The most frequent side effects of MR-HIFU treatment include slight discomfort and pain, but the level of severity of these effects is usually low. One of the most frequently reported complaints among patients is the discomfort caused by lying on their stomach on the scanner for a prolonged period. The HIFU beam can also cause pain during the treatment — particularly if therapy cells are positioned close to the fibroid capsule.
The fibroid tissue itself is not innervated. Some patients report stimulation of the sciatic nerve or other nerves as a result of the interaction between the ultrasonic energy and the nerve tissue. Monitoring during the intervention and continuous communication with the patient is critical to ensuring that no permanent damage is caused.
Coagulation of the fibroid tissue occurs immediately with MR-HIFU-guided heating. There were initially concerns that patients may experience pain in the weeks following MR-HIFU treatment, which would be similar to the pain experienced due to uterine artery embolization syndrome. Fortunately this is not the case with MR-HIFU and this type of pain has been reported in only a very small number of cases, where the supply vessels to the fibroid were coagulated.
MR-HIFU is generally a safe method for treating uterine fibroids. The most common side effects of MR-HIFU treatment of uterine fibroids include discomfort and pain, though these effects are considered to be minor. The number of serious adverse events (SAE) is low and it has been shown that this number falls as the experience of the operator increases. As the number of studies on MR-HIFU has increased, preventive action has also been taken to reduce side effects and to completely eliminate SAE.
When considering the side effects of uterine fibroid therapy, effects that may occur not only during the treatment but also between the intervention and recovery must be taken into account. The recovery period associated with MR-HIFU is shorter than with other uterine fibroid treatments. In contrast to a hysterectomy, which can have a total recovery time of six weeks, the majority of patients treated with MR-HIFU are able to continue their normal daily activities or go back to work within 1–2 days of treatment.
Patients may experience fatigue and back pain following treatment, but this can generally be treated with over-the-counter painkillers. Interventions usually take up to three hours and, in isolated cases, interventions of up to five hours have been reported. Long treatment times increase the likelihood of discomfort and subsequent pain. Less frequent and minor complications include diarrhea in 3 out of 42 patients, as well as nausea; both of these effects are likely to have been caused by the opioids administered after the treatment.
The most severe complications, which occur only rarely, include persistent leg and buttock pain as well as skin burns. Reported case of persistent leg and buttock pain has been connected to heating of the sciatic nerve.
However, contrary to initial concerns and despite the patient's discomfort, no intrinsic nerve damage was found during MR neurography or electromyography. As a result of this case, the therapy procedure was changed. Symptoms have reduced in all reported cases.
In rare cases, skin burns have occurred during the use of MR-HIFU. Most cases involved minor first degree burns, often as a result of incomplete hair removal or due to air bubbles that formed between the gel cushion and the patient's skin. Most of the burns that have been reported occurred during the early stages of this technique. Over 9000 women have since been treated with MR-guided HIFU around the world. This type of burn can also be avoided using the MR-guided temperature monitoring on multiple planes, which is integrated in the Philips Sonalleve, and with careful monitoring of near field temperature images during treatment.
The rate of recurrence of fibroids that have been treated with MR-guided HIFU has been face evaluated up to 24 months after intervention. The results show that the rate of recurrence is lower than or comparable tothe rate with other uterus-preserving therapies. The reported rate of recurrence was 7.4% after 12 months, 14% for type 1/2 fibroids and 21.7% for type 3 fibroids after 24 months. Follow-up data after 5 years is still being collected. The reported cumulative rate of recurrence after 5 years is 32% for uterine arteryembolization and 5.7–33% for myomectomy.
During HIFU treatment, the ovaries must be protected by keeping the path of the ultrasonic beam away from them. In addition, every temperature change is monitored during the treatment in real time.
The fibroid continues to shrink for one year following ablation, but the majority of the shrinkage occurs in the first six months. The amount of fibroid shrinkage from the starting value is heavily dependent on the extent of ablation achieved during the treatment.
The endometrium is not damaged during the treatment and the necrotized area remains in the intact fibroid sac and therefore does not come into contact with the surrounding tissue. Although fever has been reported in 5–6% of cases, there have been no reports of infection in the necrotized areas.
