Enterobius vermicularis Infection with Tuboovarian Abscess and Peritonitis Occurring during Pregnancy

Case Report

A 31-year-old, 30-week-pregnant female was admitted to the emergency department of a local hospital because of constant abdominal pain in her right iliac fossa radiating to the back and suprapubic area. Her medical history included two laparoscopic interventions for endometriosis and a cesarean section. Clinical evaluation did not reveal signs of peritonitis. She had a total white blood cell (WBC) count of 11,600/mm³ and a C-reactive protein (CRP) concentration of 37 mg/L. Analysis and culture of a mid-stream urine collection were negative. Cardiotocogram (CTG) showed premature uterine contractions and normal fetal condition. Atosiban treatment was started for preterm labor, and betamethasone was administered to enhance fetal lung maturity. Little clinical improvement was achieved. Five days later, the WBC count was 19,500/mm³, the CRP concentration had risen to 79 mg/L, and the patient was still suffering severe pain of the right iliac fossa, with rebound and guarding on examination.

Gynecological examination was reassuring; there was no blood or amniotic fluid loss, and fetal CTG was normal. At this point, she was transferred to our university hospital with a clinical diagnosis of appendicitis. Because of her advanced pregnancy, the surgeons opted for a classical appendectomy using a McBurney incision rather than laparoscopy. Laparotomy revealed four-quadrant peritonitis, a macroscopically normal appendix, and suspicion of a right tuboovarian abscess with large amounts of pus aspirated from the right iliac fossa and from behind the right ovary. Upon intraoperative inspection, the small intestine, gall bladder, liver, left hypochondrium, and sigmoid were normal. During aspiration, an abscess attached to the uterine wall opened and spilled its contents, which were aspirated subsequently. Frozen section of the appendix showed periappendicitis, indicating a potential right tuboovarian abscess. After extensive lavage and insertion of two drains, the abdomen was closed, without the right fallopian tube and ovary having been visualized. Culture of the intraperitoneal pus grew some colonies of Escherichia coli and yielded a rich growth of Veillonella parvula and Bacteroides fragilis. Ova of E. vermicularis were found by direct microscopic examination of the pus. Postoperatively, the infection was treated with intravenous amoxicillin–clavulanic acid and oral mebendazole. Microscopic examination of the appendix specimen confirmed the frozen section diagnosis of periappendicitis without signs of acute appendicitis. In fibrinopurulent material at the appendical serosa, a cluster of several parasitic eggs was found, the size and morphology of which were suggestive of Oxyuris (Fig. 1). No worms or eggs were found in the lumen or wall of the appendix.

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FIG. 1.

Egg of Enterobius vermicularis in fibrinopurulent material at the serosal surface of the appendix. The egg is ovoid, with one flat side and a bilayered retractile shell.

Five days later, the patient still complained of severe contraction-like suprapubic pain, but gynecological examination showed no evidence of labor, and a closed cervix. Transvaginal ultrasound suggested the presence of a collection in the space Douglas, of which was confirmed using magnetic resonance imaging that demonstrated the presence of two hypointense opposing structures with a total diameter of 8 × 2 cm and a pararectal collection suggestive of abscess formation. After multidisciplinary deliberation, an elective cesarean section was performed. When exploring the abdomen, no intestinal pathology was found. A large collection of pus and blood clots, with its origin in the right fallopian tube and extending toward the posterior uterine wall, was drained. A right salpingo-oophorectomy was performed. The patient's further postoperative course was uneventful.

Microscopic examination of the right tuba showed abscedation of the fallopian tube with a mixed inflammatory infiltrate with neutrophils, lymphocytes, and plasma cells. On the serosal surface, the pathologist identified bacterial colonies and one single pinworm ovum. The right ovary was diffusely infiltrated by neutrophils, lymphocytes, and some plasmacytes, probably originating from the fallopian tube abscess.

Discussion

This case of ectopic enterobiasis was extraordinary for two reasons; the patient had a tuboovarian abscess with generalized peritonitis, and she was 30 weeks pregnant.

Enterobius vermicularis infection of the female genital tract is unusual. In a histopathological study of 259 patients diagnosed with enterobiasis, the most common site of infection (85.5%) was found to be the lumen of the appendix [1]. Of these 259 patients, only 11 (4.2%) had worms or eggs in granulomas on the surface of the salpinx or ovaries, and they had no abscesses. In the majority of cases, the pathological changes due to parasites or ova outside the gastrointestinal tract are minor, and many lesions are incidental findings upon surgery or autopsy. Only a few cases of invasive tuboovarian E. vermicularis infections with overt clinical symptoms have been reported in the literature [2–5]. These patients all underwent oophorectomy, and the correct diagnosis of enterobiasis was made postoperatively, after pathological examination. The preoperative complaints, including lower abdominal pain, fever, dyspareunia, nausea, and vomiting, were atypical, and the results of the physical examination, blood tests, and radiological investigations also lacked any specificity. Only a past or concomitant gastrointestinal enterobiasis or the finding of E. vermicularis in cervical smears might suggest the presence of a parasitic infection of the genital tract and prompt appropriate treatment. A thorough search of the literature revealed only one previous case presenting with generalized peritonitis [6]. In this patient, the appendix contained several E. vermicularis worms, and ova were found in granulomas present in the ruptured tuboovarian abscess.

In contrast to our patient, none of the above-mentioned infections occurred during pregnancy. This patient was 30 weeks pregnant when she was transferred to our hospital with the clinical diagnosis of appendicitis. The possibility of a salpingitis, oophoaritis, or even tuboovarian abscedation was considered unlikely under the assumption that the pregnant uterus would not allow the ascent of any microorganisms this late in her pregnancy. This raises the question of how the adult worms entered the peritoneal cavity. Parasites may migrate through preexisting lesions of the intestinal wall such as appendicitis, diverticulitis, intestinal neoplasms, ulcers, abscesses, fistulae, or operation wounds [7], but perioperative exploration of the small and large intestines in our patient did not show any target site that might have allowed the escape of worms, larvae, or eggs, and microscopic examination of the appendix disclosed signs neither of acute appendicitis nor of the intraluminal presence of E. vermicularis. Therefore, we conjecture the possibility of a pre-gestational or early-gestational Oxyuris infection of the right fallopian tube that subsequently evolved to a right salpingitis and full-blown tuboovarian abscess. Immunosuppression caused by the high doses of corticosteroids given for fetal lung maturation might have accelerated this process.

First-line treatment of E. vermicularis infection includes mebendazole, but its use during pregnancy remains controversial with regard to fetal safety. Only 5% to 20% of an ingested dose is absorbed, and excretion occurs primarily through feces. Although plasma concentrations are low because of poor absorption and rapid metabolism by gut and liver, it crosses the placenta. A study of 192 pregnant women exposed to mebendazole during pregnancy (72% during the first term) showed no increase in major malformations compared with matched controls [8]. Although no teratogenic risks were reported in this and other studies, the manufacturer (Janssen-Cilag) nevertheless calls for caution in its use during the first trimester of pregnancy. Mebendazole treatment during pregnancy is classified as Class C, meaning that the potential benefit of treatment should exceed the possible risks. Treatment should include family members in close contact with the patient.

In conclusion, this case was extraordinary because of the combination of tuboovarian abscess and generalized peritonitis with E. vermicularis infection, and it was, to our best knowledge, unique in that it occurred during late pregnancy.

Author Disclosure Statement

No author has any commercial association that might create a conflict of interest in connection with this manuscript.