11

• Urinary Tract Infections


  UTI
• OUTLINE

  • Renal anatomy
  • Prevalence and etiology
  • Pathogenesis
  • Classification and clinical manifestation
  • Diagnosis
  • Treatment
  • Reference
• Prevalence and Etiology


  • The prevalence varies with age
  • Most common in children under age 1 yr
  • Asymptomatic UTIs in children over age 1 yr is~8%
  • In febrile infants is 7%
  • During the first yr of life, Male:Female ratio is 2.8 : 5.4
  • Beyond 1-2 yr, there is a female preponderance, Male:Female ratio of 1 : 10
• Uncircumcised males


  Much more common - 20% in febrile uncircumcised males under age 1 yr
• Females


  The first UTI usually occurs by the age of 5 yr, with peaks during infancy, toilet training, and onset of sexual activity
• Causative organisms


  • Escherichia coli(54–67%)
  • Klebsiella spp
  • Proteus spp
  • Enterococcus
  • Pseudomonas
  • Staphylococcus saprophyticus
  • Group B streptococcus
  • Staphylococcus aureus
  • Salmonella spp
  • Candida spp
  • Adenovirus
• Pathogenesis and Pathology


  1. Nearly all UTIs are ascending infections

  2. Fecal flora, colonize the perineum, and enter the bladder via the urethra

  3. In uncircumcised males, the bacterial pathogens arise from the flora beneath the prepuce

  4. Rarely, renal infection occurs by hematogenous spread
• Anti reflux mechanism


  • Defect in anti reflux mechanism that prevents urine in the renal pelvis from entering the collecting tubules
  • Passive anti reflux mechanism - passive compression of the ceiling of intravesical ureter against underlying detrusor muscle, intravesical ureter length and diameter
  • Active anti reflux mechanism - active shortening of the longitudinal muscle layer of transmural and submucosal ureter - active valve
• Bacterial pili or fimbriae


  • Two types of fimbriae, type I and type II
  • Type II - Mannose resistant, P fimbriae are more likely to cause pyelonephritis
  • Between 76% and 94% of pyelonephritogenic strains of E. coli have P fimbriae, compared with 19–23% of cystitis strains
• Classification


  • Pyelonephritis and cystitis
  • Focal pyelonephritis (lobar nephronia) and renal abscesses - less common
• Pyelonephritis


  Involvement of the renal parenchyma is termed acute pyelonephritis<|>No parenchymal involvement, the condition may be termed pyelitis<|>Pyelonephritic scarring<|>Acute lobar nephronia (acute lobar nephritis) - localized renal parenchymal, more commonly occurs in older children, early phase of renal abscess
• Pyelonephritis symptoms


  • Abdominal, back, or flank pain
  • Fever
  • Malaise
  • Nausea
  • Vomiting
  • Occasionally, diarrhea
• Fever


  Temperature > 39°C without another source, lasting more than 24 hr for males and more than 48 hr for females
• Newborns


  Poor feeding, irritability, jaundice, and weight loss
• Renal abscess


  Following hematogenous spread with S. aureus or pyelonephritic infection caused by the usual uropathogens<|>Most abscesses are unilateral, right sided and can affect children of all ages
• Perinephric abscess


  Diffuse throughout the capsule and is not walled off<|>Contiguous infection in the perirenal area (e.g., vertebral osteomyelitis, psoas abscess) or pyelonephritis that dissects to the renal capsule<|>The most common organisms - S. aureus and E. coli<|>Abnormal findings may not be seen on urinalysis or culture
• Xanthogranulomatous pyelonephritis


  Granulomatous inflammation with giant cells and foamy histiocytes<|>As a renal mass or an acute or chronic infection<|>Renal calculi, obstruction, and infection with Proteus spp. or E. coli<|>Usually requires total or partial nephrectomy
• Cystitis


  Only bladder involvement<|>Dysuria, urgency, frequency, suprapubic pain, incontinence, and possibly malodorous urine<|>Does not cause high fever and does not result in renal injury
• Types of cystitis


  • Uncomplicated cystitis - limited to the lower urinary tract, children older than two years with no underlying medical problems or anatomic or physiologic abnormalities
  • Complicated cystitis - Coexisting upper UTI, multiple-drug resistant uropathogens, or hosts with special considerations (Anatomic or physiologic abnormality of the urinary tract, indwelling bladder catheter, malignancy, diabetes)
• Acute hemorrhagic cystitis


  Uncommon in children<|>E. coli, adenovirus types 11 and 21 (more common in boys; it is self-limiting, with hematuria lasting approximately 4 days)<|>Patients receiving immunosuppressive therapy - adenoviruses and polyomaviruses (i.e., JC virus and BK virus)<|>Eosinophilic cystitis or interstitial cystitis
• Diagnosis


  1. Suspected based on symptoms or findings on urinalysis, or both

  2. Urine culture is necessary for confirmation and appropriate therapy

  3. Ways to obtain a urine sample - toilet-trained children (a midstream urine sample), In uncircumcised males (the prepuce must be retracted), not toilet trained - a catheterized or suprapubic aspirate urine sample

  4. If the culture shows > 50,000 colony-forming units/mL of a single pathogen (suprapubic or catheter sample) and the urinalysis has pyuria or bacteriuria in a symptomatic child
• Urinalysis findings


  • Microscopic hematuria - acute cystitis
  • WBC casts
  • Pyuria - A WBC count on urinalysis above 3-6 WBCs/high-power field is indicative of infection
  • Sterile pyuria - positive leukocytes, negative culture, May occur in partially treated bacterial UTIs, viral infections, urolithiasis, renal tuberculosis, renal abscess, urinary obstruction, urethritis, inflammation near the ureter or bladder
• Refrigeration


  A reliable method of storing the urine until it can be cultured
• Other diagnostic findings


  • Leukocytosis and neutrophilia are noted on the complete blood count
  • An elevated serum erythrocyte sedimentation rate, procalcitonin level, and C-reactive protein are common
  • Bacteremia - 3–20% of patients and is most common in infants less than 90 days old and in any child with obstructive uropathy
  • Atypical features - failure to respond with in 48 hr of appropriate antibiotics, poor urine flow, an abdominal flank or suprapubic mass, non–E. coli pathogen, urosepsis, and an elevated creatinine level
• Imaging


  1. Imaging is not needed to make the clinical diagnosis of UTI or pyelonephritis

  2. Acute lobar nephronia or renal abscess - Ultrasound is the first-line, CT scan
• AAP practice parameter


  Recommends initial ultrasound of the kidneys, ureters, and bladder for children 2-24 mo with a first episode of UTI<|>VCUG is indicated only if the ultrasound study indicates hydronephrosis, scarring or other findings suggestive of reflux or obstructive uropathy, or if the patient has other atypical complex features, recurrent febrile UTI
• Treatment


  1. Acute cystitis - 3- to 5-day course of therapy with trimethoprim-sulfamethoxazole (TMP-SMX), nitrofurantoin, or amoxicillin

  2. Acute febrile UTIs - 7-14 days, oral and parental routes are equally efficacious

  3. Dehydrated, are vomiting, are unable to drink fluids, have complicated infection, or in whom urosepsis is a possibility should be admitted to the hospital for intravenous (IV) rehydration and IV antibiotic therapy - ceftriaxone, cefepime, or cefotaxime

  4. Oral 3rd-generation cephalosporins

  5. Acute lobar nephronia is treated with the same antibiotics as pyelonephritis, duration of 14-21 days

  6. Renal or perirenal abscess or with infection in obstructed urinary tracts - surgical or percutaneous drainage in addition to antibiotic therapy

  7. Long-term antibiotic prophylaxis - Neuropathic bladder, urinary tract stasis and obstruction, severe VUR, and urinary calculi
• Long term consequences


  • Kidney loss - 10–20% of cases of renal abscess
  • Arterial hypertension
  • End-stage renal insufficiency
  • The rate of renal scarring increases between days 2 and 3 of fever, number of episodes of pyelonephritis and with the grade of reflux
• Prevention of Recurrences

  • Bowel and bladder dysfunction
  • Constipation
  • Intermittent clean catheterization
  • Treat underlying causes
• References


  • Nelson Textbook of Pediatrics, 21th edition 2020
  • Up-to-date 2018