Retrospective Cohort Study Open Access
Copyright ©The Author(s) 2016. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastrointest Surg. Oct 27, 2016; 8(10): 693-699
Published online Oct 27, 2016. doi: 10.4240/wjgs.v8.i10.693
Acute appendicitis: Epidemiology, treatment and outcomes- analysis of 16544 consecutive cases
Marco Ceresoli, Niccolò Allievi, Asaf Harbi, Michele Pisano, Giulia Montori, Gabriela E Nita, Luca Ansaloni, Federico Coccolini, General Surgery Unit, Papa Giovanni XXIII Hospital, 24127 Bergamo, Italy
Alberto Zucchi, Epidemiology unit, ATS Provincia Bergamo, 24128 Bergamo, Italy
Arianna Heyer, University of California, Berkeley, CA 94720, United States
Author contributions: Ceresoli M, Zucchi A, Pisano M, Ansaloni L and Coccolini F designed the study; Ceresoli M, Zucchi A, Allievi N and Pisano M analyzed the data; Ceresoli M, Allievi N, Harbi A and Montori G wrote the paper; Pisano M, Heyer A, Nita GE, Ansaloni L and Coccolini F revised it critically; all the authors read and approved the final version of the manuscript.
Institutional review board statement: According to the Italian law for retrospective observational cohort studies no specific approvations by the review board is needed.
Informed consent statement: This is a retrospective cohort study. According to the Italian law and the Helsinki declaration on biohetics no informed consent by single patient is needed; moreover presented data are anonymized and risk of identification is null.
Conflict-of-interest statement: No potential conflicts of interest relevant to this article were reported.
Data sharing statement: Statistical code and dataset are available from the corresponding author at Consent was not obtained but the presented data are anonymized and risk of identification is null. No additional data are available.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See:
Correspondence to: Dr. Marco Ceresoli, General Surgery Unit, Papa Giovanni XXIII Hospital, piazza OMS 1, 24127 Bergamo, Italy.
Telephone: +39-352-673486 Fax: +39-352-674963
Received: May 31, 2016
Peer-review started: June 1, 2016
First decision: July 20, 2016
Revised: August 4, 2016
Accepted: August 27, 2016
Article in press: August 29, 2016
Published online: October 27, 2016


To investigate the epidemiology, treatment and outcomes of acute appendicitis (AA) in a large population study.


This is a retrospective cohort study derived from the administrative dataset of the Bergamo district healthcare system (more than 1 million inhabitants) from 1997 to 2013. Data about treatment, surgery, length of stay were collected. Moreover for each patients were registered data about relapse of appendicitis and hospital admission due to intestinal obstruction.


From 1997 to 2013 in the Bergamo district we collected 16544 cases of AA, with a crude incidence rate of 89/100000 inhabitants per year; mean age was 24.51 ± 16.17, 54.7% were male and the mean Charlson’s comorbidity index was 0.32 ± 0.92. Mortality was < 0.0001%. Appendectomy was performed in 94.7% of the patients and the mean length of stay was 5.08 ± 2.88 d; the cumulative hospital stay was 5.19 ± 3.36 d and 1.2% of patients had at least one further hospitalization due intestinal occlusion. Laparoscopic appendectomy was performed in 48% of cases. Percent of 5.34 the patients were treated conservatively with a mean length of stay of 3.98 ± 3.96 d; the relapse rate was 23.1% and the cumulative hospital stay during the study period was 5.46 ± 6.05 d.


The treatment of acute appendicitis in Northern Italy is slowly changing, with the large diffusion of laparoscopic approach; conservative treatment of non-complicated appendicitis is still a neglected option, but rich of promising results.

Key Words: Acute appendicitis, Conservative treatment, Epidemiology, Laparoscopic appendectomy, Intestinal obstruction

Core tip: Acute appendicitis is the most common surgical emergency around the world. In the Bergamo district, northern Italy its incidence is 89/100000 inhabitants per year with a negative trend during the last years. Percent of 95 patients were treated with appendectomy, 48% of whom laparoscopically; 1.3% of operated patients had an intestinal obstruction during the follow-up. Conservative treatment resulted in a reduced length of stay but 23% of patients had a relapse during follow up. Cumulative length of stays during the study period was similar for the two treatment option.


Acute appendicitis is probably the most common surgical emergency worldwide. Since its first accurate description by Fitz[1] in 1886 and the first appendectomy performed by Treves[2] in England, appendectomy became the preferred treatment of acute appendicitis. Although appendicitis is a very common disease, nowadays it has a still poorly understood etiology, with a very heterogeneous clinical pattern of presentation, varying from simple uncomplicated appendicitis to generalized peritonitis due to perforation. For each clinical pattern the proposed treatment is the same: Appendectomy. This results in an overtreatment with a described rate of negative appendectomy (a hystopathological diagnosis of normal appendix) ranging from 6% to 20%[3,4]. Appendectomy has also a complication rate ranging from 8% to 11%, depending on the surgical technique[5]. Several reports described spontaneous resolution of uncomplicated appendicitis without the need of an operation and, since the high rate of negative appendectomy and the significative complications rate, some authors proposed and advised conservative management for uncomplicated appendicitis[6,7]. Conservative management for appendicitis has been described in 1930 by the “Ochsen-Sherren delayed[8] treatment”, which consisted of resting and fasting followed by delayed elective appendectomy; nowadays, a conservative approach based on antibiotic therapy is gaining popularity, as documented by several randomized studies and meta-analyses that analyze this peculiar issue[9-17]. Conservative treatment has been shown to be safe and effective as primary treatment compared to surgical treatment with a significative reduction in morbidity, even with a considerable one year recurrence rate of 23%[17].

Despite this positive evidence, great uncertainty and skepticism remain concerning conservative treatment among surgeons.

The aim of the study was to describe the epidemiology of acute appendicitis in a large population study during the last seventeen years in order to analyze the evolution of the treatment throughout the years - appendectomy or conservative treatment, open or laparoscopic surgery - and to study the long term follow up of patients, in order to investigate the relapse rate of acute appendicitis in conservatively-treated patients and the incidence of intestinal occlusion after surgery.


This is a retrospective analysis of patients discharged from the hospital between 1997 and 2013 with a diagnosis of acute appendicitis. Data were extracted from the administrative health care database of Bergamo’s district, a large area (2723 km2) in Northern Italy with 1094062 inhabitants. This database collects all discharge records for each citizen of the district from any hospital, public and private, intra and extra-district. On the basis of this register, patients are assigned to the respective DRG, and reimbursements are supplied to the hospitals from the regional health care system.

Patients were retrieved on the basis of the concomitant presence of an unplanned hospital admission, with a ICD9-CM code of AA (ICD9-CM code 540.X, 541.X, 542.X, 543.X) in the first three diagnostic fields and with an Italian DRG code of Acute Appendicitis.

For each patient tracked, data regarding age, sex, Charlson’s comorbidity index, surgical procedures (ICD9-CM code 47.X), length of hospital stay, time intervals between admission and operation and mortality were recorded.

For each patient further data on hospitalization related to acute appendicitis (same code) and bowel occlusion (ICD9-CM code 560.X) were collected, as well as the number of further hospitalizations, interventions, length of stay of each hospitalization and cumulative length of stay during the study period.

Continuous variables were expressed as mean ± SD and were compared with the Mann-Withney U test; association was tested with the Pearson’s χ2 test. Correlations were calculated with the Pearson’s correlation test. Multivariate analyses were performed with the logistic regression method. Survivals were calculated with the Kaplan Meier method. Statistical analysis was performed with SPSS software (SPSS version 20, IBM, United States). Trends were studied with the Jointpoint model: Joinpoint regression analysis was performed using the Joinpoint software from the Surveillance Research Program of the United States National Cancer Institute (Joinpoint Regression Program, Version 4.1.1 - August 2014; Statistical Methodology and Applications Branch, Surveillance Research Program, National Cancer Institute). Trends were summarized with Average Annual Percent Change (AAPC). Calendar years started from 1997, until 2013. Crude rates are per 100000 inhabitants.


From 1997 to 2013 in the Bergamo district we collected 16544 cases of AA, with a crude incidence rate of 89/100000 per year; mean age was 24.51 ± 16.17, 54.7% were male and mean Charlson comorbidity index was 0.32 ± 0.92. Mortality was recorded for 7 patients (< 0.0001%). Table 1 and Figure 1 show the distribution of age categories and sex: differences among sex in the different age categories were statistically significant (P < 0.001). The incidence of AA decreased during the years starting from 120/105 in 1997 to 73/105 in 2013 with a statistically significant negative value (AAPC = -2.8, P < 0.001) (Figure 2).

Table 1 Distribution of patients among age categories and sex.
Age categorySex
FMnAmong total
> 852317400.24%
Figure 1
Figure 1 Age class and sex distribution. 1: 0-1; 2: 1-6; 3: 7-13; 4: 14-17; 5: 18-25; 6: 26-35; 7: 36-45; 8: 46-55; 9: 56-65; 10: 66-75; 11: 76-85; 12: > 85.
Figure 2
Figure 2 Number of patients discharged with acute appendicitis diagnosis during the years.
Operative treatment

An appendectomy was performed in 94.7% of the patients: Mean age was 24.39 ± 15.98, mean Charlson’s comorbidity index was 0.31 ± 0.90 and 53.1% were male. Patients were operated after a mean of 0.85 ± 1.46 d and the mean length of stay was 5.08 ± 2.88 d with a negative trend over the considered period, starting from 6.09 ± 2.94 in 1997 to 4.58 ± 2.33 in 2013 (AAPC -1.5, P < 0.001). Mortality was < 0.0001%.

Data about laparoscopic procedures was available only after the year 2000: 48% of the patients were operated with the laparoscopic technique with a positive trend during the years, starting from 26% in 2000 to 68.8% in 2013 (AAPC 5.2, P < 0.001) (Figure 3A) and with a mean length of stay of 4.47 ± 2.66 d (compared to 5.43 ± 2.94 with the open technique, P < 0.001). Laparoscopy was associated with a higher age, female sex and year in both univariate and multivariate analysis (P < 0.0001) (Table 2, Figure 3B and C).

Table 2 Surgical technique: Data about surgical techniques were available only after year 2000.
Open appendectomyLaparoscopic appendectomyTotalUnivariate analysisP valueMultivariate analysis
ORP value
n (%)6321 (52)5734 (48)12055
Age22.79 (17.01)27.57 (15.19)25.06 (13.55)< 0.00011.018 (1.018-1.0121)< 0.0001
SexM: 61.5%M: 50.2%M: 54.6%< 0.00011.80 (1.66-1.94)< 0.0001
Charlson's0.33 (0.97)0.35 (0.87)0.34 (0.92)0.385
Year0.277 (Pearson Correlation)< 0.00011.15 (1.14-1.16)< 0.0001
Time to surgery (d)0.66 (1.35)0.97 (1.53)0.81 (1.45)< 0.0001
Lenght of stay (d)5.28 (3.00)4.47 (2.66)4.89 (2.85)< 0.0001
Mortality5 (0.1%)1 (0.001%)6 (< 0.0001)0.13
Figure 3
Figure 3 Surgical technique during the years (A), between sex (B) and among age classes (C).

The cumulative hospital stay during study period was 5.19 ± 3.36 d with a mean of 1.01 ± 0.13 hospital admissions. One hundred and ninty-two patients (1.2%) had at least one further hospitalization due intestinal occlusion after a mean of 30.53 ± 41.23 mo (median 11 mo) and 59.9% of them were operated on (Figures 4 and 5).

Figure 4
Figure 4 Cumulative length of stay between treatment options. Data are expressed in days (SD).
Figure 5
Figure 5 Kaplan-Meyer curve of failure of conservative treatment (blue line) and incidence of intestinal obstruction in operated patients (red line).
Conservative treatment

In general, 5.34% of the patients were treated conservatively: Mean age was 26.68 ± 19.04; 56.1% were male and mean Charlson’s comorbidity index was 0.51 ± 1.26; mean length of stay was 3.98 ± 3.96 d; mortality was 0.1%. The proportion of patients treated conservatively increased during the years, from 6.1% in 1997 to 8.7% in 2013, although the trend was not significant (P = 0.6) (Figure 6).

Figure 6
Figure 6 Treatment option during the years.

Overall, relapse rate was 23.1% and a new episode of acute appendicitis occurred after a mean of 6.5 ± 15 mo (median 32 d); 89% of patients were operated on at relapse. The mean number of hospital admissions was 1.26 ± 0.47 with a cumulative hospital stay during the study period of 5.46 ± 6.05 d (Figures 4 and 5).

After univariate analysis, conservative treatment was associated with higher age, higher comorbidity index, and year of treatment (P < 0.0001); after multivariate analysis only Carlson’s comorbidity index (P = 0.004) and year of treatment (P < 0.0001) remained significant (Table 3).

Table 3 Different treatments.
Univariate analysis P valueMultivariate analysis
AppendectomyConservativeOR (95%CI)P value
n (%)1654415661 (94.7)883 (5.3)
Age24.51 (16.17)24.39 (15.98)26.68 (19.04)< 0.00011.006 (0.999-1.013)0.095
SexM: 54.7%M: 54.6%M: 56.1%0.424
Charlson's0.32 (0.92)0.31 (0.90)0.51 (1.26)< 0.00010.826 (0.703-0.868)< 0.0001
Year-0.33 (Pearson Correlation)< 0.00010.973 (0.959-0.986)< 0.0001
Time to surgery (d)0.85 (1.46)
Length of stay (d)5.02 (2.92)5.08 (2.88)3.98 (3.46)< 0.0001
Mortality7 (< 0.0001%)6 (< 0.0001%)1 (0.1%)0.292
Relapse1.20%23.10%< 0.0001
Time to relapse (mo)Mean30 (45)6.5 (15)< 0.0001
Time to relapse (mo)Median11 (1.17-49)1 (0.16-6.63)
number of hospitalization1.03 (0.18)1.01 (0.13)1.26 (0.47)< 0.0001
Cumulative LOS5.20 (3. 56)5.19 (3.36)5.47 (6.05)0.02

Acute appendicitis in Northern Italy has a crude rate of 89 cases per 100000 inhabitants per year, and this data is comparable to similar studies in other country worldwide[18-21]. Surprisingly, during the study period the incidence decreased significantly, from 120 to 73 cases per 100000 inhabitants. This data contrasts with the data reported by Buckius et al[20] in the United States over a similar period of time. Acute appendicitis is already a poorly understood disease and its diagnosis is still based on clinical judgment, with great variability among surgeons. Clinical scores have been developed and proposed in the last years to help surgeons reaching a diagnosis of acute appendicitis, such as the Alvarado and the Andersson score[22,23]: The decrease in the incidence rate could be explained by the diffusion of these scores and a consequent increased attention in the diagnosis of acute appendicitis, in order to reduce the rate of negative appendectomies. As expected, acute appendicitis is more frequent in young and male patients (Figure 1), as reported by the literature[18-20], with augmented incidence among patients in the 7-25 years categories. In the years categories 14-25, acute appendicitis is more frequent in females: A possible reason is the starting of childbearing ages and the sexual transmitted disorders that could mime acute appendicitis - with lower quadrant abdominal pain - and a consequent higher rate of negative appendectomies, as reported by Seetahal et al[3]. Unfortunately there are no data available on the rate of negative appendectomies to confirm this hypothesis. The possibility of a diagnosis other than appendicitis in women justifies the higher frequency in this subgroup of the laparoscopic technique, which give the possibility to thoroughly explore the peritoneal cavity, as shown in Figure 3B. Laparoscopic appendectomy was performed in 48% of the cases, with an enormous increase across the years, from 26% to 69% (Figure 3). This data demonstrates the gradual diffusion of the laparoscopic technique, as shown by a similar study in the same contest for acute cholecystitis[24]. After multivariate analysis, the laparoscopic approach was correlated to the year of treatment, female sex and older age: Figure 3C demonstrates that open appendectomy is still the preferred technique for children.

Conservative treatment for acute appendicitis in Northern Italy is still a neglected option, with only 5% of patients treated not operatively; however, over the period of study there was a small increase in the proportion of patients treated conservatively. Despite the small number, conservative treatment seems to be an effective treatment option, showing a reduced length of stay and, notwithstanding an overall relapse rate of 23%, a similar cumulated length of stay and number of hospital admissions during the study period, with a clinically not significant difference (Figure 4). Conservative treatment, as shown in Figure 5, fails after a median of 32 d and leads to an operative treatment in the majority of cases. Factors involved in the choice of this approach are represented by the comorbidities of the patient and the year of treatment, showing that this option is slowly spreading, but still depends on the surgeon’s preference. Conservative treatment resulted in 77% reduction of surgical procedures for appendicitis during the study period, maintaining a similar length of stay; moreover, appendectomy exposes patients to the risk of intestinal obstruction due to adherences in 0.7%-10.7%[25-27]: In our group of patients, 1.3% of the patients needed a further hospitalization due to bowel obstruction after a median of 11 mo and required a further surgical operation in 60% of cases. Laparoscopic appendectomy has been shown to reduce the risk of intestinal obstruction[28] and our results confirm this evidence, although the clinical effect is not significant (Table 2). A cost-effectiveness study demonstrated that conservative treatment, with a failure rate of less than 40% is more cost effective than operative management: Our results on a large population study during a long period show that treating a patient with acute appendicitis conservatively could be considered the better treatment option.

The study was performed retrieving data from an administrative register that allows for a long-term follow up for each patient included; unfortunately, administrative registries do not include data about histopathological diagnosis. Moreover, figures about failure of conservative treatment could be slightly underestimated, considering the lack of data about the immediate failure during the first hospital admission.

In conclusion the treatment of acute appendicitis in Northern Italy is slowly changing, with the large diffusion of laparoscopic approach; conservative treatment of non-complicated appendicitis is still a neglected option, but full of promising results.


Acute appendicitis is the commonest surgical emergency. Despite appendectomy is considered the definitive treatment there is great interest in the conservative management.

Research frontiers

Epidemiology and treatment of acute appendicitis.

Innovations and breakthroughs

The study outlines the current epidemiology of acute appendicitis giving an overview on the state of the art of the treatment’s choice in the daily clinical practice.


The study gives the state of the art of the treatment of acute appendicitis and its changes during the last years.


Conservative treatment: Medical therapy based on antibiotics administration.


This is a well-written article with good statistical analysis.


Manuscript source: Invited manuscript

Specialty type: Gastroenterology and hepatology

Country of origin: Italy

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P- Reviewer: Handra-Luca A, Papes D S- Editor: Qi Y L- Editor: A E- Editor: Lu YJ

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