Should I treat for UTI with elevated leukocytes but no nitrites and abdominal pain radiating to the flank?

Management of Suspected UTI with Elevated Leukocytes, Negative Nitrites, and Left Flank Pain

You should treat for a urinary tract infection with empiric antibiotics despite negative nitrites, as the combination of elevated leukocytes (+125) and flank pain radiating from the abdomen strongly suggests pyelonephritis.

Diagnostic Interpretation

The clinical presentation suggests pyelonephritis rather than simple cystitis:

• Elevated leukocytes (+125) in urinalysis is significant for UTI even without nitrites 1
• Left-sided abdominal pain radiating to the flank is a classic presentation of pyelonephritis
• Negative nitrites do not rule out UTI, as:
  • Some uropathogens do not produce nitrites
  • Insufficient bladder dwell time can result in false negatives
  • Pyuria (elevated leukocytes) is the best determinant of bacteriuria requiring therapy 2

Treatment Approach

Initial Management

1. Obtain urine culture before starting antibiotics 1
2. Begin empiric antibiotic therapy immediately:
   • First-line options:
     • Fluoroquinolone (e.g., ciprofloxacin 500 mg BID) if local resistance <10%
     • Third-generation cephalosporin (e.g., ceftriaxone) if higher resistance concerns
   • Duration: 7-14 days for pyelonephritis 1

Follow-up

• Assess clinical response within 72 hours of initiating therapy 1
• If no improvement (persistent fever or flank pain) after 48-72 hours:
  • Obtain follow-up urine culture
  • Consider imaging (CT or ultrasound) to rule out complications
  • Consider changing antibiotic based on culture results

Clinical Pearls and Pitfalls

Important Considerations

• Pyuria without nitrites is still significant for UTI, especially with flank pain 2
• Leukocyte esterase has better sensitivity than nitrites for detecting UTI
• The absence of pyuria can exclude bacteriuria (negative predictive value approaches 100%) 3

Common Pitfalls to Avoid

1. Do not delay treatment waiting for culture results when clinical presentation suggests pyelonephritis
2. Do not dismiss elevated leukocytes because of negative nitrites
3. Do not treat asymptomatic bacteriuria in non-pregnant patients 1
4. Do not obtain routine imaging unless there is poor response to therapy or concern for complications 3

Special Populations

• For pregnant women, diabetics, or immunocompromised patients, lower threshold for hospitalization and IV antibiotics
• In elderly patients, consider renal function when dosing antibiotics 1

By following this approach, you can appropriately manage a patient with suspected pyelonephritis based on elevated leukocytes and flank pain, even in the absence of nitrites.