854 GASTROINTESTINAL ENDOSCOPY VOLUME 55, NO. 7, 2002 EUS-guided fine needle aspiration of idiopathic abdominal masses Marc F. Catalano, MD, Shahid Sial, MD, Amitabh Chak, MD, Michael V. Sivak, Jr., MD, Richard Erickson, MD, James Scheiman, MD, Frank Gress, MD Milwaukee, Wisconsin, Cleveland, Ohio, Temple, Texas, Ann Arbor, Michigan, and Long Island, New York Background: EUS-guided fine needle aspiration (EUS-FNA) has significantly increased the diag- nostic capability of EUS. FNA can also be helpful in the diagnosis of non-GI disorders. The role of EUS-FNA in the diagnosis of idiopathic abdominal masses has not been determined. This study evaluated the diagnostic accuracy of EUS-FNA of abdominal masses of unknown cause and its impact on subsequent evaluation and therapy. Methods: Thirty-four patients from 5 tertiary referral centers (21 women, 13 men; mean age 54 years, range 27-72 years) with idiopathic abdominal masses underwent EUS-FNA. Presenting symptoms included the following: pain (29 patients), weight loss (15), altered bowel habits (7), nausea/vomit- ing (6), abnormal liver function tests (4), palpable mass (4), and urinary retention (1). Four patients had a history of intra-abdominal cancer (2 cervical, 1 ovarian, 1 colon). A final diagnosis by EUS- FNA, surgery, autopsy, or long-term follow-up was available in all patients. Abdominal masses were classified into 3 disease categories: infectious, benign/inflammatory, and malignant. Results: Final diagnosis included infectious (5), benign/inflammatory (6), and malignant (23) abdominal mass. Overall, EUS-FNA established a tissue diagnosis in 29 of 34 patients (85%) in all 3 categories (infectious, 80%; benign/inflammatory, 67%; malignant, 91%). EUS-FNA was instru- mental in directing subsequent evaluation in 29 patients (85%) and therapy in 26 (77%). The num- ber of fine needle passes for adequate tissue sampling was lower for nonmalignant (2.2-3.2) ver- sus malignant diseases (4.6). One complication occurred (perirectal abscess) and was treated successfully with antibiotics. Conclusions: EUS-FNA of idiopathic abdominal masses is safe and accurate and helps to guide subsequent evaluation and therapy in the majority of patients. The most common and promising area seems to be EUS-FNA of malignant abdominal masses.Transluminal EUS-FNA provides min- imally invasive tissue sampling and obviates the need for exploratory laparotomy. (Gastrointest Endosc 2002;55:854-8.) An idiopathic abdominal mass can be a challeng- ing diagnostic and therapeutic problem. Although standard transabdominal US and CT have been used to guide fine needle aspiration (FNA), both modalities have disadvantages. US guidance is pre- ferred over CT because ionizing radiation is avoided and the needle is visualized in real-time, but disad- vantages include difficulty in visualizing the needle tip clearly and consistently, overlying bowel gas, and inability to delineate intervening tissues. EUS with FNA (EUS-FNA) has now emerged as an excellent method for the diagnosis of GI pathology and stag- ing of GI malignancies and may avoid the problems inherent to CT and US. Endoscopic placement of a US transducer immedi- ately adjacent to an area of interest has allowed use of higher US frequencies, which provide greater spatial resolution and better anatomic detail than are avail- able with standard US and CT. 1 Additionally, EUS- FNA offers clear and consistent visualization of the needle along its entire path, excellent delineation of intervening tissues, and no interference by bowel gas. To date, there has been no large evaluation of the diagnostic accuracy, safety, or impact of EUS-FNA on subsequent evaluation and treatment of patients with abdominal masses of unknown cause. To our knowledge, this is the first large retrospective mul- ticenter analysis of patients undergoing EUS-FNA for primary diagnosis of idiopathic abdominal mass- es and the subsequent impact of the results on eval- uation and therapy. PATIENTS AND METHODS Thirty-four patients (21 women, 13 men: mean age 58 years, range 27-73 years) presenting with idiopathic Received December 26, 2000. For revision February 23, 2001. Accepted September 19, 2001. Current affiliations: St. Lukes Medical Center, Pancreatic Biliary Center, Milwaukee, Wisconsin, the University Hospitals of Cleveland, Cleveland, Ohio, the Scott and White Clinic, Temple, Texas, the University of Michigan,Ann Arbor, Michigan, and the Winthrop Hospital, Long Island, New York. Reprint requests: Marc F. Catalano, MD, 2801 W. KK River Parkway, Suite 570, Milwaukee, WI 53215. Copyright © 2002 by the American Society for Gastrointestinal Endoscopy 0016-5107/2002/$35.00 + 0 37/1/122956 doi:10.1067/mge.2002.122956