Nonoperative Treatment of Diverticulitis and Appendicitis: Which Antibiotic Regimen Fails?

INTRODUCTION: Diverticulitis and appendicitis are common emergency general surgical conditions. Both can be treated with antibiotics alone; however, no antibiotic regimen has been identified as superior to others. In this study, we review different antibiotic regimens and their rates of failure. METHODS: Retrospective cohort study of patients treated empirically with antibiotics for diverticulitis or appendicitis from January 1, 2018, to December 31, 2020, at an independent academic hospital in the Midwest. RESULTS: A total of 587 (appendicitis, n = 43; diverticulitis, n = 544) patients were included in the cohort. They were equally male (49%) and female (51%) with a median age of 59 y. Three major antibiotic classes were compared: cephalosporin + metronidazole (C + M), penicillins, and quinolone + metronidazole. Appendicitis patients were more likely to receive C + M for empiric treatment (73%, P < 0.001), while diverticulitis patients were more likely to receive quinolone + metronidazole (45%, P < 0.001). Patients empirically treated with antibiotics for appendicitis were more likely than those treated for diverticulitis to require additional antibiotics or procedure within 90 d (33% versus 13%, respectively; P = 0.005). Empiric treatment with C + M for diverticulitis was more likely to be associated with the need for additional antibiotics or procedures within 90 d than treatment with other regimens (P = 0.003). Choice of antibiotic for empiric treatment did not correlate with death at 90 d for appendicitis or diverticulitis. Diverticulitis patients who were initially treated as inpatients and were prescribed C + M at hospital discharge had a higher rate of death than those who were prescribed the other antibiotics (P = 0.04). CONCLUSIONS: Empiric antibiotic treatment of appendicitis is more likely to be associated with additional antibiotics or procedure when compared with diverticulitis; however, antibiotic choice did not correlate with any of the other outcomes. Empiric treatment with a C + M for diverticulitis was more likely to be correlated with the need for additional antibiotics or procedure within 90 d.

Non-antibiotic treatment of uncomplicated acute diverticulitis is applicable and safe in our environment. A prospective multicenter study

Introduction: acute diverticulitis is one of the most frequent underlying causes behind individuals attending the Emergency Room with abdominal pain. The most widespread therapy for acute uncomplicated diverticulitis includes outpatient treatment with antibiotics; however, several publications indicate that patients can also be successfully treated without antibiotics. The results of the implementation of this more recent protocol in two hospitals in Madrid are presented. Methods: an observational prospective study was performed. Participants were patients diagnosed with uncomplicated acute diverticulitis at two hospitals in Madrid, Hospital Universitario de Torrejón and Hospital Universitario Puerta de Hierro Majadahonda, between December 2018 and August 2021, treated on an outpatient basis without antibiotic therapy. The study group was compared with a control group, composed of patients diagnosed with uncomplicated acute diverticulitis and treated with outpatient antibiotic therapy at Hospital Universitario Puerta de Hierro between March 2015 and March 2018. Results: three hundred and sixty-one patients were included, 182 in the study group and 179 in the control group. Diverticulitis was persistent in 19 patients (10.4 %) in the study group, who were not treated with antibiotics, and in five patients (2.8 %) in the control group, treated with outpatient antibiotic therapy (p = 0.004). Recurrences occurred in 23 patients (12.6 %) in the study group, and in 53 patients (29.6 %) in the control group (p < 0.0001). The analysis of the complications found no significant differences between both groups (p = 0.109). No urgent surgical intervention or mortality was recorded in the study group. Conclusions: in our environment, symptomatic non-antibiotic treatment of uncomplicated acute diverticulitis cases is safe, without showing a higher rate of complications. Although, there seems to be a worse initial symptom control. (AU)

Evaluation of physicians' current practices and awareness regarding the treatment of acute uncomplicated diverticulitis: results of a provincial survey.

OBJECTIVE: International guidelines now recommend nonantibiotic treatment of uncomplicated diverticulitis. We assessed physicians' current management strategies for uncomplicated diverticulitis, their awareness of the updated recommendations, and barriers to practice change. METHODS: A 21-question web-based survey conducted between 09/2022 and 11/2022 was sent to participants through their respective Quebec provincial associations or working groups. Participants included general surgeons, emergency physicians, gastroenterologists and general practitioners. Physicians who did not treat diverticulitis were excluded. The main outcomes were awareness of guideline recommendations on uncomplicated diverticulitis treatment, the use of nonantibiotic management for uncomplicated diverticulitis and identification of perceived barriers to practice change. RESULTS: The participation rate was 15.9%. The 465 participants consisted primarily of general practitioners (41.7%), general surgeons (29.2%) and emergency physicians (17.8%). Eighty-two percent had heard of the nonantibiotic treatment strategy for uncomplicated diverticulitis; 7.5% were "uncomfortable" and 44.6% "somewhat uncomfortable" with this practice. A third (31.8%) of all physicians had no knowledge of the updated guidelines on uncomplicated diverticulitis treatment. Most reported "never" (41.6%) or "rarely" (25.1%) omitting antibiotics for uncomplicated diverticulitis. When informed about nonantibiotic treatment, 28.7% and 51.4% of all physicians, respectively, indicated that this "will" change or "may" change their practice. Common perceived barriers to nonantibiotic treatment were concerns about treatment failure (69.6%), unawareness of updated recommendations (67.0%), difficulty in ensuring proper follow-up (59.0%) and workplace culture (54.9%). CONCLUSION: Physicians' awareness of practice guidelines recommending nonantibiotic treatment for uncomplicated diverticulitis and their application are suboptimal. Knowledge transfer activities, educational interventions and optimization of local protocols are needed to ensure the rational use of antibiotics.

RéSUMé: OBJECTIF: Les lignes directrices internationales recommandent désormais un traitement non antibiotique de la diverticulite non compliquée. Nous avons évalué les stratégies de traitement actuelles des médecins pour la diverticulite non compliquée, leur connaissance des recommandations mises à jour et les obstacles au changement de pratique. MéTHODES: Un sondage en ligne de 21 questions mené entre le 09/2022 et le 11/2022 a été envoyé aux participants par l'intermédiaire de leurs associations ou groupes de travail provinciaux respectifs au Québec. Les participants comprenaient des chirurgiens généraux, des urgentologues, des gastroentérologues et des médecins de famille. Les médecins qui ne traitaient pas de diverticulite ont été exclus. Les principales issues étaient la connaissance des recommandations des lignes directrices sur le traitement de la diverticulite non compliquée, l'utilisation du traitement non antibiotique pour la diverticulite non compliquée et l'identification des obstacles perçus au changement de pratique. RéSULTATS: Le taux de participation était de 15,9 %. Les 465 participants étaient principalement des médecins de famille (41,7 %), des chirurgiens généraux (29,2 %) et des urgentologues (17,8 %). Quatre-vingt-deux pour cent avaient entendu parler de la stratégie de traitement non antibiotique pour la diverticulite non compliquée; 7,5% étaient "inconfortables" et 44,6% "quelque peu inconfortables" avec cette pratique. Un tiers (31,8 %) des médecins ne connaissaient pas les lignes directrices mises à jour sur le traitement de la diverticulite non compliquée. La plupart ont rapporté "jamais" (41,6%) ou "rarement" (25,1%) omettre les antibiotiques pour la diverticulite non compliquée. Lorsqu'ils ont été informés du traitement non antibiotique, 28,7 % et 51,4 % de tous les médecins ont indiqué que cela «changera¼ ou «pourrait changer¼ leur pratique. Les fréquents obstacles au traitement non antibiotique étaient les préoccupations concernant l'échec du traitement (69,6 %), l'ignorance des recommandations mises à jour (67,0 %), la difficulté d'assurer un suivi approprié (59,0 %) et la culture en milieu de travail (54,9 %). CONCLUSIONS: La connaissance des lignes directrices recommandant un traitement non antibiotique pour la diverticulite non compliquée et leur application sont sous-optimales. Des activités de transfert de connaissances, des interventions éducatives et des protocoles locaux sont nécessaires pour assurer l'utilisation rationnelle des antibiotiques.

Treatment for acute uncomplicated diverticulitis without antibiotherapy: systematic review and meta-analysis of randomized clinical trials.

BACKGROUND: Use of antibiotics in selected cases of acute uncomplicated diverticulitis (AUD) has recently been questioned. OBJECTIVE: The aim of this study is to examine the safety and efficacy of treatment regimens without antibiotics compared with that of traditional treatments with antibiotics in selected patients with AUD. DATA SOURCES: PubMed, Medline, Embase, Web of Science, and the Cochrane Library. METHODS: A systematic review was performed according to PRISMA and AMSTAR guidelines by searching through Medline, Embase, Web of Science, and the Cochrane Library for randomized clinical trials (RCTs) published before December 2022. The outcomes assessed were the rates of readmission, change in strategy, emergency surgery, worsening, and persistent diverticulitis. STUDY SELECTION: RCTs on treating AUD without antibiotics published in English before December 2022 were included. INTERVENTION: Treatments without antibiotics were compared with treatments with antibiotics. MAIN OUTCOME MEASURES: The outcomes assessed were the rates of readmission, change in strategy, emergency surgery, worsening, and persistent diverticulitis. RESULTS: The search yielded 1163 studies. Four RCTs with 1809 patients were included in the review. Among these patients, 50.1% were treated conservatively without antibiotics. The meta-analysis showed no significant differences between nonantibiotic and antibiotic treatment groups with respect to rates of readmission [odds ratio (OR)=1.39; 95% CI: 0.93-2.06; P =0.11; I2 =0%], change in strategy (OR=1.03; 95% CI: 0.52-2,02; P =0.94; I2 =44%), emergency surgery (OR=0.43; 95% CI: 0.12-1.53; P =0.19; I2 =0%), worsening (OR=0.91; 95% CI: 0.48-1.73; P =0.78; I2 =0%), and persistent diverticulitis (OR=1.54; 95% CI: 0.63-3.26; P =0.26; I2 =0%). LIMITATIONS: Heterogeneity and a limited number of RCTs. CONCLUSIONS: Treatment for AUD without antibiotic therapy is safe and effective in selected patients. Further RTCs should confirm the present findings.

Infection or Inflammation: Are Uncomplicated Acute Appendicitis, Acute Cholecystitis, and Acute Diverticulitis Infectious Diseases?

Background: It is recognized increasingly that common surgical infections of the peritoneal cavity may be treated with antibiotic agents alone, or source control surgery with short-course antimicrobial therapy. By extension, testable hypotheses have emerged that such infections may not actually be infectious diseases, but rather represent inflammation that can be treated successfully with neither surgery nor antibiotic agents. The aim of this review is to examine extant data to determine which of uncomplicated acute appendicitis (uAA), uncomplicated acute calculous cholecystitis (uACC), or uncomplicated mild acute diverticulitis (umAD) might be amenable to management using supportive therapy alone, consistent with the principles of antimicrobial stewardship. Methods: Review of pertinent English-language literature and expert opinion. Results: Only two small trials have examined whether uAA can be managed with observation and supportive therapy alone, one of which is underpowered and was stopped prematurely because of challenging patient recruitment. Data are insufficient to determine the safety and efficacy of non-antibiotic therapy of uAA. Uncomplicated acute calculous cholecystitis is not primarily an infectious disease; infection is a secondary phenomenon. Even when bactibilia is present, there is no high-quality evidence to suggest that mild disease should be treated with antibiotic agents. There is evidence to indicate that antibiotic prophylaxis is indicated for urgent/emergency cholecystectomy for uACC, but not in the post-operative period. Uncomplicated mild acute diverticulitis, generally Hinchey 1a or 1b in current nomenclature, does not benefit from antimicrobial agents based on multiple clinical studies. The implication is that umAD is inflammatory and not an infectious disease. Non-antimicrobial management is reasonable. Conclusions: Among the considered disease entities, the evidence is strongest that umAD is not an infectious disease and can be treated without antibiotic agents, intermediate regarding uACC, and lacking for uAA. A plausible hypothesis is that these inflammatory conditions are related to disruption of the normal microbiome, resulting in dysbiosis, which is defined as an imbalance of the natural microflora, especially of the gut, that is believed to contribute to a range of conditions of ill health. As for restorative pre- or probiotic therapy to reconstitute the microbiome, no recommendation can be made in terms of treatment, but it is not recommended for prevention of primary or recurrent disease.

Evaluation of a treatment pathway for the management of uncomplicated diverticulitis.

INTRODUCTION: Recent clinical practice recommendations have radically modified the management of colonic diverticulitis. The goal of our study was to evaluate a treatment pathway for uncomplicated diverticulitis and to analyze the outcome (patient compliance, treatment failure and complications). PATIENTS AND METHODS: All patients who presented to the emergency department with the diagnosis of uncomplicated diverticulitis were prospectively included in this study. The treatment pathway included an outpatient clinical re-assessment by a gastrointestinal surgeon. In case of symptomatic treatment failure, oral antibiotics were prescribed. If developed clinical signs of severity developed, the patient was referred to the emergency department for new laboratory and imaging workup. RESULTS: Eighty-seven patients were included. The mean interval before re-assessment was 2.8 days. Fifty-nine patients (67.8%) had symptomatic treatment upon discharge from the emergency department and were reassessed as outpatients by the surgical team. Patient evolution was satisfactory for 45 (76.3%); 10 (16.9%) required oral antibiotics. One (1.7%) patient developed complicated diverticulitis. Thirty-four (39.1%) patients did not comply with the current recommendations. CONCLUSION: In our experience, uncomplicated diverticulitis can be treated effectively in an ambulatory setting followed by early re-assessment by a surgeon.

Antibiotic treatment duration in diverticulitis, complicated urinary tract infection, and endocarditis: a retrospective, single-center study.

OBJECTIVES: Despite the availability of international guidelines advocating shorter treatment durations, nonadherence to them is common. We assessed duration of antibiotic treatment for diverticulitis, complicated urinary tract infection (UTI), and endocarditis. METHODS: Medical records of patients hospitalized with the previously stated diseases in 2017 and 2018 were randomly selected at a Swiss tertiary care hospital. The appropriateness of antibiotic treatment duration was assessed according to international and local guidelines. RESULTS: A total of 243 patients were included in the study: 100 with diverticulitis, 200 with complicated UTI, and 43 with endocarditis. The dherence to local and international guidelines was 11% and 18% in diverticulitis, 39% and 40% in complicated UTI, and 84% and 86% in endocarditis, respectively. Nonadherence was primarily due to the prolonged treatment in diverticulitis and complicated UTI with a median duration of antibiotic treatment of 11 days (interquartile range 10-13) and 14 days (interquartile range 10-15), respectively. When pooling diverticulitis and complicated UTI cases, the identification of a pathogen in any microbiological sample was associated with an improved adherence to local guidelines in addition to hospitalization in a medical ward and infectious diseases consultation. CONCLUSION: Prolonged courses of antibiotic treatment were common and the treatment adherence to guidelines were poor in diverticulitis, moderate in complicated UTI, and excellent in endocarditis.

Impact of bowel preparation on elective colectomies for diverticulitis: analysis of the NSQIP database.

BACKGROUND: Recent data based on large databases show that bowel preparation (BP) is associated with improved outcomes in patients undergoing elective colorectal surgery. However, it remains unclear whether BP in elective colectomies would lead to similar results in patients with diverticulitis. The purpose of this study was to investigate whether bowel preparation affected the surgical site infections (SSI) and anastomotic leakage (AL) in patients with diverticulitis undergoing elective colectomies. STUDY DESIGN: We identified 16,380 diverticulitis patients who underwent elective colectomies from the American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) colectomy targeted database (2012-2017). Multivariate logistic regression models were employed to investigate the impact of different bowel preparation strategies on postoperative complications, including SSI and AL. RESULTS: In the identified population, a total of 2524 patients (15.4%) received no preparation (NP), 4715 (28.8%) mechanical bowel preparation (MBP) alone, 739 (4.5%) antibiotic bowel preparation (ABP) alone, and 8402 (51.3%) MBP + ABP. Compared to NP, patients who received any type of bowel preparations showed a significantly decreased risk of SSI and AL after adjustment for potential confounders (SSI: MBP [OR = 0.82, 95%CI: 0.70-0.96], ABP [0.69, 95%CI: 0.52-0.92]; AL: MBP [OR = 0.66, 95%CI: 0.51-0.86], ABP [0.56, 95%CI: 0.34-0.93]), where the combination type of MBP + ABP had the strongest effect (SSI:OR = 0.58, 95%CI:0.50-0.67; AL:OR = 0.46, 95%CI:0.36-0.59). The significantly decreased risk of 30-day mortality was observed in the bowel preparation of MBP + ABP only (OR = 0.32, 95%CI: 0.13-0.79). After the further stratification by surgery procedures, patients who received MBP + ABP showed consistently lower risk for both SSI and AL when undergoing open and laparoscopic surgeries (Open: SSI [OR = 0.51, 95%CI: 0.37-0.69], AL [OR = 0.47, 95%CI: 0.25-0.91]; Laparoscopic: SSI [OR = 0.58, 95%CI: 0.47-0.72, AL [OR = 0.49, 95%CI: 0.35-0.68]). CONCLUSIONS: MBP + ABP for diverticulitis patients undergoing elective open or laparoscopic colectomies was associated with decreased risk of SSI, AL, and 30-day mortality. Benefits of MBP + ABP for diverticulitis patients underwent robotic surgeries warrant further investigation.

Antibiotics for uncomplicated diverticulitis.

BACKGROUND: Diverticulitis is a complication of the common condition, diverticulosis. Uncomplicated diverticulitis has traditionally been treated with antibiotics, as diverticulitis has been regarded as an infectious disease. Risk factors for diverticulitis, however, may suggest that the condition is inflammatory rather than infectious which makes the use of antibiotics questionable. OBJECTIVES: The objectives of this systematic review were to determine if antibiotic treatment of uncomplicated acute diverticulitis affects the risk of complications (immediate or late) or the need for emergency surgery. SEARCH METHODS: For this update, a comprehensive systematic literature search was conducted in Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, ClinicalTrials.gov and WHO International Clinical Trial Registry Platform on February 2021. SELECTION CRITERIA: Randomised controlled trials (RCTs), including all types of patients with a radiologically confirmed diagnosis of left-sided uncomplicated acute diverticulitis. Comparator and interventions included antibiotics compared to no antibiotics, placebo, or to any other antibiotic treatment (different regimens, routes of administration, dosage or duration of treatment). Primary outcome measures were complications and emergency surgery. Secondary outcomes were recurrence, late complications, elective colonic resections, length of hospital stay, length to recovery of symptoms, adverse events and mortality. DATA COLLECTION AND ANALYSIS: Two authors performed the searches, identification and assessment of RCTs and data extraction. Disagreements were resolved by discussion or involvement of the third author. Authors of trials were contacted to obtain additional data if needed or for preliminary results of ongoing trials. The Cochrane Collaboration's tool for assessing risk of bias was used to assess the methodological quality of the identified trials. The overall quality of evidence for outcomes was evaluated using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach. Effect estimates were extracted as risk ratios (RRs) with 95% confidence intervals. Random-effects meta-analyses were performed with the Mantel-Haenzel method. MAIN RESULTS: The authors included five studies. Three studies compared no antibiotics to antibiotics; all three were original RCTs of which two also published long-term follow-up information.  For the outcome of short-term complications there may be little or no difference between antibiotics and no antibiotics (RR 0.89; 95% CI 0.30 to 2.62; 3 studies, 1329 participants; low-certainty evidence). The rate of emergency surgery within 30 days may be lower with no antibiotics compared to antibiotics (RR 0.47; 95% CI 0.13, 1.71; 1329 participants; 3 studies; low-certainty evidence). However, there is considerable imprecision due to wide confidence intervals for this effect estimate causing uncertainty which means that there may also be a benefit with antibiotics. One of the two remaining trials compared single to double compound antibiotic therapy and, due to wide confidence intervals, the estimate was imprecise and indicated an uncertain clinical effect between these two antibiotic regimens (RR 0.70; 95% CI 0.11 to 4.58; 51 participants; 1 study; low-certainty evidence). The last trial compared short to long intravenous administration of antibiotics and did not report any events for our primary outcomes. Both trials included few participants and one had overall high risk of bias. Since the first publication of this systematic review, an increasing amount of evidence supporting the treatment of uncomplicated acute diverticulitis without antibiotics has been published, but the total body of evidence is still limited. AUTHORS' CONCLUSIONS: The evidence on antibiotic treatment for uncomplicated acute diverticulitis suggests that the effect of antibiotics is uncertain for complications, emergency surgery, recurrence, elective colonic resections, and long-term complications. The quality of the evidence is low. Only three RCTs on the need for antibiotics are currently available. More trials are needed to obtain more precise effect estimates.

Efficacy and Safety of a Strategy for Reviewing Intravenous Antibiotics for Hospitalized Japanese Patients with Uncomplicated Diverticulitis: A Single-center Observational Study.

Objective Treatment for uncomplicated diverticulitis (UD) is not well established. We evaluated the strategy of reviewing intravenous antibiotics for hospitalized Japanese patients with UD. Methods Treatment was based on the physician's choice until August 2018; the indications for hospitalization and treatment have been standardized since September 2018. In this study, we monitored the use of intravenous antibiotics administered to patients hospitalized for UD and then reviewed the need for them on hospital day 3. We compared patients' length of antibiotic use, hospital stay, health care cost, and complications via the review strategy from September 2018 to December 2020 and via the previous physicians' choice strategy from January 2016 to August 2018. Results Two hundred and forty-seven patients were admitted to our hospital because of acute colonic diverticulitis from January 2016 to December 2020. After excluding complicated cases, 106 individuals were enrolled during the period of physician's choice; 87 were enrolled when treatment review was employed. There were no significant differences in age, sex, inflammation site, or severity during the first hospital visit. The median duration of antibiotic use was significantly reduced from 5 to 4 days (p=0.0075), with no marked increase in rates of transfer to surgery, mortality, or readmission due to recurrence. A more significant proportion of patients completed 3-day antibiotic treatment with the review strategy than with the physician's choice strategy (6.6% vs. 25.3%, p=0.0004). However, the length of hospital stay and total medical costs did not decrease. Conclusion The strategy of reviewing treatment on day 3 after hospitalization for UD safety reduced the duration of antibiotic use, but the hospital stay and health care costs did not decrease.

Management of acute uncomplicated diverticulitis without antibiotics: compliance and outcomes -a retrospective cohort study.

METHODS: Recent randomized control trials (RCTs) have confirmed that antibiotics in acute uncomplicated diverticulitis (AUD) neither accelerate recovery nor prevent complications or recurrences. A retrospective cohort study was conducted, including all consecutive AUD patients hospitalized 2015- 2018 at Helsingborg Hospital (HH) and Skåne University Hospital (SUS), Sweden. HH had implemented a non-antibiotic treatment protocol in 2014 while SUS had not. Main outcomes were proportion of patients treated with antibiotics, complications, recurrences, and adherence to routinely colon evaluation. RESULTS: A total of 583 AUD patients were enrolled, 388 at SUS and 195 at HH. The diagnosis was CT-verified in 320 (83%) vs. 186 (95%) patients respectively (p < 0.001). Forty-three (11%) and 94 (48%) of patients respectively did not receive antibiotics during hospitalization (p < 0.001). CRP was higher in the antibiotic group compared to the non-antibiotic group, both at admission and peak (90 mg/L vs 65 mg/L; p = 0.016) and (138 mg/L and 97 mg/L; p < 0.001). There were no significant differences in recurrences (22.0% vs. 22.6%; p = 0.87) and complications (2.5% vs. 2.9%; p = 0.77) between the antibiotic/non-antibiotic groups. CONCLUSION: The structured treatment protocol led to reduced antibiotic use and a higher standard of care in terms of CT-verification. Clinicians' compliance to the treatment protocol and best clinical practice was poor and warrants further studies.

In mild acute diverticulitis, outpatient therapy without antibiotics was noninferior to antibiotics.

SOURCE CITATION: Mora-López L, Ruiz-Edo N, Estrada-Ferrer O, et al. Efficacy and safety of nonantibiotic outpatient treatment in mild acute diverticulitis (DINAMO-study): a multicentre, randomised, open-label, noninferiority trial. Ann Surg. 2021;274:e435-42. 34183510.

Diagnostic Imaging and Medical Management of Acute Left-Sided Colonic Diverticulitis : A Systematic Review.

BACKGROUND: Clinicians need to better understand the value of computed tomography (CT) imaging and nonsurgical treatment options to manage acute left-sided colonic diverticulitis. PURPOSE: To evaluate CT imaging, outpatient treatment of uncomplicated diverticulitis, antibiotic treatment, and interventional radiology for patients with complicated diverticulitis. DATA SOURCES: MEDLINE, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, Embase, CINAHL, and ClinicalTrials.gov from 1 January 1990 through 16 November 2020. STUDY SELECTION: Existing systematic reviews of CT imaging accuracy, as well as randomized trials and adjusted nonrandomized comparative studies reporting clinical or patient-centered outcomes. DATA EXTRACTION: 6 researchers extracted study data and risk of bias, which were verified by an independent researcher. The team assessed strength of evidence across studies. DATA SYNTHESIS: Based on moderate-strength evidence, CT imaging is highly accurate for diagnosing acute diverticulitis. For patients with uncomplicated acute diverticulitis, 6 studies provide low-strength evidence that initial outpatient and inpatient management have similar risks for recurrence or elective surgery, but they provide insufficient evidence regarding other outcomes. Also, for patients with uncomplicated acute diverticulitis, 5 studies comparing antibiotics versus no antibiotics provide low-strength evidence that does not support differences in risks for treatment failure, elective surgery, recurrence, posttreatment complications, and other outcomes. Evidence is insufficient to determine choice of antibiotic regimen (7 studies) or effect of percutaneous drainage (2 studies). LIMITATIONS: The evidence base is mostly of low strength. Studies did not adequately assess heterogeneity of treatment effect. CONCLUSION: Computed tomography imaging is accurate for diagnosing acute diverticulitis. For patients with uncomplicated diverticulitis, no differences in outcomes were found between outpatient and inpatient care. Avoidance of antibiotics for uncomplicated acute diverticulitis may be safe for most patients. The evidence is too sparse for other evaluated questions. PRIMARY FUNDING SOURCE: Agency for Healthcare Research and Quality and American College of Physicians. (PROSPERO: CRD42020151246).