TRANSVAGINAL VERSUS ANAL ENDOSONOGRAPHY FOR DETECTING DAMAGE TO THE ANAL-SPHINCTER

OBJECTIVE. We undertook this study to establish the accuracy of transv aginal endosonography for detecting damage to the anal sphincter. SUBJ ECTS AND METHODS. Anal endosonography was performed in 47 parous patie nts and one nulliparous patient using a sonographic scanner, an 1850 e ndoprobe, and a 10-MHz transducer protected by a water-filled hard pla stic cone. This procedure was followed by transvaginal sonography usin g the same system but with a water-filled balloon in 43 and a dedicate d vaginal probe Type 8551 of 10-MHz frequency in five. Axial images we re obtained as low in the perineum as possible, The transvaginal image s were reviewed with the observer unaware of the findings from anal en dosonography and were then compared with the anal endosonograms. RESUL TS. The transvaginal images were inadequate for review in three patien ts, In the remaining 45 patients, anal endosonography showed internal sphincter defects in 18 and external sphincter tears in 21. Transvagin al endosonography showed eight internal and 10 external sphincter defe cts only, giving a sensitivity of 44% and a specificity of 96% for the detection of internal sphincter defects and a sensitivity of 48% and a specificity of 88% for external sphincter tears, CONCLUSION. Transva ginal examination is not accurate for assessing the anal sphincter bec ause of the anatomic limitations this approach imposes on axial imagin g of the anal canal.