Association between adipose tissue thickness and fibroid shrinkage using ultrasound-guided high‑intensity focused ultrasound

Background. Ultrasound-guided high-intensity focused ultrasound (USgHIFU) is used to noninvasively treat symptomatic uterine fibroids. The thickness of the adipose tissue that the HIFU beam travels through is thought to be associated with decreased treatment outcome, although the evidence is anecdotal.  Objectives. To determine whether the thickness of adipose tissue affects the percentage volume shrinkage of the uterine fibroid after treatment.  Method. A retrospective study was performed at Chris Hani Baragwanath Academic Hospital (CHBAH) on patients who were treated with USgHIFU for symptomatic uterine fibroids between 11 October 2015 and 11 April 2018. Magnetic resonance imaging (MRI) images were used to measure the adipose tissue thickness and the percentage volume shrinkage of the uterine fibroid. Linear regression was used to determine an association between adipose tissue thickness and the percentage volume shrinkage of the uterine fibroid after treatment.  Results . A total of 71 female patients who attended the CHBAH HIFU clinic were included in the study. Mean adipose tissue thickness was 17.49 mm (95% confidence interval (CI) 14.86 - 19.73). Mean pre- and post-treatment volume of the fibroid was 176 mL (95% CI 123.26 - 208.57) and 109 mL (95% CI 71.75 - 141.73), respectively. The mean fibroid volume reduction was 44.68% ( p <0.0001). We found no significant relationship between adipose tissue thickness and change in volume ratio of the fibroid.  Conclusion . It is unclear whether adipose thickness affects treatment outcome when symptomatic uterine fibroids are ablated using USgHIFU. This study found no correlation between adipose tissue thickness and uterine fibroid shrinkage after HIFU treatment. Our findings suggest that the exclusion criteria for USgHIFU treatment of uterine fibroids should be reviewed.