Interval appendicitis

There are a few studies that have focused on histopathologic findings in interval appendectomies compared to acute appendicitis and negative appendectomies. Our aim is to compare histopathologic features in interval appendectomies to a similar control group of stump appendectomies. A retrospective review study was conducted over a 10-year period. We found 21 (0.3 %) patients [age range: 10-70 years, average age: 40 years, male to female ratio: 1.3 to 1.0, average time interval: 6 weeks] who had interval appendectomies. Seventeen patients (81 %) showed three main patterns: xanthogranulomatous inflammatory infiltrates (48 %), Crohn-like transmural inflammatory infiltrates (33 %), and granulomatous inflammation (33 %). Postinflammatory structural changes included diverticulosis (33 %), mucosal hyperplasia (19 %), and fibrous obliteration (33 %). Other findings included fecalith (24 %), Actinomyces (19 %), hemosiderin pigment deposits (14 %) and fecal foreign body giant cells (24 %). No appendiceal neoplasms were detected. Two cases with complicated appendiceal diverticulosis showing mucosal hyperplasia, mucocele and extruded mucin pools were initially mistaken for low-grade appendiceal mucinous neoplasms. Ten patients (48 %) had residual acute inflammation, four of whom were associated with appendicolith and Actinomyces. We found eleven (0.13 %) patients [age range: 8-68 years, average age: 34 years, male to female ratio: 1.7 to 1.0, average time interval: 15 months] who had stump appendectomies. Five patients (45 %) showed xanthogranulomatous and Crohn-like changes. Epithelioid granulomas were not identified. Recurrent acute inflammation, mucosal hyperplasia, foreign body giant cell reaction and hemosiderin pigments were also found in stump appendectomies. There were no significant differences between xanthogranulomatous, Crohn-like, acute inflammatory, and hemosiderin-related changes, but there were significant differences in granulomatous inflammation, diverticulosis, mucosal hyperplasia, mucin pools, fibrous obliteration, appendicolith and Actinomyces between interval and stump appendicitis. These patterns were not correlated with age, gender or time intervals. Delayed interval and stump appendectomies exhibit a variety of subacute to chronic postinflammatory organizing reparative processes interspersed with acute inflammation.