Table
1 shows the summary of included studies. One randomized clinical trial [
17], 10 prospective cohort studies [
18‐
27] and 8 retrospective cohort studies [
28‐
35] were included. Most studies (
n = 12) were performed in Spain, the other studies were performed in Finland, Sweden, the Netherlands, Switzerland and the USA. All but one study used CT to confirm the diverticulitis diagnosis; a Dutch study [
35] used either CT or ultrasonography. Although all studies included patients that received outpatient treatment, different treatment protocols were used. In most studies, outpatient treatment consisted of ambulatory treatment at home with oral antibiotics and a liquid diet during the first couple of days followed by outpatient clinic visits after 4 to 7 days. Five studies did not define the outpatient treatment protocol. Three studies specifically stated that all patients were treated without antibiotics [
19‐
21]. Most studies selected patients as outpatient treatment candidates based on patient characteristics (such as absence of comorbidities or immunosuppressed state), clinical condition (such as having uncomplicated diverticulitis and ability to tolerate oral intake) and patients’ social environment (adequate family and social network). Importantly, seven studies [
22,
28,
29,
31,
33‐
35] also included patients with diverticular abscesses as candidates for outpatient treatment. Although most studies used outpatient treatment protocols that could be used in almost all hospitals (ambulatory treatment at home with an outpatient clinic visit after 4 to 7 days), 3 studies treated their patients in a ‘hospital at home unit’ or ‘home care unit’ [
26,
27,
33]. In case of the ‘hospital at home unit’ patients were treated at home with a nurse visiting all patients daily and a physician visiting all patients 2 to 3 times a week, while all patients were treated with intravenous antibiotics [
26,
27]. The study that treated their patients in a ‘home care unit’ did not provide a detailed description of this treatment strategy [
33]. However, the routine intravenous antibiotic treatment suggests a protocol similar to the ‘hospital at home unit’. The two ‘hospital at home unit’ studies also included a different type of patient, as these 2 studies included patients with present comorbidity [
27] or only patients older than 70 years [
26].
Table 1
Summary of included studies and readmission rates
Alonso 201018 | Pros | No | No | 100% | Yes | 4–7 days | 3% (2/70) | – |
Biondo 201417 | RCT | No | No | 100% | Yes | Daily | 4.5% (3/66) | 6.1% (4/66) |
Estrada 201619 | Pros | No | No | 100% | No | 48 h | 11.1% (4/36) | 33.3% (3/9) |
Etzioni 201028 | Retro | Yes | NR | NR | NR | NR | 5.6% (39/693) | – |
Isacson 201520 | Pros | No | No | 100% | No | 1 week | 2.3% (4/155) | – |
Joliat 201729 | Retro | Yes | Yes | 96% | Yes | NR | 10.2% (10/98) | 32.0% (54/169) |
Lorente 201330 | Retro | No | No | NR | Yes | 4–7 days | 5.6% (5/90) | 4.3% (2/46) |
Lutwak 201232 | Retro | No | No | NR | Yes | NR | 14.3% (3/21) | 0.0% (0/21) |
Mali 201621 | Pros | No | No | 94% | No | 24-48 h | 2.9% (4/140) | – |
Martin Gil 200922 | Pros | Yes | No | NR | Yes | 10 days | 5.4% (4/74) | – |
Mora 201723 | Pros | No | No | NR | Yes | 2 weeks | 8.7% (22/254) | – |
Moya 201224 | Pros | No | No | 84% | Yes | 4 days | 6.3% (2/32) | 0.0% (0/44) |
Moya 201631 | Retro | Yes | No | 95% | Yes | 4 days | 8.0% (18/224) | – |
Pelaez 200625 | Pros | No | No | 100% | Yes | 4 days | 5.0% (2/40) | – |
Rodriguez 201027 | Pros | No | Yes | NR | Yes | Daily | 0.0% (0/24) | – |
Rodriguez 201326 | Pros | No | Yes | NR | Yes | Daily | 0.0% (0/34) | – |
Rueda 201233 | Retro | Yes | No | NR | Yes | NR | 21.1% (8/38) | 27.8% (5/18) |
Sirany 201734 | Retro | Yes | Yes | 96% | Yes | NR | 12.5% (12/96) | 15.3% (22/144) |
Ünlü 201335 | Retro | Yes | Yes | 100% | Somea | 1 week | 8.5% (10/118) | – |
Thirteen studies [
17,
19,
21‐
24,
26,
29,
30,
32‐
35] compared results from the outpatient treatment group with a reference group consisting of admitted patients. However, in 11 out of these 13 studies these reference patients were admitted because of the presence of one or more exclusion criteria for outpatient treatment or because of a decision by the treating physician based on the clinical condition of the patient, and thereby not strictly comparable to those treated as outpatients. Only in a randomized clinical trial [
17] (randomizing between in- or outpatient treatment of uncomplicated diverticulitis patients) and a prospective cohort study [
24] (selecting patients based on the time period they were treated in; before or after a change in hospital guidelines), a reliable comparison of outcomes could be made. All 19 studies reported rates of readmission, 16 studies [
17‐
22,
24‐
27,
30‐
32,
34‐
36] reported rates of need for emergency surgery, 15 studies [
17‐
20,
22,
24‐
27,
30‐
32,
34‐
36] reported need for percutaneous abscess drainage, and 5 studies [
17,
22,
24,
26,
30] reported healthcare costs. All study characteristics are shown in Online Resource
4.