Impact of preoperative factors and waiting time on post-appendectomy complications: a retrospective study

Acute appendicitis is one of the most common causes of an acute abdomen and usually requires emergent surgery. Although antibiotic treatment may be effective in select patients, appendectomy is still the only way to prevent recurrent appendicitis. Several factors (i.e., age, obesity, leukocytosis, symptom duration) have been proposed to be associated with an increased risk of postoperative complications (Andert et al. 2017; Kim et al. 2018b; Schlottmann et al. 2017). However, few studies combined these potential factors to predict the risk of surgical outcomes comprehensively.

Furthermore, there has been a dispute over the impact of surgical delay on outcomes for years. Some studies claimed that a prolonged waiting time for surgery increased the risk of complications (Ditillo et al. 2006; Giraudo et al. 2013) or surgical site infection (Teixeira et al. 2012), while others disagreed (Almstrom et al. 2017; Boomer et al. 2016; Boomer et al. 2014; van Dijk et al. 2018). If those patients at high risk for complication benefit from a shorter waiting time for appendectomies remains unclear. Since the coronavirus disease 2019 (COVID-19) became a pandemic and created challenges in managing surgical emergencies, optimizing the time to the operating room (OR) for select vulnerable patients has become an important issue. In this study, we aimed to develop a risk model for postoperative complications and identify patients who might be affected by surgical delay.

From 2013 to 2018, a total of 1558 patients diagnosed with acute appendicitis were cared for at our institution, of whom 1343 were included in this study. The study flowchart is shown in Fig. 1.

There was wide disagreement about how time to surgery influences surgical outcomes (Abdul Jawad et al. 2021; Almstrom et al. 2017; Boomer et al. 2016; Boomer et al. 2014; Ditillo et al. 2006; Drake et al. 2014; Giraudo et al. 2013; Kearney et al. 2008; Meltzer et al. 2019; Teixeira et al. 2012; van Dijk et al. 2018), but few studies have attempted to identify specific patients potentially affected by the surgical delay. Several scoring or grading systems for predicting surgical outcomes were proposed, but most required intraoperative findings (Emile et al. 2021; Finnesgard et al. 2018; Noorit et al. 2018; Vasileiou et al. 2019), which means those systems could not help reverse these complications. Our study used a multivariate logistic regression model consisting of preoperative factors to classify patients into high and low risk. Although patients in our study received intravenous antibiotics within 4 hours on average after admission to ER, high-risk patients with a surgical delay of > 12 h had significantly higher complications and surgical site infection rates than low-risk patients. In contrast, outcomes were similar when surgery was performed within 12 hours. In recent years, treatment strategies for acute appendicitis have changed. Conservative treatment for appendicitis was successful in uncomplicated patients (Collaborative et al. 2020; Podda et al. 2019; Sallinen et al. 2016). When dealing with perforated appendicitis, a meta-analysis study revealed that patients might benefit from antibiotics or drainage prior to surgery despite heterogeneity in findings (Simillis et al. 2010). Nevertheless, some of the patients might eventually still need an appendectomy due to recurrence. At our institution, CT became a standard tool in ER because CT helps not only diagnose the disease but also differentiate disease severity (Bixby et al. 2006; Horrow et al. 2003; Kim et al. 2018a). In the era of the COVID-19 pandemic, it is more important than ever to accurately prioritize emergent surgeries in order to preserve our medical resources, including hospital staff and operating room schedules. A recent study reported that prolonged time to consultation due to COVID-19 quarantine might increase rates of severe peritonitis and intra-abdominal abscess formation (Dreifuss et al. 2020). Risk for postoperative complications can be calculated immediately once the patient is diagnosed with acute appendicitis. Our study suggests that low-risk patients are safe for surgical delay > 12 h under the administration of intravenous antibiotics. On the other hand, high-risk patients are advised to receive emergent surgery within 12 hours to avoid increased complications and surgical site infection rate.

The parameters of the preoperative probability calculation included age, NLR, presence of SIRS, and abdominal pain duration. Research had shown that aging patients had slower wound healing and increased risk of surgical site infection (Engeland et al. 2006; Lizán-García et al. 1997). Jawad et al. also stated that older age and a higher Charlson Comorbidity Index were related to appendicitis progression and worse outcomes (Abdul Jawad et al. 2021). Several studies reported that NLR was related to disease severity (Ishizuka et al. 2012; Shimizu et al. 2016) and thus might influence postoperative complications. We hypothesized that the presence of SIRS/sepsis was indicative of disease progression from a localized to systemic infection and therefore associated with postoperative complications. Boomer et al. (Boomer et al. 2016) echoed our hypothesis, showing that the incidence of sepsis was significantly higher in the surgical site infection group. Studies had shown that abdominal pain duration was an essential indicator for disease severity (Dreifuss et al. 2020; Oliak et al. 2000; Lai et al. 2018) and surgical outcomes (Kim et al. 2018b), which was consistent with our results since abdominal pain duration is a significant factor in the probability calculation.

There are several limitations to this study. First, it was a single-institute retrospective study, and the variation between different institutes should be considered. Further multi-institution prospective studies or population-based analysis may help validate our research. Second, the study did not include CT results due to variability in reports style between different radiologists. Furthermore, the decision for surgery was usually made before the official report was uploaded. In the future study, we will cooperate with radiologists to identify specific CT features associated with postoperative complications and add them to the prediction. Third, although most preoperative characteristics were factual data, recall bias was inevitable when recording abdominal pain duration. To limit this impact, symptom duration was triple-checked from the ER record, admission note, and nursing note. Cases with discordant descriptions were excluded. Fourth, the operator’s surgical experience is a non-negligible factor for postoperative complications but was not measurable in the study (Scarborough et al. 2012). Resident participation in the surgery and patient care should be considered in a future study.

The preoperative risk is a helpful indicator for surgeons to select vulnerable patients and arrange surgery in an appropriate time frame. The prolonged waiting time for surgery does not lead to worse surgical outcomes for low-risk patients. In contrast, high-risk patients are recommended to undergo appendectomy within 12 hours to avoid increased complications.