Introduction

Acute appendicitis (AA) is one of the most common surgical emergencies and causes of acute abdominal pain (1), with only 50% of patients presenting with the classic symptoms of migratory right iliac fossa pain, nausea, vomiting, fever, and mild leukocytosis (2). The global incidence of AA is 8.3%, with a male-to-female preponderance of 6.3% and 8.6%, respectively (3).
There is no unanimous consensus on the optimal diagnostic algorithm. Some clinicians rely solely on clinical acumen (4), while others combine clinical scoring systems (5) and preoperative radiological imaging (6). These variations contribute to differences in negative appendectomy rates (NARs), defined as the proportion of all vermiform appendices submitted without pathologic evidence of appendicitis or an intraluminal fecolith (7).
Historically, NARs of up to 10% in young males and 20% in women of reproductive age were considered acceptable (7); however, the increasing availability of imaging modalities has contributed to a reduction in these rates (8). Factors influencing NAR include patient’s sex, comorbidities, timing of presentation, experience of healthcare workers, use of preoperative imaging, and scoring systems (9).
Clinical audits are essential for benchmarking the quality of care and identifying areas for improvement (10). Although regional and global reports show NAR ranging from 6% in Nairobi to 17% in Johannesburg, no data are available from our institution on the NAR or the factors guiding surgical decision-making. This audit aims to fill that gap by providing baseline institutional data to guide quality improvement, optimize diagnostic pathways, and reduce unnecessary appendectomies. 
This 5-year clinical audit aimed to determine the institutional NAR and evaluate the factors influencing negative appendectomy, including age group, sex, use of clinical scoring systems, and preoperative imaging, with comparison to regional and global data. The study adhered to the Standards for Quality Improvement Reporting Excellence (SQUIRE) guidelines (11).

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Materials and Methods

Study design and site
This retrospective clinical audit was conducted at a private tertiary training center in an urban setting, with full radiological and surgical capabilities, including computed tomography (CT) and ultrasound (U/S) imaging and laparoscopic services.

Study duration
Medical records of patients presenting with AA from January 2017 to December 2022 were reviewed. This period was selected because it reflects the duration after full implementation of digital records, ensuring complete and reliable data capture. No major diagnostic or operative equipment changes occurred during this time.

Study population
Patients aged ≥10 years who underwent surgery (open or laparoscopic) for suspected AA during the study period were included. Patients were stratified by sex and age group: adolescents (10–19 years) and adults (≥20 years) according to the World Health Organization definitions (12).

Inclusion criteria
Patients with AA aged ≥10 years were included as the peak incidence of AA occurs in the second and third decades of life (4), encompassing both adolescents and adults.

Exclusion criteria

1. Patients with missing histopathology results from appendectomy.

2. Patients awaiting interval appendectomy.

3. Patients in whom an appendectomy was done incidentally during an open abdominal procedure.

4. Children <10 years of age were excluded because AA is uncommon in this age group and presents and is managed differently, which could introduce variability and affect the study’s focus.

Definitions and rationale

• Interval appendectomy: defined as a delayed appendectomy after 6 weeks of non-operative management of AA (5).

• These patients were excluded to maintain focus on acute cases and ensure an accurate assessment of clinical evaluation tools, as inflammation may resolve with antibiotics or be absent in incidental appendectomy; hence, the NAR would be misleading.

• The definitive diagnosis of AA was based on the histopathology report.

Sampling procedure
A census-style approach was used, including all eligible cases over the 5-year period. Although no formal sample size calculation was performed, this approach maximizes representativeness and supports generalizability to similar settings.

Data collection
Data from health management information systems, medical records, and histological specimens were used to confirm the diagnosis of AA.
The collected data included the patient’s age, sex, presence or absence of comorbidities, use of scoring systems, type of preoperative imaging, type of surgery performed (open or laparoscopic), gross appearance of the appendix, and histopathologic diagnosis. 

 

Data analysis
The data collected were entered, cleaned, sorted, coded, and analyzed using the Statistical Package for the Social Sciences (SPSS version 21.0 IBM Corp., Armonk, NY, USA). Categorical data were summarized using frequency and percentages, whereas median and interquartile range (IQR) were used for continuous variables.
Appendectomy results (positive, negative) were compared with the categorical variables using Fisher’s exact test. The Wilcoxon rank-sum test was used to compare differences in appendectomy outcomes between respondents and their age. A p value <0.05 was set as the level of significance where applicable.

Ethical considerations
Approval to access patient records and conduct this clinical audit was obtained from the hospital’s Research Committee, which oversees institutional research governance. The approval letter did not include a reference number. At the time of the study, the institution did not have a formal institutional review board (IRB); therefore, no IRB reference number was assigned. The study was conducted in accordance with the principles of the Declaration of Helsinki. Patient confidentiality was maintained using a secure laptop accessible only to the principal investigator and supervisor. Data were subsequently handed over to the Research Committee and disposed of according to institutional policies.

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Results

Sample characteristics
A total of 147 patients were included, comprising 97 males (66.0%) and 50 females (34.0%). The median age was 34.0 years (IQR: 27.0–43.0 years), with 130 patients (88.4%) being aged ≥20 years.
Only six patients (4.1%) had comorbidities, including hypertension, right nephrolithiasis, right ovarian cysts, and pregnancy in the first trimester (Table 1).

 

Table 1.

Demographic characteristics of the participants

CT, computed tomography; HTN, hypertension; IQR, interquartile range; U/S, ultrasound.
aMedian (IQR) or frequency (%).

Sixty-one patients (41.5%) were assessed using the Alvarado scoring system, with a median score of 7.0 (IQR: 6.0–8.0), a sensitivity of 80%, a specificity of 22%, and a positive predictive value of 74%.
All patients underwent preoperative imaging: 81 (55.1%) were evaluated with U/S alone, 53 (36.1%) with CT alone, and 13 (8.8%) with both U/S and CT. CT and U/S were found to be equally effective in predicting appendicitis (80.2% and 80.0%, respectively). Among those who had both imaging modalities done, appendicitis was noted in 91.6% of cases (Figure 1).

 

Figure 1.

Histological appendectomy outcomes by preoperative imaging modality. CT, computed tomography; U/S, ultrasound.

Ninety-two (62.6%) patients underwent laparoscopic appendectomy. Intraoperatively, 132 (89.8%) patients had a grossly inflamed appendix. Histologically confirmed appendicitis (positive appendectomy) results were 92.5% (n=136), with a negative rate of 7.5% (n=11) (Table 2) .

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Table 2.

Demographic characteristics of the participants by appendectomy outcome

CT, computed tomography; HTN, hypertension; IQR, interquartile range; U/S, ultrasound.
aMedian (IQR) or frequency (%).

​bWilcoxon rank-sum test; Fisher’s exact test.

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Factors affecting the negative appendectomy result
Among the 11 patients with negative results, the median age was 35 years (IQR: 27.5–42.5 years). Ten (90.9%) were adults (aged ≥20 years), while one was an adolescent. Three were admitted in 2018, 2020, and 2021, one in both 2017 and 2019, and none in 2022.
Six (54.5%, n=11) were females, whereas five (45.5%) were males. The NAR was 5.15% in males versus 12.0% in females. Only one patient had a comorbidity (right ovarian cysts).
The Alvarado score was applied to two patients (n=11), with a median score of 7.0 (IQR: 6.5–7.5).
Among patients with negative appendectomy, preoperative imaging included CT scan alone (n=5), U/S alone (n=5), and combined U/S and CT imaging (n=1) (Figure 1).
Among patients who underwent negative appendectomy, laparoscopy was performed in nine cases (81.8%), while two patients (18.2%) underwent open appendectomy. Intraoperatively, nine appendices (81.8%) appeared morphologically normal, while two (18.2%) appeared inflamed. The intraoperative morphological appearance of the appendix was significantly associated with negative appendectomy (p < 0.001) (Table 2).
When appendectomy outcomes were compared by surgical approach, there was no statistically significant association between operative technique (open vs. laparoscopic appendectomy) and NAR (p = 0.27) (Table 2).

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Discussion

Primary outcome
The 5-year audit demonstrates an institutional NAR of 7.5%, consistent with the internationally acceptable thresholds (Table 3). More appendectomies were performed in 2020 during the coronavirus disease 2019 (COVID-19) pandemic, with a slightly higher negative rate (8.3%), likely reflecting delayed presentations due to pandemic-related challenges in healthcare access. Despite encouragement of non-operative management during this period, many patients presented with advanced disease, necessitating surgery (13, 14).

 

Table 3.

NAR across different centers globally

NAR, negative appendectomy rate. 
ACS NSQIP, American College of Surgeons National Surgical Quality Improvement Program

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Secondary outcome: factors affecting NAR

1. Age and NAR

The mean age of patients with negative appendectomy was 35.0 years, compared to 33.5 years among those with positive results (Table 2). The NAR was 5.88% among adolescents and 7.6% among adults. This aligns with the global incidence of appendicitis, which is highest in the second and third decades of life (3) (ages 10–29 years); our study population included older adults, which may explain the slightly higher mean ages observed. The slightly higher NAR in adults may reflect the greater proportion of females in this group, as women of reproductive age have higher NARs than the general population (15).

     2. Sex and NAR

The NAR was 5.15% in males versus 12.0% in females, with an overall rate of 7.5%. The number of males (n=97) in the study was higher than that of females (n=50), which may introduce a bias to the lower NAR in this study.
Historically, NAR is higher in females (7), especially those of reproductive age, and this study supports that finding. Gynecological pathologies such as right ovarian cysts present similarly to AA and hence pose diagnostic challenges to clinicians.

     3. Comorbidities and NAR
Comorbidities were noted in 4% (n=6) of patients, with the majority presenting with right iliac fossa pain, such as right nephrolithiasis and right ovarian cysts. Gynecological pathologies in women of reproductive age present diagnostic challenges and contribute to the higher NAR in this cohort of patients (7).
Our study supports this, as the NAR is higher in females, with a median age of 28 years. Other cases, such as right nephrolithiasis and pregnancy, highlight diagnostic challenges where physiological changes in pregnancy-related leukocytosis may skew clinical scoring systems.
    4. Use of scoring systems and NAR
The Alvarado scoring system was the only diagnostic score used within the facility in 41% (n=61) of patients, with a median score of 7/10. Historically, the Alvarado score has been the most widely used appendicitis scoring system (6), guiding risk stratification into low-, intermediate-, and high-risk groups (16). According to the 2020 World Society of Emergency Surgery (WSES) AA guidelines, a score of <5 reliably excludes AA, while a score of >9 has 100% sensitivity for the diagnosis (5).
As this is a teaching hospital, most surgical residents (58.5%, n=86) did not routinely utilize scoring systems, instead relying on clinical assessment and preoperative imaging. This aligns with the literature supporting the value of “emergency physician gestalt” in acute care settings (4).
Among the patients with negative appendectomies, the median Alvarado score was 7.0. Although higher scores are typically associated with positive results, this difference could be attributed to the small sample size (n=11) compared to the positive cases (n=136), which may potentially skew the results.
Furthermore, conditions that present with right iliac fossa pain may mimic AA and deceptively lead to higher Alvarado scores. The use of alternative scoring systems may theoretically reduce diagnostic discrepancies, but these were not applied in this audit (17).
    5. Use of preoperative imaging and NAR
         a. U/S
The 2020 WSES AA guidelines recommend the use of U/S as the first-line imaging modality (18). The study showed that U/S was used in the majority of patients (55.1%, n=81), with a predictive value of 80.2%. 
U/S has been shown to have a sensitivity and specificity of 76% and 95%, respectively. The disadvantage of U/S, however, is the difficulty of interpretation in obese patients and its user dependence (18).
        b. CT scan abdomen
CT scans were used in 36.1% of patients (n=53), with an additional 8.8% (n=13) of patients having both a preoperative U/S and a CT scan. The predictive value of the CT scan alone in our study was 80.0%, and it was 91.6% when both U/S and CT were used together.
U/S and CT scans were used together in patients who had equivocal readings on U/S to better elucidate the morphology of the appendix on imaging.
The 2020 WSES guidelines on AA recommended CT scan as the second-line imaging modality (18). The judicious use of CT scans is necessary to avoid unnecessary radiation exposure (18). However, many urban centers adopt CT scans as the first-line imaging modality due to their higher predictive value and ability to rule out other differential diagnoses.
While imaging remains an important adjunct in the diagnostic pathway for suspected AA, it does not fully eliminate diagnostic uncertainty, particularly in patients with early or atypical presentations. This underscores the need to interpret imaging findings in conjunction with clinical assessment and scoring systems when guiding operative decision-making.
    6. Morphological appearance of appendix during operation
Intraoperative gross appearance of the appendix was statistically significant at <0.001. Most negative appendectomies (9/11) were grossly normal, supporting a generally strong correlation between gross morphology and histologically normal findings. However, in two cases, the appendix appeared inflamed intraoperatively despite being histologically negative. These exceptions highlight that while gross appearance is a practical intraoperative guide, it is not definitive, and histopathology remains the gold standard. Such discrepancies may reflect early inflammation, sampling errors, or other pathologies that mimic appendiceal inflammation (19).

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Conclusion

This 5-year clinical audit demonstrates that negative appendectomy remains a relevant issue in the management of suspected AA within our institution. Comparison with regional and global data situates institutional practice within the broader context of contemporary surgical care. In the setting of diagnostic uncertainty associated with atypical presentations of AA and variability in diagnostic approaches, structured clinical audit provides a practical framework for evaluating surgical decision-making and guiding quality improvement initiatives. These findings offer an institutional benchmark and underscore the importance of regular clinical audits in improving patient care and strengthening surgical decision-making in similar tertiary care settings (20).

Limitations
The limitations of the study are as follows:

1. A single-center study, hence difficult to infer its findings to a larger population

2. Retrospective study with a possibility of missed data from the search history

3. Limited sample size, as our hospital is a private facility located in an urban area 

4. Comparison with the preceding 5 years was not possible, as digitized medical records were only available from 2017 onward, limiting the ability to compare trends and assess changes in NARs over a longer timeframe.

 

Recommendations

1. Strengthen adherence to structured diagnostic pathways where appropriate, particularly in populations with higher diagnostic uncertainty, such as females of reproductive age.

2. Continue routine use of preoperative imaging, as it enhances diagnostic accuracy and likely contributed to the acceptable NAR observed.

3. Encourage regular audit and feedback of appendectomy outcomes, including NAR and imaging utilization, to support ongoing quality improvement.

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Author contributions

Both authors equally contributed in conceptualization, data curation, formal analysis, investigation, methodology, supervision, validation and in writing, reviewing & editing of the original draft.

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