INTRODUCTION

Enterobius vermicularis, also known as pinworm or seat worm, is a widespread parasite estimated to affect up to 209 million people worldwide both in temperate and tropical climates; it occurs most frequently in children aged 5 to 10 years and is relatively uncommon in those under the age of two years¹. It is also the most common intestinal parasite of man with the widest geographical distribution, particularly in the primary care setting regardless of race and socio-economic circumstances². The association of pinworm infestation with acute appendicitis varies from 0.2 to 41.8%³. The role of E. vermicularis in clinical appendicitis has been disputed since its discovery in the appendiceal lumen in 1898⁴. However, reviews of the literature do agree that E. vermicularis infestation of the appendix can produce clinical features of acute appendicitis referred to as appendiceal colic⁴.

In colder climates, some factors such as less exposure to sunlight, heavy clothing and fewer baths lead to higher prevalence of Enterobius vermicularis and it can inhabit the large intestine but be of low pathogenicity. Sometimes, however, ova can be found in etopic sites in the peritoneal cavity and the appendix⁵. Several authors have studied the relationship between pinworm infestation and clinical appendicitis, for instance studies carried out in England have demonstrated a prevalence of pinworm appendicitis from 1.4% to 4.2% in specimens removed for presumptive acute appendicitis⁶.

It is an accepted fact that one of the possible causes of acute abdomen in children may be parasitic infections; E. vermicularis is the commonest parasite in man infecting about 10% of the population; in the developed countries the infection rate is even higher in children⁷. The aim of this study is to evaluate and ascertain the significance of pediatric appendicitis due to histologically proven Enterobius vermicularis infection in patients operated on for suspected appendicitis.

METHODOLOGY

During the five-year period between January 2005 and December 2009, a retrospective chart review was performed on 382 consecutive patients who underwent either laparoscopic or open pediatric appendectomy for diagnosis of acute appendicitis and their consequent histology examined in Midwestern Regional Hospital, Limerick, Ireland. Hospital in-patient enquiry (HIPE) was used to identify the total number of these pediatric surgical patients who were aged from 2 to 14 years. This tertiary care facility is one of the busiest acute surgery units in Ireland providing acute surgical services among others.

Included were children aged from 2 to 14 years who had histologically proven Enterobius vermicularis following either open or laparoscopic appendectomy. Excluded were patients above 14 years and those without E. vermicularis on histology report. Data collected include age, gender, weight, symptoms and signs, length of hospital stay, histology report and complications. Measures of central tendencies and variance were used to describe the data.

RESULTS

A total of 832 appendectomies were carried out; twelve cases of Enterobius vermicularis were histologically proven including seven males and five females. The mean age was 10.2

DISCUSSION

Gastrointestinal infection due to Enterobius vermicularis is considered to be the commonest helminthic infection⁸. Pinworms have been present for thousands of years. Enterobius ova have been found in human coprolites from 7800 BC⁹. Fabricius Hildanus was the first to describe appendiceal pinworms in 1634¹⁰. Since 1899, when the association of Enterobius infestation was first described¹¹, there have been several case reports and retrospective studies on this subject.

Enterobius vermicularis of the appendix presenting with pediatric appendicitis continued to be a rare surgical presentation of this widespread parasitic infestation with a reported frequency of 1.52%¹²

Enterobius vermicularis was associated with pathologic changes ranging from lymphoid hyperplasia and acute and suppurative appendicitis to normal appendix, confirmed by our findings.

Studies support the hypothesis that appendiceal lumen obstruction by E. vermicularis gives rise to symptoms indistinguishable from suppurative appendicitis¹³. More recently, a study reviewing 2267 cases of appendicitis showed that there was a highly significant difference in the incidence of E. vermicularis in normal and in inflamed appendices, which may indicate that the presence of E. vermicularis in the appendix can cause symptoms of acute appendicitis¹⁴.

Appendectomy should be done with caution if the appendix is not acutely inflamed; worms in the vermiform appendix could be resident. Pharmacological eradication with antihelminthics (e.g. Mebendazole) and meticulous extraction of released worms are important to avoid chronic complications¹⁵. Saxena et al. reported three cases in which pinworms were released into the abdominal cavity during laparoscopic appendectomy¹⁵. It is important that surgeons should exercise maximum caution during laparoscopic appendectomy, especially when the endoloop is in use, to avoid the release of pinworms into the peritoneum upon amputation of the appendix, thereby re-infecting the patients.

In conclusion, Enterobius vermicularis is a possible cause of appendicitis in children. Patients not undergoing appendectomy can benefit from fecal sampling and night-time application of cellophane tape in the perianal area as a means of detecting the parasite as well as empirical antihelminthic therapy. Appendectomy treats the consequence and not the root cause. Family members and persons with close contact should also be treated once the diagnosis of Enterobius infestation has been confirmed.