Acute abdomen: An uncommon presentation of a common intestinal nematode.

Enterobius vermicularis is a common parasitic infection of the intestine which is rarely symptomatic. It is unusual to find it in the wall or outside the gastrointestinal tract. We encountered five such cases where we observed the worm outside the lumen of the intestine. The pathological findings and the clinical features are discussed. This case series highlight that E. vermicularis can be the cause of pathology within the abdomen and should be considered in the differential diagnosis of some commonly encountered abdominal conditions.

INTRODUCTION

Enterobius vermicularis is a very common parasite and is strictly specific for humans.[1] The helminths are found from tropical[2] to polar zones[3] irrespective of the socioeconomic status worldwide.[4] Ova of E. vermicularis are rarely seen in routine microscopic stool examination. Hence, the easy and effective “scotch-tape” test is recommended. This worm commonly infests the lumen of the intestine, the caecum usually, but on rare occasions has been found in the wall or in the tissues outside the gastrointestinal tract. In the tissues the worms can cause an inflammatory reaction simulating granulomatous lesions such as tuberculosis and Crohn's disease.[5] They can cause thickening of the bowel wall mimicking neoplastic lesions, and can also cause perforation of the intestine resulting in generalized peritonitis. We have encountered five cases in which pinworms were found outside the lumen of the gastrointestinal tract. The pathological lesions are described and their relationship to the clinical symptoms is discussed.

CASE REPORTS

Case 1

The first case is about a 60-year-old male patient who was admitted in the emergency with signs and symptoms of peritonitis. A laparotomy was conducted and two perforations were found in the jejunum. Resection and anastomoses was done. A segment of the intestine measuring 21.5 cm was sent for histopathological examination. Grossly, the external surface showed two perforations measuring 1 × 1 cm and 2.5 × 1.5 cm, respectively. On cutting through the antimesentric border the mucosa was normal looking in most of the part. Focal areas showed hemorrhage and sloughed out areas. The serosal surface was covered with an exudative membrane at places.

Microscopic examination of the sections from the perforated area showed intense mixed inflammatory infiltrate in the mucosa with an edematous submucosa containing round, walled, intact structures of E. vermicularis with a “T” shaped reproductive system [Figure 1]. The serosal surface was covered with exudative membrane comprising of serofibrinous material with numerous eosinophils, polymorphs and red blood cells along with numerous rounded structures of the parasite with chitinous wall. The patient died a few days postoperatively.

Figure 1

Case 1 nterobius vermicularis (female worm) in the wall of jejunum. Three rounded structures are present beneath the mucosa in the center of the picture with T shaped reproductive system clearly visible (H and E, ×10)

Case 2

A 50-year-old male patient was admitted in the surgery ward with the complaint of abdominal pain. A provisional diagnosis of Koch's abdomen was made. Laparotomy revealed perforation peritonitis with multiple strictures. A 26 cm segment of small intestine with attached mesentry was sent for histopathological examination. On gross examination, two perforations were identified. One measuring 2.4 cm and the other measured 1.0 cm. The mucosa between these two perforations appeared to be thickened. Rest of the bowel wall appeared to be grossly unremarkable. An area of stricture was also identified. Multiple sections were taken from the perforations and the site of the stricture. Sections from the thickened portion showed the necrotic rounded chitinous structure of E. vermicularis surrounded by foreign body giant cells and eosinophil rich inflammatory infiltrate in the serosa. All the sections showed transmural inflammation. The patient's recovery was uneventful.

Case 3

A 34-year-old female patient reported to the casualty with history of blunt trauma. An exploratory laparotomy was done in which a jejunal perforation was found. Repair was done and necrotic omental tissue measuring 10 × 6 cm was sent for histopathological examination. Sections showed numerous round definite walled chitinous structures of E. vermicularis in mixed inflammatory infiltrate accompanied by a florid giant cell reaction. The patient recovered and was discharged subsequently.

Case 4

A young 15-year-old female patient reported to the surgery outpatient department with the complaint of pain abdomen for 4 days and signs and symptoms of intestinal obstruction. A past history revealed that the patient had experienced multiple episodes of abdominal pain for which he had been given palliative treatment at the peripheral level. A provisional clinical diagnosis of tuberculosis was made. On performing a laparotomy no perforation was seen and omental tissue measuring 18 × 6 cm was received in Pathology Department for examination. Multiple sections showed fatty tissue with degenerated chitinous structure of E. vermicularis embedded in intense inflammatory infiltrate with numerous eosinophils [Figure 2].

Figure 2

Case 4 Enterobius vermicularis in the omental tissue. Numerous degenerated chitinous structures of the worm surrounded by intense inflammatory infiltrate (H and E, ×10)

Case 5

A 14-year-old female was operated in the emergency for ileio-ileal intussusception and a 17 cm segment of the proximal bowel was sent for reporting. The outer surface showed an area of blackish discoloration covering 12 cm. The outer surface was covered with a serofibrinous exudative membrane in most of the length. Multiple sections showed transmural inflammatory infiltrate. The serosal surface showed a gravid female of E. vermicularis Containing ova surrounded by inflammation [Figure 3]. Occasional calcified rounded structures were also seen.

Figure 3

Case 5 - Gravid female containing ova and surrounded by an inflammatory reaction (H and E, ×40)

DISCUSSION

There are a number of reports of E. vermicularis having been found in various tissues outside the gastrointestinal tract, which were reviewed by Symmers.[6] E. vermicularis can be identified in histopathological sections by the “spines” on either side of the body, which are the cuticular keel or crest extending the whole length of the body. In adult females, there is a “T” shaped reproductive system.

In our first case, adult female worm was found in the submucosa of the intestine. In previous studies, pin worms have been reported in the wall of the gut.[78] In a study conducted on 691 appendices[7] showed that live worms are capable of living in the wall of the appendix without causing an inflammatory reaction. Ruffer[9] noted that worms could be seen in the wall of the intestine with an intact mucosa showing no obvious site of entry. However in our case it was accompanied by intense inflammatory reaction. Attachment of the worm to the intestinal wall may produce inflammation, but any relationship between invasion and inflammation remains unproven.[10] It is difficult to say whether the presence of the helminth led to the inflammation leading to subsequent perforation and peritonitis or pre-existing inflammation allowed the entry of parasite into the bowel wall.

In our second case, the transmural inflammatory response was probably due to the necrotic worm, which had led to thickening of the wall of the intestine mimicking Koch's abdomen.

In the third and fourth cases worm were found in omental tissue with and without perforation respectively. In the third case, the blunt trauma may have resulted in perforation of the already inflamed bowel wall, facilitating the passage of the worm to the omental tissue.

In the subsequent case, which presented with ileio-ileal intussusception, the pinworms were seen in the omentum without any perforation in the bowel wall. The heavy infestation coupled with the inflammation could have altered the motility resulting in intussusception in this case. The multiple episodes of inflammation might have weakened the intestinal wall, which facilitated the penetration of the worm through a minor perforation which over a period of time may have got sealed through the healing process. The ova of E. vermicularis Measures 50-60 µ × 20-30 μ and are symmetrical, and planoconvex.[5] In this case, the calcified structures fitted this description therefore the calcified foci seen were possibly ova of the worm, which had got calcified over a period of time in long standing infestation.

Though a very common infestation which is usually not given much attention by the clinicians. However, if present at ectopic location Enterobius can be a diagnostic challenge for the clinician. The diagnosis can then be made only on histopathology. Therefore despite the fact that it has been conveniently neglected both in the teaching curriculum as well as in the clinical training in medical schools, it has managed to draw attention in the medical world by mimicking other common conditions such as granulomas, tumors and chronic inflammatory conditions.

CONCLUSION

All the five cases were found in the span of 2 months out of which only one case (case 1) had a fatal outcome. Rest of the four patients recovered successfully. These findings suggest that E. vermicularis infestation is prevalent in this region, but it still eludes the clinical diagnosis. From the present series of cases, it is evident that what was previously thought to be a simple parasitic infection can lead to medical emergencies, if ignored. In our case series, out of five cases three were associated with perforation and inflammation was seen in all the five cases. The purpose of reporting these cases is to bring to the attention of clinicians and histopathologists that E. vermicularis can be the cause of pathology within the abdomen and should be considered in the differential diagnosis of some commonly encountered abdominal conditions. However, further studies are required to ascertain whether the inflammation and perforation were the cause or consequence of the presence of Enterobius at ectopic sites.