According to the International Study Group of Rectal Cancer , AL after radical resection of colorectal cancer can be classified as grade A, B, or C. Grade C AL is generally the most serious, requiring emergency surgery. It seemed that once the AL occurred, the consequences would be serious, and most colorectal AL was grade C. According to a review, the incidence of grade C AL was approximate 60% in patients with AL. In fact, grade C AL or incidence of emergency surgery for AL might be higher. For instance, in a national study in Denmark, emergency surgery was performed at rates as high as 85% in AL cases. In addition, in a study performed in Laval University, 73% of AL cases were grade C in patients without a protective stoma. As a result, the treatment of AL after colorectal surgery was mainly focused on the emergency surgery. The main objective of emergency surgery for AL was to achieve source control. In our experience, using the DLIST tube seemed to be a useful method to establish source control. In our previous study, the DLIST was placed in the study group during radical resection of rectal cancer, and it was shown that emergency surgery was necessary in only 15% of ALs, while 60% of ALs required emergency surgery in the control group. In addition, in another of our reports, more than 2000 ml of colonic fluid and pus could be drained out within 48 hours using the DLIST. Thanks to the design of the DLIST, continuous irrigation can thin out the thick colonic fluid and make it easier to drain. We have made full use of DLIST through washing and irrigation to remove the infections. This may be one of the mechanisms leading to the pus cavity shrinkage .
In our study, it was shown that spontaneous closure was associated with the placement of DLIST after AL occurred. In addition to the adequate drainage and removal of contaminants, the result seemed to be associated with the influence of negative pressure on granulation tissue. The obvious and common manifestation of this influence is that significant shrinkage of the wound can be observed as the edge of the granulation would deform and contract under the negative pressure. Furthermore, negative pressure therapy can clear white blood cells and inflammatory factors and stimulate cellular proliferation, angiogenesis, and the formation of granulation tissue of the granuloma. In our study, the DLIST tube was used to provide negative pressure after insertion into the pus cavity. The effect of the negative pressure was to improve the filling of granulation tissue into the pus cavity and resolve the leakage. The direct reactions in our present research were the obvious shrinkage of the pus cavity and the higher incidence of spontaneous closure in the DLIST group compared with the PD group. In recent years, researchers have tried to treat rectal AL using innovative drainage methods and have achieved good clinical outcomes in a few selected patients[9,10]. However, the rates were variable in different studies. A Swedish study investigating a certain number of patients, showed that the general spontaneous closure rate seemed to be only about 50%-60% when using the EVAC and transanal irrigation. In theory, EVAC microstructure could have a better effect on forming granulation tissue and promoting granulation tissue shrinkage. In our previous study, this was demonstrated to be true. After all, the special sponge tissue with its small holes can fill the whole pus cavity and distribute pressure evenly to the cavity wall. However, what cannot be ignored is that the larger diameter holes in the tubes allow thick infections to be removed more easily compared with the vacuum-assisted closure system. In addition, removal of the infection was another important factor for spontaneous closure. This may be why EVAC seemed to have no obvious advantage compared with transanal drainage in Weréen’s study. In our study, the spontaneous closure rate was about 60% when using DLIST. The opposing views might be that DLIST did not improve the spontaneous closure rate very significantly, compared with transanal drainage and vacuum-assisted closure system. However, it should be noted that in the previous studies focused on the two methods, most patients received a stoma. In our studies, only a small number of patients had stoma. In general, compared with EVAC, DLIST might be better in clearing the thick infection, thanks to continuous irrigation of normal saline and negative pressure and forming granulation tissue. However, it was difficult to distinguish the best drainage method according to the existing research. As a result, future randomized clinical trials are necessary.
There were limitations in our study. The first limitation is that the study was retrospectively performed in two centers using similar treatments. So, selection bias was likely present. The second limitation is that the spontaneous closure was diagnosed only after colonography confirmation. As a result, we thought that diagnosis was often not timely, which might lead to bias. The third limitation is that as transferred from different units the overall number of operated cases and percentage of AL unfortunately is not possible. The fourth limitation is that the endoscopy-related information was lacking. Mucosal inflammation (with ulcers, erosion, and so on) may influence spontaneous closure time, so information regarding mucosal inflammation should be collected in future studies. In addition, our experience indicates that perioperative radiotherapy may be a very important factor for the failure of spontaneous closure. (In the present study, only four patients had perioperative radiotherapy, and spontaneous closure was not achieved in all four). However, in the present study, we could not conclude from the regression results that postoperative radiotherapy was associated with spontaneous closure. The main reason might be that the number of patients with perioperative radiotherapy was so small (four patients). Future studies should focus on this potential factor. An other limitation was that the general situation of patients in DLIST group was worse. However, we have to understand that a group of patients with worse baseline data can achieve better efficacy. It seemed to be a more favorable proof.
In addition, it might be that patients receiving the standard of care, namely surgery with end colostomy or creation of a protective ileostomy for quick and effective control. We grant that surgical control of the source of infection is more direct, faster, and more thorough than all drainage methods. Actually, symptomatic patients always had a purulent cavity and poor drainage. Patients with AL should of course undergo laparotomy at an early stage. In addition, if there was a source of infection accumulating near the AL, the operation required not only devascularization but also debridement around the AL. As a result, simple ileostomy may not solve the problem quickly. In other words, patients might still be symptomatic after ileostomy if the drainage mode did not change. The perfect operation should be take-down anastomosis plus colostomy. However, the interval from AL diagnosis to admission was 20 (18-25) days in the DLIST group. It meant that the adhesion had gradually formed, and the surgery might cause secondary injury around the leakage. We used to attempt the surgical control in very early years, but in some patients, the AL cannot be exposed well. We had to perform colostomy in a hurry, and eventually we had a distal colonic stump fistula in addition to the unresolved AL. We feel that one should be cautious about laparotomy in patients with abdominal infection following leakage one month after the first operation, because it is like a trap. The early devascularization is a good method, but sometimes it might be risky to expose the AL during surgery. As a result, when considering the complications of the surgical control, we chose to place the DLIST as often as possible for irrigation and drainage.