Enterobius granulomas as a cause of abdominal pain

Description

An 18-year-old woman presented with lower abdominal pain. Ultrasound (US) showed a dilated appendix. Laparoscopy revealed a mildly inflamed appendix with no other intra-abdominal abnormalities. Laparoscopic appendicectomy was performed. Histology revealed serosal thickening with no transmural inflammation or intraluminal worms. The patient re-presented 9 days later. US showed a peri-caecal collection and antibiotics were started. MRI demonstrated reduction in collection size. In addition, a small tubular structure deep in the pelvis, adjacent to the sigmoid colon, with no small bowel connection, was identified, with potential diagnosis of torted appendix epiploicae (figure 1). Ongoing abdominal pain prompted laparoscopy, which confirmed a normal appendix stump and area of thickened fibrotic tissue, which was excised, in the pouch of Douglas. Histology revealed an inflamed fibrotic capsule containing inflammatory cells and pinworm (figure 2). Symptoms resolved following antihelminthic treatment.

Figure 1.

Coronal fat suppressed MRI showing low signal tubular lesion (red arrow) deep in the pelvis, with surrounding high signal free fluid extending to contact the serosal surface of the sigmoid colon.

Figure 2.

Histological section showing Enterobius vermicularis (pinworm) present within intensely inflamed, fibrotic tissue containing eosinophils.

Enterobius vermicularis species, or pinworms, are the most common infection-causing helminths. They predominantly colonise the gastrointestinal tract or, rarely, the female genital tract.¹ Pinworms are associated with appendicitis; however, obstruction of the appendiceal lumen remains controversial.² As pinworms cannot migrate through tissues, peritoneal cavity entry occurs either via fallopian tubes or during appendicectomy.² Peritoneal cavity contamination can cause pelvic inflammatory disease, peritonitis or Enterobius granulomas.³ The patient as well as all close contacts should be treated. This case highlights the usefulness of MRI in such cases, obviating radiation associated with CT, and stresses the need for histological examination of all specimens and the need to consider pinworms, especially in endemic areas, during appendicectomy, to minimise the risk of contamination and to initiate early treatment.

Learning points.

• Enterobius vermicularis infestation can mimic the symptoms of acute appendicitis.

• Peritoneal cavity contamination with pinworms can lead to pelvic inflammatory disease, abdominal peritonitis and Enterobius granulomas.

• The patient as well as all close contacts should be treated.