What is the appropriate management for a patient with on and off fever, left lower quadrant (LLQ) pain, and vomiting, with potential diagnoses including diverticulitis?

Management of On-and-Off Fever, Left Lower Quadrant Pain, and Vomiting

Order CT abdomen and pelvis with IV contrast immediately—this is the single most important diagnostic step with 98% accuracy and will guide all subsequent management decisions. 1

Immediate Diagnostic Workup

Do not rely on clinical examination alone, as misdiagnosis rates range from 34-68% when imaging is not obtained 1. The classic triad of left lower quadrant pain, fever, and leukocytosis is present in only 25% of diverticulitis cases 1.

Essential Laboratory Tests

• C-reactive protein (CRP): A level >170 mg/L predicts severe diverticulitis with 87.5% sensitivity and 91.1% specificity 2
• White blood cell count with differential: Leukocytosis is present in 90% of cases 3
• Note the clinical decision rule: When all three criteria are present (left lower quadrant tenderness only, CRP >50 mg/L, and absence of vomiting), the diagnosis has 97% accuracy—but this occurs in only 24% of patients 2, 1

Your patient has vomiting, which makes clinical diagnosis unreliable and mandates imaging 2.

CT Imaging Protocol

• CT abdomen/pelvis with IV contrast is rated 8/9 (usually appropriate) by the American College of Radiology 1
• This imaging detects complications (abscess, perforation, fistula), identifies alternative diagnoses, and reduces hospital admissions by >50% 1
• Sensitivity and specificity approach 98-100% for diagnosing diverticulitis 4, 5

Management Algorithm Based on CT Findings

If Uncomplicated Diverticulitis (No Abscess, Perforation, or Fistula)

For immunocompetent patients: Conservative management WITHOUT antibiotics 2, 1, 4

• Clear liquid diet with gradual advancement 1
• Acetaminophen for pain control (avoid NSAIDs) 1, 4
• Bowel rest initially 4

Antibiotics are indicated ONLY for: 4

• Immunocompromised patients (chemotherapy, high-dose steroids, organ transplant)
• Age >80 years
• Pregnancy
• Persistent fever or chills despite conservative management
• Increasing leukocytosis
• Chronic medical conditions (cirrhosis, chronic kidney disease, heart failure, poorly controlled diabetes)

If antibiotics are needed, use for maximum 7 days: 2, 1

• Oral regimen: Amoxicillin/clavulanic acid OR cefalexin plus metronidazole 4
• IV regimen (if cannot tolerate oral): Ceftriaxone plus metronidazole OR ampicillin/sulbactam 4
• Alternative: Ertapenem 1g q24h or Eravacycline 1 mg/kg q12h 1

If Complicated Diverticulitis with Small Abscess (<4 cm)

Antibiotics alone for 7 days without drainage 2, 1

• Ceftriaxone plus metronidazole OR piperacillin-tazobactam IV 4

If Complicated Diverticulitis with Large Abscess (≥4 cm)

Percutaneous drainage PLUS antibiotics for 4 days 2, 1, 6

• This is first-line management, reserving surgery for failure of drainage 6
• Stop antibiotics at 4 days if source control is adequate in immunocompetent, non-critically ill patients 1
• Continue up to 7 days in immunocompromised or critically ill patients 1

If Perforation with Diffuse Peritonitis or Septic Shock

Emergency surgical consultation immediately 1, 4

• Hartmann's procedure (resection with end colostomy): For critically ill patients, multiple comorbidities, hemodynamic instability, or fecal peritonitis 1, 6
• Primary resection with anastomosis (±diverting stoma): For clinically stable patients without major comorbidities 1, 6
• Escalate to broad-spectrum carbapenem therapy: Meropenem 1g q6h by extended infusion, Doripenem 500 mg q8h by extended infusion, or Imipenem/cilastatin 500 mg q6h by extended infusion 1

Admission vs. Outpatient Management

Admit to hospital if ANY of the following: 1, 7

• Cannot tolerate oral fluids or medications
• Fever or signs of systemic inflammatory response
• Abnormal vital signs
• Immunocompromised status
• Significant comorbidities
• Lack of adequate home support
• Signs of peritonitis (guarding, rebound tenderness, absent bowel sounds)

Outpatient management is appropriate if: 7

• Can tolerate oral fluids and medications
• No fever
• Normal vital signs
• Immunocompetent
• Adequate home support
• Mandatory re-evaluation within 48-72 hours 7

Critical Red Flags Requiring Emergency Surgery

Immediate surgical consultation if: 1

• Free air on CT indicating perforation
• Fecal peritonitis
• Diffuse peritonitis with hemodynamic instability
• Signs of septic shock (elevated lactate, metabolic derangements)
• Complete bowel obstruction

Special Considerations

Premenopausal Women

• Consider gynecologic causes first 1
• Obtain pregnancy test before CT 1
• Pelvic/transvaginal ultrasound may be initial imaging if gynecologic pathology suspected 1

Colonoscopy Timing

Routine colonoscopy after uncomplicated diverticulitis is NOT warranted except for: 1

• Age-appropriate colon cancer screening not yet performed
• Abnormal pericolic lymph nodes on CT (>1 cm suggests cancer rather than diverticulitis) 1
• Luminal colon mass on CT
• Uncertain diagnosis
• Presence of abscess, perforation, or fistula

Delay colonoscopy 6 weeks after acute episode to reduce procedural risk 5

Common Pitfalls to Avoid

• Do not continue antibiotics beyond 7 days in uncomplicated cases—this increases resistance without improving outcomes 1
• Do not rely on absence of vomiting to rule out diverticulitis—vomiting is present in 86% of young patients with diverticulitis 3
• Do not assume right-sided pain excludes diverticulitis—24% of young patients present with right lower quadrant pain from cecal diverticulitis 3
• Do not skip imaging in young patients—while uncommon under age 40, diverticulitis in this population is frequently confused with appendicitis 3