Factors That Affect the Success of HIFU for Fibroids

Factors That Affect the Success of HIFU for Fibroids

1. Obesity
   • HIFU works by directing ultrasound beams at the fibroid. These beams must pass through the skin and abdominal layers before reaching the fibroid. In obese women, thicker abdominal walls absorb more energy, reducing the amount that reaches the fibroid. As a result, more energy is required to effectively ablate the fibroid.
   • Additionally, a thick abdominal wall can blur the ultrasound image, making it harder to see the uterus and fibroid clearly. This complicates the procedure and increases the difficulty of accurately targeting the fibroid.
2. Skin Folds
   • Obese patients often have skin folds, which can trap air. The trapped air causes shadows on the ultrasound image, interfering with visibility of the uterus and fibroid. This makes it more difficult to identify and treat the fibroid effectively.
3. Previous Surgeries and Scars
   • Scars from previous abdominal surgeries can distort the ultrasound image. This can impair the ability to visualize the uterus and fibroid accurately, making the procedure more challenging.
4. Location of the Fibroid
   • Fibroids located at the back of the uterus (posterior fibroids) are harder to see on ultrasound. Their position makes it more challenging to place the focal point of the HIFU beam accurately.
   • The maximum depth of the HIFU machine is 12 cm from the skin. If a fibroid is located deeper than this, it becomes difficult to position the focal point into the fibroid, limiting the effectiveness of the treatment.
   • Posterior fibroids are also closer to the pelvic nerves. Ablating these fibroids requires extra caution to prevent nerve damage.
5. Type of Fibroid
   • Highly vascular fibroids (those with increased blood flow) are more challenging to treat. The heat energy delivered by HIFU is dissipated by the blood flow, reducing its effectiveness in destroying the fibroid tissue.
   • Fibroids with certain types of degeneration, such as cystic or myxoid degeneration, contain excessive water. The water absorbs the heat, preventing it from effectively destroying the fibroid.
6. Multiple Fibroids
   • When a patient has several fibroids, it can be challenging to locate and target all of them. Treating multiple fibroids also requires significantly more energy.
   • In such cases, HIFU is typically focused on the largest fibroids causing symptoms. Additional sessions may be required to treat the remaining fibroids.
7. Pathway Obstruction
   • If the intestines lie in the pathway of the ultrasound beam, HIFU cannot be performed. Efforts may be made to push the intestines upward into the upper abdomen using a water balloon. However, if this cannot be achieved, HIFU cannot be offered to the patient.