Letter to the Editor regarding “Prophylactic subcutaneous drainage reduces post-operative incisional infections in colorectal surgeries: a meta-analysis of randomized controlled trials”

Abstract

We read the paper entitled “Prophylactic subcutaneous drainage reduces post-operative incisional infections in colorectal surgeries: a meta-analysis of randomized controlled trials” by Pang et al. [1] on the efficacy of subcutaneous drainage in reducing post-operative incisional infections in colorectal surgical procedures. They concluded that prophylactic subcutaneous drainage significantly reduces postoperative incisional infections in colorectal surgery but not in digestive surgery in general. In consideration that recently we have conducted a similar meta-analysis [2] on this topic also cited and discussed in the study, we have had a particular interest in this work. According to our opinion the results and the conclusions need some clarifications. Herein, we would like to raise the following concerns with the attempt to extrapolate the authors’ findings to a general readership. First, the authors considered different studies with a great heterogeneity among them either for type of procedure or for type of drain. The authors included in the study different types of surgical procedures as clean-contaminated with contaminated and dirty ones. In our meta-analysis [2] only clean-contaminated surgeries were considered; at the same time, only papers analyzing the effect of suction drains were included, with the attempt to homogenize the analyzed sample. For the same reasons we have excluded two analyses included in the study by Pang et al. one analyzing patients undergoing ileostomy closure [3] and one further study because of the presence of passive drains [4]. According to the title and the results section, a specific analysis of RCTs on colorectal surgeries is anticipated but this was not the case. In the International Guidelines for Prevention of Surgical Site Infection, ileostomy takedown is considered a procedure of “dirty surgery,” with specific risks of SSI ranging up to 38% [3, 5]. On the contrary, elective colorectal resections — such as those analyzed in the majority of studies included — are conventionally referred as cleanor clean-contaminated surgeries, which are associated with standard incidences of SSI of 20% [5–7]. Although ileostomy closure is conventionally considered as part of colorectal surgery, putting in a subcutaneous drain on a wound after colorectal resection adopting all measures to prevent SSI is obviously different of do it after the closure of a tract of bowel left opened on the skin for some periods. As for the type of drain, the action to reduce an empty space in the wound is different for a suction than a passive drain, pooling all together the data could influence the final results and one study [4] is not sufficient to consider it alone in a subgroup analysis of passive drain. The colorectal surgery subgroup of analysis is composed of four RCTs that could not be analyzed in a single group because of the great heterogeneity among them for the reasons explained above; then, the conclusions about its use are not supported by consistent findings. Second, two works have been excluded without a reasonable account: one [8] for having less than 30 cases in either arm and one [9] for supposed inadequate control. A RCT is considered the highest-level evidence among scientific studies from the initial design to the final results and publication [10]; the number of participants within the arms is not a valid motive to exclude it. The estimation of the * Diego Coletta [email protected]