The objective of this study is to evaluate the incidence of Enterobius vermicularis in the appendices of the adult population and a possible relationship between E. vermicularis and acute appendicitis. E. vermicularis was identified in 18 (2%) of 890 patients. Six hundred sixty-five operations were performed for presumptive diagnosis of acute appendicitis, and E. vermicularis was found in 12 (2%) patients. The histopathological examination revealed acute inflammatory cells in four cases (33%). Three of these four specimens included luminal ova and one E. vermicularis. Histopathological examination of six cases revealed E. vermicularis in 225 incidental appendectomies with no evidence of either acute or chronic inflammatory cells. This study suggests a relationship between the presence of E. vermicularis ova and acute inflammation, but the presence of the pinworm in the lumen of the appendix is coincidental. On the other hand E. vermicularis in the appendix lumen can cause symptoms of acute appendicitis.

Pinworm infestation of the appendix.G Chir. 2006 Jun-Jul;27(6-7):269-71.

The Authors present 2 cases of enterobiasis of appendix observed on a total of 186 appendicectomies. Enterobius infestation is an uncommon cause of acute appendicitis. Preoperative diagnosis of pinworm infestation is almost impossible without clinical suspect. Parasites may produce symptoms which resemble acute appendicitis but parasitic infection rarely causes it. It is also important considered in the differential diagnosis cases that mimic Crohn's disease.

Enterobius vermicularis: a possible cause of symptoms resembling appendicitis.Aust N Z J Surg. 1994 Oct;64(10):692-4.

The role of Enterobius vermicularis in appendicitis has been disputed. The aims of this retrospective study were to determine the prevalence of E. vermicularis in surgically removed appendices and to relate this to the age and sex of the patient, the time of the year, the presence of symptoms and the histological findings. The study included all appendices received in this laboratory during the 5 year period from 1984 through to 1988. There were 1867 appendices during this period of which 1108 were acutely inflamed and 759 were not inflamed (although 149 of these showed other pathological changes). The mean age distribution of all patients was 22.8 years. Enterobius vermicularis was identified in 63 appendices (3.4%). Infestation was more frequent in female (4.6%) than in male (1.9%) patients. The peak age was 12.8 years in females and 12.1 years in males. Of 63 patients who had E. vermicularis, 98% presented with symptoms of acute or recurrent appendicitis, yet 40 had no histological evidence of appendicitis or mucosal invasion by the parasite and only four had other possible explanations for abdominal pain. In an analysis of the subgroup of 147 patients who had incidental appendectomy at the time of laparotomy for other reasons, only one had E. vermicularis. It is concluded that E. vermicularis occurs more frequently in uninflamed appendices. It may be a cause of symptoms resembling acute appendicitis although the mechanism for this does not involve mucosal invasion by the parasite.