Accessory spleen: a potential cause of misdiagnosis at EUS

Background: Accessory spleen is a common congenital anomaly. There are curr ently no endoscopic ultrasound (EUS) criteria for the diagnosis or differen tiation of this benign splenic anomaly from pathologic disorders including neoplasms. The purpose of this study was to characterize EUS features and d evelop criteria for the diagnosis of accessory spleen. Methods: Ten patients undergoing EUS were found to have a possible pancreat ic tail or perisplenic mass later confirmed by CT to be either an accessory spleen or a prominent lobule of the spleen. EUS criteria assessed included size, shape, location, echo texture, echo density and border demarcation. Results: Ten patients (mean age 58 years) were evaluated. Indications for E US were evaluation of pancreaticobiliary disease in 9 patients and a gastri c submucosal mass in 1 patient. Eight patients had an accessory spleen and 2 had a lobulated spleen. The mean diameter of these lesions as seen on EUS was 2.70 x 3.12 cm. Nine were round and 1 was oval. Because all were locat ed inferolateral to the pancreatic tail and medial to the spleen, 5 of 10 w ere initially thought to be pancreatic masses. All of these lesions had a s harp and regular outer margin and homogenous echo texture, 4 were hypoechoi c and 6 hyperechoic. There were no specific EUS features identified that di fferentiated splenic lobulations from accessory spleen. Conclusions: Accessory spleen and splenic lobulation can be misinterpreted as neoplasm by EUS. Although homogenous, they can be hyperechoic or hypoech oic. Their sharp and regular outer margin and anatomic location may help to avoid misdiagnosis. Furthermore, computed tomography may be helpful in con firming their presence.