Diverticulitis (Uncomplicated)

Uncomplicated diverticulitis refers to localized diverticular inflammation without abscess, perforation, fistula, obstruction, or bleeding. It accounts for approximately 85% of all diverticulitis cases and can be managed in the outpatient setting in the vast majority (~95%) of patients. [1-2]

The following management algorithm from a 2025 JAMA review illustrates the clinical decision-making pathway:

• Location and quality of pain: Gradual-onset left lower quadrant pain (70% of cases); may be suprapubic or right-sided with right colonic diverticulitis or redundant sigmoid [1]
• Timing: Acute or subacute onset; characterize duration — symptoms >5 days before presentation predict progression to complicated disease [2]
• Associated symptoms: Nausea/vomiting (~30%), low-grade fever (~33%), change in bowel habits, anorexia, malaise [1][3]
• Important negatives: Rectal bleeding is not commonly seen in acute diverticulitis — its presence should prompt consideration of alternative diagnoses [3]
• Fistula screening: Ask about fecaluria, pneumaturia, pyuria (colovesical fistula) and stool per vagina (colovaginal fistula) [4]
• Prior episodes: Number, severity, imaging confirmation, and prior treatments

• Diffuse abdominal guarding or rigidity → suspect perforation/peritonitis [1]
• Hemodynamic instability (tachycardia, hypotension) → complicated disease or sepsis [1]
• High fever >38.5°C (101.3°F) with persistent chills [1]
• Rising leukocytosis or WBC >15 × 10⁹/L [5]
• CRP >140 mg/L [2][5]
• Palpable abdominal mass (~20% of complicated cases) [1]
• Symptoms >5 days, pain score >7, vomiting — predictors of progression to complicated disease [2][5]
• CT findings: pericolic extraluminal air, fluid collection, or long inflamed segment (>86 mm) [5]

Medications that increase risk

• NSAIDs (regular use ≥2 times/week), opioids, corticosteroids — all increase risk of diverticulitis and complications [1][5]
• Immunosuppressive agents (chemotherapy, high-dose steroids, post-transplant medications) — increase risk of complicated disease [1]

Treatment — when antibiotics are NOT needed

• Immunocompetent patients with mild uncomplicated diverticulitis, no systemic inflammatory response, no vomiting, WBC <15 × 10⁹/L, CRP <140 mg/L → observation with pain control alone is appropriate (ACP, AGA, Cochrane) [2][5-6]
• Acetaminophen is the preferred analgesic [1]

Treatment — when antibiotics ARE indicated

• [1][5]

If unable to tolerate PO: Ceftriaxone + metronidazole IV, or ampicillin-sulbactam IV [1]

Contraindicated: Avoid NSAIDs for pain control during acute episodes (use acetaminophen instead) [1][5]

• Acute phase: Clear liquid diet for 1–2 days after diagnosis, though evidence for this is limited; advance diet as symptoms improve [1][5]
• If unable to advance diet after 3–5 days → immediate follow-up [5]
• Long-term prevention: High-quality diet rich in fruits, vegetables, whole grains, and legumes; limit red meat and sweets [5][8]
• The old advice to avoid nuts, seeds, and popcorn has not been supported by evidence and is no longer recommended [5]
• Adequate hydration during acute illness

• GI: Bowel habit changes (constipation or diarrhea), bloating, flatus, hematochezia (atypical — consider alternative dx), tenesmus
• GU: Dysuria, pneumaturia, fecaluria, pyuria (fistula), hematuria (kidney stone)
• GYN (if applicable): Vaginal discharge, abnormal bleeding, stool per vagina
• Constitutional: Fever, chills, rigors, weight loss, night sweats (malignancy)
• Systemic: Signs of sepsis — tachycardia, altered mental status, hypotension

• Prior imaging-confirmed episodes of diverticulitis and management
• Immunosuppressive medications or conditions (transplant, chemotherapy, HIV)
• Genetic factors: Variants in TNFSF15 gene; connective tissue disorders (Ehlers-Danlos, Marfan, polycystic kidney disease) increase risk [1]
• Family history of diverticular disease, colorectal cancer, or inflammatory bowel disease
• Social context: home support system, ability to tolerate PO, access to follow-up (critical for outpatient management decisions) [2]

• Age >65 years (strongest demographic risk factor) [1]
• BMI ≥30 [1]
• Medications: NSAIDs, opioids, corticosteroids, immunosuppressants [1][9]
• Comorbidities: Hypertension, type 2 diabetes, CKD, cirrhosis, heart failure [1]
• Lifestyle: Smoking, physical inactivity, low-fiber diet, obesity [5][8]
• Connective tissue disorders: Polycystic kidney disease, Marfan syndrome, Ehlers-Danlos syndrome [1]
• Genetic predisposition: TNFSF15 gene variants [1]

• Colorectal cancer — cannot-miss; clinical diagnosis of diverticulitis is only accurate 40–65% of the time; colonoscopy recommended 6 weeks after resolution of complicated diverticulitis [3][5]
• Inflammatory bowel disease (Crohn disease, ulcerative colitis) [1]
• Appendicitis — especially with right-sided or suprapubic pain [1]
• Constipation / irritable bowel syndrome [4]
• Kidney stones / urinary tract infection [1][4]
• Bowel obstruction [1]
• Gynecologic pathology: Pelvic inflammatory disease, tubo-ovarian abscess, ovarian torsion, ectopic pregnancy [1]
• Ischemic colitis — particularly in elderly patients with vascular risk factors

• Prior episodes of diverticulitis (number, severity, imaging confirmation)
• Prior abdominal/pelvic surgery
• History of colorectal cancer screening (last colonoscopy)
• Immunocompromising conditions (organ transplant, HIV, active malignancy, chronic steroid use)
• Chronic conditions affecting management: cirrhosis, CKD, heart failure, poorly controlled diabetes [1]
• Connective tissue disorders [1]

• Vitals: Temperature (fever in ~33%), heart rate (tachycardia in ~27%), blood pressure (hypotension = red flag) [1]
• Abdomen: LLQ tenderness with localized guarding is the classic finding; assess for rebound, rigidity (peritonitis), distension (obstruction) [1]
• Palpable mass in LLQ → phlegmon or abscess (~20% of complicated cases) [1]
• Rectal exam: Tenderness may indicate pelvic abscess; assess for occult blood [1]
• Concerning findings: Diffuse peritonitis, hemodynamic instability, cool/clammy extremities → emergent surgical evaluation [1]

• CBC with differential: Leukocytosis present in ~55% of febrile patients; WBC >15 × 10⁹/L is a predictor of progression [1][5]
• CRP: >140 mg/L predicts complicated disease and progression; CRP >150 mg/L discriminates uncomplicated from complicated diverticulitis [5][10]
• BMP: Assess renal function, electrolytes (especially if poor PO intake)
• Urinalysis: Rule out UTI; sterile pyuria may suggest colovesical fistula [4]
• Lactate: If concern for sepsis or ischemia
• Blood cultures: If febrile or signs of systemic infection [1]
• Pregnancy test: In women of reproductive age
• Procalcitonin and fecal calprotectin are being explored but not currently recommended for routine use by ASCRS [4]

First-line: CT abdomen/pelvis with IV contrast — sensitivity 98–99%, specificity 99–100% [1]

• Findings: pericolic fat stranding, colonic wall thickening, diverticula; absence of abscess, free air, or extraluminal fluid confirms uncomplicated disease [1]
• CT in the ED can prevent unnecessary hospital admission by >50% [11]

Alternatives when CT is contraindicated

• Ultrasound (radiologist-performed): sensitivity 77–98%, specificity 80–99% [1]
• Point-of-care ultrasound: sensitivity 92.7%, specificity 90.9% in one multicenter study [1]
• MRI: sensitivity 86–94%, specificity 88–92%; preferred in pregnancy [1]

When imaging may be deferred

• Patients with a prior CT-confirmed diagnosis presenting with a typical mild recurrence may be managed clinically without repeat imaging (AGA) [5]
• However, err on the side of imaging if any predictors of complicated disease are present [2]

Avoid: Contrast enema (risk of perforation); plain radiographs have limited utility for diagnosis [1][5]

• Hinchey Classification: Grades severity of diverticulitis on CT (Ia = confined pericolic abscess; Ib = pelvic abscess; II = distant abscess; III = purulent peritonitis; IV = fecal peritonitis). Uncomplicated = Hinchey 0 [10]
• CRP >150 mg/L + free fluid on CT = significantly greater risk of mortality in one retrospective study [10]
• Colonoscopy: Avoid during acute episode (risk of perforation); consider 6 weeks after resolution in patients with complicated diverticulitis or those without recent high-quality colonoscopy — CRC risk is 6–8% in complicated diverticulitis [3][12]

• Not routinely indicated for uncomplicated diverticulitis
• Obtain if: elderly patient, hemodynamically unstable, concern for sepsis, or pre-procedural evaluation
• Rule out cardiac causes of referred abdominal pain in atypical presentations (especially elderly)

Uncomplicated diverticulitis = localized inflammation without abscess, perforation, fistula, obstruction, or bleeding. [2] Approximately 85% of all diverticulitis cases. [1]

Key clinical pearl: Clinical diagnosis alone is only correct in 40–65% of patients — imaging confirmation is important, especially for first episodes. [3][5]

Severity stratification for antibiotic decision-making

• Low risk (no antibiotics needed): Immunocompetent, mild symptoms, no fever, WBC <15, CRP <140, no vomiting, symptoms <5 days, no high-risk CT features [2][5]
• Higher risk (antibiotics indicated): Age >80, immunocompromised, pregnant, significant comorbidities, WBC >15, CRP >140, vomiting, symptoms >5 days, pericolic air or fluid on CT [1][5]

Symptoms typically improve within 48–72 hours, with complete resolution in 1–2 weeks. [1] Recurrence rate is approximately 15% within 2 years. [1]

Initial stabilization

• IV access, fluid resuscitation if dehydrated or unable to tolerate PO
• Pain control with acetaminophen (avoid NSAIDs and opioids when possible) [1]

Outpatient management (majority of patients)

• Clear liquid diet × 1–2 days, advance as tolerated [1][5]
• Acetaminophen for pain
• ± Antibiotics based on risk stratification (see Medications section above)
• If antibiotics prescribed: 4–7 day course; re-evaluate within 7 days [1]

Inpatient management (when indicated)

• IV fluids, bowel rest
• IV antibiotics: ceftriaxone 1 g daily + metronidazole 500 mg q8h, or ampicillin-sulbactam [1][7]
• Transition to PO when tolerating diet (typically 48–72 hours)
• Repeat CT if no improvement after 3–5 days [1]

Long-term recurrence prevention

• High-fiber diet, maintain BMI 18–25, regular physical activity, smoking cessation [5][8]
• Avoid regular NSAID use (≥2×/week) except aspirin for cardiovascular prevention [5]
• Elective surgery is not routinely recommended based on number of episodes; individualize based on quality of life, severity, and patient preference [3][5]

Discharge criteria (outpatient management)

• Immunocompetent, tolerating PO, mild symptoms, no systemic inflammatory response [2]
• Adequate home support and ability to follow up [2]
• No high-risk features (see Alarm Features)

Admission criteria

• High fever >38.5°C (101.3°F), sepsis or septic shock [1]
• Unable to tolerate oral intake [7]
• Complicated disease on CT [7]
• Immunosuppression [7]
• Serious comorbidities or medically frail [2]
• Inadequate home support or inability to follow up [7]
• Failure to improve with outpatient management [7]
• Intractable pain requiring parenteral analgesia [7]

Surgical consultation triggers

• Perforation with peritonitis → emergent laparotomy [1]
• Abscess ≥3 cm → percutaneous drainage [8]
• Failure to improve despite adequate medical therapy [3]
• Obstruction, fistula, or non-resolving abscess [3]

Follow-up timing

• If treated with antibiotics: re-evaluate within 7 days for symptom resolution [1]
• If managed without antibiotics: follow up within 2–3 days if not improving, or sooner if worsening
• If unable to advance diet after 3–5 days → immediate reassessment [5]
• Colonoscopy 6 weeks after resolution — particularly important for complicated diverticulitis (6–8% CRC risk), first episode without recent colonoscopy, or atypical features [3][12]

Return precautions — instruct patients to return immediately for:

• Worsening or spreading abdominal pain
• New or worsening fever/chills
• Inability to tolerate any oral intake
• Bloody stools
• Dizziness, lightheadedness, or fainting
• Abdominal rigidity or distension

Expected recovery

• Symptoms improve within 48–72 hours; full resolution in 1–2 weeks [1]
• ~15% recurrence rate within 2 years [1]
• Risk of complicated disease is highest with the first presentation [5]

1. Diverticulitis. — Brown RF, Lopez K, Smith CB, Charles A. The Journal of the American Medical Association. 2025.

2. Diagnosis and Management of Acute Left-Sided Colonic Diverticulitis: A Clinical Guideline From the American College of Physicians. — Qaseem A, Etxeandia-Ikobaltzeta I, Lin JS, et al. Annals of Internal Medicine. 2022.

3. Colorectal Cancer Screening and Surveillance and Other Colon Conditions in the Older Adult. — Calderwood AH, Shaukat A. The American Journal of Gastroenterology. 2025.

4. Management of Diverticulitis: A Review. — Sacks OA, Hall J. JAMA Surgery. 2024.

5. AGA Clinical Practice Update on Medical Management of Colonic Diverticulitis: Expert Review. — Peery AF, Shaukat A, Strate LL. Gastroenterology. 2021.

6. Antibiotics for Uncomplicated Diverticulitis. — Dichman ML, Rosenstock SJ, Shabanzadeh DM. The Cochrane Database of Systematic Reviews. 2022.

7. Diverticulitis. — Young-Fadok TM. The New England Journal of Medicine. 2018.

8. Diverticular Disease: Rapid Evidence Review. — Bailey J, Dattani S, Jennings A. American Family Physician. 2022.

9. Revised Version Global Guidelines on Diverticular Disease of the Colon: The Fiesole Consensus Report. — Tursi A, Brandimarte G, Di Mario F, et al. Gut. 2025.

10. The American Society of Colon and Rectal Surgeons Clinical Practice Guidelines for the Treatment of Left-Sided Colonic Diverticulitis. — Hall J, Hardiman K, Lee S, et al. Diseases of the Colon and Rectum. 2020.

11. ACR Appropriateness Criteria® Left Lower Quadrant Pain: 2023 Update. — Weinstein S, Kim DH, Fowler KJ, et al. Journal of the American College of Radiology : JACR. 2023.

12. Evaluation and Management After Acute Left-Sided Colonic Diverticulitis : A Systematic Review. — Balk EM, Adam GP, Cao W, Mehta S, Shah N. Annals of Internal Medicine. 2022.