An Umbrella Review of Systematic Reviews on the Utility of Antibiotics in Patients With Acute Uncomplicated Diverticulitis.

ACG 2026 (Peery AF et al.; Am J Gastroenterol 2026;121(7):1549-1561; published 1 July 2026) is now the current US guideline. Its clinical content matches the standard on file. Classify diverticulitis by phenotype. UNCOMPLICATED is localized inflammation of colonic diverticula without abscess, perforation, stricture or fistula. CHRONIC/SMOLDERING is inflammation lasting weeks to months that partly or fully improves on antibiotics, then relapses soon after they stop. COMPLICATED means phlegmon, abscess or perforation, graded by the CT-based modified Hinchey scale (0, Ia, Ib, II, III, IV); strictures and fistulas are delayed complications. Hinchey 0-I is usually managed without surgery. Obtain CT at first presentation and in severe cases. Repeat CT may be unnecessary for a typical recurrence after a CT-confirmed prior episode without concerning features (severe pain, fever, vomiting, chills, abnormal exam). Keep a low threshold to image immunocompromised patients. ANTIBIOTICS: suggest against routine antibiotics for low-risk patients with acute uncomplicated diverticulitis (conditional, moderate certainty; four RCTs showed no effect on complications, recurrence, surgery, readmission or mortality). Low-risk means immunocompetent, hemodynamically stable, tolerating oral intake without SIRS, not frail, and able to follow up reliably as an outpatient. Give antibiotics for high-risk clinical or imaging features, immunocompromise, frailty or medical complexity, inability to tolerate oral intake, clinical worsening or prolonged symptoms, systemic inflammatory findings, or when safe outpatient management cannot be ensured. When used, give 4-7 days of oral therapy: amoxicillin-clavulanate 875/125 mg q12h or moxifloxacin 400 mg daily as monotherapy, or metronidazole 500 mg q8h plus TMP-SMX DS q12h, ciprofloxacin 500 mg q12h or levofloxacin 500 mg q24h. COLONOSCOPY after recovery: recommended after COMPLICATED diverticulitis to exclude a missed cancer or premalignant lesion (strong, moderate), usually about 6-8 weeks after recovery. After UNCOMPLICATED diverticulitis it is suggested only with alarm symptoms (unintentional weight loss, change in bowel habits, iron-deficiency anemia, bloody stools, persistent abdominal pain) or when colorectal cancer screening is not up to date (conditional, low). Colonoscopy can be deferred if a recent high-quality exam has excluded neoplasia. Do not scope routinely during the acute phase, but move earlier for alarm features such as ongoing bleeding, obstruction, or imaging concerning for malignancy. SURGERY: suggest surgical referral to discuss elective resection when recurrent uncomplicated diverticulitis significantly impairs quality of life (conditional, low). Base the decision on symptom burden, not episode count or preventing emergency surgery, and confirm the diagnosis by CT first. Resection lowers but does not eliminate recurrence: about 15% vs about 60% at 5 years. Without surgery, recurrence is at least 22% at 10 years after a first episode and at least 55% at 10 years after a second, and stays high after 3 or more. Risk of complicated disease is highest at the first episode and falls with recurrences. PREVENTION (all conditional): a healthy high-fiber diet (fruits, vegetables, whole grains, legumes; limit red meat, refined grains, trans fats, sweets); do not avoid nuts, corn, seeds or popcorn; avoid regular NSAID use unless clinically indicated; moderate heavy alcohol use; lose weight if overweight or obese; regular physical activity; stop smoking. Recommend AGAINST mesalamine (strong, moderate), probiotics (conditional, very low) and rifaximin (conditional, very low) to reduce recurrence.