Diagnosis and Management of Acute Left-Sided Colonic Diverticulitis: A Clinical Guideline From the American College of PhysiciansFREE
- Correction(s) for this article:
The American College of Physicians (ACP) developed this guideline to provide clinical recommendations on the diagnosis and management of acute left-sided colonic diverticulitis in adults. This guideline is based on current best available evidence about benefits and harms, taken in the context of costs and patient values and preferences.
The ACP Clinical Guidelines Committee (CGC) developed this guideline based on a systematic review on the use of computed tomography (CT) for the diagnosis of acute left-sided colonic diverticulitis and on management via hospitalization, antibiotic use, and interventional percutaneous abscess drainage. The systematic review evaluated outcomes that the CGC rated as critical or important. This guideline was developed using the GRADE (Grading of Recommendations Assessment, Development and Evaluation) methodology.
Target Audience and Patient Population:
The target audience is all clinicians, and the target patient population is adults with suspected or known acute left-sided colonic diverticulitis.
ACP suggests that clinicians use abdominal CT imaging when there is diagnostic uncertainty in a patient with suspected acute left-sided colonic diverticulitis (conditional recommendation; low-certainty evidence).
ACP suggests that clinicians manage most patients with acute uncomplicated left-sided colonic diverticulitis in an outpatient setting (conditional recommendation; low-certainty evidence).
ACP suggests that clinicians initially manage select patients with acute uncomplicated left-sided colonic diverticulitis without antibiotics (conditional recommendation; low-certainty evidence).
Acute colonic diverticulitis is inflammation of diverticula, abnormal outpouchings of the large intestine (1). Diverticulosis (presence of diverticula without inflammation) precedes diverticulitis (presence of diverticula with inflammation). An estimated 5% to 10% of patients with diverticulosis may develop acute diverticulitis (2), and the risk increases with age (3, 4). From 2000 to 2007, the estimated prevalence of acute colonic diverticulitis in the general population was 180 cases per 100 000 persons per year, and incidence seems to be increasing (1, 3, 5). Right-sided colonic diverticulitis is far more prevalent in Asian countries, whereas left-sided colonic diverticulitis is predominant in Western countries (6). Approximately 200 000 hospitalizations occur annually for acute left-sided colonic diverticulitis in the United States (7), and national costs for hospitalizations with a principal diagnosis of acute diverticulitis have totaled more than $8 billion annually in recent years (8).
Acute diverticulitis episodes are usually uncomplicated (causing only localized inflammation). However, in about 12% of cases, patients have complicated diverticulitis, which is defined as inflammation associated with an abscess, a phlegmon, a fistula, an obstruction, bleeding, or perforation (9). Among patients with an index or second episode of acute diverticulitis, the reported rate of recurrence at 10 years is 22% or 55%, respectively (3).
Timely and correct diagnosis of acute left-sided colonic diverticulitis is essential for the selection of the most appropriate management options (3, 4). Given that abdominal computed tomography (CT) imaging is widely used to evaluate persons with suspected diverticulitis, many patients with acute abdominal pain will have CT scans each year (10). However, questions exist about the diagnostic accuracy, effect on clinical management and diverticulitis-related health outcomes, downstream consequences of incidental findings, and costs of CT imaging for the diagnosis of acute colonic diverticulitis. Management of uncomplicated diverticulitis has typically included bowel rest, fluids, and antibiotics, although there is uncertainty regarding the effectiveness of the routine use of antibiotics and the role of hospitalization in managing most episodes (11, 12).
Guideline Focus and Target Population
The purpose of this American College of Physicians (ACP) guideline is to present recommendations on the use of CT imaging for the diagnosis of acute left-sided colonic diverticulitis and on subsequent management, including hospitalization, antibiotic use, and interventional percutaneous drainage. The Clinical Guidelines Committee (CGC) developed the recommendations, which are based on the best available evidence on benefits and harms, patient values and preferences, and consideration of costs. These recommendations are based on a systematic review conducted by the Brown Evidence-based Practice Center and funded by the Agency for Healthcare Research and Quality (10). The development of the updated accompanying systematic review article was funded by ACP.
The target audience for this guideline is all clinicians, and the target patient population is adults with suspected or known acute left-sided colonic diverticulitis.
Systematic Review of the Evidence
Details and methods for the supporting systematic review are included in the original report and accompanying article (10) and in the Appendix. The CGC nominated the key questions, and several CGC members participated on a technical expert panel convened by the Brown Evidence-based Practice Center, which comprised key informants and technical experts to inform the systematic review and assist in refining the scope and key questions.
The systematic review searched MEDLINE (via PubMed), Embase, Cochrane, and CINAHL for randomized controlled trials (RCTs), observational studies, single-group studies, and existing systematic reviews published in English from 1 January 1990 through 1 June 2020 (updated through 16 November 2020) (10). The systematic review included studies of adults with acute (complicated or uncomplicated) left-sided colonic diverticulitis, as defined in the studies. Studies of patient populations with the following conditions were excluded: complicated diverticulosis without diverticulitis, symptomatic uncomplicated diverticular disease, Meckel diverticula (unless it was concurrent with acute diverticulitis), acute right-sided colonic diverticulitis, and noncolonic diverticulitis. The systematic review excluded right-sided diverticulitis because it is much less prevalent in Western countries and has a different natural history and management options (6).
Committee members (clinicians and nonclinician public members) and the CGC Public Panel members were asked a priori to independently rate the importance of evaluated outcomes (Table 1). All critical and important outcomes were considered in the development of the recommendations.
Values and Preferences
ACP staff searched several databases (MEDLINE, PsycINFO, PubMed, Trip database, and Google Scholar) through 24 February 2021 to identify studies on values and preferences regarding the diagnosis and management of acute left-sided colonic diverticulitis. The development of this guideline also included the perspectives, values, and preferences of 2 CGC members and a 7-member CGC Public Panel, who rated outcomes, provided input on their preferences among the intervention options via a direct choice exercise, and provided comments on the guideline and recommendations.
ACP staff searched several databases (PubMed, MEDLINE, National Health Service Economic Evaluation Database, Database of Abstracts of Reviews of Effects, and Health Technology Assessment Database) through 31 January 2021 to identify English-language publications of economic studies, including cost–utility, cost-effectiveness, cost–benefit, and cost–consequences analyses. The CGC also used the Agency for Healthcare Research and Quality Healthcare Cost and Utilization Project database to approximate information on inpatient national average cost.
Evidence to Recommendations
This guideline was developed by the CGC according to ACP's guideline development process, details of which can be found in ACP's methods papers (13, 14). When developing the recommendations, the CGC used GRADE (Grading of Recommendations Assessment, Development and Evaluation) tables derived from the accompanying systematic review (10) and graded the recommendations using the GRADE method (15) (Figure 1). The Supplement presents the GRADE evidence-to-decision tables illustrating the evidence framework supporting the recommendations.
The guideline underwent a peer review process through the journal and was posted online for comments from ACP Regents and ACP Governors, who represent internal medicine and its subspecialty physician members at the national and international levels. The CGC considered all comments before finalizing the guideline.
Summary of the Evidence
Key Findings on Critical and Important Outcomes: Role of CT in the Diagnosis of Acute Left-Sided Colonic Diverticulitis
The systematic review identified 5 observational studies (16–20) that reported on clinical sequelae related either to CT imaging for suspected acute diverticulitis or to incidental findings on CT (17, 20). The review also identified 2 previously published systematic reviews (29, 30) that reported on the diagnostic test accuracy of CT for patients with suspected diverticulitis. Both systematic reviews included the same 8 studies (21–28) with search dates through 2013.
Effect of CT Imaging on Clinical Management
Five studies reporting on clinical management decisions were of poor methodological quality, and none compared patient outcomes in association with CT-guided care versus care without CT guidance (16–20).
Among outcomes rated as critical, low-certainty evidence showed that abdominal CT after clinical diagnosis may be associated with appropriate management of patients with suspected acute left-sided colonic diverticulitis compared with clinical diagnosis based on available clinical data, laboratory and radiologic investigations, and operative and histologic reports in patients who required surgery (18, 19). Low-certainty evidence also showed that misdiagnoses with CT resulting in adverse clinical sequelae may be rare; however, the included studies did not report patient outcomes associated with misdiagnosis with CT (such as missed diagnosis of colorectal cancer) (16, 18, 19).
Among outcomes rated as important, low-certainty evidence showed that incidental extracolonic or colonic findings may be common with CT in adults with nontraumatic acute abdomen but that the clinical significance of the findings is unclear (17, 20). Although some clinically important incidental findings requiring further work-up were reported (range, 6% to 9%), such as clinically silent occult neoplasms, adrenal adenomas, colorectal polyps, perforated diverticulitis, complex renal cysts, and thickening or lesion of the lower esophagus, the included studies did not analyze the association with patient outcomes, including mortality, morbidity, and quality of life (17, 20).
Test Accuracy of CT Imaging for the Diagnosis of Acute Left-Sided Colonic Diverticulitis
Moderate-certainty evidence showed that CT with contrast (oral, intravenous, or rectal) had a pooled sensitivity of 94% (95% CI, 87% to 97%) and a pooled specificity of 99% (CI, 90% to 99.9%) compared with follow-up diagnosis based on available clinical data, laboratory and colonoscopic investigations, and operative and histologic reports in patients who required surgery (21–30). The CGC estimated low and high pretest probability rates of acute left-sided colonic diverticulitis based on the prevalence reported in the included studies (Supplement Table 1). Based on a prevalence range from 10% to 70%, an estimated 6 to 42 patients per 1000 tested would have falsely normal findings on a CT scan and 9 to 3 patients per 1000 tested would have falsely abnormal findings on a CT scan.
Key Findings on Critical and Important Outcomes: Management of Acute Left-Sided Colonic Diverticulitis
The systematic review identified 20 studies reporting on the management of acute left-sided colonic diverticulitis. Specific management approaches assessed included setting of care (outpatient vs. inpatient; 6 studies), antibiotic treatment (12 studies), and interventional percutaneous abscess drainage (2 studies).
Outpatient Versus Inpatient Management for Acute Uncomplicated Left-Sided Diverticulitis
The systematic review identified 6 studies (31–36) that evaluated outpatient versus inpatient management for acute uncomplicated diverticulitis, including 1 RCT (31), 4 retrospective observational studies (32–34, 36), and 1 prospective observational study (35). Enrollment criteria included ability to tolerate oral intake (3 studies), adequate family or social support (2 studies), willingness to continue supervised treatment at home (1 study), absence of comorbid conditions (1 study), and no recent receipt of antibiotics before presentation (1 study).
Among critical outcomes, low-certainty evidence showed that associated risk for elective surgery may not differ between outpatient and inpatient management (pooled odds ratio, 0.76 [CI, 0.21 to 2.77]) (33, 35, 36). Evidence was very uncertain (insufficient) about the effect on emergency surgery, mortality, treatment failure (heterogeneously defined), and quality of life.
Among important outcomes, low-certainty evidence showed that associated risk for recurrence may not differ between outpatient and inpatient management (odds ratio, 0.85 [CI, 0.50 to 1.43]) (33–36).
Antibiotic Treatment Versus No Antibiotic Treatment of Acute Uncomplicated Left-Sided Colonic Diverticulitis
Five studies compared the use of antibiotics with no antibiotics in patients with acute uncomplicated left-sided colonic diverticulitis in inpatient settings, including 3 RCTs (reported in 7 articles [37–41, 43, 54]), 1 retrospective study (45), and 1 prospective observational study (44). Two studies, in 3 publications (38, 40, 45), assessed the comparative effectiveness of various antibiotics; 2 studies, in 5 articles (37, 39, 41, 43, 54), assessed amoxicillin–clavulanate (1 study included additional discretionary use of intravenous [IV] cefuroxime and oral metronidazole ); and 1 study assessed cephalosporin–metronidazole (44). Studies enrolled adults with uncomplicated acute diverticulitis verified by CT, excluding patients with complicated diverticulitis, systemic inflammatory response, or immunosuppression and those with recent or ongoing antibiotic treatments.
Among critical outcomes, low-certainty evidence showed that antibiotic treatment, compared with no antibiotic treatment, may result in no differences in quality of life at 3, 6, 12, or 24 months or 11 years (38–40); in diverticulitis-related complications (1.1% vs. 1.8% at 1 month and 2.1% vs. 4.0% at 1 year); or in the need for surgery at 6 to 12 months (absolute risk difference range, −2.0% to −0.4%) (38–40) in patients with acute uncomplicated left-sided colonic diverticulitis. Low-certainty evidence from post hoc individual patient data meta-analysis of 2 RCTs (55) showed that antibiotic treatment, compared with no antibiotic treatment, may slightly decrease treatment failure (defined as “ongoing diverticulitis” within 3 months of treatment; absolute risk difference, −2.2% [CI, −4.1% to 0.8%]). Evidence was very uncertain (insufficient) about the effect on diverticulitis-related mortality (38, 39, 43).
Among important outcomes, low-certainty evidence from post hoc individual patient data meta-analysis of 2 RCTs (55) showed that, compared with no antibiotic treatment, antibiotic treatment may result in no differences in length of hospital stay (mean difference, −7.7 hours [CI, −20.2 to 4.8 hours]) or long-term diverticulitis recurrence (≥12 months: absolute risk difference, 0.9% [CI, −2.1% to 5.1%]). Evidence was very uncertain (insufficient) about the effect on any adverse events and rehospitalization.
Comparative Effectiveness of Different Antibiotic Regimens in Acute Uncomplicated Left-Sided Colonic Diverticulitis
Eight studies, including 4 RCTs (46, 48–50) and 4 observational studies (47, 51, 52), compared antibiotic regimens in acute left-sided colonic diverticulitis. Most studies enrolled immunocompetent adults with acute uncomplicated left-sided colonic diverticulitis verified by CT who presented in emergency departments. All but 2 of the studies (47, 52) evaluated antibiotics in inpatient settings. Each study evaluated a different regimen: a combination of IV gentamicin and clindamycin versus IV cefoxitin (46); a short course of IV followed by oral amoxicillin–clavulanate during inpatient care, then oral during outpatient care, versus IV-only amoxicillin–clavulanate during inpatient care, then oral during outpatient care (48); an IV versus an oral combination of ciprofloxacin and metronidazole (49); IV ertapenem, 4 versus 7 days (50); various IV antibiotics for at most 5 days versus 6 to 14 days (51); an oral combination of fluoroquinolone and metronidazole versus other oral antibiotics (52); any antibiotic for fewer than 10 days versus 10 to 13 days versus 14 days or longer (52); and a combination of metronidazole and a fluoroquinolone versus amoxicillin–clavulanate alone for the prevention of diverticulitis-related outcomes (47).
Evidence was very uncertain (insufficient) about the comparative effectiveness of various antibiotic regimens and durations for all reported outcomes.
Percutaneous Drainage of Abscess Versus Conservative Management in Acute Complicated Left-Sided Colonic Diverticulitis
Two retrospective observational studies (42, 53) compared percutaneous drainage of abscess versus conservative management (no percutaneous drainage or discretionary, undefined antibiotics) in patients with CT-diagnosed abscess (only ≥4-cm abscesses were considered in the larger study). Evidence was very uncertain (insufficient) about the association between percutaneous drainage and any reported outcomes.
Values and Preferences
No systematic reviews were identified that assessed the relative importance of outcomes or patient values and preferences for the management of acute colonic diverticulitis. Feedback from the CGC Public Panel showed variability in preferences about abdominal CT imaging for the diagnosis of acute left-sided colonic diverticulitis. This variability was influenced by physician diagnostic uncertainty, risks and costs associated with CT imaging, and the low certainty of the evidence for benefits and harms of CT. A trend was observed toward a preference for outpatient over inpatient management of acute uncomplicated left-sided colonic diverticulitis. Geographic location and caregiver support at home were identified as important factors in a choice for outpatient treatment. A strong preference for management without antibiotics was also seen. Insufficient evidence about the comparative benefits of interventional percutaneous abscess drainage versus conservative treatment resulted in important variability in patient preferences for these treatment options.
No studies were identified that reported on the cost-effectiveness of the reviewed interventions in the United States. Out-of-pocket costs of CT (abdomen and pelvis) with contrast material ranged from $56 in ambulatory surgical centers to $94 in hospital outpatient departments for Medicare beneficiaries and from $580 to $4885, respectively, for uninsured adults (56–59). Several systematic reviews of mostly European RCTs and observational studies reported absolute cost savings from outpatient treatment compared with inpatient treatment ranging from 35.0% to 83.0% (31, 60–63) per episode of acute diverticulitis; however, the reviews acknowledged a serious risk of bias in observational studies that did not properly adjust for various treatments prescribed at the discretion of physicians managing patients in inpatient and outpatient settings. A single Spanish RCT (31) included in the systematic reviews reported that the overall cost of inpatient treatment was 3 times higher than that of outpatient treatment, mostly because of administrative expenses and the cost of hospital beds rather than the cost of pharmacologic treatments, including antibiotics. Table 3 reports estimated unit costs for reviewed antibiotics, and the Supplement summarizes additional costs and resource information.
Multiple Chronic Conditions
Overall, eligible RCTs excluded patients with unstable comorbid conditions or immunosuppression and did not examine patient outcomes in subpopulations with major comorbid conditions.
Areas of Inconclusive Evidence
Evidence is inconclusive to assess benefits and harms for the following comparisons: the association between CT imaging and diverticulitis-related patient health outcomes, the comparative effectiveness of antibiotic regimens, and percutaneous drainage versus conservative management for CT-verified abscess.
Studies typically did not report on harms, adverse events, or side effects, including health care–associated infections, such as nosocomial infection (outpatient vs. inpatient comparison); side effects or adverse events attributable to antibiotics, such as Clostridioides difficile infection and antibiotic resistance (antibiotic comparisons); or adverse events related to procedures, such as bleeding and catheter infections (percutaneous drainage of abscess vs. conservative management comparisons).
Most included studies were done in the emergency department; more evidence is needed on the diagnosis and management pathway among patients presenting to primary care clinics. Future studies should aim to include a wider spectrum of patients and health care settings to better inform which patients are most likely to benefit (or not benefit) from various interventions.
Areas of No Evidence
The systematic review did not identify any comparative studies on the additional value of CT over standard care. No included studies reported on the following critical and important outcomes related to the use of abdominal CT for the diagnosis of acute diverticulitis: progression to complicated diverticulitis, diverticulitis-related complications, and diverticulitis-related mortality (critical), as well as future episodes of complicated diverticulitis, length of hospital stay, recurrent diverticulitis, and time to resolution (important). No studies were identified assessing the use of antibiotics in patients with acute complicated left-sided colonic diverticulitis.
No included studies reported on the following critical and important outcomes related to the management of acute left-sided colonic diverticulitis: progression to complicated diverticulitis (critical) and return to normal bowel function; missed work, employment, or school; and opioid misuse (important). In addition, no studies reported either on patient values and preferences for the diagnosis and management of acute colonic diverticulitis or on any related cost evaluations.
Recommendation 1: ACP suggests that clinicians use abdominal CT imaging when there is diagnostic uncertainty in a patient with suspected acute left-sided colonic diverticulitis (conditional recommendation; low-certainty evidence).
A detailed history, physical examination, and laboratory findings are the first steps in diagnosing acute colonic diverticulitis in most patients with abdominal pain or tenderness primarily in the left lower quadrant. In patients for whom diagnostic uncertainty remains (1), abdominal CT imaging can be used to complement the history, examination, and laboratory findings to establish the diagnosis of diverticulitis. Diagnostic uncertainty will vary on the basis of an individual clinician's experience and may particularly occur for patients without a history of diverticulitis or those with signs and symptoms pointing toward an alternative diagnosis (such as cancer, gynecologic or renal causes of acute abdomen, or inflammatory bowel disease) (16, 64, 65).
Moderate-certainty evidence showed that CT imaging is associated with very high sensitivity and specificity to make an accurate diagnosis of diverticulitis. However, no included studies compared patient health outcomes between CT-guided care and care without the use of routine CT for suspected diverticulitis. Low-certainty evidence from studies performed in emergency department or equivalent settings showed that misdiagnoses with CT may not be associated with downstream adverse sequelae, although the effect on patient outcomes is unclear. The clinical significance of the detection of incidental findings, which may be common with CT in adults with nontraumatic acute abdomen, is unclear. Out-of-pocket costs ranged from $56 in ambulatory surgical centers to $94 in hospital outpatient departments for Medicare beneficiaries and from $580 to $4885, respectively, for uninsured adults (56–59).
• Potential harms from CT imaging include incidental findings, radiation exposure, and side effects of or allergic reactions to any contrast used.
• Informed decision making with patients should include discussion of potential patient burdens related to CT imaging, including contraindications to use of contrast agents or limited access to CT imaging (66, 67). Abdominal ultrasonography can be considered when CT cannot be obtained (26, 28, 29). Abdominal magnetic resonance imaging can be considered when ultrasonography provides inconclusive results (for example, in obese patients and those with severe abdominal pain or extensive bowel gas) (68).
• Clinicians should err on the side of imaging in patients with predictors of progression to complicated diverticulitis. These include a symptom duration before clinical presentation of longer than 5 days (69) and signs of perforation, bleeding, obstruction, or abscess.
• The diagnostic accuracy of CT to differentiate between colorectal cancer and complicated diverticulitis is not considered here; the additional value of early cancer detection with follow-up colonoscopy after resolved episodes of acute complicated diverticulitis is discussed in another guideline.
Recommendation 2: ACP suggests that clinicians manage most patients with acute uncomplicated left-sided colonic diverticulitis in an outpatient setting (conditional recommendation; low-certainty evidence).
In the absence of evidence suggesting a benefit of routine hospitalization for patients with acute uncomplicated diverticulitis, the initial (default) management of uncomplicated diverticulitis can be as an outpatient. This applies to most immunocompetent patients with acute uncomplicated left-sided diverticulitis who have no evidence of systemic inflammatory response and can continue treatment at home under medical supervision with adequate family and social support and follow-up. For these patients, low-certainty evidence showed that there may be no differences in risk for elective surgery or long-term diverticulitis recurrence for outpatient compared with inpatient management. Although evidence was very uncertain (insufficient) for most critical and important outcomes (including emergency surgery, mortality, quality of life, and treatment failure), few patients had these outcomes after management in outpatient or inpatient settings.
Outpatient management is less intensive than inpatient management. Although these outcomes were not reported in the included studies, the CGC anticipated a lower risk for potential harms associated with hospitalization (for example, nosocomial infections) and fewer inconveniences for patients, making outpatient management a more feasible, acceptable, and equitable option. Decision making should take into account individual patient circumstances, such as the availability of adequate home care. The CGC also judged that outpatient management would likely have lower associated costs than inpatient management, on the basis of low-certainty evidence that it is not associated with increases in recurrence or elective surgery, the infrequent occurrence of undesirable clinical outcomes in the included studies, and indirect evidence from outside the United States suggesting a cost savings of 35% to 83% per episode of acute diverticulitis.
• This recommendation does not apply to patients with suspected complicated diverticulitis, recent antibiotic use, concomitant unstable comorbid conditions, immunosuppression, or signs of sepsis, given that these populations were excluded from the reviewed studies.
• Predictors of progression to complicated disease among patients with uncomplicated acute diverticulitis include symptoms lasting longer than 5 days, vomiting, systemic comorbidity, high C-reactive protein levels (>140 mg/L), CT findings of pericolic extraluminal air, fluid collection, or a longer inflamed colon segment (69, 70).
• Uncomplicated diverticulitis refers to localized inflammation, whereas complicated diverticulitis refers to inflammation associated with an abscess, a phlegmon, a fistula, an obstruction, bleeding, or perforation (emerging or frank) (71).
Recommendation 3: ACP suggests that clinicians initially manage select patients with acute uncomplicated left-sided colonic diverticulitis without antibiotics (conditional recommendation; low-certainty evidence).
Although the traditional management of patients with uncomplicated diverticulitis includes antibiotics, emerging concepts in the pathogenesis of diverticulitis suggest an inflammatory rather than an infectious cause and have challenged the traditional treatment approach (72, 73). For select patients with acute uncomplicated left-sided colonic diverticulitis presenting with abdominal tenderness, it is reasonable to initially manage them by observation with supportive care (for example, bowel rest and hydration) and without the use of antibiotics. “Select” patients are defined as immunocompetent patients with uncomplicated left-sided colonic diverticulitis, with no systemic inflammatory response or immunosuppression, who are not medically frail, do not require hospitalization, and can follow up as an outpatient under medical supervision with social and family support. For these patients, low-certainty evidence showed that there may be no differences in diverticulitis-related complications (such as abscess, fistula, stenosis, and obstruction), quality of life, need for surgery, or long-term recurrence between those receiving and those not receiving antibiotics. Low-certainty evidence also showed that antibiotic treatment may slightly decrease treatment failure rates (defined as “ongoing diverticulitis” within 3 months of treatment) compared with no antibiotic treatment.
Although evidence for mortality is insufficient (very rare events), the CGC considered that the use of antibiotics without evidence of important benefit to the patient may incur potential harms. In addition, there are increased costs, such as the cost of medication and potentially administration of medication. Finally, unnecessary or inappropriate use of antibiotics is an important contributor to antibiotic resistance, a major individual and public health threat (74).
• This recommendation does not apply to patients with complicated diverticulitis, systemic inflammatory response, immunosuppression, or ongoing or recent antibiotic treatment.
• Initial management without antibiotics should be coupled with watchful waiting and ability to continue monitoring patient status, based on individual clinical judgment. The included studies did not report how many patients randomly assigned to watchful waiting needed antibiotics at follow-up (6, 12, and 24 months and 11 years), but antibiotics did not reduce the risk for any critical or important outcomes.
• Predictors of progression to complicated disease among patients with uncomplicated acute diverticulitis include symptoms lasting longer than 5 days, an initial pain score greater than 7, vomiting, systemic comorbidity, a leukocyte count greater than 13.5 × 109 cells/L, high C-reactive protein levels (>140 mg/L), CT findings of pericolic extraluminal air, fluid collection, or a longer inflamed colon segment (69, 70).
• Implementation of this recommendation does not require a CT-confirmed diagnosis, but clinicians should err on the side of imaging in patients presenting with signs and symptoms consistent with perforation, bleeding, obstruction, or abscess.
• Uncomplicated diverticulitis refers to localized inflammation, whereas complicated diverticulitis refers to inflammation associated with an abscess, a phlegmon, a fistula, an obstruction, bleeding, or perforation.
Appendix: Detailed Methods
The Brown Evidence-based Practice Center conducted the supporting systematic review, which was funded by the Agency for Healthcare Research and Quality. Details of the ACP guideline development process can be found in ACP's methods papers (13, 14). A record of disclosures of interest and management of conflicts can be found at www.acponline.org/clinical_information/guidelines/guidelines/conflicts_cgc.htm.
Key Questions (KQs) Addressed
KQ 1: In CT imaging for the diagnosis or staging of acute diverticulitis,
• KQ 1a. What is the test accuracy of CT imaging for the diagnosis or staging of acute diverticulitis?
• KQ 1b. What are the effects of CT imaging on clinical outcomes and changes in clinical management?
• KQ 1c. What are the downstream outcomes related to falsely abnormal or falsely normal CT readings of acute uncomplicated or complicated diverticulitis?
• KQ 1d. For patients presenting with acute abdominal pain, with the possibility of acute diverticulitis, what are the downstream outcomes related to incidental findings?
∘ Do the accuracy and effects vary by patient characteristics, presentation of illness, or other factors?
KQ 2: What are the benefits and harms of various options for the treatment of acute diverticulitis?
• KQ 2a. For patients with acute uncomplicated diverticulitis, what are the effectiveness and harms of outpatient management versus hospitalization for the acute episode?
∘ Do the effects and harms vary by patient characteristics, presentation or course of illness, or other factors?
• KQ 2b. For patients with acute uncomplicated or complicated diverticulitis, what are the effects, comparative effects, and harms of antibiotic treatment?
∘ Do the effects and harms vary between patients with complicated diverticulitis and those with uncomplicated diverticulitis?
∘ Do the (comparative) effects and harms vary by route of administration of antibiotics, type of antibiotic, or duration of course of antibiotics?
∘ Do the (comparative) effects and harms vary by patient characteristics, presentation or course of illness, or other factors?
• KQ 2c. For patients with acute complicated diverticulitis, what are the effects and harms of interventional radiology procedures compared with conservative management?
∘ Do the effects and harms vary by patient characteristics, presentation or course of illness, or other factors?
Reviewers searched several databases for studies and systematic reviews published in English from 1990 to 1 June 2020. The search was updated in November 2020.
Reviewers assessed risk of bias using the Cochrane Risk of Bias Tool (75) for RCTs and a modified approach using elements from the ROBINS-I (Risk Of Bias In Non-randomised Studies – of Interventions) tool (76) and the Cochrane Risk of Bias Tool (75) for observational studies.
KQ 1 (all): Adults with a suspected or known diagnosis of acute colonic diverticulitis
KQ 1d: Adults with acute abdominal pain who receive abdominal CT
KQ 2: Adults with acute complicated or uncomplicated diverticulitis, whether first or recurrent episode:
KQ 2a: Adults with acute uncomplicated diverticulitis
KQ 2b: Adults with acute uncomplicated or complicated diverticulitis
KQ 2c: Adults with acute complicated diverticulitis
KQ 1: CT scan with or without IV, oral, or rectal contrast
KQ 2a: No hospitalization
KQ 2b: Antibiotics
KQ 2c: Interventional radiology procedure: percutaneous abscess drainage
KQ 1: No CT scanning, magnetic resonance imaging, ultrasonography, other diagnostic interventions, no comparator (single-group studies)
KQ 2a: Hospitalization
KQ 2b: No antibiotics, alternative antibiotic regimen
KQ 2c: No procedure (conservative management; for patients with complicated diverticulitis for whom no procedure is an option)
KQ 1 (critical outcomes): falsely normal CT findings in suspected acute diverticulitis, falsely abnormal CT findings in suspected acute diverticulitis, conversion to complicated diverticulitis, diverticulitis-related complications (such as abscess formation), diverticulitis-related mortality, change in management (treatment decisions), diverticulitis-related complications (such as strictures) (long-term), diverticulitis-related mortality (long-term), harms of overtreatment (due to falsely abnormal findings; for example, surgery, stress), and harms of undertreatment (due to falsely normal findings; for example, peritonitis, unnecessary surgery for other condition)
KQ 1 (important outcomes): time to resolution of acute diverticulitis, length of hospital stay, recurrent diverticulitis, future episode of complicated diverticulitis
KQ 2 (critical outcomes): avoidance of surgery, conversion to complicated diverticulitis, diverticulitis-related complications, mortality (all-cause or diverticulitis-related), quality of life, resolution of diverticulitis, length of hospital stay, rehospitalization, C difficile infection
KQ 2 (important outcomes): antibiotic resistance, hospital-based infections, missed work or school, need for second procedures or revisions, opioid misuse, return to normal bowel function, resource use, recurrence of diverticulitis, side effects or adverse events
KQ 1: Any
KQ 2: Minimum duration of follow-up = treatment duration (hospitalization, antibiotic use)
KQs 1 and 2: Inpatient, emergency department (or equivalent), outpatient
Target Patient Population
Adult patients with suspected or known acute left-sided colonic diverticulitis
Public or Patient Involvement
The development of this guideline also included the perspectives, values, and preferences of 2 nonphysician CGC members who represent the public and a 7-member CGC Public Panel.
Values and Preferences Search
ACP staff searched several databases (MEDLINE, PsycINFO, PubMed, Trip database, and Google Scholar) through 24 February 2021 to identify studies on values and preferences about evaluation and treatment of acute left-sided colonic diverticulitis.
ACP staff searched several databases (PubMed, MEDLINE, National Health Service Economic Evaluation Database, Database of Abstracts of Reviews of Effects, and Health Technology Assessment Database) to identify English-language publications of cost–utility, cost-effectiveness, cost–benefit, cost–consequences, and comparative cost analyses using peer-reviewed filters for economic studies (www.cadth.ca/resources/finding-evidence/strings-attached-cadths-database-search-filters; see below). We also used the Agency for Healthcare Research and Quality Healthcare Cost and Utilization Project database to approximate inpatient national average cost information and the Medicare Physician Fee Schedule (outpatient) to approximate outpatient national average cost information according to the Medicare reimbursement fees. Each eligible study was assessed for applicability, reporting quality, methodological limitations, and overall quality of evidence using consensus recommendations around economic evaluations in health care (77–84).
The supporting systematic review and guideline each underwent a peer review process through the journal. The guideline was posted online for comments from ACP Regents and ACP Governors, who represent internal medicine and its subspecialty physician members at the national and international levels. The CGC considered any comments before finalizing the guideline.
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Author, Article, and Disclosure Information
American College of Physicians, Philadelphia, Pennsylvania (A.Q., I.E., T.S.)
Kaiser Permanente Northwest, Portland, Oregon (J.S.L.)
Northwell Health, Huntington, New York (N.F.)
Minneapolis VA Center for Care Delivery and Outcomes Research, Minneapolis, Minnesota (T.J.W.).
Note: Clinical guidelines are meant to guide care based on the best available evidence and may not apply to all patients or individual clinical situations. They should not be used as a replacement for a clinician's judgment. Any reference to a product or process contained in a guideline is not intended as an endorsement of any specific commercial product. All ACP clinical guidelines are considered automatically withdrawn or invalid 5 years after publication or once an update has been issued.
Acknowledgment: The CGC thanks members of the ACP Guidelines Public Panel for their review and comments on the paper from a patient perspective: Cynthia Appley, Ray Haeme, Billy Oglesby, James Pantelas, Missy Carson Smith, and Lelis Vernon. The authors also thank Jennifer Yost, RN, PhD, for her methodological review and input on the draft guideline.
Financial Support: Financial support for the development of this guideline comes exclusively from the ACP operating budget.
Disclosures: Dr. Mustafa has served as a site principal investigator for a randomized controlled trial funded by Boehringer Ingelheim and subcontracted through Duke University since 2019. Disclosures can be viewed at www.acponline.org/authors/icmje/ConflictOfInterestForms.do?msNum=M21-2710. All financial and intellectual disclosures of interest were declared, and potential conflicts were discussed and managed. Ms. Tufte was recused from authorship and voting due to a moderate-level conflict (advisory committee member for ongoing relevant trial). A record of disclosures of interest and management of conflicts is kept for each CGC meeting and conference call and can be viewed at www.acponline.org/clinical_information/guidelines/guidelines/conflicts_cgc.htm.
Correction: After publication of this article, Dr. Mustafa disclosed a high-level conflict of interest that was previously not reported by her (she has served as a site principal investigator for a randomized controlled trial funded by Boehringer Ingelheim and subcontracted through Duke University since 2019). The CGC considers any active relationship with drug companies a high-level conflict of interest, regardless of whether the interest is clinically relevant to the guideline topic. The CGC policy is to not include individuals with potential conflicts of interest as guideline authors. This article was corrected on 14 February 2023 to include updated disclosure forms for Dr. Mustafa. An erratum has been published (doi:10.7326/L23-0043).
Corresponding Author: Amir Qaseem, MD, PhD, MHA, American College of Physicians, 190 N. Independence Mall West, Philadelphia, PA 19106; e-mail, aqaseem@acponline.
Author Contributions: Conception and design: N. Fitterman, A. Qaseem, T.J. Wilt.
Analysis and interpretation of the data: T.G. Cooney, C.J. Crandall, I. Etxeandia-Ikobaltzeta, N. Fitterman, J.S. Lin, R.A. Mustafa, A.J. Obley, D.K. Owens, A. Qaseem, T. Shamliyan, J. Tice, J.W. Williams, T.J. Wilt.
Drafting of the article: C.J. Crandall, J.T. Cross, I. Etxeandia-Ikobaltzeta, N. Fitterman, A. Qaseem, T. Shamliyan.
Critical revision for important intellectual content: T.G. Cooney, C.J. Crandall, J.T. Cross, I. Etxeandia-Ikobaltzeta, N. Fitterman, L.A. Hicks, J.S. Lin, A.J. Obley, D.K. Owens, A. Qaseem, T. Shamliyan, J. Tice, J.W. Williams, T.J. Wilt.
Final approval of the article: T.G. Cooney, C.J. Crandall, J.T. Cross, I. Etxeandia-Ikobaltzeta, N. Fitterman, L.A. Hicks, J.S. Lin, M. Maroto, R.A. Mustafa, A.J. Obley, D.K. Owens, A. Qaseem, T. Shamliyan, J. Tice, J.W. Williams, T.J. Wilt.
Statistical expertise: A. Qaseem, T. Shamliyan, T.J. Wilt.
Obtaining of funding: T.J. Wilt.
Administrative, technical, or logistic support: I. Etxeandia-Ikobaltzeta, A. Qaseem, T. Shamliyan, T.J. Wilt.
Collection and assembly of data: T. Shamliyan, T.J. Wilt.
This article was published at Annals.org on 18 January 2022.
* This paper, authored by Amir Qaseem, MD, PhD, MHA; Itziar Etxeandia-Ikobaltzeta, PharmD, PhD; Jennifer S. Lin, MD, MCR; Nick Fitterman, MD; Tatyana Shamliyan, MD, MS; and Timothy J. Wilt, MD, MPH, was developed for the Clinical Guidelines Committee of the American College of Physicians. Individuals who served on the Clinical Guidelines Committee from initiation of the project until its approval were Timothy J. Wilt, MD, MPH† (Chair); Carolyn J. Crandall, MD, MS† (Vice Chair); Devan Kansagara, MD, MCR‡ (Past Vice Chair); Pelin Batur, MD, NCMP‡; Thomas G. Cooney, MD†; J. Thomas Cross Jr., MD, MPH†; Nick Fitterman, MD†; Lauri A. Hicks, DO†; Jennifer S. Lin, MD, MCR†; Michael Maroto, JD, MBA†§; Reem A. Mustafa, MD, PhD, MPH†; Adam J. Obley, MD†; Douglas K. Owens, MD, MS†; Jeffrey Tice, MD†; Janice E. Tufte‡§; Sandeep Vijan, MD, MS‡; and John W. Williams Jr., MD, MHS†. Kate Carroll, MPH, was a nonauthor contributor from ACP staff. Approved by the ACP Board of Regents on 24 July 2021.
† Author (participated in discussion and voting).
‡ Nonauthor contributor (participated in discussion but excluded from voting).
§ Nonphysician public representative.