Chronic schistosomiasis: an incidental finding in sigmoid volvulus

Schistosomiasis, also known as bilharziasis, is an infection caused by trematodes of the genus schistosoma. Three schistosomal species cause most human infections, namely: S japonica, S haematobium, and S mansoni. Intestinal schistosomiasis classically associates with S mansoni, which is endemic in Africa, central south American countries, and in the Middle East.¹ Infected persons complain of abdominal pain, diarrhoea, and bloody stools. Most lesions affect the rectum and the left colon. Patients' tissues tend to be examined only when patients present with intussusception, mass lesions, or strictures that cause intestinal obstruction.² We report a case of recurrent sigmoid volvulus in a patient incidentally found to have colonic schistosomiasis.

A 40 year old man, a native of Angola who had immigrated to France five years previously, was referred to our hospital for treatment of a recurrent sigmoid volvulus. The resected colonic segment showed a dilated lumen of the greatly oedematous wall, with a 4 mm red sessile polyp located 2 cm from one edge. This polyp was composed histologically of distorted glands showing various degrees of mucoid activity, and granulation tissue, which contained viable and non‐viable parasitic eggs. These eggs were also present in the mucosa and the submucosa, surrounded by eosinophils, macrophages, plasma cells, and a giant cell granulomatous reaction, without an outer lymphocytic halo. The eggs were oval with a lateral spine, and contained what appeared to be viable nuclei on routine haematoxylin and eosin staining (fig 1). The appearance was consistent with active schistosomal infection and the capsule was demonstrated well when stained with Ziehl‐Neelsen. Many eggs were destroyed and entrapped by fibrous tissues. Adult worms were found in mesenteric veins (fig 2).

Figure 1 Parasitic egg, with a lateral spine.

Figure 2 Cross section of adult worms in the mesenteric vessels.

The diagnosis of colonic S mansoni infection with an inflammatory polyp was made. Later, a past history of intermittent diffuse abdominal pain and occasional rectal bleeding was obtained. Stool examination for schistosomal ova and serological testing for infection with S mansoni were positive. Liver enzyme values were within normal limits and renal function was preserved. One week later, the patient underwent surgery for an intestinal intussusception, and no surgical resection was performed. The patient was treated with Praziquantel and gradually recovered.

Schistosomes infect approximately 10% of the world's population and schistosomiasis ranks second only to malaria as a cause of serious morbidity and mortality.¹ Humans are the only important definitive hosts of S mansoni. After schistosomal cercariae from infected freshwater snails penetrate human skin, the parasites migrate through the venous system to the mesenteric veins, maturing over a period of many weeks into adult worms, which can live for 20 or 30 years. Most of the eggs produced are released in the faeces, but some become lodged in the intestinal wall and liver. As illustrated in fig 2, the adult worms reside in pairs in the mesenteric vessels, the larger male enfolding the female in his gynaecophoral canal.¹

The pathological changes in schistosomiasis are essentially the result of an inflammatory reaction to the eggs in the tissues of the intestinal wall. The severity of the reaction depends on host immunity and the infecting dose. In the early stages, there is an acute proctitis and colitis accompanied by oedema and haemorrhage as ova are discharged into the bowel lumen. Patients with chronic infections exhibit pronounced submucosal thickening as a result of fibrosis and lymphoid hyperplasia, accompanied by ulceration, haemorrhage, or stenosis. The disease may grossly mimic Crohn's disease or carcinoma. Extensive serosal and omental nodules may be present, and could mimic subserosal malignancy or diverticulosis.³

Extensive polyp formation may develop, as a result of inflammatory tissue thickening in response to submucosal granulomata that form around deposited eggs. This complication is common in Egypt, but, as in our case, is rarely seen in other endemic areas. When numerous, these colon polyps cause life threatening dysentery, with loss of fluids, protein, and blood.⁴,⁵

Diagnosis depends on histological recognition of the schistosomal eggs and the colitis that they induce. The eggs measure 100–180 µm in width; those of S mansoni are marginally longer than those of S japoncium, and have a distinctive subterminal lateral spine. The shells have a light brown, translucent appearance and unlike those of S haematobium contain acid fast material. This feature is diagnostically helpful if only the shell fragments are present.¹

Eggs and shells are usually circumscribed by granulomas in different stages. Colonic granulomas are smaller than hepatic ones, and often lack an outer lymphocytic halo.⁶

Colonic schistosomiasis masquerading as recurrent volvulus has not been reported previously. Whether the intestinal intussusception was also the consequence of this infection cannot be determined, because no tissue was submitted to microscopic examination.

In summary, we report an unusual presentation of chronic intestinal schistosomiasis, masquerading as recurrent volvulus. Shistosomiasis is rare outside the tropics, but with increased emigration and global travel, more cases are being recognised in developed countries. Clinicians and pathologists need to be much more aware of this diagnosis.