REV ARGENT COLOPROCT | 2024 | VOL. 35, N

2 CASE REPORT

ENTEROBIUS VERMICULARIS APPENDICITIS Escudero Sepúlveda A.

Enterobius vermicularis parasitosis as a cause of acute appendicitis

Andrés Felipe Escudero-Sepúlveda, Emilia Victoria Alzuri, Sergio Campos, Laura Beatriz Lapertosa

Hospital Interzonal General de Agudos Luisa Cravenna de Gandulfo, Lomas de Zamora, Provincia de Buenos Aires, Argentina.

ABSTRACT

Acute appendicitis is the most common cause of acute abdomen

and surgery worldwide. The prevalence of Enterobius vermicularis

infestation as a cause of acute appendicitis in the US is approxi-

mately 2%. This article presents a case of acute appendicitis

complicated with perforation and localized peritonitis associated

with the presence of a parasite that later studies classified as

Enterobius vermicularis.

Key words: appendicitis, Enterobius vermicularis, enterobiasis,

intestinal parasitosis, treatment

INTRODUCTION

Acute appendicitis is the most common cause of acute

abdomen and surgery worldwide.

1,2

The prevalence of

Enterobius vermicularis infections as a cause of acute

appendicitis in the US is approximately 2%.

The presence

of parasites in pathological samples reaches 0.5%.

Howev-

er, it is worth clarifying that the main cause of acute appen-

dicitis in adults is obstruction, fecal impaction and fecaliths.

The infestation caused by Enterobius vermicularis, also

called Oxiurus vermicularis, is called enterobiasis.

Parasites

associated with appendiceal symptoms are observed in 0.05-

3% of cases, with the cecal appendix found inflamed on

certain occasions.

The presence of the parasite in the patho-

logical sample is around 1.5-4.2%(2). The transmission of

enterobiasis is mainly fecal-oral, the life cycle is 2 to 4

weeks, and humans are known as the only reservoir.

2,3

It is

transmitted by contamination through fomites, bedding,

utensils and others. Re-infestation occurs due to new inges-

tion of eggs (auto-infestation) or acquisition from other

sources.

Appendicitis due to Enterobius vermicularis is mainly

asymptomatic and when it presents clinical manifestations,

anal and/or bulbar pruritus is characteristic,

as well as

gastrointestinal and anxiety disorders, mainly bruxism.

Some studies report that up to 54% of patients refer ab-

dominal pain in their medical history.

The presence of the parasite in the appendiceal lumen can

cause what is called appendiceal colic, whether or not

associated with acute inflammation.

1,6

The mature worm

Enterobius vermicularis lives in the proximal ascending

colon, cecum, appendix and terminal ileum and is the most

common parasite found in the cecal appendix.

The diagnosis is made with serological studies and stool

examination in suspected cases. Stool examinations are very

simple and easy to perform in laboratories.

In cases of suspected appendicitis, ultrasound and computed

tomography (CT) have been shown to be beneficial, with

reported sensitivities of 95% and 96%, respectively, and a

negative predictive value of 99%.

CASE

A 40-year-old female patient, dog groomer by profession,

with two school-age children, attended the emergency

department with a 2-day history of abdominal pain, predom-

inantly in the epigastrium and right flank, associated with

nausea and vomiting. She reported consumption of self-

medicated analgesics and antispasmodics and denied other

symptoms. On physical examination, she had pain on palpa-

tion in the epigastrium and right flank, with guarding and

rebound tenderness. Laboratory tests showed: hemoglobin

14g/dl, hematocrit 39%, WBC 27,200/mm3, CRP 91mg/dl,

BUN 23mg/dl, creatinine 0.7mg/dl. CT scan of the abdomen

and pelvis reported altered fat in the right iliac fossa and

right flank, thickening of the posterior aspect of the ascend-

ing colon, compatible with retrocecal appendicitis (Fig. 1).

Figure 1. Computed tomography reported alteration of fat in the

right iliac fossa with extension to the ipsilateral flank. Thickening of

the posterior aspect of the ascending colon, compatible with a

retrocecal appendiceal process.

Based on the clinical and imaging findings, exploratory

laparotomy was indicated, finding purulent fluid in the right

upper quadrant and an important retrocecal subserous ce-

coappendicular inflammatory process with acute gangrenous

and perforated appendicitis. When performing the appendec-

tomy, the release of live parasites was observed in the

ostium of the resected appendix (Fig. 2).

The author declare no conflicts of interest. Andrés Felipe Escudero Sepúlveda

Received: August 25, 2021. Accepted: March 18, 2024.

Andrés Felipe Escudero Sepúlveda: https://orcid.org/0000-0002-4246-5469

REV ARGENT COLOPROCT | 2024 | VOL. 35, N

2 CASE REPORT

ENTEROBIUS VERMICULARIS APPENDICITIS Escudero Sepúlveda A.

Figure 2. a. Perforated gangrenous appendix with the presence of Enterobius vermicularis in its lumen. b. Contrast adjustment of the image shows

two parasites in the appendiceal lumen (white arrows).

Histopathology reported acute gangrenous perforated ap-

pendicitis with the presence of Enterobius vermicularis and

eggs in the lumen, confirmed through the Graham test (Figs.

3 and 4). The patient had an uneventful recovery. Oral

treatment with albendazole 400 mg in a single dose was

indicated for the patient and her family.

Figure 3. Graham test. An Enterobius vermicularis egg is observed

(white arrow).

Figure 4. Enterobius vermicularis parasite (red arrows) surrounded

by eggs (blue arrows).

DISCUSSION

The most common parasitic infection worldwide is that

caused by Enterobius vermcularis which affects around one

billion people, mainly children and young people. Its distri-

bution is universal, affecting all age groups and socioeco-

nomic levels,

1,5,7

being more prevalent in developing and

tropical countries.

8,9

When the parasite obstructs the appendiceal lumen, it causes

irritation of the mucosa, inflammation and bacterial over-

growth, which would trigger acute appendicitis.

1,4,6,9

How-

ever, other authors report that chronic manifestations are

found in Enterobius vermicularis infection, so the exact

pathophysiological mechanism remains controversial.

Infections of the gastrointestinal system due to parasitic and

protozoal infestations have different incidence throughout

the world.

In a meta-analysis published in 2020, out of 59

studies with 103,195 anatomical specimens, a prevalence of

Enterobius vermicularis of 4% (95% CI, 2-6%) was found.

Another meta-analysis published by Zakaria et al, which

includes 51,815 pathological specimens, reports the pres-

ence of this parasite in 4.45% of cases of acute appendicitis.

A study carried out in Peru in 2011, where a total of 21,038

surgical resection specimens were analyzed, demonstrated

the presence of Enterobius vermicularis in 1.53% of cases,

with a higher prevalence in young women.

Another Peruvi-

an study published in 2013 reported an incidence of 5.4% in

398 cases.

In our country, in 2017 an incidence of 3.25% out of 2,000

pathological specimens was reported.

What is striking

about this study is that the appendix was normal, demon-

strating that the parasite itself is not a causal agent of acute

appendicitis, but rather an adjuvant factor.

In Canada, an incidence of less than 0.6% of cases of acute

appendicitis is reported.

Regarding the distribution accord-

ing to socioeconomic level, we found that infection by this

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ENTEROBIUS VERMICULARIS APPENDICITIS Escudero Sepúlveda A.

parasitosis in countries with high, middle-high, middle-low

and low income levels was 3% (95% CI: 2-4), 4% (95% CI:

1-10%), 8% (95% CI: 1-21%) and 1%, (95% CI: 1-3),

respectively.

The presence of Enterobius vermicularis seems to favor the

formation of fecaliths and bacterial proliferation in the

appendiceal lumen, acting as an etiopathogenic mechanism

of acute appendicitis.

5,6

Another controversial factor is the presence or invasion of

parasite eggs in the appendix,

3,8

with an incidence of 1.3%

in a study carried out in 2015 in Pakistan in 2,956 patholog-

ical specimens.

As a complement to appendectomy, benzoimidazole an-

thelmintics such as albendazole are used in the treatment.

The medication must also be administered to the family

members since they can serve as a reservoir, favoring rein-

fections.

The dose is 400 mg, repeated after 2 weeks.

CONCLUSION

Acute appendicitis associated with Enterobius vermicularis

infestation accounts for about 2% of all cases. Differences

are reported in the prevalence of parasitosis in different

environments, being the main cause of abdominal pain.

Treatment requires appendectomy associated with antipara-

sitic medication for both the patient and her family to pre-

vent reinfections.

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