Predicting factors of postoperative complications in appendectomies

1 Federal University of Rio Grande do Sul, Postgraduate Program in Surgical Sciences, Faculty of Medicine, Porto Alegre, RS, Brazil. 2 Hospital de Clínicas de Porto Alegre, General Surgery Service, Porto Alegre, RS, Brazil. 3 Federal University of Rio Grande do Sul, Faculty of Medicine, Porto Alegre, RS, Brazil. 4 Federal University of Pelotas, Faculty of Medicine, Pelotas, RS, Brazil. Moreira Predicting factors of postoperative complications in appendectomies. 2 Rev Col Bras Cir. 45(5):e1920 Pediatric patients, pregnant women, those operated in other services and referenced to HCPA due to complications, and also those with other diagnoses different from acute appendicitis were excluded from the study. This project was carried out by Grupo de Pesquisa de Oncologia Cirúrgica do Sul (SSORG) a research group on surgical oncology from the southern part of Brazil and was approved by the Research Ethics Committee under number 49697615.7.0000.5327. Patients were allocated to four different groups depending on the presence or absence of postoperative complication and on the degree of severity of the complication. We used Clavien-Dindo classification, proposed by Clavien et al., in 1992, redefined by Dindo et al., in 2004, and validated by Moreira et al. to the Portuguese language, in 2016, to compare and report postoperative complications12-14. Group 1 was composed by operated patients who did not present postoperative complications; Groups 2, 3, and 4 were composed by patients with postoperative complications classified as ClavienDindo I, II, or ≥III, respectively (Table 1). For each patient, the following epidemiological characteristics were determined: gender and age, type of access performed (open, laparoscopic, or converted), type of appendicitis (complicated or non-complicated), risk stratification (American Society of Anesthesiology ASA), surgical time in minutes, length of hospital stay in days, and occurrence or non-occurrence of postoperative complication, classified according to Clavien-Dindo. Cases in which the appendix was only hyperemic and edematous or with fibrinous exudate were considered as uncomplicated appendicitis, whereas those with necrotic and abscessed or perforated appendix were considered as complicated appendicitis. Patients undergoing contaminated surgeries (uncomplicated appendicitis) received only antibiotic prophylaxis, and patients undergoing infected surgeries (complicated appendicitis), antibiotic therapy. In laparoscopic surgeries, three incisions to the abdominal cavity were made in a triangular position: infraumbilical, left iliac fossa, and suprapubic. A three-month postoperative follow-up was performed to evaluate the presence of complications. As for the statistical analysis, a significance level ≤0.05 was established for all tests. Data were analyzed using PASW Statistics for Windows, version 18.0, Chicago: SPSS Inc. For quantitative variables, data were expressed as mean and standard deviation or median; on the other hand, the qualitative variables were expressed in frequency tables. The Table 1. Groups of the study Group Clavien-Dindo classification13 Definition 1 Absence of postoperative complication 2 I Any deviation from the ideal postoperative course without the need of pharmacological treatment or surgical, endoscopic, and radiological interventions.* 3 II Requires pharmacological treatment with drugs other than those permitted for grade I complications.** 4 III Requires surgical, endoscopic, or radiological intervention. IV Life-threatening complication. Need for UTI treatment. V Death of the patient. * Therapeutic regimens allowed: analgesics, antipyretics, antiemetics, diuretics, electrolyte replacement, and physiotherapy. This category also includes operative wounds drained at bedside; ** Blood transfusion and total parenteral nutrition are also included. Moreira Predicting factors of postoperative complications in appendectomies. 3 Rev Col Bras Cir. 45(5):e1920 Pearson's chi-square test was used for comparisons between categorical variables. The level of statistical significance for surgical and hospitalization time was calculated using the Kruskal-Wallis test of independent samples. Odds ratio (OR) was calculated using Group 1 as the control.


INTRODUCTION
T he morbidity rate of acute appendicitis is 10% and its mortality rates range from 0.24% to 4%.
It is the most frequently diagnosed disease among emergency surgeons and it accounts for about 20% of all surgical interventions [1][2][3] .Appendectomy is the gold standard treatment, recognized for more than a century, since its description by McBurney, in 1894 4 .The operation can be performed as an open or laparoscopic surgery, depending on the surgeon's experience, hospital characteristics, and factors related to the patient.
Recent studies suggest the efficacy of exclusive antibiotic therapy for the treatment of specific cases, especially for uncomplicated appendicitis, as an alternative to surgical treatment; however, such an indication remains controversial and debatable [5][6][7] .The current guideline of the

Society of American Gastrointestinal and Endoscopic
Surgeons and the consensus of The European Association for Endoscopic Surgery place surgery as the gold standard for the treatment of acute appendicitis 8,9 .Postoperative complications should be considered when choosing the best management option, however, few studies describe the relevant risk factors for these complications 10,11 .In addition, it is necessary to identify patients at higher risk for postoperative complications in order to maintain more frequent monitoring.Therefore, this study aims to identify the most common risk factors associated to postoperative complications after appendectomies.

Moreira
Predicting factors of postoperative complications in appendectomies.Pearson's chi-square test was used for comparisons between categorical variables.The level of statistical significance for surgical and hospitalization time was calculated using the Kruskal-Wallis test of independent samples.Odds ratio (OR) was calculated using Group 1 as the control.

RESULTS
Age was associated with the severity of the complications.Patients older than 38.5 years had more severe complications [age determined as cutoff point by ROC Curve (p<0.0001)].Group 1 presented the lowest percentage of patients older than 38.5 years (25.2%), as shown in table 2. Gender was not a significant predictive factor for postoperative complications.The type of surgical access showed correlation among the groups (p<0.0001).Group 1, without complications, had the majority of patients undergoing laparoscopic surgery, whereas in Groups 2, 3, and 4 most of patients were submitted to conventional surgery.
Among the groups with complications, there was a higher frequency of laparoscopic surgery in Group 4.

Uncomplicated appendicitis was associated with
Group 1, whereas Groups 2, 3, and 4 were inversely associated with uncomplicated appendicitis (p<0.0001).Complicated appendicitis presented OR of 12.41 (6.33-27.39;95% confidence interval -CI) for Group 4. ASA score was associated with the severity of the postoperative complications (p<0.0001).Group 1 was correlated to ASA score 1, Group 2 to ASA score 2, and Groups 3 and 4 to ASA scores ≥3.
Group 2 presented OR of 1.98, which increased according to the severity of the complications, reaching 2.60 in Group 3 (Table 3).

4
Rev Col Bras Cir.45( 5):e1920 Surgical duration and length of hospital stay were related to the severity of complications: the higher the mean and median of the variables, the greater the severity (p<0.0001)(Table 4 and Figure 1).

DISCUSSION
Appendectomy is one of the most frequently performed surgical procedures in the world.There has been a growing increase in the incidence of acute appendicitis in recently industrialized countries, such as Brazil 15 .In addition to this, risk factors for postoperative complications of appendectomy have not been fully elucidated yet.The Clavien-Dindo classification proved to be effective in assessing the degree of surgical complication in several countries, being a simple, objective, and reproducible method, based on the therapeutic consequences of the complications 13,14,16 .Our study demonstrated that the age over 38.5 years is predictive of postoperative complication, expected ratio due to the greater number of comorbidities in older patients.The studies that specifically analyzed postoperative complications found a correlation with the increase of age, such as Kotaluoto et al., who identified an average age of 39 years in those who developed severe complications 11 .evolution of the disease in several analyzes, mainly due to its atypical presentation, which leads to a late diagnosis possibly influencing the type of appendicitis at surgery, with an increase in complicated appendicitis [17][18][19][20] .In contrast to other studies, our work did not show statistical difference in the rate of complications when related to gender [20][21][22] .

Advanced age range was correlated with a longer
The type of surgical access was highly related to the risk of postoperative complications.The absence of complications was significantly associated with laparoscopic surgery, a treatment of choice for uncomplicated acute appendicitis, in previous studies related to a lower number of postoperative complications, shorter hospitalization time, less postoperative pain, and faster convalescence 22 .
Studies also suggest a reduction of long-term costs with laparoscopic surgery [23][24][25] .However, among the groups with complications, the laparoscopic surgery was more associated with Clavien-Dindo ≥III Group, suggesting that, despite the lower number of complications with this approach, these tend to be more severe.Thus, our study ratifies the comparison studies between laparoscopic and open surgeries, in which conventional surgery is associated with greater number of complications.
Complicated appendicitis proved to be an important predictor of risk for postoperative complications.This finding confirms other analyzes that have demonstrated association of complications with the evolutionary phase of appendicitis, although these studies do not show increase in chance as high as presented here [26][27][28][29] .Complicated appendicitis increases the risk of postoperative complications, particularly in Clavien-Dindo ≥III Group, leading to an odds ratio of 12.41.Therefore, patients diagnosed with this type of appendicitis deserve more postoperative care for the early management of possible complications.
ASA classification proved to be a predictor of postoperative complications.As expected, since ASA evaluates the preoperative condition of the patient, with a score that predicts morbimortality and is one of the risk factors for surgical site infections 30 .

2
Rev Col Bras Cir.45(5):e1920Pediatric patients, pregnant women, those operated in other services and referenced to HCPA due to complications, and also those with other diagnoses different from acute appendicitis were excluded from the study.This project was carried out by Grupo de Pesquisa de Oncologia Cirúrgica do Sul (SSORG) -a research group on surgical oncology from the southern part of Brazil -and was approved by the Research Ethics Committee under number 49697615.7.0000.5327.Patients were allocated to four different groups depending on the presence or absence of postoperative complication and on the degree of severity of the complication.We used Clavien-Dindo classification, proposed by Clavien et al., in 1992, redefined by Dindo et al., in 2004, and validated by Moreira et al. to the Portuguese language, in 2016, to compare and report postoperative complications 12-14 .Group 1 was composed by operated patients who did not present postoperative complications; Groups 2, 3, and 4 were composed by patients with postoperative complications classified as Clavien-Dindo I, II, or ≥III, respectively ( Our results allow us to determine patients at greater risk for postoperative complications.Factors such as age ≥38.5 years, open surgery, complicated appendicitis, ASA≥2, and surgical time >77 minutes should be taken into account for the early diagnosis and treatment of such complications, aiming at reducing postoperative morbimortality.

Table 1 ).
antibiotic therapy.In laparoscopic surgeries, three incisions to the abdominal cavity were made in a triangular position: infraumbilical, left iliac fossa, and suprapubic.A three-month postoperative follow-up was performed to evaluate the presence of complications.As for the statistical analysis, a significance level ≤0.05 was established for all tests.Data were analyzed using PASW Statistics for Windows, version 18.0, Chicago: SPSS Inc.For quantitative variables, data were expressed as mean and standard deviation or median; on the other hand, the qualitative variables were expressed in frequency tables.The

Table 2 .
Association among predicting variables of postoperative complications and the study groups.
Significance level calculated by chi-square test.

Table 3 .
Odds ratio of the groups that presented postoperative complications (Groups 2, 3, and 4) compared to the group of patients without postoperative complications (Group 1).

Table 4 .
Mean and median of surgical duration and length of hospital stay in each group.