What is the best management approach for a patient with a history of diverticulitis (inflammation of the diverticula) and currently presenting with leukopenia (low white blood cell count)?

Management of Low White Blood Cell Count Following Diverticulitis

For a patient with leukopenia after diverticulitis, immediately discontinue any antibiotics (particularly ciprofloxacin and metronidazole) that may be causing drug-induced neutropenia, obtain a complete blood count with differential to assess severity, and determine if the patient requires growth factor support with filgrastim if the absolute neutrophil count is critically low (<500 cells/μL). 1, 2

Immediate Assessment and Risk Stratification

Determine the Cause of Leukopenia

The first critical step is distinguishing between drug-induced leukopenia versus infection-related bone marrow suppression:

• Check the absolute neutrophil count (ANC), not just the total WBC, as this determines infection risk and need for growth factor support 2
• Review all current medications for myelosuppressive agents, particularly fluoroquinolones (ciprofloxacin), which can cause bone marrow suppression 1, 3
• Assess timing: If leukopenia developed during or shortly after antibiotic treatment for diverticulitis, drug-induced neutropenia is the most likely cause 1, 3

Severity Classification

• Mild leukopenia (WBC 3,000-4,000/μL): Monitor closely but may not require intervention 2
• Moderate leukopenia (WBC 1,000-3,000/μL): Discontinue offending agents, increase monitoring frequency 2
• Severe leukopenia (WBC <1,000/μL or ANC <500/μL): Consider filgrastim 5 mcg/kg/day subcutaneously and hospitalization for neutropenic precautions 2

Antibiotic Management Decisions

If Patient is Still on Antibiotics for Diverticulitis

Immediately discontinue ciprofloxacin and metronidazole if the patient is still within the treatment course, as fluoroquinolones are a known cause of drug-induced neutropenia 1, 3

• The standard 4-7 day course for uncomplicated diverticulitis should already be complete in most cases 1, 3
• If antibiotics are still clinically necessary (immunocompromised patient, complicated diverticulitis), switch to amoxicillin-clavulanate 875/125 mg twice daily, which has lower myelosuppressive risk 1, 3

If Diverticulitis Treatment is Complete

• No further antibiotics are needed for uncomplicated diverticulitis once the 4-7 day course is finished 1, 3
• Focus shifts entirely to managing the leukopenia and monitoring for recovery 2

Growth Factor Support Considerations

Indications for Filgrastim (Neupogen)

Filgrastim is indicated to reduce the duration of neutropenia and neutropenia-related clinical sequelae in patients with drug-induced severe neutropenia 2:

• ANC <500 cells/μL with fever or signs of infection: Start filgrastim 5 mcg/kg/day subcutaneously immediately 2
• ANC <500 cells/μL without fever but with high infection risk (diabetes, recent surgery, immunocompromised): Consider filgrastim 5 mcg/kg/day subcutaneously 2
• ANC 500-1,000 cells/μL: Monitor daily; initiate filgrastim if ANC continues to decline or fever develops 2

Monitoring During Growth Factor Therapy

• Complete blood count with differential every 1-2 days until ANC >1,500 cells/μL 2
• Discontinue filgrastim once ANC recovers to >1,000 cells/μL and is stable for 3 consecutive days 2
• Monitor for splenic rupture: Evaluate immediately if patient develops left upper abdominal or shoulder pain 2

Infection Risk Management

Neutropenic Precautions

For patients with ANC <1,000 cells/μL, implement strict neutropenic precautions 2:

• Avoid fresh fruits, vegetables, and undercooked foods until ANC recovers 2
• Strict hand hygiene and avoid contact with sick individuals 2
• Monitor temperature twice daily; any fever >100.4°F requires immediate evaluation 1, 2

Empiric Antibiotics for Febrile Neutropenia

If the patient develops fever (>100.4°F) with ANC <500 cells/μL, this constitutes a medical emergency requiring immediate broad-spectrum antibiotics 2:

• First-line: Piperacillin-tazobactam 4.5 g IV every 6 hours OR cefepime 2 g IV every 8 hours 1, 2
• Avoid fluoroquinolones given the recent drug-induced neutropenia 1, 2
• Add vancomycin if concern for catheter-related infection or mucositis 2

Monitoring for Diverticulitis Recurrence

Warning Signs Requiring Immediate Evaluation

Even with leukopenia, patients can still develop recurrent diverticulitis, though the typical leukocytosis may be absent 1, 3:

• Fever >101°F, severe left lower quadrant pain, persistent nausea/vomiting, or inability to tolerate oral intake warrant immediate CT imaging 1, 3
• C-reactive protein >140 mg/L is a more reliable marker than WBC in this setting for detecting active diverticulitis 4, 1

Imaging Considerations

• CT abdomen/pelvis with IV contrast remains the gold standard for diagnosing recurrent diverticulitis, with 98-99% sensitivity regardless of WBC count 4, 3
• Do not delay imaging if clinical suspicion is high, even with normal or low WBC 4, 3

Common Pitfalls to Avoid

• Do not continue ciprofloxacin/metronidazole beyond the standard 4-7 day course in immunocompetent patients, as this increases myelosuppression risk without clinical benefit 1, 3
• Do not assume low WBC rules out infection; immunocompromised patients and those with drug-induced neutropenia may present with severe infections despite leukopenia 1, 2, 3
• Do not delay filgrastim in patients with ANC <500 cells/μL and fever, as mortality increases significantly with delayed growth factor support 2
• Do not attribute all symptoms to diverticulitis; leukopenic patients are at high risk for opportunistic infections requiring different management 2, 3

Follow-Up Timeline

• Daily CBC with differential until ANC >1,000 cells/μL and stable 2
• Repeat CBC 1 week after antibiotic discontinuation to confirm WBC recovery 2
• If WBC does not recover within 2 weeks of stopping offending medications, refer to hematology for bone marrow evaluation 2