Statistical analysis

Statistical analysis was performed using SPSS Statistics v26 (IBM Corp., Armonk, NY, USA) and graphs were generated using Prism v8.0 (GraphPad Software, La Jolla, CA, USA). Categorical data were compared with Pearson’s chi-squared test. Group comparisons were carried out using the Mann-Whitney U test, the Chi-square test or Fisher’s exact test. All p-values <0.05 were considered statistically significant. Continuous data are represented as mean ± standard deviation.

Ethical board approval

The study was conducted under ethical approval of the Institutional Review Board of the RWTH Aachen University (EK-340/20) and in accordance with the current version of the Declaration of Helsinki, the Declaration of Istanbul, and good clinical practice guidelines (ICHGCP). Informed consent was waived due to the retrospective study design and collection of readily available clinical data.

Acute appendicitis

Of 395 patients in the AA group, 97 (25%) belonged to the pandemic cohort. These patients exhibited increased rates of clinical (44% vs. 31%, p = 0.036) and intraoperative (43% vs. 31%, p = 0.041) peritonitis. Mean WBC count (13.6±4.3 /nl vs. 12.5±4.4 /nl, p = 0.034) and CRP (50.9±70.7 mg/l vs. 37.9±59.5 mg/l, p = 0.048) were also higher in this group. Finally, the mean histology score was higher in the pandemic group (2.2±1.1 vs. 1.8±1.1, p = 0.002) and there were significantly fewer histological findings of catarrhal appendicitis in these patients (23% vs. 35%, p = 0.021). Although the preoperative and intraoperative findings of patients with AA in our study were more advanced during the onset of the pandemic, the rate of major complications did not show any significant difference in the two cohorts (CD≥3b, 2% vs. 4%, p = 0.301). A detailed comparison of AA patients can be found in Table 2.

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Table 2. Acute appendicitis.

https://doi.org/10.1371/journal.pone.0280867.t002

Acute cholecystitis

In the AC group, no statistically significant differences were observed between cohorts. Detailed information can be found in S1 Table of the Supporting information.

Mechanical bowel obstruction

In patients with MBO, 19 (16%) were operated during the pandemic period. In this group, significantly fewer primary anastomoses were carried out after intestinal resection (5% vs. 26%, p = 0.046). Interestingly, none of these patients presented with inflamed bowel, in contrast to the historic cohort (0% vs. 18%, p = 0.043). Comparisons between MBO cohorts are outlined in S2 Table of the Supporting information.

Yearly incidences

The overall incidence of AA, AC and MBO during the corresponding study periods of 2017 to 2020 is depicted in Fig 1. Fig 1A depicts the aforementioned incidences in the UH and Fig 1B the incidences in the PHHR. As can be seen in Fig 1A, there was a 48% decline in AA patients and a 43% decline in patients with MBO at the UH, in comparison to 2019. On the contrary, AC cases rose. On the other hand, only MBO cases declined in PHHR (42% reduction in 2020), whereas AA cases remained almost the same, as depicted in Fig 1B. Interestingly, the incidence of AC rose here too.

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Fig 1. Incidence distribution over the years during the respective three month study intervals.

A. University Hospital. B. Heinsberg region.

https://doi.org/10.1371/journal.pone.0280867.g001

Discussion

The COVID-19 pandemic radically changed the regularity of surgical practice. In Germany, as well as other European countries, the sudden need for more ICU beds lead to a severe reduction in elective surgical cases [15]. In the field of general surgery, mostly patients with malignant disease were operated. Moreover, most of the ICU beds were allocated to the treatment of critical COVID-19 patients, leaving little resources for the non-COVID-19 emergencies or oncological patients. Surgeons, anaesthesiologists and physicians of other specialties with ICU experience were transferred to the ICU wards to cover for personnel shortages. Some operating theatres, in areas most struck by the pandemic, were converted to ICU beds to maximize the intensive care capacity of hospitals [16]. Blood products were also becoming more scarce, since donating was drastically reduced through lockdown measures [17]. Laparoscopy, which plays a major role in emergency and elective general surgery, was associated with an increased risk of SARS-CoV-2 virus exposure for the operating personnel, leading to restrictions in its use [18]. All these sudden changes forced surgeons to adapt to new conditions, change their operative workflow and reprioritize, in order to maintain high surgical standards [19]. New measures were implemented to hinder viral spread, while the treatment of oncological and emergency patients had to be guaranteed [20, 21]. As the changes in day-to-day surgery were universal and there was no clinic left unscathed by the pandemic, we included clinics of different capacities.

This study showed an overall decrease in acute operated cases at a tertiary centre (UH), during the study period. This agrees with the results of a Spanish multicentre retrospective study, where a 58% decrease in acute care surgery was observed, as well as a decrease in AC cases between March and April 2020 [22]. In contrast to our study, the number of patients suffering from MBO was statistically higher in 2020, compared to previous years. Another interesting point was the increased time between onset of symptoms and patient arrival at the emergency department during the study period [22]. We believe that the uncertainty of the public during the pandemic was materialized in both studies. The hospitals which were functioning as main COVID-19 institutions were possibly met with hesitation by the public, thus the reduction in AA and MBO patients in the UH. Examples of patients or caregivers avoiding hospitals have also been monitored and published in an Italian paediatric article from Lazzerini et al [23], where parents reported avoiding hospitals for fear of a SARS-CoV-2 viral infection, with grave consequences for some of the children.

In our study, the rate of minor complications was similar among the two cohorts as seen in Table 1. However, the number of severe (CD≥3b) complications and the median CCI were significantly lower in the pandemic group. In contrast to our study, Cano-Valdemarra O. et al suggest, that minor complications were more common during the pandemic because of delayed clinical presentation and advanced intraoperative findings, but severe complications were probably similar in both groups [22]. Our pandemic cohort contained the lowest number of patients with MBO, compared to previous years. These patients are often older, with more comorbidities, higher ASA score, require a more extensive operative treatment and tend to require a longer ICU treatment than those with AA and AC. As a result, MBO patients are more prone to major complications, have a higher CD Score and CCI. We believe the reduced number of MBO patients in the pandemic cohort correlates with the reduced rate of major complications (CD≥3b) and lower median CCI of this cohort. Moreover, ICU LOS was also significantly shorter in our pandemic cohort. This could be attributed to the scarcity of ICU beds and reprioritization of intensive care resources [24]. Surgical patients were probably transferred sooner to intermediate care (IMC) or standard care wards, where the risk of a COVID-19 infection was reduced or were denied ICU beds for less than life-threatening indications.

In our study, the reduced number of catarrhal appendicitis, the increased rate of phlegmonous histology, higher MPI and increased WBC counts and CRP levels in the pandemic AA group demonstrate advanced inflammation in these patients. This coincides with examples from the literature, such as Romero, J. et al, whose results showed fewer appendicitis patients presented in the emergency department, but with a more severe stage of the disease during the pandemic period [25, 26]. The main reason for those findings appears to be the delayed seeking of medical help due to fear of COVID-19 infection. According to Tankel J. et al, another reason for the reduced number of cases during the pandemic could be a successful symptomatic treatment of mild appendicitis at home [27]. Some surgical societies suggested a conservative treatment of uncomplicated appendicitis with antibiotics as a means to limit surgical personnel exposure to COVID-19 aerosol [28, 29]. A reduction of appendicitis patients was observed in our study too, but only in the maximal care clinic. According to the departmental heads of the four clinics involved, a direct operative treatment was favoured in the case of AA. Our study did not investigate the prevalence of conservatively treated cases, as we believe this to be a negligible number, therefore we cannot provide an accurate presentation of conservative treatment.

On the other hand, our study showed a 24% overall increase in cholecystectomy cases during the pandemic. No significant differences were observed between pandemic and historic cohorts, suggesting that the operative treatment and postoperative course of these patients was not severely influenced by the onset of the pandemic.

As mentioned previously, MBO cases declined mostly in the tertiary centre, during the pandemic period of our study. There have been many reports concerning the impact of the pandemic on the incidence of MBO. In Spain and Italy, there was an increase in surgical interventions for MBO in March 2020 [7, 22]. Additionally, a significant reduction in anastomoses after intestinal resection was observed in the pandemic subgroup of our study. This may signify a more cautious intraoperative approach in an era of limited personnel and resources, as a postoperative anastomotic leak could further siphon the available workforce and prolong the patients’ stay in the intensive care. This cautious approach could also have attributed to the pandemic cohort’s reduced major complications.

The reduction of acute surgical cases at the university hospital during the study period could suggest a public tendency to avoid large hospitals, where COVID-19 patients were primarily treated and where a higher “crowd density” (healthcare personnel and patients) was to be expected during emergency hours. On the other hand, it may also reflect a tendency to move locally and visit the next available hospital, instead of a tertiary centre, which was common practice before, even for clinical presentations that did not warrant it. Additionally, the lack of intensive care beds at the university hospital led to a decrease in emergency patient referrals from the periphery (for example in high-risk patients with cholecystitis and mechanical bowel obstruction). This possible shift of acute surgical patients from the tertiary centre towards the peripheral clinics of Heinsberg at the onset of the pandemic could be a more generalised phenomenon that exceeds the regions of Aachen and Heinsberg.

Our study suffers from some limitations, such as its retrospective nature and the inhomogeneity of three different diagnosis-groups, each with different pre-, intra- and postoperative aspects. Nevertheless, we tried to approach and analyse each group systematically, with similar outcome parameters. As only operated patients were included, we can expect that the general incidence of the aforementioned diagnoses was probably higher. The tendency to a more conservative treatment of non-complicated surgical emergencies during the pandemic should be further explored. Additional prospective studies are required, in order to better understand the ongoing illness tendencies and the full impact of COVID-19 in general surgery.