Acute diverticulitis: workup and management
Acute diverticulitis usually presents with left lower quadrant pain, fever and leukocytosis. CT confirms the diagnosis and separates uncomplicated from complicated disease (abscess, perforation, fistula, obstruction). Most uncomplicated cases can be managed as outpatients, often without antibiotics.
Working diagnosis
Adult · US guidelines
Draft · awaiting physician review
01Orient
What's new in the evidence
- ACG 2026 diverticulitis guideline: selective rather than routine antibiotics for uncomplicated diverticulitis (no reduction in complications, surgery or recurrence in RCTs)
- Consider antibiotics for comorbidity or immunosuppression, symptoms >5 days, vomiting, CRP >140 mg/L, fluid collection or a long inflamed segment
- ACP 2022: outpatient management for most uncomplicated cases
Differential diagnoses
- Uncomplicated diverticulitis
- Complicated diverticulitis: abscess, perforation with peritonitis (can't miss)
- Colorectal cancer (can't miss)
- Ischemic colitis, inflammatory bowel disease, infectious colitis
- Ovarian torsion, ectopic pregnancy, PID (can't miss)
- Appendicitis (right-sided diverticulitis mimics it), nephrolithiasis
02Assess
Risk scores and decision tools
- Modified Hinchey classification on CT
- CRP >150–170 mg/L raises the likelihood of complicated disease
- Immunosuppression and frailty as high-risk modifiers
Key history questions
- Pain location and duration, fever
- Prior episodes and prior colonoscopy
- Bowel habit change, rectal bleeding, weight loss
- Pneumaturia or fecaluria (colovesical fistula)
- Immunosuppression, ability to take oral fluids
Examination findings
- LLQ tenderness, localized guarding
- Generalized peritonitis (perforation)
- Palpable mass (abscess or phlegmon)
- Vitals and hydration
03Investigate
Initial investigations
- CT abdomen and pelvis with IV contrast
- CBC, BMP, CRP, lactate if unwell
- Urinalysis; pregnancy test where relevant
Advanced investigations
- Colonoscopy 6–8 weeks after recovery after a first complicated episode or if no high-quality colonoscopy recently
- CT-guided drainage of abscess ≥3–4 cm
04Treat
Immediate management
- Peritonitis or sepsis: resuscitation, broad-spectrum antibiotics and emergency surgery
- Analgesia (acetaminophen; avoid NSAIDs and opioids where possible)
First-line treatment
- Uncomplicated, immunocompetent, no high-risk features: observation with clear liquids then diet as tolerated, without antibiotics
- Uncomplicated with high-risk features: amoxicillin-clavulanate, or ciprofloxacin plus metronidazole, for 4–7 days
- Complicated or inpatient: ceftriaxone plus metronidazole, or piperacillin-tazobactam
Second-line treatment
- Abscess ≥3–4 cm: percutaneous drainage plus antibiotics
- Elective colectomy decisions individualized (recurrent complicated disease, fistula, stricture), not based on number of episodes alone
Specialist referrals
- General or colorectal surgery for complicated disease
- Interventional radiology for drainage
- Gastroenterology for colonoscopy
05Disposition
Admission criteria
- Complicated diverticulitis
- Sepsis, unable to tolerate oral intake, uncontrolled pain
- Immunosuppression or significant comorbidity
Safe discharge criteria
- Uncomplicated on CT, tolerating oral intake, pain controlled
- Follow-up within a few days
Follow-up timing
- Clinical review in 2–7 days
- Colonoscopy at 6–8 weeks if indicated
Patient instructions
- Return for worsening pain, fever or vomiting
- High-fiber diet and exercise; nuts and seeds need not be avoided
Monitoring
- Pain, temperature, ability to eat
Clinical pearls and pitfalls
- Mesalamine and probiotics do not prevent recurrence
- Right-sided diverticulitis is more common in Asian populations and is usually managed conservatively
RefGuidelines and landmark evidence
For education only. Typical adult starting points; confirm doses against renal function, allergies, interactions and your institution's protocols. Not a substitute for clinical judgment or senior review.