Histological Evaluation of Urachal remnants
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Abstract
Introduction: Urachal remnant disease occurs when the fetal urachus fails to close after birth. We perform surgical excision of umbilical sinus-type urachal remnants, aiming for complete resection to prevent residual urachal epithelium, which may become a source for urachal carcinoma. This study reports immunohistochemical findings from surgical specimens to assess epithelial involvement and inform resection strategies.
Materials and Methods: We reviewed cases of urachal remnant excision performed over one year at the Department of Plastic Surgery, Kitasato University Medical Center. Patient characteristics, including age, sex, symptoms, MRI findings, length of resected cord-like structures, and histopathological results, were examined. Histological evaluation included hematoxylin and eosin (H&E) staining and immunohistochemistry. Markers used were keratin AE1/AE3 and epithelial membrane antigen (EMA) for epithelial cells, factor VIII for vascular endothelium, α-smooth muscle actin (αSMA) for smooth muscle cells, and S-100 protein for nerve fibers.
Results: Five patients (3 males, 2 females; age range 16–69 years) underwent surgery for urachal remnant disease. All presented with peri-umbilical inflammation. Preoperative MRI identified tubular structures ranging from 1.2 to 6.4 cm, while the resected cord-like structures measured 6 to 11 cm. The resected specimens were 3 to 5.2 cm longer than the tubular structures seen on MRI, and no tubular structures were observed at the surgical margins. Three cases showed clear tubular structures on H&E staining, all of which were positive for keratin AE1/AE3 and EMA, with keratin AE1/AE3 showing stronger staining. The remaining two cases, without clear tubular structures, were negative for keratin AE1/AE3 and EMA. αSMA was positive in all cases, while no significant findings were noted with factor VIII or S-100 protein.
Discussion: The ideal resection range for urachal remnants remains unclear. In this study, resecting at least 2 cm beyond inflammatory signs during surgery, combined with intraoperative confirmation of the absence of tubular structures, resulted in complete excision. Immunohistochemical staining, particularly keratin AE1/AE3, was valuable in identifying residual epithelial components, while αSMA was useful for assessing remnant structures.
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