Colonic Polyps an Unusual Manifestation of Schistosomiasis

Background

Schistosomiasis is one of the debilitating tropical diseases globally, and it is a major cause of morbidity and mortality in the Middle East, Asia, Africa, and South America.

Approximately 250 million people are infected, and 700 million people are at risk of infection. In more than 70 countries the infection is endemic with an estimated 660 million infections are concentrated in Africa, which accounts for 85% of the global at-risk estimated [1–3] Schistosoma can affect any site in the digestive tract, but the preferred site is the rectum while the sigmoid is rarely effected, and on occasion, it is found in the other parts of the large and small intestines. The polyp consists of a combination of a vascular neoformation and an inflammatory reaction to parasite eggs; worm can be found either dead or alive inside the polyp tissue [4] S. mansoni may be associated with the sexually transmitted disease as its eggs have been isolated from the condyloma acuminatum of patients with positive tests for human papillomavirus (HPV) in addition to human immunodeficiency virus (HIV) patients [5,6].

The objective of our study was to report a case of a Schistosoma-induced large rectal polyp in an immunocompetent young male, who presented with abdominal pain and bleeding from the rectum, and then was subjected to unnecessary invasive endoscopic management.

Case Report

HISTOPATHOLOGY:

The histopathology results showed an infectious polyp containing oval shape Schistosoma eggs with long sharp lateral spine (Figure 3) surrounding by granuloma (Figure 4) indicate chronicity of the infection. In addition, Schistosoma worms were found inside the polyp tissue (Figure 5). The patient received anti-helminthic treatment (praziquantel 40 mg/kg for 3 days) on an out-patient basis after which he improved during follow-up in the out-patient clinic after 3 months when he was asymptomatic.

MACROSCOPIC:

The macroscopic examination showed 2 polypoid soft tissue masses measuring 4×3×3 cm and 4×2×0.5 cm that were fixed in 10% formaldehyde. The cross-sectional surface was firm and whitish with an irregular white lining and superficial ulceration. The slide was stained with hematoxylin and eosin (H&E) and examined using an optical microscope.

MICROSCOPIC:

Microscopic sections revealed polypoid lesions lined by granulation tissue and partially by colonic epithelium. The stroma shows an eosinophil-rich granulomatous reaction surrounding many Schistosoma eggs (Figures 3, 4) and Schistosoma worms (Figure 5). No dysplasia or malignancy was seen.

Discussion

The 2 major species of Schistosomes commonly produce gastrointestinal diseases: S. mansoni and S. japonicum. The infection is usually acquired in childhood in an endemic area, such as the Middle East [7]. The World Health Organization (WHO) estimated that at least 229 million people required preventive treatment in 2018. The prophylactic treatment should be repeated over several years to reduce morbidity [8]. We describe a case of 2 large wide-base rectal polyps with irregular surfaces that mimicked dysplastic polyps that were completely removed endoscopically via an EMR. A histopathological examination confirmed that it was a case of benign polyp caused by a S. mansoni infection in a 24-year-old Yemeni male, who was most probably infected when he was an adolescent in his home country, in which he used to swim in dams and rain water streams. Most of the patients with schistosomiasis have mild to moderate disease, and only 5% to 10% will be severely infected [9]. There are no specific symptoms of colonic schistosomiasis, and its symptoms mimic other gastrointestinal problems, such as diarrhea, abdominal distension, lower abdominal pain, bleeding from the rectum, and altered bowel habits [10]. Intestinal diseases, especially in the colon, are mostly caused by S. mansoni as the most commonly implicated pathogen. The most common histopathological findings from colonic biopsies of patients are S. mansoni ova in the colonic mucosa with no or mild inflammatory cell infiltrates that correlate with the endoscopic appearance in most patients [10–12]. Patients may present with non-specific symptoms, such as lower abdominal pain, occasional diarrhea, and rectal bleeding. A differential diagnosis may include a variety of colonic diseases, such as inflammatory bowel disease, infectious colitis, and colorectal malignancies. There is a correlation between symptom frequency and infection intensity, and the spectrum of colonic schistosomiasis varies from diffuse proctocolitis to granulomatous disease or isolated polyposis [13,14]. As in our patient, all parts of the colon can be affected, but inferior mesenteric vein territory involvement in most of the cases indicates the infection most frequently involves the descending colon [13]. Intestinal Schistosoma rarely manifests as an intestinal obstruction caused either by intussusception of the ileocecal valve due to Schistosoma egg-induced fibrosis or a large polypoid mass causing luminal obstruction [14,15]. The studies concerning the pre-malignant risk potential of Schistosoma infection are limited and inconclusive with a limited causal relation between colorectal cancer and Schistosoma infection for both S. japonicum and S. mansoni [16,17].

Conclusions

It is very rare to encounter a Schistosoma infection that leads to formation of large colonic polyps manifested clinically as chronic abdominal pain and rectal bleeding in a young healthy individual. Endoscopically, it is very difficult to differentiate this type of polyp from other colonic polyps; thus, a high index of clinical suspicion is required mainly in endemic areas that may prevent the physician from performing unnecessary interventions and avoid catastrophic complications that may occur. As demonstrated in this case report, large rectal polyps manifested as rectal bleeding and an unnecessary invasive intervention was performed for this patient who could be treated medically once he was appropriately diagnosed.