogen to the renal parenchyma, and the treatment is incomplete or accompanied by urinary tract malformation. Bacteria are prone to drug resistance and can cause repeated infections.

3. Infection route: Newborns are mainly infected with blood. In addition, the physiological and anatomical features of the baby girl's urinary system can cause ascending infection.

4. Urinary tract infection: When bacteria enter the renal parenchyma, it causes infection and a series of inflammatory reactions. If not treated in time, the infection will lead to severe kidney damage and scar formation. In more serious cases, repeated infections are not properly diagnosed and treated. Causes severe renal scar formation and reflux nephropathy, entering end-stage renal disease.

Neonatal urinary tract infection prevention

Treatment of urinary tract infections in newborns and infants: Infant urinary tract infections are prone to kidney damage, which may be related to the sensitivity of the developing kidney to pyelonephritis in adults. In the treatment of neonatal urinary tract infections, several should be noted. problem:

1. Neonatal urinary tract infections are often blood-borne and part of systemic infections.

2. There may be a serious congenital malformation of the urinary tract.

3. In the first week of neonatal, there is often a severe vesicoureteral reflux, which gradually improves or disappears with age.

4. Newborns, especially premature infants or infants whose kidney function is not yet well-developed, have poor ability to regulate body fluid and electrolyte balance and metabolic changes, and are susceptible to kidney damage due to drugs. Therefore, attention should be paid to side effects when selecting antibacterial drugs.

5. Newborn urinary tract infections, mainly non-specific symptoms, mainly fever, convulsions, irritability, vomiting, anorexia, bloating, constipation and paralytic ileus, pale or bruising, irregular breathing, weight loss Increased, etc., sometimes jaundice, these are manifestations of systemic toxemia, Bergstrom et al reported that 1.4% of newborns have urinary tract infections, and currently advocate the use of sterilized plastic bags to collect urine specimens, if the culture is positive, then further Perform a suprapubic puncture to confirm the diagnosis.

In the treatment, ampicillin and cephalosporin can be used, generally 10 days for a course of treatment, bacteriuria recurring, within a year with a small dose of antibiotics to prevent recurrence, aminoglycosides and quinolones should not be used, If severe vesicoureteral reflux or urinary tract obstruction is found, it is easy to develop obstructive nephropathy, and should be reviewed regularly and surgically corrected if necessary.

Neonatal urinary tract infection complications Complications

Can be complicated by jaundice, convulsions, vomiting, abdominal distension, urethral obstruction may be complicated by hydronephrosis, but also complicated by renal scar and reflux nephropathy, high blood pressure and so on.

Symptoms of neonatal urinary tract infections Common symptoms Urinary infections pale complexion Newborn proteinuria bloating jaundice weight loss drowsiness convulsions diarrhea

Most of the urinary tract infections in the neonatal period are blood-borne infections, and there are systemic or local infections. The symptoms are extremely inconsistent. The systemic symptoms are predominant and lack specificity. They are characterized by fever or hypothermia, lethargy, dark skin, poor feeding, and vomiting. Or diarrhea, bloating, pale, wilting or restless and weight loss, may have jaundice or convulsions, such as due to urethral obstruction, can touch the swollen bladder in the abdomen, or hydronephrosis or ureteral hydrops Lump.

Clinical manifestation

The symptoms of urinary tract infection in neonatal period are atypical, and it is highly vigilant when clinical symptoms appear. It is reported that 100% of urinary tract infections in 100 cases have fever, 70% of which exceeds 39 °C, 60% irritability, 50 % feeding is difficult, 40% have vomiting or diarrhea. In the first few days after birth, the newborn should have blood, urine, cerebrospinal fluid routine and bacterial culture to confirm the diagnosis.

2. Laboratory examination

(1) Urine culture: The number of colonies is >100,000/ml.

(2) Urine routine: sediment white blood cells > 5 / HP, or the above clinical symptoms appear in newborns.

(3) Pathogen examination: The pubic puncture takes the urine specimen positive.

Examination of neonatal urinary tract infections

1. Urine routine examination

(1) Urine collection: The common methods for collecting urine samples from newborn urine are urine collection bag and catheterization method. The urine collection method is to clean the plastic in the vulva and disinfect (1:1000 benzalkonium bromide) with clean plastic. The bag is fixed in the vulva to retain urine, but if it is not left in the urine for 30 minutes, the catheterization method is simple and convenient, and can provide reliable culture results, especially after discarding the first 2 to 3 ml of potentially contaminated urine. Urinary puncture urine is the gold standard for urine culture urine specimens. It is rarely used clinically. The method is to take the supine position of the child. In the bladder filling state, the skin is routinely disinfected, and the pubic symphysis is a transverse wide midline. Puncture, take 1 ~ 2ml of urine to send culture, experienced can safely operate, rarely bleeding, infection and intestinal perforation.

(2) routine urine examination: sediment microscopy after urine sedimentation, such as white blood cells > 10 / high power field, or microscopic examination of non-centrifugal urine specimens, white blood cells > 5 / high power field, that should be considered for urinary tract infection, For example, there is a tubular type in the urine, especially a granular tube type, suggesting that the renal parenchyma has been damaged.

2. Urine direct smear to find bacteria

Mixing fresh urine, if more than one bacteria can be found in each field of view under the oil microscope, it indicates that the bacteria in the urine are above 100,000/ml, which is of diagnostic significance.

3. Urine culture and colony count

It is an important basis for diagnosis. The method is to take a urine specimen with a suprapubic bladder puncture. The bacteria are cultured immediately after the urine is taken. If there is bacterial growth, the diagnosis can be made. At the same time, the colony count must be made, and the colony count is >105/ml. Can be diagnosed, 104 ~ 105 / ml is suspicious, <104 / ml multi-line pollution, urine culture should be done at the same time drug sensitivity test to guide clinical treatment.

4. Other inspections

Bedside testing of fresh urine specimens is helpful in diagnosis: pyuria (boys > 10 white blood cells / l, girls > 50 white blood cells / l) have a good negative predictive value, nitrite reduction test has a good positive prediction Value, if nitrite test, leukocyte esterase screening test and microscopic examination of clean urine are negative results, can completely exclude urinary tract infection, because in the newborn often with sepsis or meningitis, comprehensive examination including blood culture And cerebrospinal fluid examination is necessary.

If the treatment is not cured or repeated, further examination should be done, including abdominal plain film, intravenous pyelography, bladder urography, ultrasound, kidney scan, kidney map, etc., to understand whether there is abnormality or dysfunction.

Radiographic examination: About 30% of urinary tract infections in infants and children have anatomical abnormalities of the urinary system. When the diagnosis and treatment of urinary tract infections is established and treated, it is important to use radiographic methods to eliminate potential anatomical abnormalities. Imaging examination is usually performed 2 to 4 weeks after infection. Common radiographic examinations include ultrasound examination of the urinary system and voiding cystoureterogram (VCUG). If necessary, renal CT or radionuclide examination should be noted. Before the VCUG examination, urine specimen examination must be sterile and preventive antibiotic treatment. VCUG plays an important role in the discovery of anatomical abnormalities and vesicoureteral reflux grading.

99mTc-DMSA (dithiosuccinic acid) renal static imaging examination, if the abnormal distribution of DMSA radioactivity is shown, can help the diagnosis of urinary tract infection in neonates, especially those who have been treated with preventive anti-infective treatment.

Diagnosis and diagnosis of neonatal urinary tract infection

According to the clinical features plus laboratory tests in accordance with the first, second or third can be diagnosed, at the same time pay attention to the presence or absence of urinary tract malformations, stenosis, stones, if the antibiotics are not effective after use or positive findings in the physical examination (kidney package Block, reproductive line and lumbosacral midline abnormalities, high blood pressure, increased serum creatinine should be immediately examined to determine whether there is urinary tract malformation and reflux.

Should be differentiated from neonatal infectious diseases, such as sepsis, intracranial infection, etc., it should be noted that the above diseases can occur blood circulation, causing urinary tract infections, relying on the high vigilance of the disease and the corresponding laboratory tests to confirm the diagnosis.

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