URINARY TRACT INFECTIONS - UTI
 
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URINARY TRACT INFECTIONS

 

DEFINITION:

Urinary tract infections (UTI) are characterized by the presence of significant numbers of bacteria in the urine.

EPIDEMIOLOGY:

  • incidence:
    • females: 3.0 - 28/1000
    • males: 1.5 - 7/1000
    • most common disorder of the kidneys and urinary tract in childhood
  • risk factors:
  • 1. Sex
    • F > M (2:1)
  • 2. Anatomical defects
    • obstructive lesions
    • posterior urethral valves (PRV)
    • urolithiasis
  • 3. Functional voiding disturbances
    • uncontrolled bladder contractions (maturational defect)
    • neurogenic bladder
    • constipation (with secondary bladder dysfunction)
  • 4. Infants
    • M > F
    • uncircumcised under 3 months of age
  • 5. Residual urine
    • "holding-on" behaviour
    • F > M
    • squatter, squirmer, dancer, starer

    • PATHOGENESIS:

      1. Pathogen (%)

    • E. coli (72%)
    • Klebsiella-Enterobacter (16.5%)
    • Proteus (5%)
    • Staphylococcus (5%)
    • Others i.e., Pseudomonas sp. (1.5%)

    CLINICAL FEATURES:

    1. UTI

    1. Neonates

    • nonspecific - loss of appetite, nausea/vomiting, diarrhea, seizures, jaundice, lethargy, irritability, sepsis with temperature instability

    2. Toddlers

    • more specific - frequency, fever, abdominal pain but also quite nonspecific

    3. Children

    • cystitis - dysuria, frequency, urgency
    • pyelonephritis - fever, flank pain, malaise, chills
    • clinically cannot differentiate between an upper UTI (pyelonephritis) and a lower UTI (cystitis)

    2. Voiding Dysfunction

    • urgency and urge incontinence
    • day and night wetting
    • daytime frequency and incontinence
    • infrequent voiding
    • urinary retention

    3. Physical Findings

    • meatal stenosis
    • diminished anal sphincter tone
    • fecal accumulation
    • labial fusion
    • examination of the lower spine:
      • sacral genesis
      • evidence for occult spinal dyraphism
        • hairy patch, sacral dimple or tract, lipoma, abnormal gluteal fold, bony irregularity

    4. UTI Complications

    1. Vesicoureteral Reflux (20 - 35%)

    • features:
      • shrunken kidneys
      • hypertension
      • renal scarring
      • proteinuria
      • distal renal tubular acidosis (acidosis, enuresis, hyperkalemia)
    • majority of cases improve over time
    • close follow-up important even when reflux has been surgically corrected

    2. Injuries associated with chronic reflux and infections:

    1. Renal

    • calculi
    • chronic pyelonephritis
    • end stage renal disease
    • hypertension (10-30%)
    • pyelonephritic scars (10-20%)
      • tend to occur early
      • decreases in incidence with prophylactic therapy
      • scarred kidneys will tend to increase in size during adolescence

    2. Bladder

    • trabeculations
    • diverticula

    3. recurrence rate 50% with symptomatic UTI

    4. adverse reactions to long-term antibiotics

    INVESTIGATIONS:

    1. Diagnosis

    1. Quantitative Urine Culture

    • Gold Standard
    • fresh - bagged < clean-catch < midstream < catherized (#5 feeding tube) < suprapubic (best)
    • BAP and MacConkey Plates
    • UTI present if:
      • 100,000 colonies/cc (F) - bag/clean-catch
      • 10,000 colonies/cc (M) - bag/clean-catch
      • 1,000 colonies/cc - catheterized, suprapubic

    2. Screening Tests

    1. Microscopy:

    1. Bacteriuria
    • 5 org/oif
    • sen. 95%, spe. 87% - gram stain on centrifuged urine
    • if organisms seen, then the colony count will be greater than 100,000 colonies/cc
    2. Pyuria
    • 5 WBC/hpf
    • sen. 43%, PPV 75% - correlates poorly with bacteruria

    2. Dipstick:

    1. Leukocytes
    • positive
    2. Nitrites
    • bacterial conversion of nitrates -> nitrites
    • except Strep. and Pseudomonas
    • positive on centrifuged urine
    3. Urine pH
    • alkaline urine (pH > 6.5)
    • Proteus organisms split urea -> increased ammonia formation
    4. Blood
    • hematuria

    2. First Line Investigations

    • Principle: to rule out anatomical defects and vesico-ureteral reflux (VUR)

    1. Ultrasound

    • to rule out any major urinary tract obstruction in upper urinary tract
    • kidney - size, scarring, hydro-(uretero) nephrosis, urolithiasis
    • bladder - complete emptying, lack of thick walls
    • does not rule out vesico-ureteral reflux

    2. VCUG (Voiding Cystourethrogram; cystogram; MCU)

    • to rule out vesico-ureteral reflux (VUR)
      • include postvoid film to look for residual urine
    • best performed
      • 3 to 5 weeks after antibiotic therapy (if performed earlier then increased false positive (FP) results)
      • when urine is sterile
    • indications (controversial)
      • all children with first UTI

    3. Second Line Investigations

    1. Static Radionucleotide (DMSA) Scan

    • to rule out small renal scars; assess upper urinary tract function
    • best performed 4-6 weeks after the most recent infection

    2. Others

    • IVP - hydronephrosis or complex congenital anomalies
    • abdominal x-ray - to rule out small calculi and spinal/sacral anomalies
    • Ga scan - to rule out microabscesses

    3. Rare

    • Cystoscopy
    • Bladder Washout Technique

    MANAGEMENT:

    1. Education

    • bubble baths, foreign bodies, self-induced, tight jeans, wiping front-to-back

    2. Treat Underlying Disorders

    • constipation - bowel programs
    • enuresis - treat "holding-on" behaviour with increased fluids and a voiding routine
    • anatomical defects - surgery
    • VUR - medical or surgical therapy

    3. Antibiotic Therapy

    1. Acute Infection

    1. Children

    • Septra 2.5 cc po bid (less than 2 years) x 10 days
    • Septra 5.0 cc po bid (from 2.5 years) x 10 days
    • Septra 10 cc po bid (greater than 5 years) x 10 days
    • Amoxicillin 30 mg/kg/day po tid x 10 days

    2. Infants

    • Ampicillin 100 mg/kg/day IV q6h x 5-7 days
    • Gentamicin 5 mg/kg/day IV q8h x 5-7 days
    • 7 days to cover for abscesses
    • 5 days - if repeat urinalysis on day 3 shows no pyruia (inflammatory focus-abscess)
    • goal - no fever, leukocytosis, clinical improvement

    2. Prophylactic Therapy

    • Indication: greater than 3 UTI's in 6 months with no underlying cause detected

    1. Children

    • Trimethoprim-Sulfa 10 mg/kg/day of the sulfa component od at bedtime
    • Nitrofurantoin 1-2 mg/kg/day x 1-2 months then 1 mg/kg/day od at bedtime
    • treat for 3-6 months then repeat urine C&S, if UTI recurs continue with prophylactic therapy

    2. Infants (> 2 years)

    • Keflex 125 mg po od at bedtime
    • treat for 6 months then repeat VCUG, if abnormal then continue with prophylactic therapy

     

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