Recently, the endo-anal ultrasound is increasingly used in the preoperative diagnostic work up of anal fistula. The newly introduced 3D ultrasound is expected to provide more improved diagnostic accuracy. However, the clinical usefulness of 3D endo-an...
Recently, the endo-anal ultrasound is increasingly used in the preoperative diagnostic work up of anal fistula. The newly introduced 3D ultrasound is expected to provide more improved diagnostic accuracy. However, the clinical usefulness of 3D endo-anal ultrasound on anal fistula has not been clearly elucidated yet. The aim of this study is to evaluate the accuracy of 3D endo-anal ultrasound in localizing the internal opening and 2^(nd) extension of anal fistulous tract. Thirty patients (18 men and 12 women, mean age of 42 years) underwent endo-anal sonographic studies for perianal fistula. Contrast enhanced image was acquired using hydrogen peroxide injection. Three dimensional image reconstruction was performed for all the cases. The ultrasonic finding was compared with surgical finding as a reference standard. The intraoperative internal opening correlated with the ultrasound report in 22 of 30 patients(73%). The sensitivity and positive predictive value of ultrasound study for internal opening were 82.6% each and negative predictive value was 42.8%. Two of the 4 patients with false negative ultrasound findings had supra-sphincteric type fistula. The contrast enhanced ultrasound scan with hydrogen peroxide detected 36% more internal opening or 2^(nd) tract than non-contrast one. The present study showed that the 3D ultrasound detect the internal opening and 2^(nd) extension of anal fistula with high accuracy. Therefore the preoperative 3D ultrasonic examination may be very useful in the management of anal fistula. In addition, the use of contrast material (H₂O₂) is recommended otherwise contraindicated since the contrast enhanced scan is superior to non-contrast one.