Shear Wave Elastography: Is the potential method in Assessing Anal Fistulas and Perianal Tissue strain？

BACKGROUND Shear wave elastography, an ultrasound-based technique, has been widely used in China to assess tissue stiffness, but its application in perianal tissues remains limited. This study investigates its potential for diagnosing anal fistulas and evaluating perianal tissue characteristics. METHOD Between January 1st, 2022, and April 30th, 2023, shear wave elastography was performed in 152 patients with single-site simple anal fistulas to evaluate normal perianal tissue, fistula tissue, and postoperative scar tissue following lay-open surgery. Statistical analyses, including receiver operating characteristic (ROC) curve analysis and logistic regression, were employed to establish reference thresholds for differentiating among these tissue types. RESULTS Young’s modulus can serve as a key indicator for differentiating perianal tissues of different types, including normal tissue, fistula tissue, and scar tissue, and its values are not affected by sex, age, or BMI. However, the measurement location significantly influenced the results. When distinguishing normal tissue from fistula tissue, a measurement at the 7 ~ 5 o’clock position (lithotomy position) yielded a threshold of > 40.08 kPa for identifying fistula tissue (preset threshold = 0.45), whereas a measurement at the 5 ~ 7 o’clock position suggested fistula tissue at a threshold of > 54.95 kPa. For scar tissue, Young’s modulus was independent of measurement location, with values > 104.34 kPa indicating fistula tissue. CONCLUSION Shecar wave elastography shows potential for diagnosing anal fistulas, differentiating tissues of different types, and evaluating postoperative prognosis, enhancing diagnostic accuracy and providing a convenient tool for clinical assessment.