The Prevalence of Appendiceal Tumours in Periappendicular Abscess
The Prevalence of Appendiceal Tumours in Periappendicular Abscess
Complicated and uncomplicated appendicitis follow different epidemiological trends also
 suggesting different pathophysiology behind these two different forms of appendicitis. In
 3-10% of patients complicated acute appendicitis is enclosed by formation of a circumscribed
 periappendicular abscess. The clinically established practice of antibiotic therapy and
 drainage, if necessary, has been shown safe and effective, allowing the acute inflammatory
 process to subside in more than 90% of cases without surgery. The need of subsequent interval
 appendectomy has been questioned with appendicitis recurrence risk varying between 5-26%.

 During trial enrollment in our randomized Peri-APPAC trial based on the interim analysis
 results with 17% appendiceal tumor rate in the study population, the trial was prematurely
 terminated based on ethical concerns. All the follow-up group patients were re-evaluated and
 surgery was offered and recommended to all follow-up group patients. After this assessment
 and additional appendectomies, two more tumors were diagnosed resulting in neoplasm rate of
 20% in the whole study group all diagnosed in patients over 40 years and the neoplasm rate in
 patients over 40 years was 29%.

 Based on high appendiceal tumor rate in patients over 40 years, the appendiceal neoplasm rate
 needs to be further evaluated in prospective patient cohorts undergoing interval appendectomy
 as interval appendectomy is generally well tolerated and obliterates the risk of missing a
 possible tumor. In a recent systematic review of retrospective cohort studies with 13.244
 acute appendicitis patients the overall appendiceal tumor rate was 1% after appendectomy, but
 in patients presenting with appendiceal inflammatory mass the neoplasm rate varied from 10%
 to 29%.

 This nationwide prospective multicenter cohort study is designed to assess the prevalence of
 appendiceal tumors associated with a periappendicular abscess. All consecutive patients
 presenting with a periappendicular abscess are recommended to undergo interval appendectomy
 after initial conservative treatment with antibiotic therapy and drainage, if necessary. All
 patients older than 35 years will undergo laparoscopic interval appendectomy at 2 to 3 months
 and this is also recommended for the patients between 18 and 35 years of age. Asymptomatic
 patients under 35 years not willing to undergo interval appendectomy, will undergo a
 follow-up MRI at 1 year after the initial non-operative treatment.
Complicated and uncomplicated appendicitis follow different epidemiological trends also
 suggesting different pathophysiology behind these two different forms of appendicitis. In
 3-10% of patients complicated acute appendicitis is enclosed by formation of a circumscribed
 periappendicular abscess. The clinically established practice of antibiotic therapy and
 drainage, if necessary, has been shown safe and effective, allowing the acute inflammatory
 process to subside in more than 90% of cases without surgery. The need of subsequent interval
 appendectomy has been questioned with appendicitis recurrence risk varying between 5-26%.

 During trial enrollment in our randomized Peri-APPAC trial, the high incidence of appendiceal
 tumors in the study population alarmed the researchers. Based on the interim analysis results
 with 17% appendiceal tumor rate in the study population, the trial was prematurely terminated
 based on ethical concerns. All the follow-up group patients were re-evaluated and surgery was
 offered and recommended to all follow-up group patients. After this assessment and additional
 appendectomies, two more tumors were diagnosed resulting in neoplasm rate of 20% in the whole
 study group all diagnosed in patients over 40 years and the neoplasm rate in patients over 40
 years was 29%.

 Based on high appendiceal tumor rate in patients over 40 years, the appendiceal neoplasm rate
 needs to be further evaluated in prospective patient cohorts undergoing interval appendectomy
 as interval appendectomy is generally well tolerated and obliterates the risk of missing a
 possible tumor. In a recent systematic review of retrospective cohort studies with 13.244
 acute appendicitis patients the overall appendiceal tumor rate was 1% after appendectomy, but
 in patients presenting with appendiceal inflammatory mass the neoplasm rate varied from 10%
 to 29%.

 This nationwide prospective multicenter cohort study is designed to assess the prevalence of
 appendiceal tumors associated with a periappendicular abscess. All of the study hospitals
 will have a common clinical protocol of recommending interval appendectomy to all patients
 presenting with a periappendicular abscess after initial conservative treatment with
 antibiotic therapy and drainage, if necessary. Considering the high rate of appendiceal
 neoplasms, all patients older than 35 years will undergo laparoscopic interval appendectomy
 at 2 to 3 months after the successful initial non-operative treatment and this is also
 recommended for the patients between 18 and 35 years of age. Asymptomatic patients under 35
 years not willing to undergo interval appendectomy, will undergo a follow-up MRI at 1 year
 after the initial non-operative treatment.
Inclusion Criteria:

 -  periappendiceal abscess proven by CT, Mri or US

 Exclusion Criteria:

 -  patient declines to participate, complicated appendicitis without periappendiceal
 abscess