Complicated excision of colonic fistula is not an easy process. In a previous study, the incidence of anastomotic leakage was shown to be about 30%[11]. In patients with colonic fistula following SAP, corrosion and contracture of mesocolon also occurred[14]. This pathological change may result in the relative ischemia of colonic anastomosis, which is regarded as a risk factor for anastomotic leakage[15]. In theory, in addition to anatomical changes and severe adhesion caused by retroperitoneal tissue necrosis, patients with colonic fistula following SAP may have a higher risk of postoperative anastomotic leakage.
The present study was the first to evaluate the feasibility and effect of chyme reinfusion in patients with loop ileostomy for colonic fistula following severe acute pancreatitis on outcomes after excision of colonic fistula. Evidently, despite having patients with colonic obstruction (n = 4), drainage tubes falling off (n = 6) and a cavity around the fistula (n = 5) in recurrent years where CR was widely used, 55 of the 70 patients were scheduled for CR, which was successful in all 55 patients (100%). In other words, CR via loop ileostomy for colonic fistula was noted to be feasible following infection control and sufficient drainage.
In this study, the drainage tube for colonic fistula was retained even after treatment for SAP was completed. What requires attention is that even if the diversion (loop ileostomy) is carried out, it may be possible that a small amount of intestinal fluid can enter the colon via distal end of the ileostomy. During the 3-month interval from getting rid of SAP to the treatment of colonic fistula, the drainage tube fell off in seven patients, and recurrent sinus rupture occurred in six of the seven patients (85.71%), demonstrating that the infection source was always present.
Evidently, the anastomotic leakage rate was found to be lower in the CR group (22.2% vs. 45.0%). In addition, the inflammatory indexes after excision were also investigated, and it was confirmed that the CRP and WBC were lower on the 7th day after excision despite being comparable when the surgery was immediately finished. These phenomena seemed to be in line with the findings of previous studies [11, 16] in that the incidence of postoperative anastomotic leakage and postoperative ileus were associated with postoperative inflammation.
Excision of colonic fistula following SAP was noted to be very difficult, which was associated with extensive bleeding, difficult anatomy, huge surgical trauma and inflammatory attack. Necrosis factor -α released by mast cells under the condition of high inflammation will inhibit the movement of the gastrointestinal tract and the wound healing process after intestinal anastomosis [17], thus increasing the risk of anastomotic leakage and prolonging defecation time. In addition, the invasion of neutrophils can directly damage smooth muscle [18, 19], and the imbalance of polarized macrophages can affect collagen deposition and tissue repair, leading to anastomotic leakage occurrence [20, 21]. In patients with disused digestive tract, the pathological changes of digestive tract following the disuse may aggravate the postoperative inflammation after complicated excision of enterocutaneous fistula[22], which would be followed by high incidence of complications. Reversing the pathological changes is the key point to improve postoperative outcomes [4, 5, 8]. Furthermore, in current study, the peristalsis of the colonic smooth muscle will be stimulated by chyme after CR. This effect may make the smooth muscle get proper exercise and make the colon stronger, and the most direct effect would lead to the colon anastomosis easier to be performed and the patency of the anastomosis better guaranteed. Therefore, these factors work together and reduce the incidence of anastomotic leakage and defecation time.
However, laparotomy for SAP in controlling infections was found to be associated with poor outcomes following excision. This did not seem peculiar as patients requiring laparotomy may have serious disease progression and a more pessimistic intra-abdominal situation[23], signifying that the anatomy was more difficult to distinguish, adhesions were more serious, and trauma was greater when excision was.
This study has certain limitations. First, this was a retrospective study; therefore, selection bias was likely present. Second, the sample size of this study was small; however, the colonic fistula following SAP was not a common disease, and to our knowledge, this study had the largest relevant sample size. The third limitation was that mechanisms of the advantages of CR for prognosis were not fully explored. Accordingly, future animal experiments or RCTs should be performed so as to elucidate this matter. Furthermore, the follow-up time was insufficient, and the incidence of leakage was potentially biased. That is to say, some leakage may not become apparent until a certain point after discharge from hospital. As a result, the recurrent rate may have been reported to be falsely lower. However, in our study, a colonography was performed to diagnose the anastomotic leakage. As a result, delayed leakage after discharge should be rare in our study.