04. Editorial M. Minguez

ic changes in the anus and nearby structures of patients with anal incontinence, perineal sepsis, and anal tumors (1). From a technical viewstand, most work groups currently operate 7to 10-MHz transducers allowing 360o, high-resolution images. The study is performed with no previous intestinal preparation and having the patient lye on his/her left side with both legs flexed 90o; except for rare instances, it requires no sedation or topic anesthesia. It lasts just a few minutes, may be performed anywhere (patient's room, examination room, operating room, etc.), and allows record storage in any format (electronic, paper) for further evaluation. The learning curve for benign anal conditions has not been studied thus far; however, it is deemed to be short when ultrasonography is performed by professionals with experience in the ano-rectal region. To validate their results, some authors document at least 100 examinations (2). While this is an observer-dependent test, intraand inter-observer variability has been shown to be acceptable –with a higher concordance in the former case– regarding the measurement and identification of anal sphincter rupture (3). Many studies have assessed the ultrasonographic anatomic patterns of the anal canal in healthy volunteers (4-7), and demonstrated this technique's reproducibility (6,7). In normal subjects conventional anal ultrasonography is very useful to identify those basic structures in the anal canal that will serve as reference items in classifying and establishing the complexity of fistulas, the hypoechoic internal anal sphincter (IAS), the hyperechoic external anal sphincter (EAS), and proximally the puborectal muscle, which exhibits the same ultrasonographic characteristics of EAS, and forms an anteriorly-open U-shaped loop embracing the rectum. Under normal conditions identifying and measuring these structures is usually an easy task. However, when traumatic, septic or fibrotic alterations are concurrently present tissues change their ultrasound refringence and render the process much more difficult. Similarly, a lesion's extent or height may on occasion result in technical difficulties regarding assessment. The most widely used anal fistula classification is that by Parks (8), who divided fistulas according to their anatomic relation to anal sphincters into interspincteric, transsphincteric, suprasphincteric, and extrasphincteric types. Secondary routes (extensions of the primary traject) may turn to the intersphincteric plane, ischiorectal fossa, postanal space, and supraelevator space. Furthermore, in the case of transsphincteric fistulas the theoretical EAS portion including the primary traject separates "higher" from "lower" lesions. By using these classification descriptive guidelines a good topographic relationship is established between the fistula and involved muscles, which will allow a preview of functional damage as induced by fisUsefulness of anal ultrasonography in anal fistula 1130-0108/2006/98/8/563-572 REVISTA ESPAÑOLA DE ENFERMEDADES DIGESTIVAS Copyright © 2006 ARÁN EDICIONES, S. L. REV ESP ENFERM DIG (Madrid) Vol. 98, N.° 8, pp. 563-572, 2006