Key messages

• The use of antibiotics to treat acute uncomplicated appendicitis may be less effective than appendectomy.
• The use of antibiotics to treat acute uncomplicated appendicitis probably increases major complications compared with appendectomy.
• The conclusions of this summary are consistent with existing systematic reviews and the recommendations of the main guidelines.

What is the evidence.
See evidence matrix  in Epistemonikos later

We found nine systematic reviews [5],[6],[7],[8],[9],[10],[11],[12],[13] including seven primary studies [14],[15],[16],[17],[18],[19],[20], from which five correspond to randomized controlled trials [14],[15],[18],[19],[20]. This table and the summary in general are based on the latter.

What types of patients were included

All studies included adult patients with suspected acute appendicitis.
All studies excluded pediatric patients and one study also excluded women [15].
One study established the suspected acute appendicitis based on clinical and laboratory parameters [15], one study on clinical criteria and images [20] and three studies on clinical criteria, laboratory parameters and images [14],[18],[19].

What types of interventions were included

Four of the studies used intravenous antibiotics for 48 hours [14],[15],[18],[19]. Of these, two studies used a combination of cefotaxime with tinidazole [14],[15], another study used ciprofloxacin plus metronidazole [18] and one used associated ampicillin with gentamicin and metronidazole [19].

The remaining study [20] used a combination of amoxicillin with clavulanic acid intravenously only if the patient had nausea or vomiting and for a time not specified.
All studies continued oral antibiotic therapy. One study completed 7 days of treatment [18], another study completed eight days of treatment [20] and three studies completed 10 days [14],[15],[19].

To complete oral treatment, two studies used a combination of ofloxacin with tinidazole [14],[15], another a combination of ciprofloxacin with tinidazole [18], one used amoxicillin with clavulanic acid [20] and one study did not specify the antibiotic used orally [19].
All of the studies compared antibiotic treatment versus appendectomy.

What types of outcomes
were measured

1. Treatment efficacy, defined as absence of symptoms within two weeks, without major complications (including recurrence) within one year.
2. Major complications defined as the need of further invasive treatment or prolonged admission (e.g. abscesses, ileus, deep wound infection, recurrence, re-operation, secondary perforation).
3. Minor complications (e.g. negative appendectomy, diarrhea, and superficial wound infection).
4. Duration of hospital stay.
5. Period of sick leave.
6. Cost effectiveness.

We found three systematic reviews [5], [6], [7], including 14 studies   reported in 21 references [8], [9], [10], [11], [12], [13], [14], [15], [16],   [17], [18], [19], [20], [21], [22], [23], [24], [25], [26], [27], [28]. Eight   studies correspond to randomized controlled trials (15 references [9], [10],   [11], [12], [13], [14], [16], [17], [19], [21], [22], [23], [24], [26], [27]).   This table and the summary in general are based on the latter. One study [15]   did not contribute data to any of the outcomes of interest.

To whom this evidence does and does not apply

• The evidence included in this summary is applicable to adult patients with acute uncomplicated appendicitis, independent of sex and age.
• It does not apply to patients presenting complications of acute appendicitis (such as drilling, appendicular mass, peritonitis, gangrene or other), since they have a clinical course and treatment indication different than acute uncomplicated appendicitis.
• Studies in pediatric patients were not included in this summary, so this evidence cannot be extrapolated to that population.

• Effectiveness of treatment and presence of major complications were selected as critical outcomes for decision-making.
• Other outcomes such as length of hospital stay or time to return to work, were considered less important when choosing a treatment over the other.

• While the certainty of the evidence is low or moderate for major outcomes, it is an intervention which benefits are likely to outweigh the low risk associated with appendectomy.
• In patients with a high surgical risk, this balance could eventually favor antibiotic treatment [2],[21].

• It is highly likely that patients and their carers would be inclined to surgery, since it is the established treatment for both clinicians and patients, which is reinforced by the evidence.

• Although surgery has a higher cost, it is likely that the costs of complications and low effectiveness of antibiotic treatment make surgery the most cost-effective intervention

Differences between this summary and other sources

• The conclusions of this summary are consistent with those of the systematic reviews identified and existing overviews of  reviews [1],[21].
• The main guideline on the subject [22] recommends appendectomy as the treatment of choice for acute appendicitis. It states antibiotic therapy as primary treatment is safe for patients with acute uncomplicated appendicitis, but less effective in the long-term because of higher rate of recurrence.

• The probability that future studies change what we know is low, because of the certainty of the evidence.
• However, there is at least one randomized controlled trial that is not included in any of the identified systematic reviews [23] and at least one ongoing study, which will provide new evidence in this regard [24].