Introduction
Urinary tract infection (UTI) is one of the most common bacterial infections in children. This occurs when infection ascends from the urethra to the urinary tract.
Epidemiology
Urinary tract infections are among the most common bacterial infections in children and represent a significant global health burden. In 2021, approximately 50.17 million childhood UTI cases were reported worldwide. Urinary tract infections in children are most common during the first two years of life, accounting for approximately 75% of pediatric cases. The incidence is highest during the first year of life, with another peak occurring between 2-4 years old. Higher rates are observed among females compared to males.
Higher incidence rates were observed in North America, South America, Russia, Eastern Europe, and several regions of Asia and the Middle East. South Asia, particularly India, carries the highest overall burden, while Latin America has experienced a continuing increase in incidence. In contrast, East Asia has shown a consistent decline, with China and Southeast Asian nations reporting relatively lower incidence rates.
Etiology
Probable Pathogens
Escherichia coli is the causative agent of the majority of urinary tract infections. Other probable pathogens include Klebsiella spp, Citrobacter spp, Enterococcus spp, Pseudomonas aeruginosa, Staphylococcus saprophyticus, S aureus, and Proteus sp.
Probable Non-pathogens
Coagulase-negative staphylococci, Viridans streptococci, diphtheroids, and lactobacilli are the probable non-pathogens.
Pathophysiology
Urinary Tract Infection Pediatric_Disease Background
The most common route of urinary tract infection is the ascending spread of bacteria from the urethra to the bladder These bacteria first colonize the periurethral area before entering the urinary tract, where they can multiply and travel up the ureters, potentially causing upper urinary tract infections such as pyelonephritis.
Risk Factors
Risk factors for urinary tract infection include: Temperature ≥38°C; uncircumcised boys <1 year old; sexual activity among young girls; fecal and perineal colonization; family history of vesicoureteral reflux (VUR), pyelonephritis, or renal disease; urinary tract malformation, functional urinary abnormalities (eg VUR, neurogenic bladder), enlarged bladder; history of urinary tract infection or dysfunctional voiding; presence of a spinal lesion, abdominal mass; high blood pressure (BP); and fever of uncertain origin.
Classification
Classification of Urinary Tract Infection Based on Location
Lower Urinary Tract Infection (UTI)/Cystitis
Lower urinary tract infection is the inflammation of urinary bladder mucosa. This is rarely diagnosed in newborns and infants. Symptoms include dysuria, stranguria, frequency, urgency, malodorous urine, incontinence, hematuria, and suprapubic pain.
Upper Urinary Tract Infection (UTI)/Pyelonephritis
Upper urinary tract infection is a diffuse pyogenic infection of the renal pelvis and parenchyma. Signs and symptoms include fever (temperature ≥38°C), chills, and flank pain or tenderness with non-specific signs (eg poor appetite, failure to thrive, lethargy, irritability, vomiting, or diarrhea).
Classification of Urinary Tract Infection (UTI) Based on Clinical Presentation
Febrile Urinary Tract Infection (UTI)
Febrile urinary tract infection usually involves the upper urinary tract. Mild fever may be seen in lower UTI. This may increase the risk of renal damage.
Non-febrile Urinary Tract Infection (UTI)
Non-febrile urinary tract infection is limited to the lower urinary tract. This should be differentiated from asymptomatic bacteriuria.
Classification of Urinary Tract Infection (UTI) Based on Clinical Course
Typical Urinary Tract Infection (UTI)
A typical urinary tract infection is an infection with E coli. Symptoms do not require hospitalization and respond quickly to antibiotic therapy.
Atypical Urinary Tract Infection (UTI)
Atypical urinary tract infection is an infection with non-E coli organisms or multi-resistant bacteria. This may indicate serious illness and may have poor urine flow, abdominal or bladder mass, elevated creatinine, and septicemia. There is failure to respond within 48 hours to appropriate antibiotic therapy.
Classification of Urinary Tract Infection (UTI) According to Episode
First Urinary Tract Infection (UTI)
First urinary tract infection may indicate anatomical abnormalities.
Breakthrough Urinary Tract Infection (UTI)
Breakthrough urinary tract infection is UTI in patients on antibacterial prophylaxis due to bacterial resistance. This may be due to non-compliance or underlying urogenital anomalies.
Recurrent Urinary Tract Infection (UTI)
Recurrent urinary tract infection may be ≥2 episodes of UTI with acute pyelonephritis/upper UTI or one episode of UTI with acute pyelonephritis/upper UTI plus ≥1 episodes of cystitis/lower UTI or ≥3 episodes of UTI with cystitis/lower UTI.
Classification of Urinary Tract Infection (UTI) Based on Complicating Factors
Uncomplicated Urinary Tract Infection (UTI)
An uncomplicated urinary tract infection is an infected patient with morphologic and functional normal upper and lower urinary tracts, normal renal function, and a competent immune system.
Complicated Urinary Tract Infection (UTI)
Complicated urinary tract infection occurs in newborns with clinical evidence of pyelonephritis and in children with known mechanical or functional obstructions or upper or lower urinary tract problems.
Classification of Urinary Tract Infection (UTI) Based on Symptoms
Asymptomatic Bacteriuria
Asymptomatic bacteriuria is when bacteria are present in the bladder but do not cause symptoms due to less harmful bacteria or the body limiting its effects.
Symptomatic Urinary Tract Infection (UTI)
Symptomatic urinary tract infection presents with dysuria, suprapubic pain, malaise, or fever.
Other Urinary Tract Infections (UTIs)
Presumed Urinary Tract Infection (UTI)
Presumed urinary tract infection is diagnosed while urine culture results are pending in a patient with abnormal lab exams and clinical findings consistent with urinary tract infection.
Definite Urinary Tract Infection (UTI)
The diagnosis of a definitive urinary tract infection requires both positive results from urinalysis and culture obtained through catheterization or suprapubic aspiration (SPA). Culture results should have a presence of >50,000 cfu/mL. Acute pyelonephritis is suggested in a patient who presents with dysuria and urinary frequency associated with flank pain, high-grade fever (temperature >38.5°C), and chills. An immunocompromised patient or patient <2 months old is assumed to have acute pyelonephritis or a complicated urinary tract infection.