Histology with immunohistochemistry of the fistula region in female anorectal malformation: Can it be used for neo-anus reconstruction?

AIM: Female anorectal malformation is characterised by communication to the exterior by a fistula. There are conflicting reports of the presence of normal anus in the fistula region. This study was undertaken to assess the histopathology and immunohistochemical correlation of the terminal portion of the fistula in female patients and suitability of fistula incorporation in the reconstruction of the neo-anus.

METHODS: This prospective study included 13 patients of female anorectal malformation. Of these, seven had a vestibular fistula (VF), and the rest had an anterior ectopic anus (AEA). Histopathology of the fistula region was undertaken, along with immunohistochemistry. Various findings were evaluated.

RESULTS: Of seven VF patients, four showed atrophic or disrupted internal sphincter smooth muscle, whereas the remaining three showed hypertropic internal sphincteric smooth muscle. Six patients showed hypertrophic nerve bundle. Five VF patients showed subepithelial fibrosis, and none of them showed ganglion cells. Of six patients of AEA, internal sphincteric smooth muscle was normal in five. It was hypertrophic in one patient. Transitional epithelium was present in four patients. All patients showed hypertrophic nerve bundle and aganglionosis. Subepithelial fibrosis was observed in six patients.

CONCLUSION: The fistula region in VF and AEA patients appears to be an abnormal structure. Rather than preservation of the terminal fistulous region, resection followed by anoplasty may be a viable option.