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Burden of negative appendectomy at a District General Hospital: a two-year cross-sectional review

Burden of negative appendectomy at a District General Hospital: a two-year cross-sectional review

Bankole Oyewole1,&, Mira Runkel2, Andrew Gordon1, Nicholas Farkas3


1Department of General Surgery, East Surrey Hospital, Redhill, United Kingdom, 2Department of General and Visceral Surgery, Medical Center- University of Freiburg, Hugstetterstrasse 55, 79106 Freiburg, Germany, 3Department of General Surgery St Richard´s Hospital, Chichester, United Kingdom



&Corresponding author
Bankole Oyewole, Department of General Surgery, East Surrey Hospital, Redhill, United Kingdom




Introduction: the average negative appendectomy rate (NAR) in the UK is relatively high when compared to other high-income countries. Associated factors and complications following NAR defer in literature. The main objective of this paper is to report the short and long-term re-admission following a NAR, secondary objectives were to assess the characteristics of NAR patients and their Alvarado´s score.


Methods: a two-year retrospective observational study was performed on patients undergoing emergency appendectomy. Patient demography, data and follow-up records were extracted from electronic patient records.


Results: four hundred and seventy-eight (478) patients underwent emergency appendectomy over the study period. Seven (7) patients were excluded due to incomplete patient records. Four hundred and seventy-one (471) patients met the study criteria; median age at presentation was 27 (IQR 19 - 39) years, mean age of 32 (SD 16.3) years. Two hundred and forty-five (245 (52%) were male. Among this cohort, 355 patients (75.4%) underwent appendectomy for histologically proven appendicitis, while 12 patients (2.5%) and 19 patients (4%) were diagnosed via histology to have appendicular faecolith without inflammatory change and lymphoid hyperplasia respectively, an additional 12 patients (2.5%) had unexpected histological findings. Conversely, 73 patients (15.5%) underwent negative appendectomy. Re-presentation within thirty-days was 5.5% vs. 11% (p=0.2001) while re-presentation beyond thirty-days was 21.9% vs. 4.2% (p<0.001) among those who underwent negative appendectomy versus histologically confirmed acute appendicitis respectively


Conclusion: the negative appendectomy rate of our study population was lower than national average and reported no significant increase in complication rates or re-admission within the first 30 days.



Introduction    Down

Suspected acute appendicitis is one of the most common acute surgical presentations within the United Kingdom (U.K.). The lifetime risk of acute appendicitis is approximately 6% and over 70,000 appendectomies are carried out each year [1]. Despite advances in medical technology and research, a clinical diagnosis acute appendicitis can still be problematic. The increased utilization of diagnostic laparoscopy over a traditional open approach has resulted in an increase in the Negative Appendectomy Rate (NAR) [2,3]. While various definitions of NAR exist in literature, a widely used definition is the absence of inflammation or pathology in the appendix. This definition puts into account patient symptoms might be due to pathologies like faecolith, neoplasm or other unexpected findings which justify the need for an appendectomy, howbeit sometimes retrospectively [3,4].


Appendectomy without the presence of pathology is concerning due to the potential complications that come with surgery [4,5]. With recent advances in technology and wider availability of radiological imaging for the diagnosis of acute appendicitis, the routine uses of ultrasound and computerized tomography scan (CT scan) especially in the United States of America (USA) has been described to result in a decline in the negative appendectomy rate to between 5-10%. This is in contrast to the UK whereby there is still a mixed approach between the use of imaging, clinical scoring methods and diagnostic laparoscopy for the diagnosis of acute appendicitis, this has been described as a possible explanation of the national U.K average NAR of 20-26% [1,2,4]. Scoring systems such as the Alvarado score may also be used to aid in a clinical diagnosis. The Alvarado´s score is however inconsistent among children and over-predicts the probability of appendicitis in women [6,7].


The main objective of this paper is to report the short and long-term re-admission following a negative appendectomy at a University Hospital, secondary objective is to assess the characteristics of patients who had negative appendectomy and their Alvarado´s score.



Methods Up    Down

Data collection

Patient information with regards age, sex, operative and histological findings and re-admission data was collected retrospectively from electronic patient records. Consecutive patients seen in the Surgical Assessment Unit (SAU) over the study period were assessed for eligibility.


Statistical analysis and variables

Data was stratified according to age at presentation, sex and histological findings. Re-admission data was obtained and thirty-day morbidity stratified according to the Clavien-Dindo Classification, thirty days taken as the cut off for early and late outcomes. The Alvarado score predicts the likelihood for a diagnosis of acute appendicitis from clinical signs, symptoms and laboratory values (tenderness right lower quadrant, rebound tenderness, elevated temperature, migration of pain, anorexia, nausea/vomiting, leucocytosis or leukocyte left shift) [7]. This was retrospectively calculated for negative appendectomy patients. Fisher´s exact test was utilized to calculate statistical significance. A p-value of <0.05 was considered statistically significant. Data was analyzed using the Statistical Package for the Social Sciences (SPSS) Version 19.


Clinical work up pathway

Patients assessed by the surgical team due to right iliac fossa (RIF) pain had a clinical evaluation which involved a comprehensive history taking and examination, routine blood tests like a Full Blood Count (FBC), C-reactive protein (CRP) and a urinalysis in addition to a urinary pregnancy test. Patients with a strong suspicion for acute appendicitis proceed to have a diagnostic laparoscopy while patients with either a low suspicion for acute appendicitis or an alternative diagnosis proceeded to have either an ultrasound especially in female and younger patients or a CT scan usually for patients above the age of 35 years. At diagnostic laparoscopy, patients with obviously inflamed appendicitis proceeded to have an appendectomy while patients with an equivocal or normal looking appendix in the absence of other pathology on laparoscopy proceeded to have an appendectomy, this is due to the possibility if microscopic appendicitis despite a macroscopically normal looking appendix. Patients with obvious pathology in the setting of a normal looking appendix did not have an appendectomy. We believe this approach represents a common theme in other UK hospitals [1,2].


Ethical considerations


The UK Medical research council uses a two-part tool to determine the need for ethic approval for studies. The first part assesses if the study is considered "research" and the second part assesses if research requires ethical approval [8]. Based on this tool, this study was considered research that did not require an ethical review being a retrospective observational case series. Ethical standards were maintained following the applicable principles of the World Medical Association Declaration of Helsinki and all data was anonymized.



Results Up    Down

General characteristics of the study population and histological findings


Following retrospective patient record review, 478 patients who underwent appendectomy over the study period at the University Hospital were identified. Seven patients were excluded due to incomplete patient records. Of the remaining 471 patients, 245 (52%) were male and 226 (48%) females. The median age at presentation was 27 (IQR 19 - 39) years with a mean age of 32 (SD 16.3) years. Histological findings were divided into either “typical findings (TF)” or “unexpected findings (UF)” (Table 1, Table 2, Table 3); typical findings include normal (macro and microscopic features), acute appendicitis (histology showing inflammation), faecolith (without inflammatory change) or lymphoid hyperplasia. New unexpected findings included appendicular polypoid disease, lymphoma, carcinoid and adenocarcinoma. Three hundred and fifty-five (355) patients (75.4%) underwent appendectomy for histologically proven acute appendicitis, 12 patients (2.5%) and 19 patients (4%) patients were diagnosed via histology with appendicular faecolith (without inflammatory change) or lymphoid hyperplasia respectively while 12 patients (2.5%) had unexpected histological findings. Seventy-three (73) patients (15.5%) patients underwent a negative appendectomy, previously defined as the absence of inflammation or pathology in the appendix. Eighty-two point nine percent (82.9% (203/245) of men had histologically proven acute appendicitis, compared with 67.3% (152/226) of women (p<0.001). Negative appendectomy rates were significantly more common in women at 20.8% (47/226), compared to men at 10.6% (26/245) (p=0.003). The incidence of negative appendectomy significantly decreased with age. Negative appendectomy was seen among 18% (65/361) of patients less than 40 years compared to 7.3% (8/110) above 40 years old (p=0.0063). The presence of unexpected findings increased with age and was seen in only 1.7% (6/361) of patients 40 years and younger, compared to 5.5% (6/110) for patients older than 40 years (p=0.0380).

Alvarado score and medical imaging


We retrospectively applied the Alvarado score to the group of negative appendectomies´ performed at University Hospital. Out of 73 patients who underwent negative appendectomy 38 patients (52%) were identified as low probability, 15 patients classified as intermediate probability (20.5%) while 20 patients classified as high probability (27.5%) for acute appendicitis. Medical imaging was performed in 52% of patients who underwent a negative appendectomy (38/73).


Re-presentation following surgery


Of the 471 patients who had an appendectomy, 74 patients (15.7%) were re-admitted with conditions relating to their surgery or pathology. 58% re-presented to acute services within thirty post-operative days (43 patients) while 42% re-presented after more than 30 days (31 patients). Re-presentation within 30-days was 11% (39/355) vs. 5.5% (4/73) (p=0.2001) among patients who underwent surgery for histologically confirmed appendicitis and negative appendectomy respectively (Table 2, Table 3, Table 4). Re-presentation was most commonly due to ongoing abdominal pain (without collection), wound sepsis and intra-abdominal collection (Table 4, Table 5). Around 21.9% (16/73) of patients re-presented after 30 days after negative appendectomy, compared to 4.2% (15/355) of patients with histologically confirmed acute appendicitis (p>0.001). Among 73 patients who underwent negative appendectomy surgery, 14 re-presented beyond 30-days with recurrent abdominal pain. 1 patient re-presented with constipation and another with ascending colon colitis. Among those presenting with recurrent abdominal pain 8 patients were diagnosed with a gynaecological pathology (n=7 ovarian accident, n=1 endometriosis). Among 355 patients with histologically confirmed appendicitis, 15 re-presented beyond 30-days to acute services, presenting pathology included abdominal pain of undetermined etiology (n=9), pelvic inflammatory disease (n=2), urinary infection (n=10, constipation (n=1), lateral cutaneous nerve of thigh neuralgia due to patient positioning (n=1) and testicular discomfort since surgery (varicocele).



Discussion Up    Down

The objective of this paper is to report the short and long-term re-admission of patients that have had a negative appendectomy and to describe the characteristics of these patients along with the clinical setting in which they are cared for. Acute appendicitis is one of the most prevalent acute abdominal pathologies; making appendectomies one of the most commonly performed operations world-wide. The pathogenesis of acute appendicitis is still unclear: One of the most prominent theories describes the role of an obstructive picture (e.g., faecolith) that subsequently causes infection due to increased intraluminal pressure and subsequent ischemia and bacterial translocation, however appendiceal obstruction isn´t often found in cases of appendicitis [1,3,9-11].


Among eligible patients who underwent appendectomy in our study, the negative appendectomy rate was 15.5% (n=73). This is lower than the reported NAR in the UK of 20%, however this is significantly greater when compared with other high-income countries with a NAR ranging from 2 to 6.2%. In countries like the USA, diagnosis of acute appendicitis is predominantly guided by radiological imaging and this has been reported to have decreased both the rates of appendectomies and the incidence of NAR. Scandinavian countries employ the routine use of diagnostic laparoscopy however normal looking appendixes are left in-situ [2,9,10]. The UK employs a mix of clinical assessment, radiology and diagnostic laparoscopy. This inconsistency may account for the higher NAR in the UK especially when compared with similar high-income countries [1]. The argument for the removal of normal looking appendixes being microscopic inflammation might account for 10 to 30% of visually normal appendixes [9-11]. Among our cohort and in keeping with other studies, negative appendectomy was twice as common among women, we reported a NAR of 20.8% in females compared with 10.6% in males. The higher incidence of NAR in females has been thought to be due to the presence of other causes of RIF pain like gynaecological pathologies like ovarian accidents or endometriosis. There is also a common perception that perforated appendicitis would affect female fertility however the studies regarding this have been inconclusive [1,9,10].


Negative appendectomy was also most common among those younger than 40 years of age with a rate of 18% when compared to 7.3% in patients above the age of 40 years. The rationale behind this might be the increased use of imaging in older patients as alluded to by the clinical work-up pathway described in our methodology. Among our cohort the incidence of intra-operative complications was low; 1 patient sustained an inferior epigastric vessel injury which required open ligation intra-operatively. No visceral injury was sustained through port access.


Unexpected findings (including carcinoid, neoplasms, lymphoma and polyps) were found in 2.4% of all appendectomies. Appendiceal tumours are a relatively well-known incidental findings on appendix histology (1:300), as they can mimic acute appendicitis clinically [11,12]. This study identified similar prevalence rates to those quoted in the literature (0.3%-2%) [9,13-15]. Carcinoid tumours are well described in the literature and can cause future complications. Sandor and Modlin describe highest incidences in the 4th decade of life, particularly in females, which correlates with our findings with unexpected findings reported in 1.7% of patients below 40 years old when compared to 5.5% in patients above 40 years old and this finding was statistically significant [16,17]. In keeping with Lee et al. in 2014, our 30-day morbidity rate for negative appendectomy patients was similar to that of patients undergoing appendectomy for acute appendicitis [3,4, 18,19]. We did however identify a significant late re-admission rate of 21.9% (p<0.001) among those who underwent negative appendectomy. Recurrent abdominal pain of gynaecological origin was the most common presentation [20].


The reattendance rate within 30 days was higher in patients with confirmed appendicitis as opposed to patients with negative appendectomies and this could be due to the a sequalae of the inflammatory process and contamination from appendicitis as exemplified from the fact that the majority of these patients presented with wound infections and post-operative collections. Patients should be informed that a negative diagnostic appendectomy carries a similar morbidity to that of an operation for appendicitis and that there is a significant risk of recurrent symptoms.


Our study is limited by not looking at the length of stay of patients with negative appendectomies at the initial and subsequent presentation as this would give a clearer picture of the economic and resource costs of repeated admission. The strength of our study includes a real-world report of the outcomes of negative appendectomy in a clinical setting that employs a mix of clinical and radiological diagnosis of appendicitis, the study covered a relatively large population of people and gives a detailed account of the histological findings.



Conclusion Up    Down

The NAR at our study centre was below the national average. We reported no significant increase in complications from negative appendectomies, but the high rate of re-attendance poses a significant burden. Emphasis should be made to reach an alternate diagnosis and appropriate treatment instituted in cases of negative appendectomies. Especially in young women, focus should be placed to exclude gynaecological pathologies before proceeding to surgery.

What is known about this topic

  • The Negative appendicectomy rate is relatively high in the United Kingdom due to variation in the diagnosis of acute appendicitis;
  • Negative appendicectomy can be defined as the absence of pathology in the appendix as opposed to absence of inflammation.

What this study adds

  • The morbidity associated with negative appendicectomy was low;
  • The re-admission rate associated with negative appendicectomy was higher when compared with patients with acute appendicitis.



Competing interests Up    Down

The authors declare no competing interests.



Authors' contributions Up    Down

Conception and study design: MR and NF. Data collection: AG, MR and NF. Data analysis and interpretation: BO and MR. Manuscript drafting: BO and MR. Manuscript revision: BO, AG and MR. Guarantor of the study: BO. All authors read and approved the final version of the manuscript.



Tables Up    Down

Table 1: histological findings

Table 2: histological findings based on gender

Table 3: histology based on age

Table 4: rate of re-admission

Table 5: complications following appendectomy



References Up    Down

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