Uterine rupture after high-intensity focused ultrasound ablation of adenomyosis: a case report and literature review

Abstract Aim High-intensity focused ultrasound (HIFU) is a non-invasive treatment of adenomyosis. Uterine rupture during pregnancy is a rare adverse event after HIFU treatment, because HIFU treatment results in tissue coagulative necrosis. Methods We reported a case of uterine rupture in a 34-year-old woman. The woman had HIFU treatment for adenomyosis eight months before unplanned pregnancy. She was closely monitored during the pregnancy and the antenatal course was uneventful. At the gestational age of 38 weeks and 2 days, an emergency lower segment cesarean section was performed because of inexplainable abdominal pain. After delivery of the fetus, a 2 × 2 cm serous membrane rupture was observed in the HIFU treatment area. Conclusion Uterine rupture during pregnancy after HIFU is a rare adverse event, however, attention is required during the whole pregnancy in case of unexpected uterine rupture.


Introduction
Adenomyosis is a common gynecological disease that occurs in 8.8%-61.5% of women undergoing hysterectomy, with an estimated prevalence ranging between 20% and 34% [1,2].Surgical treatments such as hysterectomy and hormonal treatments such as oral contraceptive pills are traditional treatments of adenomyosis.High-intensity focused ultrasound (HIFU) is a noninvasive technique that results in tissue coagulative necrosis using highly focused ultrasound energy [3].Currently, HIFU is wildly used for treatment of adenomyosis in women who want to retain their uterus or wish to preserve fertility [4][5][6][7].
Pregnancy outcomes after HIFU in women of reproductive age have been assessed for several years because the procedure may lead to local tissue weakness, which may result in uterine rupture during pregnancy [8][9][10][11].To date, only a few cases of uterine rupture have been reported following HIFU treatment [10,11].Herein, we report a case of spontaneous uterine rupture during late pregnancy after HIFU treatment of adenomyosis eight months before an unplanned pregnancy.

Case presentation
The study was performed in accordance with the Declarations of Helsinki and approved by the ethics committee of West China Second University Hospital, Sichuan University (IRB Approval Number: 046).Written informed consent for publication of their details was obtained from the patient.
A 34-year-old woman, G2P2, with a nine-year history of worsening dysmenorrhea visited our hospital.The patient had two successful pregnancies with no complications, 12 and 10 years prior, both ended in cesarean section.
Bimanual examination revealed an enlarged uterus.Additionally, pelvic magnetic resonance imaging (MRI) revealed an enlarged uterus with a 70.1 Â 44.0 Â 63.0 mm distinct thickened lesion on the anterior wall (Figure 1(A, B)).No remarkable findings were observed in the remaining pelvic regions.On the basis of her symptoms and imaging findings, the patient was diagnosed with adenomyosis.The patient had no desire for fertility but wanted uterus-sparing treatment.
After evaluating the safety of HIFU treatment of adenomyosis, HIFU was administered under intravenous sedation.HIFU ablation was performed in the prone position for 71 min.The real ablation time was 560 s, and the mean power of the beam was 400 W. Since the patient was young and had no desire for fertility, the treatment was performed in a relatively aggressive manner, and the distances between the focal point to the endometrium and the serosal layer were both less than 1.0 cm.Except for skin pain, no adverse events occurred during HIFU treatment.Contrast-enhanced ultrasound revealed a 56.4 Â 40.0 Â 45.3 mm non-perfused area (Figure 1(C, D)) immediately after treatment and the non-perfused volume (NPV) ratio was 52.59%.The patient was discharged from the hospital 3 days post treatment in good health.Three courses of gonadotropin-releasing hormone agonists (GnRH-a) were administered every 28 days to treat residual adenomyosis after HIFU.Three months after HIFU treatment, pelvic MRI revealed a 44.0 Â 27.2 Â 33.8 mm lesion in the anterior uterine wall, without signal enhancement after contrast injection (Figure 1(E, F)), which indicated necrotic region in the uterine anterior wall after HIFU.
Unexpectedly, an unplanned pregnancy occurred eight months after HIFU treatment.Due to the aggressive HIFU treatment and short interval time between pregnancy and HIFU, potential uterine abruption during pregnancy was emphasized.However, the patient insisted on preserving the fetus.Since there was no relevant experience to rely on in such a situation, the emphasis on uterine rupture was maintained throughout pregnancy in cases of emergent uterine rupture.The antenatal course was uneventful.Ultrasound scans showed anterior adenomyosis and posterior placenta.The patient was asked to stay near the hospital after a gestational age of 37 weeks in case of medical emergencies such as uterine rupture, as the uterine tension increased with fetus growth.At the gestational age of 38 weeks and 2 days, the patient was admitted to the hospital with slight but continuous abdominal pain.Fetal monitoring results were unremarkable.An emergency lower segment cesarean section was performed because uterine rupture could not be excluded.
After the delivery of a 2960 g fetus and a 520 g placenta, a 5 Â 6 cm uterine defect with only a serous membrane was found in the anterior wall.Furthermore, a 2 Â 2 cm serous membrane rupture was observed (Figure 2).Gray tissue (5 Â 4 Â 3 cm) was observed in the uterine cavity.Pathologically, the gray tissue found in the uterine cavity was necrotic tissue, which was highly suspected of necrotic adenomyotic tissue after HIFU (Figure 3).The patient was discharged from the hospital three days postoperatively and recovered well.No complications were reported in the newborn.

Discussion
Introduced by Lynn et al. in the 1940s [12], thermal ablation has become a popular therapeutic option for treating bone, liver, pancreatic, breast, and kidney cancers [13].An increasing number of studies have demonstrated the safety and effectiveness of HIFU in destroying tumor tissue without damaging the surrounding tissues using ultrasound-or MRIguided high-intensity ultrasound energy [14][15][16].
To inhibit the growth of residual lesions after HIFU and relieve symptoms, a GnRH-a or levonorgestrel-releasing intrauterine system (LNG-INS) was applied.One study evaluated the combined efficacy of HIFU, GnRH-a, and LNG-IUS in the treatment of severe adenomyosis.Patients were administered GnRH-a at day one, one month, and three months after HIFU treatment, and LNG-IUS was performed when the uterine length was less than 9 cm.The study found that combined treatment significantly relieved dysmenorrhea and menorrhagia.It induced uterine shrinkage [21].Another study compared the treatment efficacy of HIFU alone, HIFU combined with LNG-IUS, and HIFU combined with GnRH-a.At six and 12 months after HIFU treatment, the dysmenorrhea score, menstrual blood volume, uterine volume, and adenomyotic lesion volume decreased significantly more in the HIFU/LNG-IUS and HIFU/GnRH-a groups than in the HIFU group [22].
The adverse events associated with HIFU treatment include skin burns; vaginal discharge or bleeding; intrauterine infection; lower abdominal pain; leg pain; urinary retention; acute renal failure; intestinal perforation; deep vein  thrombosis; pubic symphysis injury; post-HIFU thrombocytopenia; sciatic nerve injury; and hydronephrosis [23].
Uterine rupture is the major complication for patients who try to have vaginal birth after cesarean sections.Uterine rupture during trial of labor after a single cesarean section is estimated to be 0.2-0.8%,and after two or more it is estimated to 1.8% [24,25].In patients who had previous adenomyomectomy, 2.8-12.5% patients suffered from uterine rupture during pregnancy at any gestational age [26,27].Sugiyama et al. reported elective or emergent cesarean section in 10 patients who had previous adenomyomectomy.Although no uterine rupture occurred, myometrial thinning was observed in three patients at the site of previous adenomyomectomy [28].
Uterine rupture is a rare adverse event that occurs during pregnancy in women with a history of HIFU treatment.Ricabinovi et al. reported that a patient conceived spontaneously three menstrual cycles after HIFU treatment (NPV ratio was 39.29%) and she successfully had a full-term healthy baby through vaginal delivery [29].In a study by Zhou et al. 54 out of 68 patients conceived at a median interval time of 10 months after HIFU treatment and 21 of them delivered healthy babies, without uterine rupture occurred [30].Li et al. reported a spontaneous uterine rupture at 38 weeks of gestation after HIFU for an anterior wall leiomyoma 8.2 cm in diameter 20 months before pregnancy [10].Lai et al. reported a uterine rupture at 37 weeks of gestation; the patient received HIFU treatment for fibroids and adenomyosis 13 months prior to in vitro fertilization [11].In our reported case, the patient already had two healthy children, and she had no desire for fertility anymore.Therefore, HIFU treatment was relatively aggressive performed to avoid recurrence, which resulted in weakness of the uterine wall and uterine rupture during pregnancy.Since only a few cases of uterine rupture after HIFU have been reported, the risk factors for uterine rupture remain unclear.It leads to the fact that every pregnancy after HIFU should be closely monitored.HIFU treatment results in tissue coagulation necrosis.Therefore, careful attention should be paid to pregnant women with twins, polyhydramnios, and macrosomia as uterine tension increases in these women.Whether patients had previous cesarean section were more vulnerable for uterine rupture remains unknown due to the very few cases that have been reported.
The preferred gestational age for delivery and indications for vaginal delivery or cesarean section remain controversial.However, various studies have indicated the safety of vaginal delivery in women with previous HIFU treatment [8,9].Based on our experience, patients with unplanned pregnancies after aggressive HIFU treatment should reduce activities in late pregnancy and live close to the hospital in case of medical emergencies.Pelvic MRI during the third trimester may be helpful for evaluating the thickness of the uterine wall, particularly the ablated area by HIFU treatment.It is necessary to admit to hospital when uterine contractions were observed.Inexplainable abdominal pain and fetal intrauterine distress could be signs of uterine rupture.After delivery to the fetus and placenta, the entire uterus, specifically the areas receiving HIFU treatment, should be carefully examined for local weakness or rupture.
Further studies are required to ensure the safety and efficacy of HIFU treatment of adenomyosis in women who wish to preserve their uteri and fertility.

Figure 1 .
Figure 1.Magnetic resonance imaging of the uterus before HIFU treatment (A, B) and 3 months after HIFU treatment (E, F).Contrast-enhanced ultrasound immediately after HIFU treatment (C, D).HIFU: high-intensity focused ultrasound.

Figure 2 .
Figure 2. Full-thickness defect in anterior uterine wall (arrow) noticed during cesarean section.

Figure 3 .
Figure 3. Necrotic tissue found in the uterine cavity during cesarean section.