Concomitant appendectomy at the time of gynecologic surgery for benign indications can be performed in the surgical evaluation and treatment of endometriosis and chronic pelvic pain.1,2 Studies have shown the incidence of appendiceal endometriosis is as high as 50% in patients with severe endometriosis.3–5 Additionally, there are data to support that appendectomy can lead to significant improvement in patients with unexplained chronic pelvic pain.1,6
However, the practice of concomitant appendectomy at the time of a gynecologic procedure remains controversial, and many gynecologic surgeons do not perform appendectomy due to the concern for increased risks of infection, ileus, blood loss, operating time, and morbidity.1,2 Although single-institution studies support the safety and cost effectiveness of concomitant appendectomy in gynecologic surgery for benign indications,1,7,8 other studies have shown increased risk of postoperative complications.9,10 A large retrospective cohort study of patients with ovarian cancer who underwent noncytoreductive staging procedures demonstrated that patients who had concomitant appendectomy were two times more likely to have a postoperative surgical site infection.9 In a general surgery population that is undergoing concomitant appendectomy during open abdominal and trauma surgeries, appendectomy was associated with increased risk of postoperative wound complications and sepsis.10
This study was conducted using a large national database to assess whether concomitant appendectomy in patients who underwent laparoscopic surgery for benign gynecologic indications is associated with an increased rate of complications in the 30-day postoperative period.
The American College of Surgeons National Surgical Quality Improvement Program (ACS NSQIP) database was used to analyze outcomes of patients undergoing laparoscopic surgery for benign gynecologic indications. Access to ACS NSQIP participant use files was granted by the ACS, and participant use files from 2010 to 2020 were combined for analysis. This study was deemed exempt by the institutional review board (protocol no. 21.0759) at University of Louisville. The population was narrowed to include only cases performed by gynecologists and included presumed premenopausal adult patients aged 18–51 years to focus on the population most likely to undergo gynecologic surgery for indications that might benefit from concomitant appendectomy, such as endometriosis or chronic pelvic pain. Each case included in the analysis had at least one Current Procedural Terminology (CPT) code listed that represented a laparoscopic surgery that could include traditional laparoscopy or surgery with robotic assistance. Patients were excluded if they had any CPT code indicative of an open abdominal surgery, bowel resection, or urogynecology procedure in which there was potential for use of mesh. Figure 1 outlines how exclusion criteria were applied to create the population cohort, and Appendix 1 (available online at https://links.lww.com/AOG/C976) lists the CPT codes that were included or excluded in the population cohort. If a laparoscopic CPT code was present, a CPT code for vaginal or hysteroscopic procedure did not exclude patient from analysis. Because this study aimed to focus on gynecologic surgery for benign indications, any patient with a possible cancer diagnosis based on an answer of “yes” to disseminated cancer, a CPT code that includes debulking or lymphadenectomy, or an International Classification of Diseases code indicating a postoperative diagnosis of cancer was excluded. Patients with an International Classification of Diseases postoperative diagnosis of appendicitis or with a postoperative wound classification of class 4, or “dirty or infected” were also excluded to focus on elective procedures.
The exposure of interest was concomitant appendectomy at time of gynecologic surgery for benign indications. Patients were categorized into groups with appendectomy and without appendectomy based on CPT codes for laparoscopic appendectomy. Patient demographic information and postoperative outcomes within the 30-day postoperative period were collected for analysis. Demographic and patient characteristic data included age; race (as reported in the ACS NSQIP); body mass index (BMI, calculated as weight in kilograms divided by height in meters squared); tobacco use; presence of chronic conditions such as diabetes, hypertension, or chronic lung disease; and American Society of Anesthesiologists classification. Data suggest that people of different races often are offered different surgical treatment options, specifically that patients of marginalized races are less likely to be offered minimally invasive approaches.11,12 We included race as a variable in our propensity match to make sure the two populations had a similar racial composition. Postoperative complications included surgical site infections defined as superficial, deep, or organ space infection; sepsis; wound disruption; thromboembolic events that included deep venous thrombosis, pulmonary embolism, and stroke; blood transfusion; reoperation; readmission, and length of hospital stay. The primary outcome was a composite of postoperative complications compared between the two groups.
Demographics and outcome variables were compared between the appendectomy group and the without-appendectomy group using the χ2 or Fisher exact test for categorical variables and the Mann-Whitney U test for numeric variables. Propensity scores were estimated using patient demographic information and surgical characteristics. Demographic information used for propensity matching included age, race, BMI, presence of medical comorbidities, and American Society of Anesthesiologists classification. Surgical characteristics used were year of surgery, number of CPT codes, and emergency surgery. All patients undergoing appendectomy were 1:1 matched to a unique patient who did not undergo appendectomy by using a greedy matching based on the propensity score estimated using a gradient boosting approach. Matching was confirmed by evaluating the standardized mean difference for the group with appendectomy and the group without appendectomy and confirming these quantities to be less than 0.1.13,14 All comparisons were two-sided and performed at the α=0.05 significance level. Statistical analysis was performed using R 4.1.2.
The population cohort included 246,987 patients. A total of 1,760 patients (0.7%) underwent concomitant laparoscopic appendectomy. Due to a substantial imbalance in the sample sizes between the group with appendectomy and the group without appendectomy, the demographic and patient characteristic data in the total patient cohort analysis exhibit many statistically significant differences. Patients who underwent appendectomy were younger (mean age 36.6±8.4 years vs 39.1±7.6 years, P<.001) and more likely to be White (63% vs 55%, P<.001) and to have BMIs in the normal range (35% vs 25%, P<.001). Patients who underwent surgery without-appendectomy were more likely to have emergency surgery (Table 1). The propensity-matched sample was used to create a comparison group that was similar to the appendectomy group in terms of preoperative demographic variables. In the propensity-matched sample, there are no statistically significant differences in demographic data or patient characteristics among groups (Table 1).
When looking at our primary outcome in the overall population cohort, the risk of any complication was 8.0% in the appendectomy group, compared with 5.5% in the without-appendectomy group (P<.001) (Table 2). Participants who underwent appendectomy were more likely to develop sepsis (0.6% vs 0.3%, P<.001), and had higher reoperation (2.2% vs 1.1%, P<.001) and readmission (4.3% vs 2.3%, P<.001) when compared with those in the without-appendectomy group (Table 2). The appendectomy group had statistically significant longer operative times (115 minutes vs 98 minutes). There was no significant difference in the total combined rate of surgical site infections, including all superficial, deep, and organ space infections (2.8% in appendectomy group and 2.2% in without-appendectomy group, P=.071) and rates of wound disruption, thromboembolic events, and blood transfusion were also similar between the two groups (Table 2).
In our propensity weighed analysis, we again found a significantly higher overall complication rate (8.0% vs 5.8%, P=.017), as well as increased rates of hospital readmission (4.3% vs 2.7%, P=.009) in the appendectomy group (Table 2). There was an increased rate of superficial surgical site infections in the appendectomy group, compared with the without-appendectomy group (1.6% vs 0.8%, P=.042). However, there were no significant differences in sepsis (0.6% vs 0.6%, P>.99) or reoperation (2.2% vs 1.4%, P=.127) in the propensity-weighted analysis. There also were no differences in wound disruption, thromboembolic events, or blood transfusion. There were no significant differences in operative time and hospital stay in the propensity-matched sample (Table 2). Wound classification was statistically significant in both the overall and propensity-weighted analysis with the appendectomy group more likely to be classified as class 3 or “contaminated” (6% vs 2%, P<.001) (Table 2).
Because procedure type was not included as a matching variable in the propensity scores, we note that there was a significant difference in whether patients had a hysterectomy CPT code after matching. The appendectomy group was less likely to undergo hysterectomy as part of the laparoscopic surgery (49% vs 57%, P<.001). In the matched cohort, hysterectomy CPT code was associated with higher rates of overall complication (odds ratio 1.32, P=.039). Sensitivity analysis that used a matched sample that incorporated hysterectomy as a matching variable continued to find significantly higher rates of overall complications in the appendectomy group (8.0% vs 5.6%, P=.005) (Appendices 2 and 3, available online at https://links.lww.com/AOG/C976). This analysis continues to find significantly higher readmission rates for patients who are undergoing appendectomy, and now suggests significantly longer operative time (median 115 vs 113, P=.001) and longer hospital stay (0 days: 47.2% vs 51.6%, P<.001).
Postoperative diagnoses in the appendectomy group were analyzed. The most common postoperative diagnoses by International Classification of Diseases, Ninth or Tenth Revision codes in patients who were undergoing concomitant appendectomy were endometriosis (31.9%, n=561); adnexal pathology that included ovarian cysts and benign neoplasms (17.8%, n=314); uterine pathology, most commonly leiomyomas (15.3%, n=270); and abdominal or pelvic pain (15.2%, n=268). Less frequent diagnoses were disorders of menstruation and peritoneal disease, such as adhesive disease (Fig. 2).
This study shows an increased risk of postoperative complications, driven primarily by hospital readmission, among patients who undergo concomitant appendectomy at the time of gynecologic surgery when compared with those undergoing gynecologic surgery without appendectomy. This finding is in contrast to studies that have reported no increased risks of concomitant appendectomy. Despite a statistically significant increase in composite postoperative outcomes, the rates of each individual complication in the appendectomy group were low, ranging from 0.1% to 2.8%. Rates of major complications, including venous thromboembolism, blood transfusion and reoperation, were similar between the groups.
Existing literature is inconsistent, with some studies highlighting the safety of concomitant appendectomy and others demonstrating increased rates of postoperative infection.9,10 Although we did not find statistically significant differences in deep surgical site infections, organ space infections, or sepsis, we found an increase in superficial surgical site infections. Surgical wound classification has been validated as a predictor of surgical site infections.15 However, surgical wound classification, specifically for appendectomy, is subject to a wide range of interpretation, and there are often discrepancies in wound classification based on who reports the data—surgeon compared with operating room nurse.16,17 A concomitant appendectomy is often categorized as “clean contaminated” because the gastrointestinal tract is entered in a controlled manner; however, it may be categorized as “contaminated” if there is presumed surrounding nonpurulent inflammation. The increased number of cases in the “contaminated” wound classification may have contributed to the increased rates of sepsis in the overall cohort or increased rates of superficial surgical site infections in the propensity-weighted analysis.
Patients were not matched using CPT codes because patients frequently underwent numerous different procedures concurrently. Hysterectomy is considered a major laparoscopic procedure and is associated with higher postoperative complications rates.18 When evaluating each group for presence of concurrent hysterectomy CPT code, we noted that the appendectomy group was less likely to undergo a hysterectomy, and the presence of hysterectomy CPT code was associated with higher rates of overall complications. In the sensitivity analysis that incorporated hysterectomy as a matching variable, there were still significantly higher rates of overall complications in the appendectomy group, suggesting the matched cohort may be underestimating the effect of appendectomy on the overall complication rate, given that the appendectomy group had fewer hysterectomies.
It should be noted this study focuses only on complications and potential risks associated with concomitant appendectomy and does not acknowledge the potential benefits that have been shown in previous data.1,6 Studies have demonstrated the benefit of appendectomy in the reduction of pelvic pain and endometriosis, and the benefits of appendectomy may outweigh the increased risk of sepsis and readmission when indicated.1–6 These data should be used toward counseling patients about their postoperative risks.
The strength of this study lies in its use of a large-volume, nationally representative database. The ACS NSQIP currently quotes a 95% success rate in capturing 30-day outcomes on all cases in the program database, and previous studies have verified ACS NSQIP accuracy and reliability.19 This study also aims to build a population cohort that is representative of patients that are most likely to undergo appendectomy and aims to exclude patients or procedure that may falsely elevate complications.
This study has some inherent limitations. It relies on the ACS NSQIP, which is dependent on accurately documented and coded information by health care professionals. Further, this study is limited by the variables reported in the ACS NSQIP database. There may be contributing factors that are not captured by database, including preoperative hemodynamic stability, the use of appropriate antibiotic prophylaxis, intra-operative findings, surgical strategy, difficulty of surgery secondary to factors such as severe endometriosis or intra-abdominal adhesions, and surgeon experience level among a list of many other factors. Pathologic diagnoses may have also contributed to study findings; however, this information is not provided in the database. Despite using a large database of surgeries for analysis, it is not always possible to adequately match every patient in the appendectomy group to a similar patient who did not undergo appendectomy. A sensitivity analysis that excluded appendectomy patients who could not be adequately matched revealed no meaningful differences from the results discussed here (Appendices 4 and 5, available online at https://links.lww.com/AOG/C976). An additional limitation is that many postoperative complications such as wound disruption and stroke are quite rare, and we have low power to detect differences in our matched cohort. Lastly, as a retrospective study, we are unable to establish a causal relationship between exposure and outcome.
In conclusion, secondary analysis of a large surgical database reveals an increased overall complication rate after concomitant appendectomy at the time of laparoscopic gynecologic surgery for benign indications. Future studies are needed to demonstrate the effect of appendectomy on pelvic pain and identify patients with optimal risk benefit ratios when considering performing concomitant appendectomy at time of gynecologic surgery.
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