Comparative Imaging of the Anal Sphincter Complex: Insights from Trans-perineal and Transvaginal Ultrasound Approaches

Abstract

Background: Endoanal ultrasound is considered the gold standard for assessing anal sphincter pathology; however, its reliance on specialized equipment and invasiveness has led clinicians to investigate alternative imaging methods. This study aims to evaluate the anal sphincter complex in asymptomatic female subjects using transvaginal and trans-perineal routes, with the objective of comparing the findings.
Patients & methods: The cross-sectional study was conducted at the Institute of Nuclear Medicine & Allied Sciences (INMAS), Mitford, Dhaka from March to September 2025. Trans-perineal image was obtained with a linear transducer placed on the perineum with patient in dorsal lithotomy position. Internal and external anal sphincters were identified, and thickness were measured. The procedure is repeated with an endo-vaginal probe,
first placed on the perineum and then during insertion into the vaginal canal. Findings were later statistically analyzed.
Result: Total 30 females were enrolled in the study, age ranging between 18 – 45 years (mean ± SD 30.6 ± 7.7 years). Mean thickness of internal anal sphincter (IAS) was 2.53 ± 0.64 mm and 2.67 ± 0.50 mm in TVUS and TPUS respectively. Mean thickness of external anal sphincter (EAS) was 5.92 ± 0.49 mm and 6.20 ± 0.40 mm in TVUS and TPUS respectively. There is no statistically significant difference between the two routes.
Conclusion: This study demonstrates that either trans-perineal or transvaginal route can be used for measuring anal sphincter thickness as per
convenience.

BJusg. vol. 27, no. 1, June 2026, Page: 10-16