Pseudotumoral Schistosomiasis Mimicking Locally Advanced Rectal Carcinoma: A Case Report

Technical Summary: Pseudotumoral Schistosomiasis Mimicking Locally Advanced Rectal Carcinoma

Problem Statement
Pseudotumoral rectal schistosomiasis is a rare complication of chronic Schistosoma mansoni infection, characterized by mass-forming granulomatous inflammation and fibrosis. In endemic regions, this condition presents a significant diagnostic challenge because it closely mimics locally advanced rectal carcinoma both clinically and radiologically. The similarity in presentation—featuring rectal bleeding, weight loss, bowel wall thickening, and mesorectal invasion—often leads to misdiagnosis, potentially resulting in unnecessary oncologic interventions such as radical surgery. The specific difficulty lies in distinguishing benign, inflammatory fibrotic lesions from invasive malignancy when superficial biopsies fail to yield diagnostic tissue.

Methodology
This study is a single-case report of a 50-year-old HIV-negative Ethiopian man presenting with rectal bleeding, abdominal pain, urinary intermittency, and weight loss. The diagnostic approach followed a multi-modal workflow:

1. Clinical and Laboratory Assessment: Initial evaluation included physical examination and laboratory testing for leukocytosis, eosinophilia, anemia, renal function, and tumor markers (specifically Carcinoembryonic Antigen [CEA]).
2. Radiological Imaging: Contrast-enhanced Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) were utilized to stage the lesion, assessing wall thickening, mesorectal involvement, lymphadenopathy, and ureteric encasement.
3. Endoscopic Evaluation: Colonoscopy was performed to visualize the rectal mass and obtain tissue samples.
4. Histopathological Analysis: Initial superficial biopsies were reviewed. Due to non-diagnostic results (showing only necrosis and inflammation), repeat deep biopsies were performed.
5. Therapeutic Intervention: The patient received antiparasitic treatment (praziquantel) and urological decompression (percutaneous nephrostomy and ureteric stenting) for obstructive uropathy.

Key Results

• Clinical Presentation: The patient exhibited marked eosinophilia (9.4%), microcytic anemia, and acute kidney injury (creatinine rising to 7.27 mg/dL) due to bilateral distal ureteric obstruction. CEA levels were normal (1.27 ng/mL).
• Radiological Findings: CT and MRI revealed a long-segment (12 cm) rectal wall thickening with mesorectal fat stranding, lymphadenopathy, and bilateral ureteric encasement. These findings were radiologically staged as cT4bN1 locally advanced rectal carcinoma.
• Histopathological Evolution:
  • Initial Biopsy: Showed necrosis, granulation tissue, and mixed inflammatory infiltrates but was non-diagnostic for malignancy or specific etiology.
  • Repeat Deep Biopsy: Revealed the diagnostic triad: extensive eosinophil-rich inflammatory infiltrates, epithelioid granulomas with Langhans giant cells, and scattered calcified Schistosoma ova. No dysplasia or malignancy was identified.
• Outcome: Following praziquantel administration and urological intervention, the patient's renal function partially recovered (creatinine decreased to 3.61 mg/dL), and obstructive symptoms improved. Follow-up imaging showed persistent rectal wall thickening, consistent with established fibrosis.

Key Contributions
The paper contributes to the medical literature by:

1. Documenting a Rare Phenotype: It details a severe case of pseudotumoral schistosomiasis that radiologically and clinically indistinguishable from cT4b rectal cancer, including extensive pelvic invasion and ureteric obstruction.
2. Highlighting Diagnostic Pitfalls: It demonstrates the limitation of superficial endoscopic biopsies in schistosomal lesions, where eggs may be located deep within the submucosa or obscured by necrosis.
3. Identifying Diagnostic Clues: The report emphasizes the utility of peripheral eosinophilia and discordant findings between highly suspicious radiology and non-malignant initial pathology as critical indicators for deep tissue sampling.
4. Validating Management Strategies: It illustrates the efficacy of combining antiparasitic therapy with mechanical decompression for managing complications of advanced fibrotic schistosomiasis, even when structural damage is partially irreversible.

Significance and Claims
The authors assert that pseudotumoral rectal schistosomiasis must be included in the differential diagnosis of colorectal masses in endemic regions. The primary significance of this case is the prevention of misdiagnosis and the avoidance of unnecessary radical oncologic interventions. The paper claims that:

• Awareness is Critical: Clinicians in endemic areas must recognize that benign infectious processes can produce mass-forming lesions with adjacent organ compression.
• Histopathology is Definitive: Confirmation requires adequate deep biopsy to identify Schistosoma ova and granulomatous inflammation, especially when initial samples are non-diagnostic.
• Clinical Integration: The integration of clinical clues (eosinophilia), laboratory data (normal CEA), and radiological-pathological discordance is essential for timely and appropriate management.

The authors conclude that while praziquantel effectively treats the infection, established fibrosis may persist; therefore, early recognition is vital to prevent irreversible organ damage and unnecessary surgery.