Acute eosinophilic appendicitis and the significance of eosinophil - Edema lesion

Abstract

Eight cases of a histological entity that we name 'acute eosinophilic appendicitis' (AEA) are described and compared with classical acute appendicitis and appendices, which turned out to be normal after emergency appendicectomy. These 8 cases formed part of a dataset of 128 emergency appendicectomies, which also included 78 cases of classical acute appendicitis and 42 cases of normal appendix. The clinical and pathological variables were compared between these three. Acute eosinophilic appendicitis is characterized by acute presentation and a grossly inflamed appendix, but with absence of neutrophils in the muscle layer. The histological hallmark of the entity is eosinophil infiltration of the muscularis propria with accompanying edema separating muscle fibers (the Eosinophil - Edema lesion). The duration and prevalence of symptoms, the male female ratio and the gross maximum circumference of the appendix in these 8 cases resembled classical acute appendicitis rather than those cases in which the morphology of the appendix was normal. The Eosinophil-Edema lesion was also seen in many cases of classical appendicitis in non-suppurative areas where neutrophils were sparse or absent. We hypothesize that this lesion is an allergic response and is probably an early event in the evolution of acute phlegmonous appendicitis. Acute eosinophilic appendicitis may merely be those cases that do not proceed on to suppuration.

Epidemiologic Features of Appendicitis

“…Our observation of an association between appendicitis and air pollution was corroborated by a study from Western Canada (Kaplan, et al, 2009). The significance of these observations is underscored by pathological studies linking appendicitis to eosinophilic degranulation (Santosh & Aravindan, 2008;Aravindan, et al, 2010). Seasonal variation of appendicitis with its peak associated with a season characterized by high ambient pollen and other phyto-allergens or sandstorm is an observation that can neither be explained by diet nor fecaliths but may have a bearing on immune modulation playing a role.…”

Alvarado score: can it reduce unnecessary CT scans for evaluation of acute appendicitis?

“…The false-negative case was a 19-year-old man with the final diagnosis of acute eosinophilic appendicitis confirmed by the surgical pathology specimen. Acute eosinophilic appendicitis was characterized by a grossly inflamed appendix with the infiltration of eosinophils (not neutrophils) in the muscularis propria [23]. This case presented with 3 hours of abdominal pain before the CT scan and had an Alvarado score of 7, and the CT images showed a normal air-filled appendix with no appendiceal wall thickening or adjacent fat stranding.…”

Acute appendicitis in preschoolers: a study of two different populations of children

“…Primary bacterial and viral infections [6], blunt abdominal trauma, and ischemia of the appendix [7] have been also investigated as possible causes. It has also been suggested that there is a genetic predisposition [8] or a type I hypersensitivity reaction involved in the development of acute appendicitis [9]. Furthermore, two hypotheses have been proposed in this regard: the "hygiene hypothesis" [10] and the "diet hypothesis" [11].…”