If the study did not report mean and standard deviation (SD), these parameters were estimated from median and range in the study using method described by Hozo et al. [20]. Heterogeneity

of the studies was assessed using Cochran Q test and a degree of heterogeneity was quantified using I2. If either I2 ≥ 25% or the Q test was significant, the intervention effects were considered heterogeneous. A meta-regression was performed by fitting co-variables (i.e. age group, type of patients, LDE225 chemical structure and use of perioperative antibiotics) into a model to explore sources of heterogeneity. A subgroup or sensitivity analysis was done accordingly if a source of heterogeneity was suggested. The Egger test and a funnel plot were performed to assess publication bias [21, 22]. If publication bias was suspected either by Egger test or a funnel plot, a contour enhanced-funnel plot and meta-trim and fill Barasertib supplier were applied where appropriated. Analyses were done using STATA version 12.0. A p value of less than 0.05 was considered statistically significant, except for heterogeneity where

0.10 was used. Results A total of 1348 studies (145 and 1328 studies from Medline and Scopus, respectively) were identified after removing duplicates. Screening titles and abstracts were performed and removed 1317 non-relevant studies with reason described in Figure  1, leaving 9 eligible studies to review [7, 16–18, 23–27]

(see Figure  1). One study [27] had insufficient data and thus was later Rolziracetam excluded after attempting to contact the author twice; leaving 8 studies included in further poolings. Figure 1 Studies selection flow. Characteristics of these 8 eligible studies have been demonstrated in Table  1. Most (5/8) RCTs had studied in patients with complicated appendicitis [16, 18, 23–25], 2 studied in mixed complicated appendicitis and other type of contaminated abdominal diseases (e.g. typhoid perforation, traumatic bowel injury) [7, 26], and 1 RCT with ileostomy closure [17]. Studied patients were adults or mixed of adults and children in most studies (6/8) whereas only 2 studies were in children. All studies had performed open surgeries, 5/8 had prescribed prophylaxis antibiotics. Table 1 Characteristics of eligible studies Study Diseases Age group Incision Prophylaxis antibiotics Follow up time   Intervention Pettigrew 1981 [24] Perforated and gangrenous appendicitis Adults and children Abdominal right lower quadrant (grid iron) and paramedian No 4 weeks PC (n = 80) Interrupted nylon sutures (with topical ampicillin in group B (n = 39) DPC (n =42) Dressing changed was not specified.