Colonic schistosomiasis: A case report

Abstract

BACKGROUND

Schistosomiasis is a chronic parasitic infection endemic in many countries. Colonic schistosomiasis is a rare entity with no specific clinical manifestations or endoscopic aspects, which delays the diagnosis. Diagnosis is primarily dependent on histopathological analysis, and treatment with antihelminthics typically resolves the infection.

CASE SUMMARY

We present the case of a 21-year-old male who suffered from chronic diarrhea and abdominal pain. Physical examination found no abnormalities, blood tests were normal, and stool examination was negative. A colonoscopy revealed a nodular terminal ileal mucosa, two cecal polypoid lesions with no particular surface pattern, and millimetric erosions in the rectum. The presence of Schistosoma eggs with thick peripheral capsules and viable embryos inside and numerous eosinophils surrounding the egg capsule were observed on histopathological examination. The patient received praziquantel, and his symptoms were resolved.

CONCLUSION

Colonic schistosomiasis should be considered as a differential diagnosis, especially in endemic countries. Endoscopy and histopathological examination can confirm the diagnosis, and antihelminthics are an effective treatment.

Key Words: Schistosoma; Colon; Polyps; Colonoscopy; Histopathology; Ova

Core Tip: Colonic schistosomiasis is a rare disease, often mistaken for other pathologies, such as inflammatory bowel disease, because the clinical and endoscopic manifestations are non-specific and can be misleading. Histopathological examination is key to diagnosis when the stool examination shows no ova. We present a case of colonic schistosomiasis in a 21-year-old male presenting with chronic diarrhea and abdominal pain. The stool examination was negative and colposcopy showed multiple polyps. Histopathological examination confirmed the diagnosis of colonic schistosomiasis. Antiparasitic treatment was effective.

INTRODUCTION

Schistosomiasis is a serious chronic parasitic infection caused by trematodes, primarily Schistosoma mansoni and Schistosoma japonicum. Humans are accidental hosts; infection occurs after ingesting larva-infested water. According to the World Health Organization, 236.6 million people needed preventative treatment in 2019 and the global death rate ranged between 24000 and 200000. Schistosoma commonly infects the urinary tract, and intestinal infection is rare. Its clinical manifestations are non-specific, ranging from asymptomatic to intestinal occlusion secondary to larva deposits, diarrhea, abdominal pain, malnutrition, and chronic anemia. Colonoscopy can reveal lesions, among which mucosal edema, ulcerations, and polypoid lesions are frequently observed[1].

Herein, we present a case of a 21-year-old male with colonic schistosomiasis.

CASE PRESENTATION

Chief complaints

A 21-year-old male, originally from Madagascar but living in Morocco for the past 5 years, presented with chronic diarrhea up to 3-4 times a day, diffuse abdominal pain prominent to the right iliac fossa and intermittent subocclusive symptoms for 3 years with no recent aggravation.

History of present illness

The patient suffered from his complaints for 3 years prior to presentation, and they occurred in a flare-up/remission pattern.

Physical examination

The physical examination found no abnormalities. The patient had a normal body mass index. No abdominal tenderness nor mass was noted.

Laboratory examinations

Blood tests gave normal findings, showing negativity for C-reactive protein levels. Stool examination for parasite ova and bacterial culture were negative.

Imaging examinations

A thoracic abdominopelvic computed tomography scan revealed no abnormalities.

ENDOSCOPIC EXAMINATION

Colonoscopy revealed a nodular terminal ileal mucosa, two cecal polypoid lesions with no particular surface pattern, and millimetric erosions in the rectum (Figure 1A). Biopsies were taken with jumbo forceps. Histopathological examination showed the presence of Schistosoma eggs with thick peripheral capsules and viable embryos inside (Figure 1B). The egg capsules were surrounded by numerous eosinophils (Figure 1C).

Figure 1 Colonoscopy and histopathological findings. A: Polyps were observed during colonoscopy; B: Microphotography showed the presence of three Schistosoma eggs in the colic mucosa (hematoxylin and eosin, × 40); C: Microphotography of a Schistosoma egg showed a thick peripheral capsule and a viable embryo inside. The egg capsule was surrounded by numerous eosinophils (hematoxylin and eosin, × 400).

FINAL DIAGNOSIS

Colonic schistosomiasis.

TREATMENT

The patient received praziquantel (60 mg/kg in two doses over a 1-d period).

OUTCOME AND FOLLOW-UP

The treatment resolved the diarrhea and alleviated the abdominal pain.

DISCUSSION

Schistosomiasis, also known as Bilharzia, is a parasitic infectious disease caused by schistosomes. Its geographical distribution is widespread, with endemic foci in some regions of the world (Africa, South America and Asia). S. mansoni and S. japonicum are typically involved in digestive schistosomiasis. In Africa, colonic polyposis is generally associated with S. mansoni infection[2]. Patients are infected after direct contact with water contaminated with snails carrying the parasite. The urinary system is preferentially affected, while intestinal involvement is rare.

Symptoms can be non-specific, and the evolution of the infection can last for long periods (as reported in our case). Diarrhea is the main symptom, as 3%-55% of a population study presented with diarrhea, with 11%-50% of cases presenting with bloody diarrhea[1]. In a study of 216 patients with intestinal schistomiasis, by Mohamed et al[2], abdominal pain and diarrhea were the most frequent symptoms, accounting for 39 % and 27% of cases respectively. In another study by Rocha et al[3], diarrhea was also the most common symptom, observed in 56% of cases. Abdominal pain, constipation, weight loss and fatigue are commonly observed, while obstructive symptoms, such as intestinal stenosis, are rare.

Differential diagnosis with inflammatory bowel disease and malignancy can be challenging. Hypereosinophelia is a nonspecific finding of schistomiasis correlating to the stage, intensity, and duration of infection. Stool examination may reveal ova, which is essential in determining larva species[1,2]. However, detecting ova in the stool can be difficult, as the numbers decrease as the infection evolves. Quantitative sampling according to the Kato-Katz technique coupled with concentration technique improves the sensitivity of egg detection; the diagnosis sensitivity could also be improved by associating Kato-Katz sampling examination with serological testing (e.g., IgG anti-Schistosoma mansoni-enzyme-linked immunosorbent assay technique)[4]. Serological diagnosis by detection of serum antibody titer is also available, especially in endemic areas, but it cannot differentiate between active or chronic infection; meanwhile, a negative serological test can rule out infection in endemic areas but cannot be used in post-treatment follow-up due to prolonged positivity post-therapy[5]. Detection of free circulating DNA by polymerase chain reaction can be used for early diagnosis of prepatent schistosomiasis infection[6], with good sensitivity and specificity for urine samples (94.4% and 99.9% respectively)[7]. Serologic tests for the detection of one of the two gut-associated parasite proteins ¾ circulating anodic antigen and circulating cathodic antigen ¾ can also be used for diagnosis[8].

When digestive colonization occurs, superficial submucosal deposits of Schistosoma eggs lead to the formation of polypoid lesions corresponding to inflammatory granulation tissue and hypertrophy of the adjacent muscular layer. Colonoscopy can show polypoid lesions, edema, ulcers, and granular patterns[9-13]. In the study mentioned above by Mohamed et al[2], polyps were found in only 8 cases (3 were rectal and 5 were colonic), and histopathological examination showed schistosomal ova in all 8 of the polyps. Cao et al[10] observed that nodular lesions and polyps are more frequent in the left colon, while mucosal edema, erythema, granular pattern, and ulcers are often seen in the right colon. In this study, 4 patients were misdiagnosed as ulcerative colitis, 1 as Crohn’s disease, and 7 as ischemic colitis. While intestinal lesions associated with S. mansoni are usually observed in the ileum and the colon, duodenal involvement has been reported as well. Based upon visualization of schistosomal ova, biopsies and histopathological examination are the golden diagnostic standard of colonic schistomiasis. The ova are mainly deposited in the lamina propria and/or submucosa[11], with an observable inflammatory reaction in the tissue surrounding them[10,12]. Other characteristic features are excessive mucus and diffuse or focal infiltration of eosinophilic granulocytes, which may be highly suggestive of colonic schistosomiasis[14], as seen in our patient. In addition, intestinal ultrasound and computed tomography may reveal wall thickening, but they show no abnormalities in most cases. Abdominal X-rays and barium enemas can show images of polyps and structures but are not typically utilized due to their lack of specificity.

Intestinal schistosomiasis is amenable to medical treatment, including praziquantel, with a safe and effective outcome and cure rates ranging between 60% and 90%[15]. It has been shown that antigen tests become negative as early as 5-10 d after successful therapy[16]. A study from Africa that aimed to evaluate the efficacy and safety of praziquantel in preschool-aged children in an area co-endemic for Schistosoma concluded the efficacy of crushed praziquantel administered to preschool-aged children at a dose of 40 mg/kg against S. mansoni and Schistosoma haematobium[17]. Mutapi et al[18] had also concluded from their study that praziquantel is safe and efficacious in children aged 1-10 years.

Praziquantel is substantially excreted by the kidney, and elderly patients with decreased renal function may be at greater risk of toxic reactions. In a study conducted by Putri et al[19], the group aged 45 to 69 experienced a high proportion of side effects.

A second praziquantel regimen can be prescribed in case of persistence of the infection; oxamniquine alone or combinated with praziquantel and trioxolane can also be used as second-line therapy.

Following treatment, stool analysis or colon biopsy could be considered for assessment of treatment success but should be performed at least 6 wk post-treatment[20]. No data are available in the literature regarding colonic polyps’ endoscopic follow-up and monitoring.

Cases of colon cancer associated with S. japonicum have been reported. However, the carcinogenic pathways are unclear, and the association is not well established[2,10,21]. A Chinese study including 454 colorectal carcinoma specimens showed that more than half (n = 289) were associated with S japonicum infection[22]. Furthermore, a study by Kaw et al[23] including 1277 colonic carcinoma patients showed that schistosomiasis was often accompanied by rectal cancer.

Schistosomiasis prevention is key to its elimination; public health awareness campaigns, water sanitation, hygiene programs, and chemotherapy programs are necessary. Preventive chemotherapy in preschool-aged children is deemed appropriate for those aged ≥ 2 years in endemic communities, according to the World Health Organization. While an antischistosomal vaccine will be ideal for long-term protection, clinical trials for its development are still in progress.

CONCLUSION

Colonic schistosomiasis is a rare disease that should be considered a differential diagnosis in endemic regions. Endoscopic appearance is non-specific. Histopathological and stool examinations have a significant role in diagnosis.