Enterobius vermicularis as a Mimic of Acute Appendicitis: A Case Report and Updated Systematic Review

Abstract

A 12-year-old premenarchal female patient presented with right iliac fossa pain, perianal pruritus, urticaria, angioedema, arthralgia, peripheral eosinophilia, and an initially undetectable C-reactive protein. Serial ultrasonography demonstrated increasing intra-abdominal free fluid. Diagnostic laparoscopy demonstrated appendiceal serosal injection, turbid pelvic fluid, and mesenteric lymphadenopathy, prompting appendectomy. Histopathology identified Enterobius vermicularis (EV) within the appendiceal lumen, with reactive lymphoid hyperplasia but no acute suppurative inflammation. Symptoms resolved following surgery and mebendazole treatment.

A descriptive updated systematic review of appendectomy specimens containing EV was performed. Seventy-six studies comprising 196,138 appendectomy specimens were included. EV was identified in 3,913 specimens, corresponding to a crude proportion among appendectomy specimens of 2.00% (95% CI: 1.93-2.06%). Among 11 newly identified studies reporting histological subclassification, 247 of 694 EV-positive specimens (35.6%) demonstrated histological acute appendicitis, whereas most showed non-suppurative or reactive pathology.

This case and review suggest that appendiceal enterobiasis may present as an appendicitis-like illness, particularly when abdominal pain occurs alongside atypical features such as perianal pruritus, eosinophilia, urticaria, or angioedema. Recognition of enterobiasis may guide anthelmintic therapy and consideration of household treatment; however, a causal relationship between EV and systemic hypersensitivity features cannot be established from a single case. Importantly, clinical deterioration should continue to prompt urgent surgical assessment.

Introduction

Enterobius vermicularis (EV), commonly known as pinworm or threadworm, is the most prevalent intestinal helminth in developed countries, with a global burden estimated to exceed 200 million individuals [1]. Transmission occurs through ingestion or inhalation of embryonated eggs, with autoinfection and household spread contributing to recurrence [1]. Appendiceal involvement is uncommon and is often detected incidentally on histopathological examination after appendectomy [2,3].

The relationship between EV and acute appendicitis remains uncertain and is likely heterogeneous. In some cases, EV may be an incidental luminal finding in an appendix removed for abdominal pain or another indication [2,3]. In others, worms within the appendiceal lumen may produce appendicitis-like symptoms through colic, intermittent obstruction, or local irritation without classical bacterial appendicitis [4,5]. True acute suppurative appendicitis may also coexist with appendiceal enterobiasis, although causality is not consistently established [4,5]. These distinctions are clinically important because many EV-positive appendices show normal histology, reactive lymphoid hyperplasia, or other non-specific changes rather than acute suppurative inflammation [2-5].

Systemic allergic manifestations are less well characterized. Helminth infections can induce type 2 immune responses, eosinophilia, IgE production, and mast-cell activation, providing a plausible mechanism for urticaria or angioedema in selected patients [6-9]. In pediatric populations, abdominal pain with rash, arthralgia, and systemic inflammatory features may also mimic alternative diagnoses, including IgA vasculitis, viral exanthem, and drug reaction [10]. However, hypersensitivity-related features are not routinely reported in appendectomy series involving EV, and their clinical relevance remains unclear.

Taghipour et al. published the first systematic review and meta-analysis of EV in appendicitis, identifying 59 studies and reporting a pooled prevalence of 4% (95% confidence interval (CI): 2-6%) with substantial heterogeneity (I² = 98%) [11]. Additional appendectomy series have since been published, warranting an updated descriptive synthesis. The present review differs from the prior meta-analysis by incorporating newly published studies and by focusing on three clinically relevant questions: the crude proportion of appendectomy specimens containing EV, the proportion of EV-positive appendices showing histologically confirmed acute appendicitis in newly identified studies with available subclassification, and the extent to which eosinophilia or systemic hypersensitivity manifestations are reported.

We therefore present an illustrative pediatric case of appendiceal EV presenting with right iliac fossa pain, perianal pruritus, eosinophilia, urticaria, and angioedema, along with an updated, descriptive systematic review of appendiceal EV in appendectomy specimens.

Case presentation

A 12-year-old premenarchal female patient presented to the emergency department with a three-day history of abdominal pain that was initially periumbilical and subsequently localized to the right iliac fossa. Associated symptoms included nausea, reduced appetite, perianal pruritus with bilateral buttock excoriations, and arthralgia involving the knees and ankles. There was no fever, vomiting, or urinary symptoms. Her past medical history was notable only for umbilical hernia repair at two years of age, and there was no regular medication use.

On examination, the abdomen was soft with localized right iliac fossa tenderness but no peritonitis. Bilateral buttock excoriations were present. A transient lower limb rash had been reported by the patient's mother but was not present at initial review.

Initial laboratory investigations demonstrated leukocytosis (15.8 × 10⁹/L), neutrophilia (12.0 × 10⁹/L), and peripheral eosinophilia (0.8 × 10⁹/L), with an initially normal C-reactive protein (CRP <1 mg/L). CRP subsequently rose during admission, reaching 78 mg/L preoperatively (Table 1). Hemoglobin, liver function tests, and urinalysis were within normal limits. Abdominal ultrasound demonstrated a mildly prominent appendix measuring 7 x 9 mm, a small appendicolith, and minimal free fluid and was reported as equivocal for early appendicitis (Figure 1).

Table 1. Serial hematological and biochemical results from presentation (Day 0) to postoperative Day 2 (Day 5).

* Day 3 corresponds to the date of surgery.

WBC: white blood cell count, CRP: C-reactive protein, (H): above reference range

Investigation	Day 0	Day 1	Day 2	Day 3*	Day 4	Day 5	Reference range
CRP (mg/L)	<1	17 (H)	31 (H)	78 (H)	113 (H)	45 (H)	<10
Hemoglobin (g/L)	136	122	126	129	113	117	110-150
WBC (×109/L)	15.8 (H)	10.0	14.9 (H)	13.9 (H)	10.6	11.6 (H)	4.0-11.0
Neutrophils (×109/L)	12.0 (H)	7.8	12.5 (H)	11.4 (H)	9.0 (H)	8.4 (H)	2.0-8.0
Lymphocytes (×109/L)	1.9	1.3	1.6	1.8	1.3	2.8	1.5-5.5
Monocytes (×109/L)	1.1 (H)	0.4	0.6	0.3	0.3	0.2	0.0-1.0
Eosinophils (×109/L)	0.8 (H)	0.8 (H)	0.8 (H)	0.8 (H)	0.0	0.2	0.0-0.5
Platelets (×109/L)	307	254	288	298	310	352	150-450

Figure 1. Initial abdominal ultrasound equivocal for early appendicitis.

(A) Focally prominent appendiceal mid/distal segment with a small appendicolith (yellow arrow). (B) Reactive mesenteric lymphadenopathy in the right iliac fossa (yellow arrow).

During admission, an annular urticarial rash developed over the trunk and lower limbs. Dermatology consultation characterized the rash as most consistent with urticaria, with a clinical impression of gastrointestinal angioedema as a possible contributor to abdominal pain based on the concurrent urticarial eruption and initially discordant inflammatory markers. IgA vasculitis, viral exanthem, drug eruption, and infective causes were considered as alternative explanations. Investigations for infective and autoimmune causes, including respiratory polymerase chain reaction (PCR) testing, Epstein-Barr virus serology, antistreptolysin O titer, antinuclear antibody screen, complement levels (C3/C4), lipase, and blood cultures, were negative.

A dedicated preoperative perianal adhesive tape test was not performed because enterobiasis was not initially considered the primary diagnosis. Routine fecal microscopy/culture/sensitivity and PCR testing were negative, but these investigations are not considered sufficient to exclude EV.

The patient was initially treated with empiric intravenous antibiotics, methylprednisolone, and oral cetirizine. She was then discharged on Day 2 with an improving rash on oral prednisolone, cetirizine, and antibiotics. Within 12 hours, she re-presented with worsening abdominal pain, fever (38.5°C), and periorbital and lip angioedema. Repeat ultrasound demonstrated a significant interval increase in pelvic and perihepatic free fluid (Figure 2). Given clinical deterioration and progressive inflammatory markers, diagnostic laparoscopy was performed. Operative findings included appendiceal serosal injection, turbid pelvic free fluid, and mesenteric lymphadenopathy. The gallbladder, liver, sigmoid colon, ovaries, fallopian tubes, and uterus appeared normal. Appendectomy was performed via a three-port technique.

Figure 2. Repeat abdominal ultrasound demonstrating interval increase in pelvic and perihepatic free fluid.

(A) Free fluid in the pelvis adjacent to the bladder/uterus (yellow arrow). (B) Free fluid along the hepatic margin/perihepatic space (yellow arrow).

Histopathological examination demonstrated multiple EV organisms within the lumen and prominent reactive lymphoid hyperplasia, without features of acute suppurative appendicitis (Figures 3-5). Macroscopically, the appendix measured 60 x 6 mm, with an attached mesoappendix up to 45 mm; the serosa was tan and shiny with a wall thickness of 2 mm, and no macroscopic lesions were identified. Microscopically, numerous cross-sections of EV organisms were present in the lumen. Prominent reactive lymphoid hyperplasia was identified, while the muscularis propria and serosa were within normal limits and there were no features of peritonitis. Peritoneal fluid culture grew Clostridium tertium and mixed anaerobic flora, interpreted as possible contamination or secondary bacterial translocation in the absence of perforation [12].

Figure 3. Appendiceal EV identified on histopathology.

Hematoxylin and eosin-stained section of the appendix demonstrating two transverse sections of EV within the appendiceal lumen. The organisms show a thick eosinophilic cuticle with internal visceral/reproductive structures. Yellow arrows indicate the parasitic cross-sections. Original magnification: ×20.

EV: Enterobius vermicularis

Figure 4. High-power histopathological features of appendiceal EV.

High-power hematoxylin and eosin-stained section demonstrating a transverse section of EV within the appendiceal lumen. Characteristic features include a thick eosinophilic cuticle, lateral alae, and internal structures, supporting the diagnosis of appendiceal enterobiasis. Original magnification: ×40.

EV: Enterobius vermicularis

Figure 5. Reactive appendiceal lymphoid hyperplasia with prominent germinal centers.

Low-power hematoxylin and eosin-stained section of the appendix demonstrating preserved appendiceal architecture with prominent mucosal and submucosal lymphoid follicles containing reactive germinal centers, consistent with lymphoid hyperplasia. No overt transmural suppurative inflammation is evident in this field. Original magnification: ×10.

Postoperatively, abdominal pain, rash, and angioedema improved rapidly. Mebendazole was commenced, and treatment of household contacts was recommended. The patient was discharged in stable condition. A summary of the clinical timeline is presented in Table 2.

Table 2. Summary of clinical timeline.

ED: emergency department, CRP: C-reactive protein, WBC: white blood cell count, EV: Enterobius vermicularis

Timepoint	Event	Key findings/actions
Day 0 (presentation)	ED presentation	Three-day history of abdominal pain; perianal pruritus with bilateral buttock scratch marks; WBC 15.8 × 10⁹/L, eosinophils 0.8 × 10⁹/L, CRP <1 mg/L; ultrasound equivocal for early appendicitis.
Day 0 (evening)	Urticarial rash; treatment commenced	Annular urticarial rash over trunk and lower limbs; intravenous antibiotics, methylprednisolone, and cetirizine commenced; dermatology consulted.
Day 1	Inpatient monitoring	Rash spreading; bilateral knee and ankle arthralgia; CRP 17 mg/L.
Day 2	Discharge	Rash improving; transitioned to oral prednisolone, cetirizine, and antibiotics.
Day 2 (<12 hours post-discharge)	Re-presentation	Periorbital and lip angioedema; abdominal pain; febrile to 38.5°C.
Day 3	Repeat ultrasound	CRP 78 mg/L; interval increase in free fluid.
Day 3 (procedure)	Diagnostic laparoscopy and appendectomy	Appendiceal serosal injection; turbid pelvic fluid; mesenteric lymphadenopathy; appendectomy performed.
Day 4	Postoperative Day 1	CRP peaked at 113 mg/L; tolerating diet; rash and angioedema resolving.
Day 5	Postoperative Day 2	CRP 45 mg/L; eosinophils normalizing; abdominal pain resolved.
Discharge	Anthelmintic therapy	Histopathology confirmed EV; mebendazole prescribed; household treatment recommended.

Discussion

Updated systematic review

Study Design and Registration

An updated systematic review was performed in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 guidelines [13]. The review integrated data from the previous systematic review by Taghipour et al. (2020) [11] with newly identified studies after the prior search period. Prospective registration was not performed; this is acknowledged as a limitation.

Search Strategy

A systematic search was conducted across PubMed, MEDLINE, and Embase for studies published between January 1, 2019, and April 30, 2026. The search intentionally overlapped with the final months of the Taghipour et al. search window, which ended on August 15, 2019, to reduce the risk of missing eligible transition-period studies. The same search concepts were applied across all databases, with database-specific syntax adapted as required. Search terms combined synonyms for EV and appendectomy/appendicitis, including ("Enterobius vermicularis” OR “E. vermicularis” OR “Enterobiasis” OR “Oxyuris vermicularis” OR “Oxyuriasis” OR “Pinworm” OR “Roundworm” OR “Threadworm” OR “Seatworm”) AND (“Appendix” OR “Appendices” OR “Appendicitis” OR “Appendectomy” OR “Appendicectomy”). Searches were limited to English-language studies.

Eligibility Criteria

Eligible studies were peer-reviewed original research studies published in English that reported the total number of appendectomy specimens examined and the number of histopathologically confirmed EV-positive specimens. Studies were eligible if the full text or abstract provided sufficient data for extraction. Case reports, editorials, narrative reviews without extractable primary data, and studies restricted to highly selected populations such as immunocompromised cohorts were excluded.

Study Selection and Data Extraction

Records were imported into Covidence (Veritas Health Innovation Ltd, Melbourne, Victoria, Australia), where duplicate records were automatically removed prior to screening. Titles and abstracts were screened independently by two reviewers (AT and MAH). Full texts were then reviewed independently by the same reviewers, with disagreements resolved by consensus or consultation with a third reviewer (KJ). Data were independently extracted by two reviewers (AT and MAH) using a predesigned standardized extraction form. Extracted variables included first author, publication year, country, continent, sample size, number of EV-positive specimens, and, where reported, the proportion of EV-positive specimens with histologically confirmed acute appendicitis and the presence of eosinophilia. For the 59 studies included in Taghipour et al., data were adopted from the published review and verified against reported aggregate totals.

Quality Assessment

The methodological quality of newly identified studies was assessed using the Joanna Briggs Institute Checklist for Prevalence Studies [14]. Quality appraisal was performed independently by two reviewers (AT and MAH). Most studies were retrospective histopathology series with variable reporting of sampling frame, diagnostic criteria, and histological subclassification. Taghipour et al. reported significant publication bias in their extracted papers (p < 0.001) using Egger’s regression, but this could not be reassessed due to the absence of pooled modeling in the present review [11].

Data Synthesis

Given substantial heterogeneity across study populations, geography, time periods, operative selection, sample size, and histopathological criteria, formal random-effects meta-analysis was not performed. A pooled model was considered inappropriate because the included studies spanned 1939 to 2026, included pediatric, adult, and mixed cohorts, used non-standardized histological definitions, and contained extreme between-study variability in reported EV-positive proportions. Instead, a descriptive crude proportion was calculated as the total number of EV-positive specimens divided by the total number of appendectomy specimens. This value is reported for descriptive comparability only and should not be interpreted as a modeled prevalence estimate. Sensitivity analyses were performed by excluding Chan et al. [15] as an outlying tropical pediatric cohort; Stĕrba and Vlcek [16] because of disproportionate sample size; and Oztas et al. [17] and Akbulut et al. [18] because of unusually high reported prevalence. Results were summarized narratively.

Study Selection and Characteristics

The updated search identified 160 records across PubMed (n = 81), Embase (n = 42), and MEDLINE (n = 37). After removing 21 duplicates in Covidence, 139 records underwent title and abstract screening, of which 118 were excluded. Twenty-one full-text articles were assessed for eligibility, of which four were excluded: one because of a differing patient population and three because they had already been included in Taghipour et al. [19-21]. The updated review incorporated the 59 studies from Taghipour et al. [2,3,5,16-71]. Seventeen newly identified studies were then added [15,72-87], yielding 76 studies encompassing 196,138 appendectomy specimens from 26 countries (Figure 6).

Figure 6. PRISMA 2020 flow diagram for the updated systematic review.

PRISMA: Preferred Reporting Items for Systematic Reviews and Meta-Analyses

Of the 76 included studies, 42 originated from Europe (including 27 from Turkey), 13 from Asia, 12 from the Americas, five from Africa, and four from Oceania. All were retrospective histopathology audits. Publication dates ranged from 1939 to 2026, and sample sizes ranged from 27 to 21,916. A summary of the study characteristics is presented in the Appendices.

Crude Proportion of EV in Appendectomy Specimens

A total of 3,913 EV-positive cases were identified among 196,138 appendectomy specimens, corresponding to a crude proportion of 2.00% (95% CI: 1.93-2.06%). Individual study proportions ranged from 0.2% to 77.1% [17,21], demonstrating marked heterogeneity. The overall crude proportion was influenced by a small number of large studies: Stĕrba and Vlcek [16] alone accounted for 11.2% of the total denominator and 33.8% of all EV-positive cases.

Sensitivity analyses demonstrated similar overall findings. Exclusion of Chan et al. [15] yielded a crude proportion of 1.98%; exclusion of Stĕrba and Vlcek [16] yielded 1.49%; and exclusion of Oztas et al. [17] and Akbulut et al. [18] yielded 1.96%. The crude proportion of 2.00% was broadly consistent with the range of estimates reported by Taghipour et al. (pooled prevalence 4%; 95% CI: 2-6%) [11], although direct comparison is limited because the present review reports an aggregate crude proportion among appendectomy specimens rather than a random-effects pooled prevalence estimate.

By continent, the crude proportion was 2.16% in Europe (2,614/121,053; 42 studies), 2.04% in the Americas (426/20,851; 12 studies), 1.20% in Asia (531/44,366; 13 studies), 3.43% in Africa (117/3,409; five studies), and 3.48% in Oceania (225/6,459; four studies).

Histologically Confirmed Acute Appendicitis in EV-Positive Specimens

Taghipour et al. did not systematically extract the proportion of EV-positive cases with histologically confirmed acute appendicitis. Among 11 of the 17 newly identified studies reporting histological subclassification, 247 of 694 EV-positive specimens (35.6%) demonstrated histological features of acute appendicitis. Reported proportions varied widely, from 3.2% (1/31) [74] to 72.0% (36/50) [80], reflecting heterogeneity in histopathological diagnostic criteria across centers. Approximately two-thirds of EV-positive appendices did not show features of acute bacterial inflammation, consistent with the histopathological findings in the present case.

Eosinophilia and Hypersensitivity-Related Findings

Two newly identified studies provided data on eosinophilia. Aydemir et al. [80] reported significantly higher eosinophilia in EV-positive patients than in EV-negative patients (p = 0.003). Tuzun et al. [87] observed tissue eosinophilia in all EV-positive cases. No included study systematically reported systemic hypersensitivity manifestations such as urticaria or angioedema. These findings are therefore hypothesis-generating rather than confirmatory.

Heterogeneity

Extreme heterogeneity was observed across the included studies. Individual study proportions varied more than 300-fold, from 0.2% to 77%. Sources of heterogeneity include population composition (pediatric, adult, or mixed), geographic setting (36% of studies from Turkey), temporal span (1939-2026), sample size (27-21,916), operative selection, and non-standardized histopathological criteria. No formal I² was calculated for the combined 76-study dataset because no pooled meta-analysis was performed.

Principal findings and clinical interpretation

Summary of the Updated Systematic Review

Our descriptive updated systematic review nearly doubles the evidence base from 103,195 to 196,138 appendectomy specimens across 76 studies and 26 countries. EV remained an uncommon but recurring finding, identified in 3,913 specimens, corresponding to a crude proportion of 2.00% (95% CI: 1.93-2.06%).

More clinically important than the absolute frequency was the pattern of inflammation. Among newly identified studies that reported histological subclassification, only 35.6% of EV-positive specimens showed features of acute appendicitis. Most did not show acute suppurative inflammation, supporting the concept that appendiceal enterobiasis may clinically mimic acute appendicitis while producing non-suppurative pathology, commonly reactive lymphoid hyperplasia. This finding is consistent with prior observational data describing a predominance of non-suppurative pathology in EV-positive appendices [27,31].

Clinical Interpretation of the Present Case

This pattern fits the clinical course of our patient. She presented with severe right iliac fossa pain and leukocytosis but also had features that were atypical for bacterial appendicitis: perianal pruritus, urticaria, angioedema, arthralgias, eosinophilia, and an initially undetectable CRP. Histology later showed multiple EV organisms in the appendiceal lumen with prominent reactive lymphoid hyperplasia but without acute suppurative appendicitis.

The subsequent fever, elevated CRP, and increasing intra-abdominal free fluid remained clinically significant and justified operative management. However, those later findings do not necessarily mean the initial illness was classical transmural bacterial appendicitis. Possible explanations include progression of local inflammation, secondary bacterial translocation, partially treated infection, contamination of peritoneal fluid, or an evolving inflammatory response in the setting of appendiceal enterobiasis. The case therefore illustrates the diagnostic grey zone in which EV may be more than an incidental histological finding, rather a distinct clinical entity from conventional bacterial appendicitis.

Perianal Pruritus as a Diagnostic Clue

Perianal pruritus was a particularly important clue in this case. It was present from the outset and was associated with buttock excoriations. In enterobiasis, pruritus occurs when gravid female worms migrate nocturnally to the perianal region and deposit eggs [1]. In a patient with right iliac fossa pain, this symptom should prompt consideration of EV, especially when eosinophilia is present or inflammatory markers are discordant with the severity of pain.

Systemic Hypersensitivity Features

A notable feature of this case is the concurrent systemic hypersensitivity phenotype, including widespread urticaria, facial angioedema, arthralgias, and peripheral eosinophilia. The association with appendiceal enterobiasis is biologically plausible, although causality cannot be proven from a single case. Helminth infections are associated with type 2 immune responses, with interleukin-5 promoting eosinophil production and survival and interleukins 4 and 13 promoting IgE class switching [6,7]. IgE-mediated mast-cell activation may then contribute to urticaria and angioedema through the release of histamine, prostaglandins, and leukotrienes [6,7].

The arthralgias are less specific and poorly described in relation to enterobiasis. They may have reflected the release of systemic inflammatory mediators, immune complex phenomena, or a parallel reactive process. The normalization of eosinophilia after treatment provides some temporal support for an association, and parasitic infection has been described in relation to urticaria more broadly [8]. Nevertheless, the allergic manifestations in this case should be interpreted cautiously because the patient also received antihistamines, corticosteroids, antibiotics, surgery, and mebendazole.

The updated review also highlights a reporting gap. Only two newly identified studies reported eosinophilia in relation to EV, and none of the newly identified studies systematically reported hypersensitivity manifestations such as urticaria or angioedema. Because these variables were not re-extracted from the 59 studies incorporated from the prior systematic review, the absence of such findings in the present dataset should not be taken as evidence that they are rare. Rather, they appear to be poorly captured in recent histopathology studies of appendectomy specimens.

Microbiological Findings

The positive peritoneal fluid culture also requires cautious interpretation. Clostridium tertium and mixed anaerobic flora were isolated, but there was no macroscopic perforation, and histology did not show acute suppurative appendicitis. The patient had received antibiotics before operative sampling, which may have altered culture yield and complicates interpretation. Clostridium tertium is an uncommon anaerobe that has been reported in association with gastrointestinal compromise and immunocompromised states, particularly hematological malignancy [12]. In this case, the culture may have represented bacterial translocation, contamination, partially treated infection, or secondary inflammatory change. Its clinical significance is uncertain, particularly given the absence of ongoing sepsis and the patient’s clinical improvement. The culture result did not alter postoperative management because the patient was clinically improving and there was no evidence of ongoing sepsis.

Management Implications

Treatment of enterobiasis requires anthelmintic therapy, with mebendazole or albendazole commonly used as first-line agents [88]. Household treatment is important because transmission occurs by the fecal-oral route and autoinfection is common [1]. Symptomatic treatment with antihistamines or corticosteroids may be useful when urticaria or angioedema is present, but these measures do not address the underlying infestation.

This case does not suggest that surgery should be avoided when appendicitis is clinically suspected. The patient had worsening pain, fever, rising inflammatory markers, and increasing free fluid, making diagnostic laparoscopy appropriate. However, it does suggest that earlier recognition of enterobiasis may be useful in selected stable patients. In a child with abdominal pain, perianal pruritus, eosinophilia, and low or discordant inflammatory markers, targeted questioning about nocturnal perianal itch, household symptoms, and a perianal adhesive tape test may help identify enterobiasis. Empiric mebendazole with treatment of household contacts is a low-risk intervention when enterobiasis is suspected. Still, it should not delay operative management if there is clinical deterioration, peritonism, increasing free fluid, or concern for complicated appendicitis.

Limitations

This report is limited by its single-case design. Although the patient’s eosinophilia, urticaria, angioedema, and pruritus were temporally associated with confirmed appendiceal EV, causality cannot be established. Symptom improvement also occurred after multiple concurrent interventions, including antihistamines, corticosteroids, antibiotics, surgery, and mebendazole.

The updated review has several limitations. The denominator was appendectomy specimens rather than the general population, so the 2.00% figure represents a crude proportion among surgically removed appendices, not true prevalence. The included studies were heterogeneous in design, population, geography, operative selection, and histological reporting, precluding meaningful meta-analysis. Histological subclassification was available only for 11 newly identified studies, so the 35.6% acute appendicitis estimate should not be extrapolated to all 76 included studies. Conclusions regarding eosinophilia, urticaria, angioedema, and related features are limited to the newly identified studies and the present case. Future studies should report clinical features, inflammatory markers, eosinophil counts, histological subclassification, treatment, and follow-up more consistently.

Conclusions

Appendiceal EV is an uncommon but important mimic of acute appendicitis. This case highlights that right iliac fossa pain with perianal pruritus, eosinophilia, urticaria, angioedema, or discordant inflammatory markers should prompt consideration of enterobiasis. Histology may show non-suppurative pathology, such as reactive lymphoid hyperplasia, rather than classical acute appendicitis.

This updated, descriptive systematic review supports this distinction, with most EV-positive appendectomy specimens lacking histological evidence of acute appendicitis when subclassification was reported. Early recognition may allow timely anthelmintic treatment and household therapy, although suspected complicated appendicitis should still be managed surgically when clinically indicated. The association between appendiceal enterobiasis and systemic hypersensitivity features remains hypothesis-generating and requires more systematic reporting in future studies.

Appendices

Table 3. Main characteristics of included studies.

Studies classified as “prior review” were retained from the previous systematic review; “newly identified” studies were identified in the updated search. The total for histologically confirmed appendicitis reflects the 11 newly identified studies reporting histological subclassification.

EV: Enterobius vermicularis, NE: not extracted from the prior systematic review, NR: not reported by the original study

No.	Author, reference	Publication year	Country	Continent	Sample size	EV-positive specimens, n (%)	Histologically confirmed appendicitis in EV+ specimens, % (n/N)	Study origin
1	Botsford et al. [22]	1939	USA	Americas	1,343	71 (5.3%)	NE	Prior review
2	Ashburn [23]	1941	USA	Americas	1,319	133 (10.1%)	NE	Prior review
3	Wax and Cooper [24]	1941	USA	Americas	1,016	8 (0.8%)	NE	Prior review
4	Duran-Jorda [25]	1957	UK	Europe	691	52 (7.5%)	NE	Prior review
5	Boulos and Cowie [26]	1973	UK	Europe	293	8 (2.7%)	NE	Prior review
6	Stĕrba and Vlcek [16]	1984	Czech Republic	Europe	21,916	1,321 (6.0%)	NE	Prior review
7	Budd and Armstrong [27]	1987	UK	Europe	1,529	38 (2.5%)	NE	Prior review
8	Bredesen et al. [28]	1988	Denmark	Europe	303	38 (12.5%)	NE	Prior review
9	Babekir and Devi [29]	1990	UAE	Asia	405	26 (6.4%)	NE	Prior review
10	Wiebe [3]	1991	Denmark	Europe	2,267	93 (4.1%)	NE	Prior review
11	Dalimi and Khoshzaban [30]	1993	Iran	Asia	1,590	38 (2.4%)	NE	Prior review
12	Dahlstrom and Macarthur [31]	1994	Australia	Oceania	1,867	63 (3.4%)	NE	Prior review
13	Dorfman et al. [32]	1995	Venezuela	Americas	3,465	14 (0.4%)	NE	Prior review
14	Listorto et al. [33]	1996	Italy	Europe	1,093	14 (1.3%)	NE	Prior review
15	Saxena et al. [34]	2001	Germany	Europe	62	3 (4.8%)	NE	Prior review
16	Agarwala and Liu [35]	2003	USA	Americas	317	1 (0.3%)	NE	Prior review
17	Arca et al. [2]	2004	USA	Americas	1,549	21 (1.4%)	NE	Prior review
18	Yildirim et al. [36]	2005	Turkey	Europe	104	4 (3.8%)	NE	Prior review
19	Di et al. [39]	2006	Argentina	Americas	186	2 (1.1%)	NE	Prior review
20	Sah and Bhadani [37]	2006	Nepal	Asia	624	9 (1.4%)	NE	Prior review
21	Isik et al. [41]	2007	Turkey	Europe	890	18 (2.0%)	NE	Prior review
22	Aydin [42]	2007	Turkey	Europe	190	4 (2.1%)	NE	Prior review
23	da Silva et al. [40]	2007	Brazil	Americas	1,600	23 (1.4%)	NE	Prior review
24	Ramezani and Dehghani [43]	2007	Iran	Asia	5,048	144 (2.9%)	NE	Prior review
25	Fallah and Dehgani [38]	2008	Iran	Asia	5,981	38 (0.6%)	NE	Prior review
26	Okolie et al. [44]	2008	Nigeria	Africa	27	9 (33.3%)	NE	Prior review
27	Sodergren et al. [5]	2009	UK	Europe	1,150	18 (1.6%)	NE	Prior review
28	Karatepe et al. [45]	2009	Turkey	Europe	5,100	12 (0.2%)	NE	Prior review
29	Ariyarathenam et al. [46]	2010	UK	Europe	498	13 (2.6%)	NE	Prior review
30	Engin et al. [47]	2010	Turkey	Europe	1,969	7 (0.4%)	NE	Prior review
31	Karaman et al. [48]	2010	Turkey	Europe	916	23 (2.5%)	NE	Prior review
32	Akbulut et al. [18]	2011	Turkey	Europe	54	37 (68.5%)	NE	Prior review
33	Mekhail et al. [49]	2011	UK	Europe	268	8 (3.0%)	NE	Prior review
34	Gialamas et al. [50]	2012	Greece	Europe	1,085	7 (0.6%)	NE	Prior review
35	Maki et al. [51]	2012	USA	Americas	913	16 (1.8%)	NE	Prior review
36	Yilmaz et al. [52]	2013	Turkey	Europe	134	31 (23.1%)	NE	Prior review
37	Ilhan et al. [53]	2013	Turkey	Europe	3,863	16 (0.4%)	NE	Prior review
38	Zakaria et al. [54]	2013	Saudi Arabia	Asia	1,600	45 (2.8%)	NE	Prior review
39	Yabanoglu et al. [55]	2014	Turkey	Europe	57	15 (26.3%)	NE	Prior review
40	Yabanoglu et al. [56]	2014	Turkey	Europe	1,159	15 (1.3%)	NE	Prior review
41	Alemayehu et al. [57]	2014	USA	Americas	3,602	34 (0.9%)	NE	Prior review
42	Fleming et al. [58]	2015	Ireland	Europe	182	13 (7.1%)	NE	Prior review
43	Yıldız et al. [59]	2015	Turkey	Europe	846	12 (1.4%)	NE	Prior review
44	Ahmed et al. [61]	2015	Pakistan	Asia	2,956	84 (2.8%)	NE	Prior review
45	Zaghlool et al. [62]	2015	Saudi Arabia	Asia	1,536	4 (0.3%)	NE	Prior review
46	Limaiem et al. [60]	2015	Tunisia	Africa	1,627	23 (1.4%)	NE	Prior review
47	Akkapulu and Abdullazade [63]	2016	Turkey	Europe	1,446	9 (0.6%)	NE	Prior review
48	Hamdona et al. [65]	2016	Palestine	Asia	200	30 (15.0%)	NE	Prior review
49	Lala and Upadhyay [64]	2016	New Zealand	Oceania	2,923	109 (3.7%)	NE	Prior review
50	Gorter et al. [67]	2017	Netherlands	Europe	484	5 (1.0%)	NE	Prior review
51	Altun et al. [66]	2017	Turkey	Europe	660	9 (1.4%)	NE	Prior review
52	Spitale et al. [68]	2017	Argentina	Americas	2,000	65 (3.2%)	NE	Prior review
53	Dincel et al. [69]	2018	Turkey	Europe	1,970	11 (0.6%)	NE	Prior review
54	Zouari et al. [70]	2018	Tunisia	Africa	540	53 (9.8%)	NE	Prior review
55	Amer et al. [71]	2018	Egypt	Africa	65	1 (1.5%)	NE	Prior review
56	Ünver et al. [21]	2019	Turkey	Europe	2,047	4 (0.2%)	NE	Prior review
57	Tayfur and Balci [20]	2019	Turkey	Europe	2,400	22 (0.9%)	NE	Prior review
58	Pehlivanoğlu et al. [19]	2019	Turkey	Europe	3,222	24 (0.7%)	NE	Prior review
59	Oztas et al. [17]	2019	Turkey	Europe	48	37 (77.1%)	NE	Prior review
60	Elfaedy et al. [72]	2019	Turkey	Europe	4,012	14 (0.3%)	NR	Newly identified
61	Kinnear et al. [73]	2019	Australia	Oceania	1,214	8 (0.7%)	NR	Newly identified
62	Hasan et al. [74]	2020	Egypt	Africa	1,150	31 (2.7%)	3.2% (1/31)	Newly identified
63	Sarici et al. [75]	2020	Turkey	Europe	2,754	38 (1.4%)	NR	Newly identified
64	Al-Balas et al. [76]	2021	Jordan	Asia	1,510	12 (0.8%)	25.0% (3/12)	Newly identified
65	Gümüş and Söğütçü [77]	2021	Turkey	Europe	14,797	268 (1.8%)	31.7% (85/268)	Newly identified
66	Sousa et al. [78]	2022	USA	Americas	3,541	38 (1.1%)	NR	Newly identified
67	Agholi et al. [79]	2023	Iran	Asia	13,013	73 (0.6%)	39.7% (29/73)	Newly identified
68	Aydemir et al. [80]	2023	Turkey	Europe	7,814	50 (0.6%)	72.0% (36/50)	Newly identified
69	Issin et al. [81]	2023	Turkey	Europe	9,480	45 (0.5%)	28.9% (13/45)	Newly identified
70	Mohtasebi et al. [82]	2023	Iran	Asia	7,628	20 (0.3%)	30.0% (6/20)	Newly identified
71	Özen and Celep [83]	2023	Turkey	Europe	3,650	48 (1.3%)	33.33% (16/48)	Newly identified
72	Pogorelić et al. [84]	2024	Croatia	Europe	6,359	61 (1.0%)	34.4% (21/61)	Newly identified
73	Baykara and Erdoğan [85]	2025	Turkey	Europe	2,633	41 (1.6%)	43.9% (18/41)	Newly identified
74	Obeidat et al. [86]	2025	Jordan	Asia	2,275	8 (0.4%)	NR	Newly identified
75	Tüzün et al. [87]	2025	Turkey	Europe	10,658	108 (1.0%)	NR	Newly identified
76	Chan et al. [15]	2026	Australia	Oceania	455	45 (9.9%)	42.2% (19/45)	Newly identified
Total					196,138	3,913 (2.0%)	35.6% (247/694)