Urinary Tract Infections (UTIs) in Children
Introduction:
Urinary tract infections (UTIs) are a common condition in children, particularly in girls. UTIs can lead to serious complications if not diagnosed and treated promptly.
Incidence:
– 5-20% of children between the ages of 2 months and 2 years experience UTIs.
– Children under 2 years old often only present with fever, making it difficult to identify.
Bacteremia:
– Approximately 30% of UTIs can lead to bacteremia (bacteria in the bloodstream).
– Bacteremia can result in serious complications such as:
– Meningitis
– Septic shock
Importance of Early Recognition and Management of UTIs:
– 10-20% of children with UTIs may develop renal scarring, leading to chronic kidney disease (CKD).
– 10-30% of children with UTIs may develop hypertension (high blood pressure).
– 20-50% of children with UTIs may have accompanying urinary tract abnormalities (e.g., vesicoureteral reflux).
Classification of UTIs:
– Upper UTI: Acute pyelonephritis (inflammation of the kidney pelvis and kidney).
– Lower UTI: Cystitis (inflammation of the bladder).
Acute Pyelonephritis:
– An infection of the urinary tract caused by bacteria.
– Involves systemic inflammation and renal parenchymal damage.
– Can progress to acute and chronic cystitis, necessitating prompt management.
Cystitis:
– An infection of the urinary tract caused by bacteria.
– Does not involve systemic inflammation or renal parenchymal damage.
Causes:
– Most common bacteria causing first-time UTIs in children: Escherichia coli (E. coli) (accounts for about 90%).
– 5 common bacteria found in children with UTIs and urinary tract abnormalities:
– Enterococcus
– Pseudomonas
– Klebsiella
– Proteus
– Staphylococcus
Route of Bacterial Entry:
– Ascending: From the perineal-rectal area into the urinary tract.
– Hematogenous: Bacteria enter the body through the bloodstream.
Conditions that Facilitate Bacterial UTI Development:
– “Uropathogenic” strains: Bacterial strains capable of causing UTIs.
– P-fimbriae: Ability to adhere to the urinary tract mucosa.
– Lipopolysaccharide, hemolysin: Enhance bacterial toxicity.
Abnormalities in Defense Mechanisms:
– Abnormalities in mechanical and chemical defense mechanisms:
– Bladder mucosal abnormalities, cilia, urine pH, sphincter function…
– Obstruction: Bladder abnormalities, vesicoureteral reflux, stones, constipation…
– Sphincter dysfunction: Neurogenic bladder, overactive bladder, posterior urethral valves, pinworms…
– Changes in urine pH
– Increased urinary crystals…
Initiation of the Inflammatory Process:
– Bacteria adhere to the urinary tract mucosa:
– Damage the mucosal barrier, triggering inflammatory responses.
– Mobilize inflammatory cells to the site of injury.
– Destroy tissue.
Gold Standard for UTI Diagnosis:
– Quantitative urine culture:
Note:
– Traditional gold standard not applicable:
– Result turnaround time is approximately 3 days, while UTIs need early diagnosis and treatment.
– Not all laboratories can perform quantitative urine cultures.
– Confounding factors: culture methods, sample storage and handling time, laboratory reliability.
Urine Sample Collection for Quantitative Culture:
– Non-invasive:
– Urine bag
– Midstream urine
– Invasive:
– Urinary catheterization
– Suprapubic bladder aspiration
Analysis of Urine Culture Results:
– Non-invasive methods:
– Bacterial count >= 50 x 10^4 /ml: Possible UTI (this threshold is wider than quantitative urine culture, as it may be contaminated from the outside).
– White blood cell (WBC) count >= 10^4 /ml: Possible UTI.
– Negative bacterial and WBC counts: UTI can be ruled out.
– Leucoesterase (+): More reliable urine culture methods should be used.
– APP does not accept midstream urine testing (usually the first step).
– Urinary catheterization:
– Accuracy: 72-100%.
– Bacterial count > 10^5 /ml: Confirms UTI (95% probability).
– Bacterial count 10^4 – 10^5 /ml: Highly likely UTI.
– Bacterial count 10^3 – 10^4 /ml: Possible contamination, requires additional criteria to decide whether to repeat culture.
– Bacterial count < 10^3 /ml: Rule out UTI.
– Suprapubic bladder aspiration:
– Accuracy: 20-90%.
– Gram-negative bacteria: Confirms UTI.
– Gram-positive bacteria: Must be present in counts > 10^3 /ml to confirm UTI.
– Less frequently used.
Urine Sample Storage:
– Temperature: 4oC
– Time: 60 minutes
Other Supporting Diagnostic Criteria:
– Clinical: Clinical symptoms.
– Blood biochemistry: Blood tests to assess infection status, renal function…
– Urine biochemistry: Urine tests to assess abnormalities in urine composition.
– Urine cytology: Cytological examination to detect bacteria, white blood cells…
– Ultrasound: Ultrasound of the urinary tract to assess urinary tract structure, presence of congenital malformations…
Rapid Diagnostic Methods:
– Urine dipstick: Can detect 7-10 parameters related to UTIs.
– Nitrite:
– Gram-negative bacteria have nitrate reductase, which converts nitrate to nitrite (after 4 hours).
– Specificity: 98% (if nitrite (+) then UTI is confirmed).
– Sensitivity: 53% (if nitrite (-) then UTI cannot be ruled out).
– White blood cells:
– White blood cells have leucoesterase, which changes the color of the dipstick.
– Specificity: 78% (WBC count > 10), 67% (WBC count > 5).
– Sensitivity: 83%.
– White blood cells and nitrite:
– Specificity: 99-100%.
– Sensitivity: 60-92%.
Clinical Symptoms:
– The younger the child, the harder it is to recognize clinical symptoms.
– Children under 2 years old:
– UTI should be suspected in all children under 2 years old with unexplained fever.
– Other symptoms: vomiting, diarrhea, unexplained fussiness, poor weight gain, lethargy, excessive sleepiness, strong-smelling urine, blood in urine.
– Older children:
– Painful urination, frequent urination, urinary incontinence.
– Abdominal pain, lower back pain, positive kidney tenderness.
– Distinguishing upper UTI from lower UTI:
– Elevated WBC, CRP, PCT: Indicates systemic inflammation, suggesting upper UTI.
– Blood culture: Blood culture is required if bacteremia is suspected, which can occur in upper UTI.
Definitive Diagnosis (DD) of UTI:
– Quantitative urine culture:
– Microbiological examination: Microscopy and Gram staining, urine culture to identify the causative bacterium.
Differential Diagnosis (DD):
– For difficult cases with only fever, especially in children under 3 months old:
– Lumbar puncture (LP) to examine cerebrospinal fluid (CSF), chest X-ray, stool culture, dengue fever tests…
Supplementary Tests:
– WBC: Elevated neutrophil count indicates infection.
– NS1Ag: NS1Ag test to diagnose dengue fever.
– CRP: Elevated CRP (> 20 mg/l) after 48 hours indicates infection.
– PCT: High specificity and sensitivity, especially in children under 90 days old.
– Blood culture: Mandatory if upper UTI is suspected.
– LP: Standard practice in children under 3 months old.
– Urine culture: Mandatory if UTI is suspected and TPTNT is positive.
– Chest X-ray: Screen if no other infection site is found.
– TPTNT: Mandatory if no other infection site is found.
Initial Diagnosis of Upper UTI:
– Based on clinical symptoms and TPTNT (no need to wait for microbiology results).
Quantitative Urine Culture:
– Used for DD and treatment monitoring.
High-Risk Groups Requiring In-Depth Investigation:
1. Recurrent UTIs: 2 or more episodes of upper UTI / 3 or more episodes of lower UTI.
2. Enlarged kidney, weak urine stream: Suspected urinary tract obstruction.
3. Occurrence in boys > 4 years old: Rule out urinary tract abnormalities.
4. Poor response to treatment after 72 hours: Suspected complications or antibiotic resistance.
5. Positive blood culture: Suspected bacteremia.
6. Elevated creatinine: Suspected kidney failure.
7. Bacteria other than E. coli: Suspected urinary tract abnormalities or antibiotic resistance.
8. Abnormal urinary tract ultrasound: Further investigation needed to assess urinary tract abnormalities.
Imaging:
– Ultrasound of the urinary tract:
– Routine indication: Non-invasive, affordable.
– Purpose: Detect congenital malformations, identify obstruction location, measure kidney size, bladder status.
– Voiding cystourethrogram (VCUG):
– Invasive
– Indications: Children under 6 months old, recurrent UTIs, complex UTIs (high risk).
– DMSA renal scintigraphy:
– Static renal scintigraphy: Uses iodine 131 attached to DMSA.
– Purpose: Examine location, structure, size, shape of the kidney based on the radiation uptake of renal tubular cells.
– Performed 4-6 months after UTI: Assess renal scarring.
– Performed during UTI: Assess location and radiation uptake of the kidney.
– Cannot assess kidney function.
– Cannot differentiate new or old scarring.
– DTPA renal scintigraphy:
– Dynamic renal scintigraphy: Uses iodine 131 attached to DTPA.
– Purpose: Investigate kidney function, assess obstruction.
– Diuretic test: Helps differentiate functional obstruction from mechanical obstruction (based on half-life and renogram).
Normal renogram (renogram) consists of 3 phases:
– Phase I: Vascular perfusion phase (30-60 seconds).
– Phase II: Renal cortical uptake phase (1-3 minutes).
– Phase III: Excretion phase due to radioactive excretion.
Common Congenital Urinary Tract Anomalies:
– Vesicoureteral reflux: Urine reflux from the bladder to the ureter.
– Uretero-pelvic junction obstruction: Narrowing at the junction between the renal pelvis and ureter.
– Ureterovesical junction obstruction: Narrowing at the junction between the bladder and ureter.
– Neurogenic bladder: Abnormal bladder function due to neurological disorders.
– Posterior urethral valves: Posterior urethral valves only occur in boys, causing bladder distension, two ureters, two renal pelvises, also known as obstructive bladder / bladder diverticulum.
Vesicoureteral reflux:
– Classification: 4 grades + 1 (I, II, III, IV, *).
– Requires testing: Voiding cystourethrogram (VCUG).
Diagnostic Flowchart:
– Normal ultrasound:
– Not in high-risk group: End.
– In high-risk group: Voiding cystourethrogram.
– Normal VCUG: End.
– Abnormal VCUG: DMSA after 6 months.
– Abnormal ultrasound:
– No dilatation: Voiding cystourethrogram + other tests.
– Dilatation present: Voiding cystourethrogram.
– DMSA after 6 months.
– DTPA (+/-)
Treatment:
Acute Pyelonephritis:
– Antibiotics:
– Ceph III: Cefotaxime 100 mg/kg IV (minimum 4 days), Ceftriaxone 75 mg/kg IV (minimum 4 days).
– May be combined with aminoglycoside (within 72 hours): Gentamicin, Amikacin.
– If acute pyelonephritis + severe urinary tract dilatation:
– Intravenous injection for at least 10 days: Then switch to oral medication.
– Total duration of oral and intravenous medication = 14 days.
Assessment of Treatment Response:
– After 2 days: Negative urine culture.
– After 3 days: Complete resolution of fever.
– After 4 days: Significant decrease in CRP.
– After 5 days: Resolution of all urinary disturbances.
Criteria for Hospital Admission:
– Under 3 months old.
– Poor general condition, lethargy, systemic inflammatory response.
– Hemodynamic instability.
– Severe urinary tract dilatation.
– Premature birth, immunodeficiency.
– Outpatient treatment is not feasible or fails.
Cystitis:
– No emergency.
– Choose antibiotics excreted through the urine.
– Supportive treatment: Drink plenty of fluids, treat constipation, pinworms.
Commonly Used Antibiotics Excreted Through the Urine:
– Quinolones: Ciprofloxacin, Ofloxacin.
– Bactrim: Sulfamethoxazole/trimethoprim.
– Augmentin: Amoxicillin/clavulanate.
– Cefixime: Cefixime.
– Nitrofurantoin: Nitrofurantoin.
Indications for Prophylactic Antibiotics:
– Vesicoureteral reflux > grade III: While awaiting surgical treatment.
– Recurrent UTIs.
– Megaureter.
– Neurogenic bladder.
Dosage and Duration of Prophylactic Antibiotics:
– Once a day at bedtime.
– Dosage = 1/3 of treatment dosage.
– Use until the underlying cause is resolved.
Note:
– UTIs are a serious condition that can lead to many dangerous complications.
– If you suspect your child has a UTI, take them to a doctor immediately for prompt diagnosis and treatment.
– Follow your doctor’s instructions regarding antibiotic use and monitoring your child’s health.
Conclusion:
UTIs are a common health concern in children, and can cause serious complications if left untreated. Early recognition, accurate diagnosis, and effective UTI treatment are critical to protect your child’s health.
Leave a Reply