Differential Diagnosis for Urinalysis + Nitrite, + Leukocytosis, Culture Negative

• Single Most Likely Diagnosis
  • Contaminated Urine Culture: The presence of nitrite and leukocytosis in the urinalysis suggests a bacterial infection. However, a negative culture could indicate contamination of the urine sample, which is a common issue, especially in women or when proper collection techniques are not followed.
• Other Likely Diagnoses
  • Recent Antibiotic Use: The patient might have recently taken antibiotics, which could have temporarily cleared the bacteria from the urine, resulting in a negative culture despite the presence of infection indicators like nitrite and leukocytosis.
  • Fastidious Organisms: Some bacteria, such as certain strains of Streptococcus or Chlamydia, may not grow well in standard urine culture media, leading to false-negative results.
  • Tuberculosis (TB) of the Urinary Tract: Although less common, TB can infect the urinary tract and may not be detected by standard urine cultures. The presence of leukocytosis and nitrite could suggest an infection, but specific tests for TB would be needed for diagnosis.
• Do Not Miss Diagnoses
  • Urinary Tract Malignancy: While rare, malignancies of the urinary tract can cause leukocytosis and potentially a false-positive nitrite test. It's crucial to consider this diagnosis, especially in patients with risk factors or other symptoms suggestive of cancer.
  • Kidney Stones with Infection: The presence of a kidney stone can obstruct the flow of urine, leading to an increased risk of infection. Even if the culture is negative, the clinical presentation and imaging studies could support this diagnosis.
• Rare Diagnoses
  • Malakoplakia: A rare inflammatory condition that can affect the urinary tract, malakoplakia might present with leukocytosis and could potentially cause a false-positive nitrite test. It's often associated with chronic bacterial infection.
  • Fungal Infections: In immunocompromised patients, fungal infections of the urinary tract can occur. These might not be detected by standard bacterial urine cultures, and specific fungal cultures or other diagnostic tests would be necessary.