Differential Diagnosis for a 6-year-old with Urinalysis (UA) Showing +Leukocytes and Everything Else Negative

• Single most likely diagnosis:

  • Urinary Tract Infection (UTI): This is the most common cause of leukocytes in the urine in a pediatric patient. The presence of leukocytes indicates an inflammatory response, which is consistent with a UTI.

• Other Likely diagnoses:

  • Contamination: Given the age of the patient, contamination during the urine collection process is a possibility, especially if the urine was collected by the clean-catch midstream method or if the patient is not yet toilet-trained.
  • Asymptomatic Bacteriuria: Some children can have bacteria in their urine without symptoms, which could lead to a positive leukocyte test.

• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.):

  • Pyelonephritis: An infection of the kidney, which can be serious and requires prompt treatment. Although the UA does not show other abnormalities like nitrites or blood, which are often seen in pyelonephritis, it's crucial not to miss this diagnosis due to its potential severity.
  • Tubulointerstitial Nephritis: This condition involves inflammation of the tubules and interstitial tissue of the kidneys and can be caused by various factors, including infections, drugs, and systemic diseases.

• Rare diagnoses:

  • Glomerulonephritis: An inflammation of the glomeruli, which are the filtering units of the kidneys. While it can present with hematuria (blood in the urine), some forms might initially show only leukocytes.
  • Interstitial Cystitis/Painful Bladder Syndrome: A condition causing bladder pressure, bladder pain, and sometimes pelvic pain. The symptoms can be non-specific, and it might be considered in the differential diagnosis of a child with persistent urinary symptoms and leukocytes in the urine without evidence of infection.