Thermal bowel injury after ultrasound-guided high-intensity focused ultrasound treatment of uterine adenomyosis

Adenomyosis can have a significant impact on the quality of life of women of reproductive age. Increasing importance of uterine preservation and advances in technology have resulted in the emerging use of minimally invasive treatment options, including high-intensity focused ultrasound (HIFU) therapy. HIFU involves the use of an extracorporeal source of focused ultrasonic energy to cause coagulative necrosis of the target tissue without damage to the adjacent organs, thereby reducing the size of the uterine mass and the associated symptoms1-4. A 46-year-old woman, who had a 3-year history of heavy menstrual bleeding, underwent ultrasound-guided HIFU for a 12-week size uterus of 10 × 9 × 6 cm with posterior uterine wall adenomyosis (Figure 1). She had no history of abdominal or pelvic surgery. She was given pretreatment mechanical bowel preparation. HIFU was performed by the senior author (V.Y.T.C) who obtained the Model-JC HIFU Tumor Therapeutic System Certificate of Clinical Training Level C from the HIFU Training Base of China, Chongqing, China in 2011 and since then has performed over 30 HIFU treatments without major complications (Society of Interventional Radiology Standards of Practice Committee Classification of Complications by Outcome Class C or above, unpublished data). Using the JC HIFU system (Chongqing Haifu Technology, Chongqing, China) under intravenous sedation, the treatment was completed in 113 min with a sonication time of 1518 s. A total of 614 335 J of energy was delivered. During HIFU, a water balloon was used to displace the bowel out of the pelvis. No skin burn was noted after the treatment. In our center, post-treatment non-perfused volume measurement was not done routinely as magnetic resonance imaging was not available readily. Eight days after HIFU, the patient developed acute abdominal pain with peritoneal signs, hypotension and tachycardia. Computed tomography showed pneumoperitoneum, with free gas seen mostly in the perigastric area. There was no evidence of dilated bowel, ascites or pelvic collection (Figure 2). Laparotomy showed a 1-cm necrotic area with a perforation in a segment of inflamed small bowel 40 cm from the ileocecal valve (Figure 3), which was resected with primary anastomosis of bowel vessels. No pelvic–peritoneal adhesions or evidence of endometriosis were noted. She recovered well and was discharged 11 days after the laparotomy. Her first period was light and painless. To our knowledge, only two other cases of thermal bowel injury have been reported following ultrasound-guided HIFU; one had tissue ablation reaching the outer wall of the uterus and the other had possible reflected energy from a calcified fibroid; both patients presented 10–20 days after HIFU therapy5. Although HIFU has been used widely in China for the treatment of adenomyosis2, 5-7, the clinical application of this treatment modality in most other countries is still considered novel. We believe that reporting on a case with a complication is important for enhancing experience. In our opinion, this case illustrates the following practical messages: (1) HIFU causes tissue ablation at a temperature of only 56–90 °C and, therefore, bowel perforation following HIFU is generally subtle and delayed, and may not be obvious on computed tomography; and (2) on review of the computed tomography (Figure 4), the ablated area can be close to the serosa, suggesting that the treatment might be overly extensive. These messages stress the importance of the physician's experience in avoiding and recognizing bowel injury when performing HIFU treatment.