Nephrology

Urinary Tract Infections

Risk Factors for UTI

Females

  1. Sexual activity
  2. Bubble bath
  3. Pinworms
  4. Sexual abuse
  5. Constipation
  6. Incomplete and infrequent voiding

Males

  1. Uncircumcised males have a 5-20x greater incidence of UTIs
  2. Males and Females
  3. Reflux
  4. Catheterization
  5. Neurogenic bladder
  6. Urinary tract infections should be considered in any infant 2 months to 2 years who presents with a fever without localization. The earlier the diagnosis, the less risk of renal scarring and the earlier detection of anatomical abnormalities. In older children, symptoms will lead to evaluation for an infection.

Pathogenesis

  1. Escherischia coli. by far the most common organism causing UTIs and accounts for 85 percent of all UTIs in children. Other organism to consider are Klebsiella pneumoniae, Proteus vulgaris, Enterobacter, Staphylocoocus saprophyticus, Citrobacter, Enterococcus and Pseudomonas aeruginosa. Gram positive organism are uncommon pathogens of UTIs in children
  2. Usually are secondary to ascending infection.
  3. Once the bladder is contaminated the risk of infection is related to the emptying of the bladder and voiding habits. Incomplete or infrequent emptying will lead to bacterial overgrowth. 
  4. Reflux allows urine to reach the kidneys and develop pyelonephritis. 
  5. Obstruction anywhere along the urinary tract 

Clinical Presentation

  1. Infants-jaundice, fever or hypothermia, septic appearance, failure to thrive, abdominal distention, poor feeding, and vomiting
  2. Toddlers and preschoolers- Strong smelling urine, fever, and failure to thrive
  3. School aged and older- fever, dysuria, frequency, urgency, daytime wetting, enuresis, abdominal pain, flank pain
  4. Pyelonephritis- indirect evidence of renal infection with fever, increased ESR and CRP, increased WBCs on CBC, decreased concentrating ability of the kidney, and CVA tenderness. These changes are not specific and sensitive when DMSA scan is done to verify kidney involvement

History

  1. Positive family history of reflux
  2. Incomplete voiding, dribbling, daytime wetting
  3. Weak urinary stream

Physical Examination

  1. Growth record 
  2. Blood pressure
  3. Abdominal exam- palpating for mass. Check for CVA tenderness.
  4. Examination of external genitalia for signs of irritation, trauma, and other abnormalities
  5. Suprapubic or costovertebral tenderness is a sign of a UTI, but other findings are nonspecific.
  6. Observation of urinary stream
  7. Rectal exam to rule out impaction

Laboratory Findings

  1. Often urine will contain red blood cells, white blood cells, bacteria, and protein.
  2. Nitrite test- Best in overnight urine to allow time for bacteria to convert nitrate to nitrite in the bladder. Gram positive organisms will not give a positive nitrite test. About 50% sensitivity and 98% specific
  3. Bacteria on microscopy: 81 percent sensitivity and 83 percent specificity
  4. Leukocyte on microscopy: 73 percent sensitivity and 81 percent specificity
  5. Blood: 47 percent sensitivity and 78 percent specificity
  6. Protein: 50 percent sensitivity and 76 percent specificity
  7. Leukocyte esterase test- 83% sensitive and 78% specific. Other conditions may cause pyuria without infection.
  8. WBCs- are markers for inflammation. Bacteriuria without WBCs of questionable significance and may obviate need for urine culture.
  9. Culture- should be fresh (<30 minutes and kept cold)
    1. A bagged urine is only significant if culture is negative
    2. Midstream urine is useful in older females and males
    3. Catheterized and suprapubic specimens are most reliable for culture.
    4. Interpretation
      1. Suprapubic specimen
        1. any gram negative organism is positive. 
        2. > 1,000 CFU per mL is positice
  10. Catheterized specimen
    1. > 10,000 organisms infection likely
  11. Clean Void
    1. Boy- > 100,000 infection likely
    2. Girl 3 specimens of > 100,000 infection likely 95%
    3. 2 specimens of > 100,000 infection likely 90%
    4. 1 specimen of > 100,000 infection likely 80%
    5. 10,000-100,000 and clinical suspicion suggest repeating culture
    6. < 10,000 infection unlikely

Management of Positive Culture

  1. If symptoms are mild, treat with PO Bactrim, Augmentin or 2nd or 3rd generation Cephalosporin
    1. Followup assessment should be done at 48 to 72 hours to confirm adequate clinical response.
  2. If symptoms are severe, use parenteral antibiotics to cover gram positive and gram negatives. Can use 2nd or 3rd generation Cephalosporin and Gentamycin. Must adjust treatment after obtaining results of the culture and sensitivity.
  3. Treat for 10-14 days---However, a review in American Family Physician notes that a two to four day course of oral antibiotics is just as effective for lower UTIs
  4. Repeat culture if symptoms are persisting after two days of therapy, sensitivities not done prior to treatment, and at the end of treatment.
  5. Child should be on prophylaxis awaiting imaging studies. Acceptable drugs include Bactrim, Nitrofurantoin, Sulfisoxazole, Nalidixic Acid. Prophylaxis is controversial, however, and may not reduce risk of recurrent UTIs in patients with mild reflux.
  6. Treatment of young infants with fever and UTI- a recent study has demonstrated that oral treatment with Cefixime is as effective as intravenous treatment with Cefotaxime and there was no increase of renal, scarring, length of fever, time to sterilize the urine, and reinfections.
  7. Acute pyelonephritis can be treated with oral antibiotics, such as cefixime, amoxicillin/clavulanate, ceftibuten for 14 days or a two to four day course of IV therapy followed by oral therapy.          

Imaging Studies

  1. Imaging studies are necessary to demonstrate the urinary tract anatomy and functional status. There are differing opinions on who and when they should be performed.
  2. Ultrasound and voiding cystourethrogram (VCU) should be done after the first UTI for all boys, girls younger than three and girls three to seven years old with a temperature of 101.3 or more. If a followup VUG is needed, usually do nuclear cystogram to decrease radiation exposure.
    1. Alternative is ultrasound and renal cortical scan
  3. The presence of a normal fetal ultrasound may obviate the need for further imaging studies. This is presently under study.

Follow-up

  1. May follow urines at home with nitrite reagent sticks
  2. Refer to pediatric urologist if there are recurrent infections associated with anatomic defects or obstruction.

Prevention

  1. Prevent urethral colonization by avoiding bubble baths, good local hygiene, increase bathing
  2. Prevent bladder colonization by encouraging frequent and complete voiding
  3. Circumcision; however, routine circumcision does not reduce risk of UTI enough to outweigh risk of surgical complications
  4. Front to back wiping in females
  5. Proper catherization technique with neurogenic bladders
  6. Antibiotic prophylaxis may be effective for children with severe vesicoureteral reflux, but there is no apparent benefit for children with no reflux or mild to moderate vesicoureteral reflux.
    1. Continuous prophylaxis does not appear to reduce risk of pyelonephritis and renal damage in children younger than 30 months
  7. Cranberry juice may be effective in children, though compliance is lower for children than for adults.

References

  1. Committee on Quality Improvement. Subcommittee on Urinary Tract Infection. The Diagnosis,Treatment, and Evaluation of the Initial UTI in Febrile Infants and Young Children. Pediatrics. April 1999.
  2. Goldman M et al. Imaging after Urinary Tract Infection in Male Neonates. Pediatrics. 2000; 105(6):1232-1235.
  3. Hoberman, A et al. Oral Versus Inital Intravenous Therapy for Urinary Tact Infection in Young Febrile Children. Pediatrics  Pediatrics. 1999; 104(1):79-86
  4. McDonald A et al. Voiding Cystourethrograms and Urinary Tract Infections: How Long to Wait? Pediatrics. 2000; 105(4):e50.
  5. Roberts KB. A Synopsis of the American Academy of Pediatrics' Practice Parameters on the Diagnosis, Treatment and Evaluation of the Initial Urinary Tract Infection in Febrile Infants and Young Children. Pediatrics in Review. 1999; 20:344-347...
  6. Fihn Stephen. Acute Uncomplicated Urinary Tract Infection in Women. NEJM Vol 349 NO. 3 Page 259 July 17, 2003
  7. Hoberman A. et al. Imaging Studies after First Febgrile Uinary Tract Infection in Young Children. NEJM Vol 348 No. 3 Page 195.  Janulary 18 2003
  8. Zamir G. et al. Urinary Tract Infection: Is there a Need for Rooutine Renal Ultrasonography? Arch Dis Child. 2004;89:466
  9. Zorc J.J. et al. Urinary Tract Infection in Young Febrile Infants. Pediatrics Sept. 2005
  10. Raszka W. and Khan O. Pyelonephritis. Pediatrics in Review October 2005
  11. Oreskovic N, Sembrano E. Repeat Urine Cultures in Children Who Are Aadmitted with Urinary Tract Infections.  Pediatrics Feb 2007 e325
  12. Cystitis Pediatrics in Review December 2007
  13. Ismali K. et al.  Characteristics of First Urinary Tract Infection in Children. Pediatric Infectious Disease Journal 2011 30(5) 371
  14. Montini G. et al. Febrile Urinary Tract Infections in Children. New England Journal of Medicine July 2011.
  15. White, B. Febrile Urinary Tract Infections in Children. American Family Physician February 2011
  16. AAP. Clinical Practice Guideline. UTI in Children 2 to 24 months  Pediatrics September 2011
  17. Newman TB. Commentary;The New American Academy of Pediatrics UTI Guidelines Sept 2011
  18. Hannula A. Long-Term Follow-up of Patients after Urinary Tract Infections.  Archives of Pediagtrics and Adolescent Medicine.  December 2012