The PeriAPPAC trial is a prospective randomised study comparing interval laparoscopic appendectomy with follow-up MRI in patients with initially successfully treated periappendicular abscess.

Periappendicular abscess is generally initially treated conservatively with antibiotic therapy and if necessary, drainage. Operative treatment in the acute abscess phase is associated with increased morbidity and thus complicated appendicitis with a periappendicular abscess is initially treated conservatively. However, there is debate on whether interval appendectomy is required.

After initial successful conservative treatment of a CT- or MRI-diagnosed periappendicular abscess, patients enrolled in the PeriAPPAC study are randomised either to interval appendectomy or to follow-up with MRI at two months after the initial treatment. All patients also undergo a colonoscopy, appendectomy patients prior to surgery and MRI patients after the MRI (outpatient visit at endoscopy unit with information on the MRI).

The primary endpoint is the treatment success in both treatment arms. In the interval appendectomy evaluated as possible morbidity related to appendectomy and in the follow-up treatment arm as possible recurrence of the appendicitis and/or abscess during a one-year follow-up.

The PeriAPPAC study is a multi centre trial and the participating hospitals are Turku University Hospital, Oulu University Hospital, Tampere University Hospital, Kuopio University Hospital and Seinäjoki Central Hospital.

The PeriAPPAC trial is a prospective randomised study comparing interval laparoscopic appendectomy with follow-up MRI in patients with initially successfully treated periappendicular abscess.

Periappendicular abscess is generally initially treated conservatively with antibiotic therapy and if necessary, drainage. Operative treatment in the acute abscess phase is associated with increased morbidity and thus complicated appendicitis with a periappendicular abscess is initially treated conservatively. However, there is debate on whether interval appendectomy is required.

After initial successful conservative treatment of a CT- or MRI-diagnosed periappendicular abscess, patients enrolled in the PeriAPPAC study are randomised either to interval appendectomy or to follow-up with MRI at two months after the initial treatment. All patients also undergo a colonoscopy, appendectomy patients prior to surgery and MRI patients after the MRI (outpatient visit at endoscopy unit with information on the MRI).

The primary endpoint is the treatment success in both treatment arms. In the interval appendectomy evaluated as possible morbidity related to appendectomy and in the follow-up treatment arm as possible recurrence of the appendicitis and/or abscess during a one-year follow-up.

The PeriAPPAC study is a multi centre trial and the participating hospitals are Turku University Hospital, Oulu University Hospital, Tampere University Hospital, Kuopio University Hospital and Seinäjoki Central Hospital.

Inclusion Criteria:

• Age 18-60 years
• CT- or MRI-diagnosed periappendicular abscess, that has initially undergone successful conservative treatment with antibiotic therapy and drainage, if necessary

Exclusion Criteria:

• Suspicion of a tumour on CT or MRI
• Age under 18 years or over 60 years
• Pregnancy or lactating
• Allergy to contrast media or iodine
• Renal insufficiency
• Metformin medication (DM)
• Unsuccessful initial conservative treatment of periappendicular abscess
• Lack of co-operation (unable to give consent)
• A severe medical condition
• Previous acute appendicitis treated conservatively with antibiotics