Presenting features of Enterobius vermicularis in the vermiform appendix

Objective. Enterobius vermicularis (pinworm) infestation can present with symptoms resembling acute appendicitis, although current evidence suggests that it does not necessarily cause acute appendicitis. The purpose of this study was to characterize the clinical presentation of patients with pinworms in the vermiform appendix and to establish features suggestive of this condition. Material and methods. A retrospective analysis of all patients undergoing appendicectomy with appendicular pinworms between 1998 and 2003 was undertaken. Patients were compared against 54 controls with confirmed acute suppurative appendicitis from the same time period. Presenting features, vital signs and modified Alvarado scores were obtained from the patients’ records. Results. Eighteen out of 1150 patients (1.5%) undergoing appendicectomy were proven to have pinworms (age range 8–37 years, 12 F, 6 M). Two of 18 appendices containing pinworms showed evidence of inflammation. Patients with pinworms had significantly lower white cell counts (WCCs) than the control group (median 8.9 versus 14.7, p=0.045), lower total Alvarado scores (median 5.5 versus 7, p=0.01) and were more likely to have had recurrent episodes of right iliac fossa (RIF) pain and previous hospital admissions (p<0.001). Conclusions. E. vermicularis infestation of the appendix should be considered in the differential diagnosis of patients who present with recurrent RIF pain but do not have a significantly raised WCCs, or high Alvarado scores. These patients should be investigated with early fecal sampling and night-time application of cellophane tape, and they may benefit from empirical antiparasitic treatment.