S1783 The Diagnosis of Rectosigmoid Endometriosis Using EUS and EUS-Guided FNA

INTRODUCTION: Among the various etiologies of Gastrointestinal bleed (GIB), endometriosis (EMS) is less common, it occurs when the disease invades the GI tract, including the colon4-8. EMS induced GIB is typically cyclical, and peri-menstrual. Bowel EMS is hard to diagnose using colonoscopy mucosal biopsy because endometrial tissue is primarily located in the serosal and muscular layer. Recently, EUS and EUS-FNA are being utilized for evaluations of subepithelial masses in the GI tract, as they are noninvasive and accurately characterize tissue histology9,10. Several studies have investigated the use of EUS-FNA for the diagnosis of rectosigmoid EMS11,12. Here we report a case of EMS presenting as a GIB without the typical EMS symptoms that was primarily diagnosed using EUS-FNA. CASE DESCRIPTION/METHODS: A 35 years old African American female with a past medical history of systemic lupus erythematosus, was seen by gastroenterology for rectal bleeding for the past few months. She describes dark red blood rectal bleed without clots that coincide with her menstrual cycle. She denies any unintentional weight loss, any abdominal pain, bloating, cramping, or tenesmus with her GIB. A recent pelvic MRI had diagnosed uterine fibroids without any evidence of adenomyosis or EMS. Patient underwent sigmoidoscopy followed by a colonoscopy that showed intramural lesion measuring 3 cm in the distal sigmoid colon (Figure 1). Biopsies done during sigmoidoscopy showed some patchy chronic inflammation and was negative for any glandular dysplasia and EMS. Random biopsies during colonoscopy, showed hyperplastic polyp fragments. Next, an EUS appreciated a large, heterogeneous, ill-defined (without distinct borders) subepithelial mass in the rectosigmoid colon (Figure 2). FNA of the lesion ruled out malignancies and was positive for EMS. At that time patient was referred to a gynecologist. Here we report a case of GIB caused by EMS involvement of the rectosigmoid colon primarily diagnosed with EUS-FNA. DISCUSSION: Bowel EMS causing GI bleed is rare but has been reported. EUS-FNA, have previously been used in the confirmation of EMS as the cause of GIB. What makes our case unique however, is the fact that the patient did not exhibit any of the typical EMS symptoms. Also, the primary EMS diagnosis was made via EUS-FNA after a previous workup had been negative for the disease. This case report sheds a light on the potential utility of EUS-FNA in the diagnosis of various disease that may involve the GI.Figure 1.: Endoscopic appearance of SEM representing rectosigmoid endometriotic implants.Figure 2.: EUS of rectosigmoid endometriotic implants.Figure 3.: Hematoxylin and Eosin staining of endometrial gland.