The severity of the appendix inflammation is believed to be the main risk factor associated with IAA. The IAA rate after laparoscopic appendectomy reported in non-perforated appendicitis is 1-4%, but the incidence of postoperative IAA increases by up to 26% in patients with gangrenous perforated appendicitis [10-13]. We found perforated appendicitis in 45.9% of patients that developed a postoperative IAA but in only 8% of the patients who did not suffer this complication (Table 2). According to Schlottmann et al. the higher the grade of intraperitoneal bacterial contamination, the higher the risk of postoperative IAA [14], and few doubts exist about the fact that perforation increases the grade of contamination of the peritoneum surrounding the appendix. Indeed, this study strongly supports the hypothesis that a perforated appendix should be regarded as a predictive factor for postoperative IAA (Table 3). Also, pelvic peritonitis was significantly more frequent in patients who developed postoperative IAAs (43.2% vs. 17.5%; p<0.0001) (Table 2) and was recognized as a predictive factor for postoperative IAA via multivariate analysis (OR 2.9; p = 0.004) (Table 3).
According to the WISS study, acute appendicitis is still the most frequent cause of intra-abdominal sepsis [15]. A delayed diagnosis, mostly occurring in patients who are unreliable or have an atypical clinical onset, may lead to severe, life-threatening complications such as gangrene, perforation, appendiceal mass, and peritonitis [16]. Overall, 17.5% of the patients enrolled in the study had a peritonitis localized to the pelvis or the paracolic gutter: this result is in line with rate reported in the literature (17.3%) [13].
The clipping of the mesoappendix is associated with a higher incidence of postoperative IAAs. In this study, the use of clips was left to the operating surgeon’s discretion, but such use was always limited to the management of the mesoappendix. Compared to bipolar coagulation, we recorded a significantly higher occurrence of IAA when the mesoappendix was secured with polymeric clips (62.1% vs. 29.7%; p < 0.0001). Polymeric clips have been increasingly used for the closure of the appendiceal stump [17-18], but the correlation between the use of polymeric clips and the increased rate of IAA, if it exists, remains unexplained. Some studies have indeed investigated the possible correlation between the method of mesoappendix dissection and the onset of IAA, with no significant conclusion. Wright et al., in a review of 565 patients undergoing laparoscopic appendectomy for uncomplicated appendicitis, analyzed 149 patients (26%) who had a transection of the mesoappendix and appendix with a single staple line, 259 (46%) who had multiple staple lines, and 157 (28%) who had their mesoappendix dissected with the aid of ultrasonic shears and their appendix divided by a single staple line. They found that the incidence of complications was low, with hematoma/abscess, transfusion, and reoperation occurring in only 1.4%, 0.4%, and 0.9% of cases, respectively. There were no significant differences between groups [19]. In a retrospective study of about 1178 patients who received laparoscopic appendectomy, Lee et al. compared 460 (39%) patients who had their mesoappendix managed with endoclips, 346 (29%) who had their mesoappendix managed by an ultrasonic device, and 346 (32%) who had their mesoappendix managed by monopolar electrocautery. They found no significant differences in terms of postoperative complications, including wound infection, abscess, paralytic ileus, and hemorrhage [20].
It emerges from this study that a prolonged administration of postoperative antibiotics had no significant effect on the occurrence of postoperative IAA. From this point of view, we confirm the data reported by Kimbrell et al. on a cohort of 52 young patients undergoing appendectomies for complicated appendicitis. They found that the occurrence of an abdominal abscess was not significantly lower if the postoperative antibiotics regimen was prolonged for more than 24 hours compared to when antibiotics were withdrawn within 24 hours after surgery. Thus, they concluded that postoperative antibiotics might not provide an appreciable clinical benefit in terms of preventing intra-abdominal abscesses [21]. The postoperative use of antibiotics for complicated appendicitis has proven to be beneficial [22], but the optimal duration of treatment has not yet been established. In a recent retrospective study on 6,412 patients with complicated acute appendicitis, Anderson et al. suggested that not all patients with complicated appendicitis should be discharged with antibiotics after surgery. Accordingly, only patients exhibiting SSI before discharge or those whose clinical progress requires a more extended in-hospital stay might benefit from extra-time antibiotic treatment. [23].
The present study suffers several limitations. Primarily, this is a retrospective study. Secondly, this series represents a vastly complex, heterogeneous patient population scattered over a considerable period. Thirdly, the lack of including other risks factor can affect the statistics of the multivariate analysis. Furthermore, the number of patients presenting a postoperative IAA constitutes a small cohort of cases. However, since the study was carried out at a tertiary referral center, the high volume of patients undergoing laparoscopy for acute appendicitis makes the statistical analysis credible and valuable. Lastly, we acknowledge that the patients were not routinely followed once symptoms resolved after the surgical intervention, making it possible that patients could have been lost during follow up.