Urinary tract infection Mohamed Ahmed Fouad Lecturer of pediatrics Jazan faculty of medicine
Objectives To differentiate between types of urinary tract infections To recognize the epidemiology of UTI in pediatric age group To identify the causative organisms that cause UTI in pediatric age group To plan the suitable methods to diagnose UTI in pediatric age group To formulate the treatment of UTI in pediatric age group
*Paediatric urinary tract infection (UTI) is defined as a common bacterial infection involving the lower urinary tract (cystitis), the upper urinary tract (pyelonephritis), or both, causing illness in children. *Recognising and treating these infections promptly and accurately is important. *UTI is associated with pyelonephritis, which has potential sequelae, including renal scarring. Untreated UTI can also lead to hypertension and ESRD.
Upper urinary tract infections (ie, acute pyelonephritis) may lead to renal scarring, hypertension, and end-stage renal disease. Although children with pyelonephritis tend to present with fever, it is often difficult on clinical grounds to distinguish cystitis from pyelonephritis, particularly in young children (those younger than two years).
Epidemiology Girls have a 2- to 4-fold higher incidence of UTI than circumcised boys. Uncircumcised boys in the first year of life have a >8-fold higher incidence than girls or circumcised boys. At least 8% of girls and 2% of boys will have had a UTI by the age of 7 years. The overall prevalence of UTI in children <2 years of age with an undifferentiated febrile illness is approximately 5%. Prevalence is higher among white than among black infants. White girls with fever >39.0 C, without another potential source of infection, have a 30% prevalence of UTI.
Pathophysiology Colonisation of periurethral mucosa with genitourinary bacteria is hypothesised to precede UTI. Ascending infection into the bladder is the mechanism for most episodes of cystitis. In cases where vesicoureteral reflux exists, upper tract disease (pyelonephritis) may occur and can lead to development of renal damage and scarring. Bacterial infection of the bladder is more likely to occur if abnormalities in bladder emptying exist (neurogenic bladder, obstructive uropathy, and chronic constipation), allowing for incomplete elimination of bacteria from the bladder. Pathogens can also infect the urinary tract through direct spread via the fecal-perineal-urethral route.
MICROBIOLOGY Escherichia coli is the most common bacterial cause of UTI; it accounts for approximately 80 percent of UTI in children Other gram-negative bacterial pathogens include Klebsiella, Proteus, Enterobacter, and Citrobacter. Gram-positive bacterial pathogens include Staphylococcus saprophyticus, Enterococcus, and, rarely, Staphylococcus aureus. Viruses (eg, adenovirus, enteroviruses,echoviruses) and fungi (eg, Candida spp, Aspergillus spp, Cryptococcus neoformans) are uncommon causes of UTI in children Risk factors for fungal UTI include immunosuppression and long-term use of broad-spectrum antibiotic therapy, and indwelling urinary catheter.
Clinical presentation Newborns and infants with UTI have nonspecific signs, including fever, jaundice, poor feeding, irritability, vomiting, failure to thrive, and sepsis. Preschool children may have abdominal or flank pain, vomiting, fever, urinary frequency, dysuria, urgency, or enuresis. School-aged children commonly have classic signs of cystitis (frequency, dysuria, and urgency) or pyelonephritis (fever, vomiting, and flank pain). Costovertebral tenderness is unusual in young children, but may be demonstrated by school-aged children.
Fever & UTI in infancy *Fever Several studies have shown that infants and children younger than two years can present with fever as the sole manifestation of UTI. *The prevalence of UTI is greater among infants and young children with maximum temperatures 39ºC than in those with lesser degrees of fever *The presence of another potential source of fever (upper respiratory tract infection, acute otitis media) does not rule out the possibility of UTI. *This highlights the importance of obtaining urine cultures in febrile infants and young children without a definite source for fever.
Investigations
Urine specimen collection: *The standard for obtaining urine specimens in infants and younger children is suprapubic aspiration. However, catheterization is the most commonly used. *Midstream clean-catch urine specimens are adequate for older children who can provide them. *urine specimen from a sterile bag attached to the perineal area is not suitable for diagnosing UTI. The only value of it is to give ve results
Urine analysis Microscopy : the presence of 5 or more WBCs per high-power field suggests an infection. Gram stain of unspun urine may reveal organisms dipstick testing: The leukocyte esterase test The detection of urinary nitrite Negative microscopic findings for bacteria do not rule out a UTI, nor do negative results of dipstick testing for nitrite and leukocyte esterase So The gold standard for diagnosis remains the culture of a properly collected urine specimen.
We define significant bacteriuria as : 100,000 CFU/mL of a uropathogen from a clean catch specimen 50,000 CFU/mL of a uropathogen from a catheterized specimen, however, UTI may be present with 10,000-50,000 CFU/mL of a single organism.*(*patients with urinary frequency (ie, decreased bladder incubation time) are those most likely to have bacteria proliferating in the urinary bladder in the presence of low colony counts.) any uropathogenic bacteria from a suprapubic aspirate.
The rationale of imaging There is divergent clinical opinion as to whether to perform imaging in all children after first UTI or only in those who have urinary tract abnormalities that may have predisposed the child to infection (e.g., obstruction or VUR) and for complications of the infection, typically renal scarring.
*we suggest RBUS for the following children: > two years of age with a first febrile UTI(APP recommendation,2011) any age with recurrent febrile UTIs any age with a UTI who have a family history of renal or urologic disease, poor growth, or hypertension do not respond as expected to appropriate antimicrobial therapy. *RBUS can identify abnormalities of the genitourinary tract that require additional evaluation or management identify renal or perirenal abscess or pyonephrosis in children with acute UTI who fail to improve with antimicrobial therapy. *It is not reliable in detecting renal scarring or VUR
Voiding cystourethrogram Vesicoureteral reflux (VUR) is the retrograde passage of urine from the bladder into the upper urinary tract. The voiding cystourethrogram (VCUG) is the test of choice to establish the presence and degree of VUR(Approximately 40 percent of young children with a first febrile UTI have VUR). we suggest VCUG to evaluate possible VUR for: Children of any age with two or more febrile UTIs. Children of any age with a first febrile UTI who have a family history of renal or urologic disease; children with poor growth or hypertension.
Prognosis Cystitis may cause voiding symptoms and require antibiotics, but it is not associated with long-term, deleterious kidney damage. The voiding symptoms are usually transient, clearing within 24-48 hours of effective treatment. Morbidity associated with pyelonephritis is characterized by systemic symptoms, such as fever, abdominal pain, vomiting, and dehydration. Bacteremia and clinical sepsis may occur. Children with pyelonephritis may develop focal inflammation of the kidney (focal pyelonephritis) or renal abscess. Any inflammation of the renal parenchyma may lead to scar formation.
Approximately 10-30% of children with UTI develop some renal scarring; however, the degree of scarring required for the development of long-term sequelae is unknown. Long-term complications of pyelonephritis are hypertension, impaired renal function, and end-stage renal disease. Dehydration is the most common acute complication of UTI in the pediatric population. Intravenous fluid replacement is necessary in more severe cases.
Treatment Patients with a nontoxic appearance may be treated with oral fluids and antibiotics. Toxic-appearing patients must be aggressively treated with intravenous (IV) fluids and parenteral antibiotics. Most cases of uncomplicated UTI respond readily to outpatient antibiotic treatments without further sequelae Outpatient care is reasonable if the following criteria are met: A caregiver with appropriate observational and coping skills The ability to return within 24 hours The patient has no need for oxygen therapy, IV fluids, or other inpatient measures
Hospitalization is necessary for the following patients with UTI: Patients who are toxemic or septic Patients unable to tolerate adequate oral fluids or medications Infants younger than 2 months with febrile UTI (presumed pyelonephritis) All infants younger than 1 month with suspected UTI, even if not febrile
ANTIBIOTIC THERAPY: Empiric therapy Early and aggressive antibiotic therapy (eg, within 72 hours of presentation) is necessary to prevent renal damage. Decisions regarding the initiation of empiric antimicrobial therapy for UTI are best made on demographic and clinical factors. Empiric antimicrobial therapy should be initiated immediately after appropriate urine collection in children with suspected UTI and a positive urinalysis.
Empiric therapy for UTI in infants and children should include an antibiotic that provides adequate coverage for E. coli. Third-generation cephalosporins(cefixime, cefdinir, cefotaxime, ceftriaxone) and aminoglycosides (gentamicin, amikacin) are appropriate first-line agents for empiric treatment of UTI in children. However, these drugs are not effective in treating Enterococcus and should not be used as monotherapy for patients in whom enterococcal UTI is suspected (those with a urinary catheter in place, instrumentation of the urinary tract, or an anatomical abnormality). In such patients, amoxicillin or ampicillin should be added.
Hydration status and renal function should be assessed in patients who are treated with aminoglycosides. Amoxicillin and ampicillin are not routinely recommended for empiric therapy because of the high rate of resistance of E. coli. Similarly, amoxicillin-clavulanate, first-generation cephalosporins (eg, cephalexin), and TMP-SMX should be used with caution because of the increasing rates of resistance to these drugs in some communities.
For parenteral therapy initial treatment may consist of a single dose of ceftriaxone (75 mg/kg IV/IM q12-24h). If the patient has cephalosporin allergy, use gentamicin (2.5 mg/kg IV/IM as a single dose). Patients who demonstrate a satisfactory response can be switched to an oral antibacterial agent at therapeutic doses within the next 12-18 hours. Arrange for a follow-up (which is usually performed by telephone) at 24 hours to monitor the patient's response to treatment and at 48 hours to modify treatment if the results of antibacterial sensitivity studies indicate a need to change. Arrange for a follow-up visit after 7-10 days to check the patient's clinical course
The (AAP) recommends that the use of ciprofloxacin for UTI in children be limited to UTI caused by Pseudomonas aeruginosa or other multidrug-resistant, gram -ve bacteria Definitive therapy is based upon the results of urine culture and sensitivities.
In the meantime, we recommend a longer course of therapy for febrile children (usually 10 days) and a short course of therapy (three to five days) for immune competent children presenting without fever. In children whose clinical condition (other than persistent fever) worsens or fails to improve as expected within 48 hours of initiation of antimicrobial therapy, broadening antimicrobial therapy may be indicated if the culture and sensitivity results are not yet available. Most of the empiric regimens suggested above do not provide adequate coverage for Enterococcus.
Follow up A repeat urine culture 24 48 hours after beginning therapy is not needed if the child is improving and doing well.
Prevention of Urinary Tract Infection use of antibiotic prophylaxis is based on expert opinion. Antibiotic prophylaxis is more often recommended for children with high-grade reflux (grade 3-5). The current AAP guidelines do not recommend prophylactic antibiotics to prevent UTI recurrences Trimethoprim sulfamethoxazole and nitrofurantoin are approved for prophylaxis Parents of children with a history of UTI should also be advised to avoid unnecessary use of antibiotics for upper respiratory infections and otitis media.
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