Histopathology of interval (delayed) appendectomy specimens: strong association with granulomatous and xanthogranulomatous appendicitis.

Patients who present with a ruptured acute appendicitis are often treated with antibiotic therapy and drainage followed by a delayed or interval appendectomy. We noticed interval appendectomy specimens with granulomatous inflammation and postulated that interval appendectomy may lead to granulomatous appendicitis. To test this hypothesis, we reviewed the histopathology of all interval appendectomy specimens within a 4-year period and compared them with a control group of patients who had acute appendicitis and underwent routine acute appendectomy. All slides were randomized and reviewed blindly to assess the inflammatory patterns, with special attention given to the presence of granulomas and other Crohn-like features. Twenty-two cases of interval appendectomy were found. The interval between symptom onset and appendectomy ranged from 30 to 95 days with a mean of 58 days, whereas all 44 control patients had surgery within 72 hours of symptoms onset. Thirteen (59.1%) of the 22 interval appendectomy cases contained granulomas compared with only 3 of 44 controls (P < 0.0001). Eight (36.4%) of the interval appendectomy cases had xanthogranulomatous inflammation compared with none in the acute appendicitis group (P < 0.0001). A Crohn-like appearance was seen in 11 (50.0%) of the interval appendectomy cases and 1 of the controls (P < 0.0001). Follow-up data were available in 8 of 11 cases with Crohn-like features; none developed Crohn disease during an average follow-up period of 23 months. Delayed or interval appendectomy specimens often have a characteristic inflammatory pattern that includes granulomas, xanthogranulomatous inflammation, mural fibrosis/thickening, and transmural chronic inflammation. Without the appropriate clinical history, these changes may be misinterpreted as Crohn disease.