eMedicine Specialties > Pediatrics: General Medicine > Infectious Disease

Urinary Tract Infection: Differential Diagnoses & Workup

Author: Stanley Hellerstein, MD, Pediatric Nephrologist, Children's Mercy Hospital of Kansas City; Ernest L Glasscock, MD Chair in Pediatric Research, Professor of Pediatrics, University of Missouri School of Medicine at Kansas City
Contributor Information and Disclosures

Updated: Sep 17, 2008

Differential Diagnoses

Fever in the Toddler
Fever in the Young Infant
Fever Without a Focus
Pyelonephritis
Voiding Dysfunction

Other Problems to Be Considered

Cystitis
Epididymitis
Orchitis
Prostatitis
Urethritis

Workup

Laboratory Studies

  • The diagnosis is based onquantitative cultures of a properly collected urine specimen (see Table 1 and Table 2).
    • A midstream, clean-catch specimen may be obtained from children who have urinary control. In the infant or child unable to void on request, the specimen for culture should be obtained by means of suprapubic aspiration or urethral catheterization. Suprapubic aspiration is the method of choice for obtaining urine from the uncircumcised boy with a redundant or tight foreskin and from children of either sex with clinically significant periurethral irritation.
    • A culture of a urinary specimen from a sterile bag attached to the perineal area that shows no or scant growth (<10,000 colony-forming units [CFUs]/mL) is strong evidence of absent urinary tract infection (UTI). However, the false-positive rate is so high that this method of urine collection is not suitable for diagnosing a UTI.
    • Urinalysis does not substitute for urine culture to document the presence of a UTI. However, it can help in identifying febrile children who should receive antibacterial treatment while culture results from a properly collected urine specimen are pending.
  • Numerous recent studies have compared dipstick tests for leukocyte esterase and nitrite with microscopic examination of the urinary sediment for bacteria with urinary culture. These studies have been performed to determine whether the dipstick test can eliminate the need for urinary culture. The invasiveness, time involved, and cost of the culture could be eliminated. Current studies report that the specific components of the dipstick test and complete urinalysis cannot detect positive culture findings in all children who have positive urinary culture findings and unexplained fever or voiding symptoms. The conclusion is that urine should be obtained for culture, and initial treatment should be given to those children with fever and a presumptive diagnosis of a UTI, regardless of the result of urinary dipstick testing or urinalysis.3,4,5,6,7,8,9
  • Methods of urine collection, examination, and salient findings are shown in Tables 1 and 2. 
    • Table 1. Urinalysis for Presumptive Diagnosis of UTI*

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      Table
      MethodFindings
      Bright-field or phase-contrast microscopy of centrifuged urinary sedimentBacteria
      Gram stain of uncentrifuged or centrifuged urinary sedimentBacteria
      Nitrite and leukocyte esterase testPositive = UTI likely
      Nitrite testPositive = UTI probable
      Leukocyte esterase testPositive = Nonspecific
      MethodFindings
      Bright-field or phase-contrast microscopy of centrifuged urinary sedimentBacteria
      Gram stain of uncentrifuged or centrifuged urinary sedimentBacteria
      Nitrite and leukocyte esterase testPositive = UTI likely
      Nitrite testPositive = UTI probable
      Leukocyte esterase testPositive = Nonspecific
      *Negative microscopic findings for bacteria do not rule out a UTI, nor do negative results of dipstick testing for nitrite and leukocyte esterase. 
    • Table 2. Quantitative Urine Culture for the Diagnosis of UTI*

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      Table
      MethodFinding
      Suprapubic aspirationIf a UTI is present, bacteria are likely to be proliferating in bladder urine with growth of any organism except 2000-3000 CFU/mL coagulase-negative staphylococci.
      Catheterization in a girl or midstream clean-void collection in a circumcised boyFebrile infants and children with UTI usually have >50,000 CFU/mL of a single urinary pathogen; however, UTI may be present with 10,000-50,000 CFU/mL of a single organism.*
      Midstream clean-void collection in a girl or uncircumcised boyUTI is indicated when >100,000 CFU/mL of a single urinary pathogen is present in a symptomatic patient. Pyuria usually present. A UTI may be present with 10,000-50,000 CFU/mL of a single bacterium.*
      Any method in a girl or boyIf the patient is asymptomatic, bacterial growth is usually >100,000 CFU/mL of the same organism on different days. If pyuria is absent, this result probably indicates colonization rather than infection.
      MethodFinding
      Suprapubic aspirationIf a UTI is present, bacteria are likely to be proliferating in bladder urine with growth of any organism except 2000-3000 CFU/mL coagulase-negative staphylococci.
      Catheterization in a girl or midstream clean-void collection in a circumcised boyFebrile infants and children with UTI usually have >50,000 CFU/mL of a single urinary pathogen; however, UTI may be present with 10,000-50,000 CFU/mL of a single organism.*
      Midstream clean-void collection in a girl or uncircumcised boyUTI is indicated when >100,000 CFU/mL of a single urinary pathogen is present in a symptomatic patient. Pyuria usually present. A UTI may be present with 10,000-50,000 CFU/mL of a single bacterium.*
      Any method in a girl or boyIf the patient is asymptomatic, bacterial growth is usually >100,000 CFU/mL of the same organism on different days. If pyuria is absent, this result probably indicates colonization rather than infection.
      *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.
  • Obtain a CBC count and basic metabolic panel for children with a presumptive diagnosis of pyelonephritis.
  • Perform blood cultures in febrile infants and older patients who are clinically ill, toxic, or severely febrile.

Imaging Studies

  • General considerations
    • History of imaging: In the past, the recommendation was that an infant or a child with a first febrile UTI should undergo imaging of the urinary tract. In the early years, intravenous pyelography (IVP) and voiding cystourethrography (VCUG) were performed, IVP immediately and VCUG 4-6 weeks later.
    • Ultrasonography: Sonography of the urinary tract subsequently replaced IVP. However, recent studies show that sonograms of the urinary tract obtained after a first febrile UTI seldom provide information that change management. A current recommendation is that urinary sonography should be omitted after a first febrile UTI in infants and children if they respond to treatment (afebrile within 72 h), good follow-up is assured, and no voiding abnormality (no dribbling of urine) or abdominal mass is present. The clinician's judgment should guide the decision regarding imaging studies, as opposed to a rigid rule. Urinary sonography is a safe, noninvasive study that is easy to perform. It is useful in excluding obstructive urography and in identifying children with a solitary or ectopic kidney and some patients with moderate renal damage caused by pyelonephritis.
    • Voiding cystourethrography or nuclear cystography
      • Traditionally VCUG has been recommended for infants and children after a first febrile UTI. This is based on the assumptions that most upper UTIs occur because of urinary bladder infection and that vesicoureteral reflux (VUR) transfers bacteria in the bladder to the kidney. However, using cortical imaging, current data show that upper tract infection occurs equally in children with and without VUR. The assumption that antibacterial prophylaxis prevents a recurrence of UTI seems reasonable, although this has not been proven. A lack of sufficient randomized control studies comparing antibacterial prophylaxis with placebo prohibits an evidence-based recommendation to prevent recurrent UTIs. Long-term, prospective randomized studies are needed.
      • Of note, a first febrile UTI is as frequent in infants with VUR as in those without radiographically demonstrated reflux. The recommendation for VCUG after a first febrile UTI is based on expert opinion and judgment, not on evidence-based guidelines.
      • Some experts suggest that cystography that requires catheterization of the urinary bladder be avoided. Their recommendation, which is not evidence based, is that renal cortical scanning (renal scintigraphy) should be performed. This study helps in identifying kidney injury and/or pyelonephritis. If the scan findings are normal, cystography is not needed. However, if the results are abnormal, VCUG should be obtained.
      • If a VCUG is to be obtained, it should obtained after the voiding pattern returns to its pre-UTI state. If the organism that caused the UTI was susceptible to the antibacterial used to treat the febrile UTI and if the response to therapy was satisfactory, follow-up urinalysis or cultures are not needed. The child should receive antibacterial therapy at least until the cystogram is obtained.
      • Some clinicians recommend waiting 4-6 weeks after febrile UTI is treated to perform VCUG. If the child is given suppressive antibacterial treatment during this period, this recommendation is acceptable. However, recent studies showed that the VCUG may be obtained within the first few days of treating febrile UTI, if the voiding pattern has returned to its pre-UTI state.
    • General recommendation: If imaging studies of the urinary tract are warranted, they should not be obtained until the diagnosis is confirmed with a quantitative urinary culture.
  • Summary of imaging recommendations
    • Which children should undergo ultrasonography of the urinary tract after a first febrile UTI?
      • Patients who have a delayed or unsatisfactory response to treatment of the first febrile UTI
      • Children with an abdominal mass or abnormal voiding (dribbling of urine)
      • Any child with a first febrile UTI in whom good follow-up cannot be ensured (Good clinical and experimental data support the opinion that the best way to prevent kidney damage due to a UTI is by prompt diagnosis and effective treatment of a febrile UTI.)
      • Children with a first febrile UTI caused by an organism other than E coli
      • Children with recurrence of a febrile UTI after they have a satisfactory response to treatment of the initial febrile UTI
    • Which children should undergo VCUG after a first febrile UTI?
      • Those in whom treatment fails after 48-72 hours
      • Patients with an abnormal voiding pattern (dribbling of urine)
      • Infants and children in whom good follow-up is not assured
      • Those with an abdominal mass
      • Infants and children with recurrence of a febrile UTI
    • Which pediatric patients do not need imaging studies after a first UTI?
      • Infants and children with a first febrile UTI who are assured follow-up, who respond promptly to treatment (afebrile within 72 h), and who have a normal voiding pattern (no dribbling) and no abdominal mass
      • Infants and children with cystitis: Those with an abnormal voiding pattern after receiving effective treatment of the UTI may need to undergo an evaluation for voiding dysfunction; this may include standard VCUG.

More on Urinary Tract Infection

Overview: Urinary Tract Infection
Differential Diagnoses & Workup: Urinary Tract Infection
Treatment & Medication: Urinary Tract Infection
Follow-up: Urinary Tract Infection
References
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Further Reading

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Contributor Information and Disclosures

Author

Stanley Hellerstein, MD, Pediatric Nephrologist, Children's Mercy Hospital of Kansas City; Ernest L Glasscock, MD Chair in Pediatric Research, Professor of Pediatrics, University of Missouri School of Medicine at Kansas City
Stanley Hellerstein, MD is a member of the following medical societies: American Academy of Pediatrics, American Pediatric Society, and American Society of Pediatric Nephrology
Disclosure: Nothing to disclose.

Medical Editor

Robert W Tolan Jr, MD, Chief, Division of Allergy, Immunology and Infectious Diseases, The Children's Hospital at Saint Peter's University Hospital; Clinical Associate Professor of Pediatrics, Drexel University College of Medicine
Robert W Tolan Jr, MD is a member of the following medical societies: American Academy of Pediatrics, American Medical Association, American Society for Microbiology, American Society of Tropical Medicine and Hygiene, Infectious Diseases Society of America, Pediatric Infectious Diseases Society, Phi Beta Kappa, and Physicians for Social Responsibility
Disclosure: GlaxoSmithKline Honoraria Speaking and teaching; MedImmune Honoraria Consulting; MedImmune Honoraria Speaking and teaching; Merck Honoraria Speaking and teaching; Novartis Honoraria Speaking and teaching; sanofi pasteur Grant/research funds Unrestricted research grant; sanofi pasteur  Consulting; sanofi pasteur Honoraria Speaking and teaching; Tap Honoraria Speaking and teaching

Pharmacy Editor

Mary L Windle, PharmD, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy, Pharmacy Editor, eMedicine
Disclosure: Pfizer Inc Stock Investment from broker recommendation; Avanir Pharma Stock Investment from broker recommendation

Managing Editor

Leslie L Barton, MD, Professor, Program Director, Department of Pediatrics, University of Arizona School of Medicine
Leslie L Barton, MD is a member of the following medical societies: American Academy of Pediatrics, Association of Pediatric Program Directors, Infectious Diseases Society of America, and Pediatric Infectious Diseases Society
Disclosure: Nothing to disclose.

CME Editor

Daniel Rauch, MD, FAAP, Director, Pediatric Hospitalist Program, Associate Professor, Department of Pediatrics, New York University School of Medicine
Daniel Rauch, MD, FAAP is a member of the following medical societies: Ambulatory Pediatric Association, American Academy of Pediatrics, and Society of Hospital Medicine
Disclosure: Baxter Honoraria Consulting; Pfizer Honoraria Consulting

Chief Editor

Russell W Steele, MD, Head, Division of Pediatric Infectious Diseases, Ochsner Children's Health Center; Clinical Professor, Department of Pediatrics, Tulane University School of Medicine
Russell W Steele, MD is a member of the following medical societies: American Academy of Pediatrics, American Association of Immunologists, American Pediatric Society, American Society for Microbiology, Infectious Diseases Society of America, Louisiana State Medical Society, Pediatric Infectious Diseases Society, Society for Pediatric Research, and Southern Medical Association
Disclosure: None None None

 
 
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