Large-bowel obstruction secondary to Enterobius vermicularis pseudotumour

Abstract

Enterobius vermicularis infection is typically observed in paediatric patients and manifests with perianal pruritus, but other manifestations or ectopic presentations have been reported in the literature. We present the case of a man in his 60ss with a large-bowel obstruction with symptoms including a 4-day history of progressive abdominal pain, distension, vomiting and absolute constipation. On examination, his abdomen was distended with tinkling bowel sounds on auscultation. Cross-sectional imaging demonstrated an obstructing mass in the distal descending colon. An emergency laparoscopic Hartmann’s procedure was performed and the patient made an uneventful recovery. An intraoperative colonoscopy demonstrated numerous white threadworms in the colon. Histological analysis demonstrated a pseudotumour related to Enterobius vermicularis infection. This case represents a rare differential diagnosis for a large-bowel obstruction.

Background

Enterobius vermicularis infection is estimated to have significant prevalence worldwide.¹ Infection can have a relatively indolent course with patients being asymptomatic or reporting symptoms such as pruritus ani. E. vermicularis can be present as an incidental finding on appendicectomy histology specimens.¹ There are case reports of other manifestations of E. vermicularis in the literature, effecting gastrointestinal, genitourinary and gynaecological organs.^2–6 Although the vast majority of manifestations do not cause significant complaints to an individual patient, it is important to recognise the rare manifestations which can have considerable associated morbidity. This case report describes the rare presentation of a patient with a large-bowel obstruction secondary to an E. vermicularis pseudotumour, and underwent an emergency Hartmann’s procedure.

Case presentation

A man in his 60’s was transferred from an outside hospital with a 4-day history of progressive diffuse abdominal pain, nausea and vomiting, and absolute constipation.

The pain was gradual in onset, and the nausea and vomiting began in the hours following the abdominal pain. The vomit was bilious in nature. There was no preceding weight loss or blood per rectum. Before this acute illness, the patient was in good health, and did not take any regular medication.

The surgical history was significant for a sports-related subdural haematoma and left knee cartilage repair 40 years earlier. He had had a spinal decompression 5 years earlier. A colonoscopy was performed 10 years prior to this acute presentation, which was normal.

There was no family history of colorectal cancer or inflammatory bowel disease. The patient was a lifelong non-smoker, and had social alcohol consumption.

On examination, the patient was moving with ease and appeared well. His heart rate was 70 beats per minute, blood pressure 131/71, respiratory rate 16 per minute and oxygen saturations of 96% on room air and apyrexial. A nasogastric tube had been inserted in the outside hospital, which relieved the abdominal pain but had minimal output. The abdomen was distended and non-tender. A mass was not palpable. Tinkling bowel sounds were audible on auscultation. On digital rectal examination, a mass was not palpable and there was stool in the rectum. There was no frank or occult blood.

Investigations

Blood results

The white cell count was 13.7 (×10⁹/mL), with neutrophils of 11.8 (×10⁹/mL) and eosinophils of 0 (×10⁹/ml). The haemoglobin was 137 (g/L). The urea was 9.5 (mmol/L), creatinine 101 (mmol/L), albumin 40 g/dL and C reactive protein 14.5 mg/L.

Imaging

A CT abdomen and pelvis was performed with oral and intravenous contrast in the outside hospital. This demonstrated large-bowel distension from the caecal pole to the distal descending colon measuring 8 cm maximally, indicating a closed loop large-bowel obstruction. There was a transition point in the distal descending colon secondary to a 34×48×40mm soft tissue mass, with associated fat stranding and trace free fluid. There were adjacent subcentimetre lymph nodes. There were subcentimetre para-aortic lymph nodes (figure 1).

Figure 1.

Representative images from CT scan of the abdomen and pelvis. There is an obvious dilated large-bowel seen in both the axial and coronal images (blue arrows). There is significant dilation of the cecum (yellow arrows). There is a soft tissue mass (red arrows) causing a distal obstruction in the descending colon and proximal sigmoid colon, with associated fat stranding and trace free fluid. There were adjacent subcentimetre lymph nodes.

Differential diagnosis

Although the patient arrived to the hospital with clinical symptoms and diagnostic confirmation of a large-bowel obstruction, the underlying aetiology was unclear. Differential diagnoses included obstructing malignancy, diverticular stricture and a benign soft tissue tumour. An obstructing colonic malignancy was the main differential, given the appearance on the CT scan. Approximately 20% of colorectal cancer can present as a bowel obstruction.^{7 8} The patient did not report any symptoms of diverticular disease and there was no evidence of diverticular disease on the colonoscopy performed 10-year ago. This would make the diagnosis of a diverticular stricture less likely. An obstructing soft tissue tumour, such as a lipoma, is less common that an obstructing primary colonic adenocarcinoma, but would be another differential to consider.

Treatment

Regardless of the underlying aetiology, the patient required empiric treatment for a large-bowel obstruction.

The patient was resuscitated with intravenous Hartmann’s solution and made nil by mouth. He was also given intravenous analgesia, antiemetics and piperacillin/tazobactam. A urinary catheter was placed.

The patient was taken that evening for a Hartmann’s procedure with an intent of an initial assessment with laparoscopy. A left colonoscopy was performed with minimal air insufflation to examine the mass and to approximate the distance from the anal verge.

During the colonoscopy, multiple small white thread worms were observed (figure 2). At approximately 50 cm, the lumen was not visible with only normal apparent mucosa visible.

Figure 2.

Intraoperative colonoscopy image. Multiple small white threadworms were seen in the colon up to the point of the obstruction.

A diagnostic laparoscopy was performed and a decision was made to proceed with a laparoscopic Hartmann’s procedure. A large descending colon mass was identified and was densely adherent to retroperitoneal structures. The mass was removed en bloc with a segment of retroperitoneum and Gerota’s fascia. The specimen was extracted using a small midline laparotomy incision. An end colostomy was matured.

Outcome and follow-up

The patient made steady progress and had colostomy output day 1 postoperatively. He was reviewed by physiotherapy for mobility and was at baseline mobility at day 3 postoperative. He was reviewed by the stoma care nurse for stoma education. A treatment course of mebendazole was administered for the threadworm infection. The patient was discharged well 6 days postoperatively.

Histology

A section of sigmoid colon 23 cm in length was submitted for histological analysis. Macroscopically on opening the specimen, there was a 3.9 cm well circumscribed tan polypoidal mass. The mass corresponded to a zone of dense fibrosis with areas of geographic necrosis surrounded by eosinophilic fibrin-like material, mixed lymphohistiocytic inflammation with giant cells and occasional well-formed granulomas, in association with diverticula. The inflammation and fibrosis extended into pericolic tissue and contained scattered parasitic worms each with a thick cuticle, lateral alae and visible gut structures (figure 3). Some worms contained innumerable small plane-convex eggs with a thin hyaline transparent shell lacking spinous processes or polar plugs. Eggs were also present embedded in the surrounding fibroinflammatory tissue. The features were most consistent with an inflammatory pseudotumour related to E. vermicularis infection.

Figure 3.

Resected mass (H&E, ×100). An Enterobius vermicularis pinworm with a thick cuticle is seen in transverse section (upper left), adjacent to numerous plane/convex eggs, and surrounded by dense fibroinflammatory debris.

There was no evidence of malignancy. The remainder of the colorectal mucosa was normal. Twenty-nine regional lymph nodes show reactive changes only.

Follow-up

The patient was reviewed in the outpatient clinic 4 weeks after discharge and was clinically well. In retrospect, there were no clinical symptoms of helminth infection.

Discussion

The prevalence of E. vermicularis is estimated to be between 0.21% and 54.86% of individuals.¹ In setting of acute appendicitis, infestation with E. vermicularis is seen in up to 7% of appendicectomy specimens.⁹ A recent case report discussed an 18-year-old patient with a small pelvic inflammatory mass, who presented following an appendicectomy, that was found to contain E. vermicularis worms on histological examination. This was a particularly unexpected finding given that there were no E. vermicularis organisms identified on histological examination of the appendicectomy specimen.¹⁰ E. vermicularis has been found on histological examination of an omental mass,² an epididymal pseudotumour⁴ and a perianal polypoidal mass.¹¹

E. vermicularis can also be present within the small bowel, with a previous report noting their presence on capsule endoscopy.¹² E. vermicularis has been reported as the nidus for intussusception in a number of case reports. In both a 16-year-old man and 20-year-old woman, an operative reduction was performed.^{13 14} In contrast, conservative management was employed in an 8-year old boy with intestinal obstruction, and on follow-up colonoscopy, multiple E. vermicularis worms were identified.¹⁵

E. vermicularis infestation has also been reported to mimic colorectal tumours. A 76-year-old male patient underwent a transverse colectomy for a presumed adenocarcinoma. The mass was non-obstructing and on histological examination had E. vermicularis eggs in the submucosa layer.¹⁶ Similarly, in a patient with an apparent sigmoid mass, E. vermicularis was found on histological examination of the resected specimen.¹⁷

Although E. vermicularis typically does not invade or erode through tissues, there are case reports of patients with large and small bowel perforations that are secondary to E. vermicularis infestation.^{5 18} These are exceptionally rare cases. In the current case, the presence of worms and eggs outside the bowel wall is probably due to colonisation by the organisms of pre-existing diverticulosis, rather than transmural invasion by the worms.

Learning points.

• While the majority of Enterobius vermicularis infections result in minimal symptoms, it is important to consider the major morbidity that can results in untreated infections.

• E. vermicularis is more commonly seen in appendicectomy specimens, but has been associated with the formation of pseudotumours in other anatomical locations.

• It is important to consider eradication therapy for threadworm infections when identified on colonoscopy and on histology specimens.

Ethics statements

Patient consent for publication

Consent obtained directly from patient(s).