What is the interpretation of a urinalysis (specific gravity ≥1.030, pH 6.0, cloudy appearance, trace leukocyte esterase, 1+ protein, negative glucose, trace ketones, negative occult blood, negative bilirubin, urobilinogen 1.0 mg/dL, negative nitrite) showing calcium oxalate crystals, >10 non‑renal epithelial cells, moderate bacteria, and a reflex urine culture that grew >2 organisms with >100,000 CFU/mL?

Interpretation of Contaminated Urine Culture with Mixed Flora

This urinalysis and culture result represents specimen contamination rather than a true urinary tract infection, and antibiotics should not be prescribed. The presence of >2 organisms with >100,000 CFU/mL, combined with >10 non-renal epithelial cells per high-power field and moderate bacteria, indicates peri-urethral contamination from improper collection technique. 1

Why This Result Indicates Contamination

• Mixed flora (>2 organisms) at any colony count lacks diagnostic validity for urinary tract infection and almost always represents contamination from skin or genital flora rather than true bladder infection. 2

• High epithelial cell counts (>10/HPF) are a hallmark of contaminated specimens, signaling that peri-urethral cells and their associated bacteria were collected rather than bladder urine. 1, 2

• True polymicrobial UTIs are rare (≈3–11% of cases) and occur only in high-risk settings such as structural urinary abnormalities, neurogenic bladder with intermittent catheterization, or long-term indwelling catheters—none of which appear to be present here. 2

• The laboratory explicitly states the specimen was submitted in a non-refrigerated sterile cup, which allows excessive bacterial overgrowth during transport, further invalidating the colony count. 1

Critical Diagnostic Requirements Before Treating Any UTI

Both of the following must be documented before prescribing antibiotics:

1. Acute urinary symptoms (dysuria, frequency, urgency, fever >38.3°C, gross hematuria, or suprapubic pain). 2

2. Pyuria (≥10 WBC/HPF on microscopy or positive leukocyte esterase). 2

This urinalysis shows only 0–5 WBC/HPF, which is normal and effectively rules out bacterial UTI with a negative predictive value of 82–91%. 2 The trace leukocyte esterase is below the diagnostic threshold and does not constitute pyuria. 2

What to Do Next

If the Patient Has NO Urinary Symptoms

• Do not prescribe antibiotics. Treating contaminated cultures or asymptomatic bacteriuria provides no clinical benefit and increases antimicrobial resistance, risk of Clostridioides difficile infection, and unnecessary drug toxicity. 2

• Educate the patient to seek care only if specific urinary symptoms develop (dysuria, fever, frequency, urgency, suprapubic pain, or visible blood). 2

• No repeat testing is needed unless symptoms arise. 2

If the Patient HAS Urinary Symptoms

• Obtain a properly collected specimen before starting antibiotics:

  • Women: In-and-out catheterization is preferred to avoid peri-urethral contamination. 2
  • Men: Midstream clean-catch after thorough cleansing of the urethral meatus. 2

• Process the specimen within 1 hour at room temperature or refrigerate within 4 hours to prevent bacterial overgrowth. 1, 2

• Verify pyuria (≥10 WBC/HPF or positive leukocyte esterase) on the new specimen before proceeding to culture. 2

• Order urine culture only if pyuria is confirmed and symptoms are present. 2

Common Pitfalls to Avoid

• Never treat based solely on culture results without confirming both urinary symptoms and pyuria; doing so leads to unnecessary antibiotic exposure and promotes resistance. 2

• Do not interpret "many bacteria" or high colony counts as infection when mixed flora is present—this finding reflects contamination, not true bladder infection. 2

• Do not assume all positive urine cultures represent infection; asymptomatic bacteriuria occurs in 15–50% of elderly patients and should never be treated except in pregnancy or before urologic procedures with anticipated mucosal bleeding. 2

• Cloudy or foul-smelling urine alone does not indicate infection and should not trigger testing or treatment in asymptomatic individuals. 2

Special Considerations

• Calcium oxalate crystals are a common incidental finding and have no relationship to infection; they reflect dietary oxalate intake or urine concentration. 1

• Trace protein and ketones are non-specific findings that can occur with dehydration, exercise, or concentrated urine and do not indicate infection. 1

• The laboratory's recommendation to use a urine culture transport device for future specimens is appropriate to maintain specimen integrity during transport. 1

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