Urinary tract infections in children

Urinary tract infections in children are microbial inflammatory diseases of the urinary system organs without specifying a specific location. The term "urinary tract infection" is used until the localization of the inflammatory process and the etiology of the inflammation are specified. The term is valid at the first stage of the disease, when there is no evidence of kidney damage during examination of the patient, but there are signs of microbial damage to the urinary tract. The diagnosis of "urinary tract infection" is especially valid in infants and young children due to the anatomical and physiological features of the ureter (long and with a wide lumen, prone to kinks) and the features of the body's immunological reactivity, the consequence of which is the ease of infection spread.

ICD-10 codes

• N10. Acute tubulointerstitial nephritis.
• N11. Chronic tubulointerstitial nephritis.
• N11.0. Non-obstructive chronic pyelonephritis associated with reflux.
• N11.1. Chronic obstructive pyelonephritis.
• N13.7. Uropathy due to vesicoureteral reflux.
• N30. Cystitis.
• N30.0. Acute cystitis.
• N30.1. Interstitial cystitis (chronic).
• N30.9. Cystitis, unspecified.
• N31.1. Reflex bladder, not elsewhere classified.
• N34. Urethritis and urethral syndrome.
• N39.0. Urinary tract infection of unknown site.

Epidemiology of urinary tract infections

The prevalence of urinary tract infections ranges from 5.6 to 27.5%. On average, it is 18 cases per 1000 children.

Analysis of global statistics shows that in developed countries of Western Europe the problem of urinary tract infections becomes relevant from the first days of a child’s life.

Prevalence of urinary tract infections in Western European countries

Country	Year	Authors	Prevalence of IMS, %	Object of study
England	2000	Christian MT et al.	8.40	Girls up to 7 years old
			1.70	Boys up to 7 years old
Sweden	2000	Jakobsson B. et at.	1.70	Girls
			1.50	Boys (multicenter study; data from 26 pediatric centers in Sweden)
England	1999	Poole S.	5.00	Girls
			1.00	Boys
Sweden	1999	Hansson S, et al.	1.60	Multicenter study of pediatric population
Finland	1994	Nuutinen M. et al.	1.62	Girls under 15 years old
			0.88	Boys under 15 years old

Among full-term newborns, the frequency of urinary tract infections reaches 1%, and among premature infants - 4-25%. Newborns with extremely low body weight (<1000 g) have a risk of developing urinary tract infections throughout the first year of life. The manifestation of urinary tract infection in children in the first year of life is usually associated with the development of a microbial inflammatory process in the renal parenchyma (pyelonephritis). If the correct diagnosis is not made at this age and appropriate treatment is not carried out, then the probability of recurrent pyelonephritis with subsequent formation of foci of nephrosclerosis (wrinkling of the kidney) is very high.

It has been shown repeatedly that the overwhelming majority of patients with urinary tract infections are girls, with the exception of children in their first year of life: among newborns, urinary tract infections are diagnosed in boys 4 times more often. From the 2nd to the 12th month of life, urinary tract infections are equally common in boys and girls, after one year - more often in girls. By the age of 7, 7-9% of girls and 1.6-2% of boys have at least one episode of urinary tract infection, confirmed bacteriologically.

The most likely diagnosis of urinary tract infections is in children in the first 2 years of life who have a fever, the cause of which remains unclear when collecting the anamnesis and examining the child.

Frequency of urinary tract infections in children with fever

Country	Year	Authors	Prevalence of IMS, %	Object of study
USA	2002	Reddy P.P., Redman J.F.	3-10	Children in the first 2-3 months of life with fever
USA	2000	Baraff LJ.	3-4	Boys under 2 years of age with fever
			8-9	Girls under 2 years of age with fever
USA	2000	Kaplan R. L. et al.	7.5	Girls under 2 years of age with fever
Australia	1999	Haddon RA et al.	5	Children from 3 months to 3 years with fever
USA	1999	Shaw KN, Gorelik MH	3-5	Children under 4 years of age with fever
USA	1999	American Academy of Pediatrics	5	Children in the first 2 years of life with fever

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Causes of Urinary Tract Infections

Bacteriological studies have shown that the spectrum of microflora depends on many factors:

• age of the child;
• gender;
• gestational age at the time of birth of the child;
• period of the disease (onset or relapse);
• conditions of infection (community-acquired or hospital-acquired).

What causes urinary tract infections?

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Pathogenesis of urinary tract infections

Three routes of infection are discussed for urinary tract infection: ascending (or urinogenous), hematogenous, and lymphogenous.

The urinogenic (or ascending) route of infection is most common in children. The ascending route of infection is facilitated by colonization of the vaginal vestibule, periurethral area, preputial sac and distal parts of the urethra by uropathogenic microorganisms. Normally, colonization by uropathogenic flora in girls is prevented by normal vaginal microflora, represented mainly by lactobacilli, which produce lactic acid (reduce vaginal pH), and hydrogen peroxide, which creates an unfavorable environment for the growth of uropathogenic microbes.

Pathogenesis of urinary tract infections

Symptoms of urinary tract infections

Clinical signs of cystitis in children:

• frequent painful urination in small portions (dysuria);
• pain in the bladder area, tenderness on palpation in the suprapubic area;
• incomplete one-time emptying of the bladder, urinary incontinence;
• subfebrile or normal temperature;
• leukocyturia;
• bacteriuria.

Symptoms of urinary tract infections

Classification of urinary tract infections

Depending on the localization of the inflammatory process, infections of the upper urinary tract (pyelonephritis, pyelitis, ureteritis) and lower urinary tract (cystitis, urethritis) are distinguished:

• pyelonephritis is a microbial inflammatory disease of the renal parenchyma;
• pyelitis is a microbial inflammatory disease of the collecting system of the kidney (pelvis and calyces), which is rarely encountered in isolation;
• ureteritis - microbial inflammatory disease of the ureters;
• cystitis is a microbial inflammatory disease of the bladder;
• Urethritis is a microbial inflammatory disease of the urethra.

The most common types of urinary tract infections in children are pyelonephritis and cystitis.

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Diagnosis of urinary tract infections

When examining children with suspected urinary tract infection, preference is given to minimally invasive methods with high sensitivity. The difficulty of diagnosing urinary tract infection is primarily noted in young children (newborns and the first 2 years of life).

Diagnosis of urinary tract infections

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Treatment of urinary tract infections

Late initiation of adequate antimicrobial therapy in children with urinary tract infection leads to serious consequences: damage to the renal parenchyma (with possible formation of areas of shrinkage) and sepsis. Analysis of the results of scintigraphy performed within 120 hours from the start of treatment showed that antimicrobial therapy prescribed to children with fever and suspected urinary tract infection in the first 24 hours of illness allows to completely avoid focal defects in the renal parenchyma. Starting treatment at a later date (2-5 days) leads to the appearance of parenchymal defects in 30-40% of children.

How are urinary tract infections treated?