Aim To determine clinical and imaging predictors of recurrent appendicitis after non-operative management for children with perforated appendicitis presenting with an appendicular inflammatory mass.

Methods A case-control study was carried out of children with clinical and ultrasonographic diagnosis of an appendicular inflammatory mass. Patients were divided into two groups according to the presence or not of recurrent appendicitis (or predisposing pathological findings during interval appendectomy). Several clinical and imaging factors were compared between both groups using an independent and progressive analysis to identify which were the most relevant predictors.

Results The persistence of symptoms after resolution of the appendicular inflammatory mass, as well as its time of resolution (p<0.001), were the most relevant factors during group classification. The identification of an ultrasonographic image of an appendicolith and the initial size of the mass were also identified as independent predictors (p<0.018 and p<0.01). The presence of the first two factors in a patient was strongly associated with recurrent appendicitis.

Conclusions Persistent symptoms after the recovery of the initial episode, associated with a slow resolution of the appendicular inflammatory mass, are indications for an interval appendectomy. A previous history of appendicitis or detection of an ultrasonographic image of an appendicolith is the other indication for an interval appendectomy.