The treatment strategies for acute appendicitis are controversial [5–8]. EA has not been recommended for complicated appendicitis because it increases the incidence of extended resection and postoperative complications. Some recent reports have recommended NOM even for uncomplicated appendicitis, and repeating NOM in cases of recurrence leads to a reduction of medical expenses [9–11]. However, NOM or IA may be problematic because some cases fail, and repeating NOM may be problematic because some cases of appendicitis are caused by malignant tumors. Failure refers to the requirement for emergency surgery when performing treatment by NOM. These cases should be performed EA at the first decision. However, the cases caused by malignant tumor should be performed appendectomy without complications. In this study, we considered the treatment strategy for acute appendicitis from the following three perspectives: prediction of which patients should avoid emergency surgery, prevention of failure of IA or NOM, and a malignant tumor as the etiology of the appendicitis. We focused on the presence of a PAFC on preoperative CT.
In the PAFC-positive group, the rate of postoperative complications was significantly higher in the patients who underwent EA than in those who underwent IA (40.5% vs. 24.0%, p = 0.037). In the PAFC-negative group, however, there was no significant difference between patients who underwent EA and IA (5.3% vs. 6.2%, p = 0.71). The multivariate analysis showed that only PAFC positivity was a risk factor for postoperative complications after EA (OR, 7.11; 95% CI, 2.73–18.60; p < 0.001). According to a recent report, laparoscopic surgery is associated with few postoperative complications even in patients with complicated appendicitis [12–15]. However, the present study showed that the PAFC-positive group had a higher rate of postoperative complications than the PAFC-negative group regardless of the surgical approach. This difference was likely to have been affected by bias in the surgical procedure depending on the time point of treatment during the study. A prospective study of patients with preoperative PAFC positivity is necessary.
The risk factors for treatment failure have not been clarified [10, 16]. The incidence of NOM failure in patients with complicated appendicitis reportedly ranges from 15.6–25.7%, which is higher than that in patients with uncomplicated appendicitis [17–19]. Various methods for diagnosing complicated appendicitis and predicting the risk of NOM failure before surgery, such as scoring systems, have been investigated [20–22]. We examined whether PAFC positivity is a risk factor for NOM failure. Our univariate analysis showed that the failure rate was significantly higher in the PAFC-positive than PAFC-negative group (20.4% vs. 4.1%, p = 0.004). However, the multivariate analysis showed no significant difference (OR, 1.48; 95% CI, 0.19–11.7; p = 0.71), and the presence of fecaliths on CT was the only risk factor (OR, 24.5; 95% CI, 2.2–273; p = 0.009). Of course, various factors are involved in failure; PAFC positivity alone does not substantially increase the risk.
Neoplasms can cause acute appendicitis, and they are difficult to diagnose by preoperative examination alone . The guidelines recommend against routine IA for patients under the age of 40 years . One report indicated that repeated NOM in patients with recurrence leads to a reduction of medical expenses [10, 11]. However, among patients undergoing IA, neoplasia is reportedly found in about 10% of cases by pathological diagnosis [23, 24]. Likewise, in the present study, neoplasia was found in 12.2% and carcinoma in 3.5% of patients aged 40 years or older in the PAFC-positive group. Therefore, the possibility of a tumor should not be forgotten in patients with a PAFC.
This study had two main limitations. First, there was bias in the surgical procedure depending on the time point at which treatment was performed. Laparotomy was common in the first half of the study period, and most procedures were laparoscopic surgeries in the second half. Laparoscopic surgery reportedly reduces complications and may need to be considered separately from laparotomy. Second, the definition of NOM failure has not been determined, and the physician’s judgment has strong influence on the outcome. Although cases of NOM failure were treated as complications of IA in our study, the study design may arguably need to be reconsidered.