We report a case of sigmoid endometriosis diagnosed preoperatively based on endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA) findings. A 42-year-old female came to us with left lower abdominal pain and bloating that had started 3 months prior. CT and MRI results showed wall thickening of the sigmoid colon. A colonoscopy procedure could not be completed because passage through the sigmoid colon was blocked due to severe stenosis, while mucosal biopsy samples obtained during that procedure could not confirm a diagnosis. EUS-FNA was then performed and specimens were obtained from the muscular layer with stenosis, which revealed a thickened hypoechoic lesion. Histological findings obtained by use of EUS-FNA demonstrated a large amount of fibrosis in endometrial glands and a diagnosis of sigmoid endometriosis was confirmed by additional immunostaining. Thus, a laparoscopic sigmoidectomy was performed, with sigmoid endometriosis finally diagnosed. Confirmation of a diagnosis of intestinal endometriosis based on histological findings of mucosal biopsy specimens obtained by colonoscopy is difficult, because endometrial implants are primarily located in the serosal and/or muscular layer. When safe aspiration is possible, we consider that EUS-FNA can be an effective method for preoperative diagnosis of intestinal endometriosis, which may contribute to avoidance of unnecessary or excessive surgery.
Keywords: EUS-FNA; Preoperative diagnosis; Sigmoid endometriosis.