Abstract
Basidiobolomycosis is a rare subcutaneous fungal infection caused by Basidiobolus ranarum. Gastrointestinal Basidiobolomycosis GIB has been increasingly reported in the literature.
We present a case of a 50-year-old male patient who presented by abdominal pain and weight loss. Imaging showed a left colon mass with a small liver lesion. Provisional diagnosis of colon cancer with liver metastasis was made. Endoscopic stenting and biopsy were done, and the results of the biopsy were not conclusive. The condition was complicated by perforation, and emergency laparotomy was done. The diagnosis of colon Basidiobolomycosis was reached from surgical histopathology. Unfortunately, the patient's condition deteriorated post operatively and the patient passed away a few days after surgery.
GIB is a rare fungal infection commonly presenting as a colonic neoplastic mass or inflammatory bowel disease. The endoscopy biopsy usually fails to provide definitive diagnosis. Post-operative histopathological examination with or without culture provides a definite diagnosis. Treatment of GIB includes surgical resection with appropriate antifungal therapy which revealed dramatic response in most of the cases. However, delayed diagnosis and treatment lead to dissemination of the disease which is life-threatening condition.
Introduction
Basidiobolomycosis is a rare fungal infection caused by Basidiobolus ranarum which is endemic in areas with warm arid climate such as India, Saudi Arabia, Iran, and Arizona in the United States [1]. It was first described in 1886 in frogs [2]. In 1956, the first human case was reported from Indonesia as a case of subcutaneous infection [1, 3].
Although basidiobolomycosis mainly presents as subcutaneous infection, gastrointestinal basidiobolomycosis (GIB) has been reported due to ingestion of soil, animal feces, and food. The clinical manifestations are diverse and nonspecific depending on the underlying disease, but fever, abdominal pain, weight loss, diarrhea, constipation, and chills are hallmarks. Most of the GIB cases have been misdiagnosed as inflammatory bowel disease, intestinal tuberculosis, sarcoidosis, amebiasis, malignancy or Crohn's disease [2, 4].
We present a case of colonic Basidiobolomycosis misdiagnosed as colon cancer with liver metastasis.
Case report
A 50-year-old gentleman presented to the clinic complaining from nausea, weight loss, abdominal pain, and distension for one month duration which has progressed in the few preceding days. His past medical history was unremarkable except for hypertension and smoking for 20 years.
The physical examination was unremarkable except for mild abdominal tenderness. Laboratory tests showed high weight blood cell count (16000/cc). CA 19-9 and CEA were normal.
CT examination was performed and showed a large mass involving the sigmoid and descending colon (Fig. 1), and a hypodense liver lesion. A colonoscopy was done and showed sigmoid colon stricture measuring 2.5 cm, biopsies were performed, and a metallic stent was placed (Fig. 2). CT chest was performed for staging and was unremarkable. MRI (Fig. 3) was done for assessment of the liver lesion and the results were in favor of a metastatic lesion. The biopsy results came as atypical cells with histolymphocytic inflammation. The decision of the multidisciplinary team was to repeat the biopsy in order to start the patient on chemotherapy and plan for surgery. Two days later, the patient complained from increased distension and stent displacement was suspected. A revision colonoscopy was done and showed stent migration, a repeat biopsy was done, and a second stent was placed (Fig. 4). The second biopsy showed colonic mucosa with nonspecific inflammation. Surgery was scheduled and the patient went on a leave-on pass.
Axial and coronal CT scan shows a large left descending colon mass with surrounding fat strandings
Citation: Imaging 15, 2; 10.1556/1647.2023.00183
Abdomen x-ray shows metallic stent in the left colon. No bowel dilatation
Citation: Imaging 15, 2; 10.1556/1647.2023.00183
Axial post contrast MRI in the arterial (a), portovenous (b), delayed (c) phases show a small peripherally enhancing lesion in the right liver lobe with no progressive enhancement, axial diffusion weighted image (d) shows peripheral diffusion restriction
Citation: Imaging 15, 2; 10.1556/1647.2023.00183
Abdominal x-ray after the revision colonoscopy and re-stenting shows two overlapping stents in the left colon
Citation: Imaging 15, 2; 10.1556/1647.2023.00183
Two days later, the patient was presented to the ER with sudden severe abdominal pain, guarding and low blood pressure. X-ray showed pneumoperitoneum. After discussion with the patient and explaining the risks and treatment options, the decision was to perform an urgent laparotomy with attempt of mass resection or performing diverting stoma. At surgery, they found perforated left colon with adherent small bowel loops. About 1.5 L of pus was found in all abdominal quadrants, left hemicolectomy was performed with primary anastomosis of the small bowel loops, frozen sections from the colon mass as well as a Tru-Cut biopsy from the liver lesion were sent for histopathological assessment. The results of the frozen section came as suspicious for fungal infection without evidence of malignancy. Due to massive bowel edema, stoma creation was not possible, VAC dressing was applied, and the patient was shifted to the ICU with the plan to do a revision surgery after 48 h for wound closure and stoma creation.
The final pathology results showed fungal colitis consistent with basidiobolous ranarum species, the liver lesion demonstrated portal eosinophils rich in inflammatory infiltrate with no detected fungal elements. The patient started antifungal therapy (Voriconazole 200 mg twice daily). Second exploration was performed, the gallbladder was gangrenous, and a partial cholecystectomy was done, stoma was created, and VAC dressing was re-applied. The patient's condition started to deteriorate in the ICU with a picture of acute respiratory distress syndrome ARSD. Unfortunately, the patient died after 3 days from acute respiratory failure.
Discussion
The clinical presentations of GIB are non-specific and include abdominal pain, fever, and sometimes palpable abdominal masses. The problem of considering GIB in the differential diagnosis of these cases is that it occurs in immunocompetent patients, as in our patient, unlike other fungal infections which tend to occur in immunocompromised patients. The route of infection is not totally understood, it is believed that skin infection results from skin contact with contaminated soil after minor trauma or insect bites. For GIB, the proposed theories are that of ingestion of infected food or water. Liver involvement occurs due to dissemination of the fungus elements through the gastrointestinal tract lymphatics. Old reports discussed the possibility of contamination of surgical wounds by the fungus as some reported cases had an old surgical history [5, 6]. Our patient was presented with abdominal pain and weight loss, he had negative surgical history.
GIB has a distinctive histopathological appearance of necrotizing granulomatous inflammation with multiple inflammatory cells rich in eosinophils and deposits of intense bright granular eosinophilic material surrounding the fungal hyphae (Splendore-Hoeppli phenomenon). This histological finding is very characteristic of this fungus and other invasive fungi with gastrointestinal involvement such as mucormycosis but their granulomas are morphologically different with no eosinophil [7].
In our patient, the pre-operative endoscopic biopsy failed twice to diagnose the disease. This is similar to almost all of the reported cases. This is explained by the deep submucosal location of the fungus within the bowel wall which requires deeper biopsies [8]. The diagnosis was completed after surgical excision and biopsy.
Imaging plays an important role in diagnosis, and computed tomography CT is the most commonly used imaging modality. Abdominal Basidiobolomycosis commonly manifests as colonic and/or liver masses, and bowel wall thickening. Abdominal ultrasonography was commonly used in the reported pediatric cases. With the advance of cross-sectional imaging, the use of conventional barium studies for the assessment of bowel pathology has been significantly decreased. In some reported cases, the appearance of GIB on barium studies was similar to that of colonic masses with irregular luminal narrowing [8].
In our case, the CT findings were similar to that of colon cancer, and the differentiation between both entities was not possible.
The treatment of GIB consists of surgical resection of the inflammatory mass with adjunctive antifungal therapy [1]. Treatment with only antifungal therapy without the need of surgical intervention was reported [9], however, the strategy of early surgical intervention has shown to decrease morbidity and allow for disease eradication [1, 4, 10]. Unfortunately, the delayed diagnosis of our patient led to inevitable morbidity and mortality.
Conclusion
Basidiobolomycosis is a rare chronic subcutaneous fungal infection that occurs mainly in immunocompetent patients. The involvement of gastrointestinal tract by basidiobolomycosis has been increasingly reported. GIB has non-specific clinical and imaging findings resembling inflammatory bowel disease and colon cancer. The diagnosis is based on histopathology with or without culture. Early and accurate diagnosis is necessary to prevent disease dissemination and avoid morbidity and mortality.
Authors' contribution
All authors made significant contribution to the work and have read and approved the manuscript. This manuscript has not been published and is not being considered for publication elsewhere, in whole or in part in any language.
Conflict of interest
The authors declare that they have no competing interests.
Funding sources
No funding was obtained for this study.
Ethical statement
The study is exempt from ethics committee approval. It is a retrospective case report; full patient anonymity was preserved.
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