Enterobius vermicularis threadworm infestation of paraovarian tissue in a woman who has had a hysterectomy

Abstract

A 36 year old woman was admitted complaining of constant left iliac fossa pain and deep dyspareunia over the previous three weeks. On examination she was tender in the left iliac fossa and on bimanual pelvic examination a tender mass was felt. Her white cell count was normal at 60 × 109L (eosinophils 0.1 × 109/L), and urine gram stain was negative. Ultrasound examination of the pelvis showed four left-sided cysts measuring approximately 5 cm and 4 cm and two which were 2 cm in diameter. Five years previously, a total abdominal hysterectomy with ovarian conservation had been performed for men orrhagia. The pathology report showed no abnormality. For three months prior to this admission she had com plained of urgency and urge incontinence which had been diagnosed as demsor instability and treated with oxybutinin. The pain remained severe and so a laparo tomy was performed. At operation the pelvis was obscured by dense adhesions. The left-sided mass seen on scan was adherent to the pelvic side wall behind the sigmoid and descending colon. This 11 × 10 × 10 cm multi-loculated cystic structure was arising from the paraovarian tissue. It contained turbid brown fluid. The left ovary was firmly adherent to the pelvic side wall and vaginal vault. This ovary contained several small, soft, round yellow nodules measuring 0.5 cm diameter thought to be luteal tissue. After mobilisation of the descending and sigmoid colon and division of adhesions, left ovarian cystectomy and oophrectomy and was performed. Due to the dense adhesions the cyst was removed piecemeal. The normal right ovary was con served. She made an uneventful recovery. Histological examination of the cyst wall showed an increase in fibroblastic tissue. The ovarian tissue showed a number of corpora lutea and normal ovarian tissue. The cyst fluid showed reactive mesothelial cells and culture of this fluid showed no growth. The paraovarian and paratubal tissue contained a focus of dense sclerosis embedded within which were numerous ova of Enterobius vermicularis organisms and surrounded by mild scattered chronic inflammatory cellular infiltrate including eosinophils. No ova were seen within the fallopian tube lumen (1, 2). Low power view of tuba1 and paratubal tissue. Solid arrow shows fimbrial end of the fallopian tube. Open arrow points to the parasites with dense surrounding sclerosis. High power view showing a collection of ova of Enterobius vermicularis. On further questioning, the patient stated that her nine year old daughter recently had had two episodes of thread worm infection. The patient and her family were treated with mebendazole and given advice on hygienic measures. At six week follow up the patient had made an excellent recovery; she had no pain and had noticed a decrease in her urgency and urge incontinence. This case is remarkable because the patient had no history of previous threadworm infestation and may have acquired the infection by penetration of the vaginal vault or of the bowel wall. It might be argued that the presence of the parasite was fortuitous, but its situation in the paraovarian tissue suggests it caused an inflammatory reaction and formation of an ovarian mass. It may also account for the urinary symptoms in this case. Granulomatous lesions caused by Enterobius ver micularis (originally Oxyuris vermicularis) are rare in ectopic sites such as the ovary1. Pelvic peritoneal granulomas due to Enterobius vermicularis have been reported only in females2. The common route of entry to the female genital tract is by the female worm migrating from rectum to vagina and ascending via the uterine cavity. The mature threadworm is usually located in the lumen of terminal ileum or caecum and infestation is usually asymptomatic. After fertilisation, the female passes to the anus to lay eggs but may also migrate to the genital tract or via the urethra to the bladder where infestation causes incontinence. It is interesting to note that our patient had a threemonth history of urge incontinence. A second possible route of entry is directly through the bowel wall but E. vermicularis is seldom found within the bowel wall. In this case no evidence of perforation was seen, but the infestation was sited posterior to the sigmoid colon which may suggest bowel entry. It has been reported that E. vermicularis has the capacity to penetrate undamaged tissues3. These authors3 refer to a congress communication by Menken in 1953 describing a series of Douglascopic pictures in which he was able to watch “Oxyuris vermicularis from the very perforation of vaginal vault until it settled and was encapsulated by the peritoneum”. No faecal specimen was tested in this patient, but it seems likely that the paraovarian tissue was infested by a penetration of the vaginal vault, after infection acquired from the patient's daughter. Khan et al4. cite a case of tubo-ovarian abscesses secondary to E. vermicularis in a woman who had had a hysterectomy; their patient had vaginal discharge prior to her hysterectomy and the authors concluded that the infection had been longstanding. The threadworm eggs are much more resistant to degeneration than the worms and therefore the worm is a less usual finding. This adds to the likelihood of recent infestation in this patient.