Leukocytosis Alone Does Not Justify Continuing Antibiotics in This Clinical Scenario
In a patient with known ulcerative colitis presenting with severe diarrhea, normal CRP, normal procalcitonin, and no fever, antibiotics should be discontinued even if leukocytosis is present, as this constellation of findings strongly suggests an UC flare rather than bacterial infection.
Clinical Reasoning
The presence of leukocytosis in isolation, without other markers of bacterial infection, is insufficient to justify antibiotic continuation in this context. Here's why:
Infection Markers Are Reassuring
Normal procalcitonin is particularly significant. Procalcitonin is a more specific marker for bacterial infections than CRP 1. In UC patients, procalcitonin typically remains within normal ranges even during active disease, whereas it becomes markedly elevated in true bacterial infections 1.
Normal CRP further argues against active bacterial infection. While CRP can be elevated in UC flares, its absence alongside normal procalcitonin makes bacterial infection highly unlikely 2.
Absence of fever is another critical negative finding. The combination of afebrile status with normal inflammatory markers strongly points toward UC activity rather than infection.
Leukocytosis in UC Context
Leukocytosis alone is not specific for infection in UC patients. The white blood cell count can be elevated due to:
- The inflammatory process of UC itself 3
- Corticosteroid therapy (if being used), which commonly causes leukocytosis
- Stress response from severe diarrhea and dehydration
Guidelines for severe UC specifically mention monitoring white blood cell count as part of disease activity assessment—not as an infection marker in isolation 3.
Antibiotic Risks in UC
Continuing unnecessary antibiotics in UC patients carries significant risks:
Increased risk of Clostridioides difficile infection (CDI): Continued antibiotic use is significantly associated with increased risk of CDI recurrence 4, which would further complicate management.
Disruption of gut microbiota: Antibiotics further disrupt the intestinal flora, potentially worsening UC symptoms and increasing recurrence risk 5, 4.
Delayed appropriate UC treatment: Continuing antibiotics may delay escalation of appropriate UC-directed therapy 3.
Evidence on Antibiotics in UC
The evidence for antibiotics in UC is limited and context-specific:
A 2022 Cochrane review found high certainty evidence that antibiotics provide no benefit over placebo for achieving clinical remission in UC 6.
Antibiotics may have been considered historically in severe UC when infection cannot be confidently excluded 7, but your patient has multiple negative infection markers.
One small 1993 study suggested benefit in "nontoxic" severe UC 8, but this predates modern understanding and the patients in that study had persistent fever and leukocytosis after 7 days of steroids—a different clinical picture than your patient.
Recommended Approach
Discontinue antibiotics immediately and focus on:
Stool studies: Ensure C. difficile toxin, routine bacterial cultures, and ova/parasites are negative (if not already done) 3.
Escalate UC-directed therapy:
Close monitoring: Daily assessment of vital signs, stool frequency, and inflammatory markers to identify those who may need colectomy 3.
Common Pitfall to Avoid
Do not be falsely reassured by isolated leukocytosis into continuing antibiotics. This is a common error that delays appropriate UC treatment and exposes patients to antibiotic-related complications. The combination of normal procalcitonin, normal CRP, and absence of fever provides strong evidence against bacterial infection, regardless of the white blood cell count.