Utility of hysterosalpingo-contrast sonography with Sonazoid®: a single-center experience

Jun Kitazawa: Writing – review & editing, Writing – original draft, Resources, Project administration, Investigation, Formal analysis, Conceptualization. Hiromi Kawaguchi: Writing – review & editing, Resources. Izumi Suganuma: Writing – review & editing, Resources. Kounosuke Suzuki: Writing – review & editing, Resources. Koichi Takebayashi: Writing – review & editing, Supervision, Project administration, Methodology, Formal analysis, Conceptualization.

This study was approved by the institutional ethics committee, and an opt-out approach was employed.

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Patients who attended our clinic for infertility treatment were evaluated. At our clinic, HyCoSy is performed as part of our infertility screening for nearly all patients who wish to conceive naturally. HyCoSy was performed between the end of menstruation and ovulation. Before examination, the absence of bacterial vaginosis and chlamydia infection was confirmed. All patients were informed that the use of perflubutane for HyCoSy constituted an off-label application, and written informed consent regarding the safety of the agent was obtained. This study was approved by our hospital’s ethics committee, which adopted an opt-out policy (Takebayashi Women’s Clinic Ethics Committee, Approval No. 0055). Fig. 1 presents the materials needed for the examination. Except for the use of Sonazoid® (perflubutane; GE HealthCare, Chicago, IL, USA) as the contrast agent, the procedure requires equipment similar to that used in conventional HSG. Fig. 1 Supplies for use with HyCoSy. Supplies for use with HyCoSy. The examination was performed as follows: 1. Following vaginal disinfection, an 8-Fr balloon catheter was inserted into the uterine cavity, and the balloon was filled with 0.4–0.5 mL of sterile water. 2. Under transvaginal ultrasonographic guidance, saline was infused into the uterine cavity to confirm the absence of leakage into the vagina and evaluate intrauterine lesions, such as endometrial polyps. 3. After achievement of an appropriate uterine section, a solution prepared by diluting one vial (16 μL) of Sonazoid in 100 mL of saline was slowly infused into the uterine cavity. Then, evaluation of tubal patency and intraperitoneal spillage was conducted via color Doppler imaging. 4. After balloon deflation, the uterine cavity was flushed using saline, and the catheter was removed. Following vaginal disinfection, an 8-Fr balloon catheter was inserted into the uterine cavity, and the balloon was filled with 0.4–0.5 mL of sterile water. Under transvaginal ultrasonographic guidance, saline was infused into the uterine cavity to confirm the absence of leakage into the vagina and evaluate intrauterine lesions, such as endometrial polyps. After achievement of an appropriate uterine section, a solution prepared by diluting one vial (16 μL) of Sonazoid in 100 mL of saline was slowly infused into the uterine cavity. Then, evaluation of tubal patency and intraperitoneal spillage was conducted via color Doppler imaging. After balloon deflation, the uterine cavity was flushed using saline, and the catheter was removed. Fig. 2 presents representative imaging findings. For transverse observation, the transvaginal probe was positioned at the uterine level and adjusted to visualize the uterine cornua and surrounding tissues ( Fig. 2 A). For sagittal observation, contrast was infused while monitoring the uterine midline, and the probe was slowly shifted laterally to trace the course of the fallopian tubes ( Fig. 2 B). Fig. 2 Transvaginal ultrasound images during HyCoSy. (A) Transverse view. Diluted Sonazoid is shown flowing through the fallopian tubes (red arrows), with subsequent spillage into the peritoneal cavity (blue arrows). (B) Sagittal view. By moving the transvaginal probe laterally from the uterine midline, the flow of the diluted Sonazoid within the fallopian tubes can be visualized (red arrows). (C) Right pelvic cavity. The diluted Sonazoid spilled from the fallopian tubes is seen spreading around the right ovary, demonstrating a moscaic pattern (yellow arrows). Transvaginal ultrasound images during HyCoSy. (A) Transverse view. Diluted Sonazoid is shown flowing through the fallopian tubes (red arrows), with subsequent spillage into the peritoneal cavity (blue arrows). (B) Sagittal view. By moving the transvaginal probe laterally from the uterine midline, the flow of the diluted Sonazoid within the fallopian tubes can be visualized (red arrows). (C) Right pelvic cavity. The diluted Sonazoid spilled from the fallopian tubes is seen spreading around the right ovary, demonstrating a moscaic pattern (yellow arrows). When diluted Sonazoid was infused into the uterine cavity, color flow from the uterus to the peritoneal cavity was observed in patients with tubal patency. The mosaic-like echogenic patterns of Sonazoid in the peritoneal cavity enabled the evaluation of the presence or absence of intraperitoneal adhesions ( Fig. 2 C). Contrarily, in patients with bilateral tubal obstruction, color flow was observed only within the uterine cavity. A retrospective analysis was conducted using medical records to summarize the test results and pregnancy outcomes until December 2024 for patients who underwent HyCoSy at our clinic between May 2023 and December 2023.

During the study period, 100 patients underwent HyCoSy using Sonazoid. Table 1 presents the history of the patients. Bilateral tubal patency was confirmed in 94 patients, unilateral patency in 5, and bilateral tubal occlusion in 1. Table 2 lists the patients in whom the patency of both fallopian tubes could not be confirmed. These patients presented with risk factors for fallopian tube obstruction, including a history of abdominal surgery, chlamydia infection, or endometriosis. One patient experienced mild abdominal pain during the procedure; no other adverse events occurred. In most cases, a total volume of 10–20 mL was sufficient once the operator became familiar with the technique. Table 1 Baseline characteristics of patients undergoing HyCoSy. Patients(n = 100) Age(years), mean±SD 33.6 ± 4.6 Multipara, n 24(24%) History of laparotomy, n 8(8%) Chlamydia antibody positive, n 15(15%) Cause of infertility  Endometriosis, n 8(8%)  PCOS, n 6(6%)  Tubal factor, n 3(3%)  Ovarian factor, n 5(5%)  Cervical factor, n 5(5%)  Uterine factor, n 2(2%)  Immune factor, n 2(2%)  Sexual dysfunction, n 1(1%)  Unexplained infertility, n 48(48%) n, number of participants Table 2 Baseline characteristics of patients with tubal obstruction. Case Results of HyCoSy History of laparotomy Chlamydia antibody positive Endometriosis Pregnancy outcomes after HyCoSy 1 Unilateral obstruction Laparoscopic Adnexectomy No No No 2 Unilateral obstruction None No No Yes (timed intercourse) 3 Unilateral obstruction Appendectomy No No No 4 Unilateral obstruction Laparoscopic myomectomy No No Yes (in vitro fertilization) 5 Unilateral obstruction None Yes No Unknown (lost to follow-up) 6 Bilateral obstruction None Yes Yes Yes (in vitro fertilization) Baseline characteristics of patients undergoing HyCoSy. Baseline characteristics of patients with tubal obstruction. A total of 10 patients were not followed up as they transferred to other hospitals or discontinued their visits. For the remaining 90 patients, the course of infertility treatment following HyCoSy was reviewed, and 24 patients conceived through timed intercourse, 7 through intrauterine insemination, and 32 through in vitro fertilization. At our clinic, artificial insemination is performed in cases with abnormal semen analysis results, a negative Huhner test result, or sexual dysfunction. For other patients, advancing to in vitro fertilization (IVF) is recommended if pregnancy is not achieved after approximately 6 months of timed intercourse therapy. If fallopian tube obstruction is detected by HyCoSy, timed intercourse for approximately 6 months followed by progression to IVF in cases of unilateral obstruction is recommended. In cases of bilateral obstruction, tubal reconstruction or IVF is recommended.

We focused on the use of Sonazoid as a safe and simple method for evaluating fallopian tube patency and summarized the testing procedure and results. In Japan, FemVue® (Bayer AG, Leverkusen, Germany) is commonly used for HyCoSy; however, concerns have been raised regarding the need to use the solution within minutes of preparation and the potential pain caused by air bubbles entering the abdominal cavity. To address these concerns, we focused on Sonazoid, which offers a high safety profile and can be used for a longer duration following preparation. Sonazoid is composed of microbubbles containing poorly soluble perflubutane gas encapsulated by an egg-yolk–derived lipid shell [ 1 ]. Perflubutane is ultimately excreted via expiration, and the lipid shell is metabolized via normal lipid pathways, posing no renal burden. Perflubutane has been widely utilized in contrast-enhanced ultrasonography for hepatic tumors and breast lesions to distinguish between benign and malignant lesions, evaluate tumor extent, and assess therapeutic response [ 2 , 3 ]. More recently, perflubutane has also been used in the detection of sentinel lymph node in melanoma and the differentiation of endometrial cancer from benign gynecological lesions [ 4 , 5 ]. The use of iodine-based contrast agents in HSG raises several safety concerns. First, contrast media injected into the uterine cavity may enter myometrial vessels or lymphatics, with reported frequencies ranging from 0.4% to 6.9% [ 6 ]. Although usually clinically insignificant, there have been reported cases of embolic events affecting the brain, lungs, and retina after intravascular migration of oil-based contrast agents [ [7] , [8] , [9] ]. In contrast, perflubutane was originally designed for intravenous administration and is excreted via expiration, rendering intravascular entry clinically acceptable. Second, iodine-based contrast agents are reportedly associated with long-term intraperitoneal retention and inflammatory reactions. Oil-based agents are slowly absorbed from the fallopian tubes and peritoneum and may remain encapsulated in the abdominal cavity for prolonged periods. Granuloma formation and complications caused by the use of intraperitoneal iodine contrast have also been reported [ 10 ]. Finally, iodine-based contrast agents potentially affect thyroid function. The incidence rates of subclinical hypothyroidism following HSG have been reported to be 22.6% and 9.5% with oil-based and water-soluble agents, respectively [ 11 ]. Although adverse effects on neonates following pregnancy after HSG have not been clearly established, caution is warranted [ 12 ]. Perflubutane does not pose these risks, making it a reassuring option for tubal evaluation. Compared with conventional HSG, HyCoSy has several advantages, including higher safety, rapid assessment, absence of radiation exposure, and low incidence of allergic reactions [ 13 ]. The diagnostic accuracy has also been suggested to be comparable to that of laparoscopy [ 14 ]. However, HyCoSy also has limitations, such as reduced image clarity owing to the tortuous course of the fallopian tubes and the need for skilled techniques to promptly capture the uterus and tubes [ 15 ]. To overcome these limitations, three- and four-dimensional HyCoSy using SonoVue® (Bracco Imaging, Milan, Italy)　has been reported; however, specialized ultrasound equipment and software are required [ 15 , 16 ]. Contrarily, HyCoSy using perflubutane can be performed in many facilities equipped with a transvaginal probe and color Doppler function. One limitation of this technique is the difficulty in accurately identifying the site of tubal stenosis. Furthermore, detailed observation of perflubutane-induced color flow in standard ultrasound modes is challenging. In our practice, using a Voluson Signature 18 system (GE HealthCare, Chicago, IL, USA), we optimize image quality by increasing magnification, using compound scanning to reduce artifacts, increasing pulse repetition frequency to avoid aliasing, and adjusting the wall motion filter and color gain to minimize noise. These adjustments improve image clarity. In other words, in resource-limited settings where adjustment of the ultrasound parameters as described above is difficult, or when the procedure is performed by an inexperienced operator unable to visualize the entire course of the fallopian tube from the uterine cavity to the fimbrial end using ultrasound, a HyCoSy examination using Sonazoid may not enable an adequate assessment. As Sonazoid contains egg-yolk components, it should not be used in patients with egg allergy. A limitation of this report is that the results of fallopian tube patency assessment using HyCoSy with Sonazoid were not validated against other methods, such as conventional HSG or laparoscopy. As fallopian tube disorders are associated with 30%–40% of female infertility cases, the results from our institution—five cases of unilateral fallopian tube obstruction and one case of bilateral fallopian tube obstruction—may reflect a bias in the patient population. In the future, the sensitivity and specificity of HyCoSy should be evaluated by comparing its results with those obtained using other methods of fallopian tube patency assessment. Furthermore, although almost no adverse events were observed among the 100 cases included in this study, the single-center design and small sample size may have prevented sufficient assessment of rare adverse events. We plan to evaluate more cases and conduct collaborative studies with other institutions in the future.

HyCoSy using perflubutane is a highly safe and simple method for tubal patency evaluation, avoiding radiation exposure and adverse effects on thyroid function. As tubal patency evaluation is typically the initial examination conducted in women attempting to conceive, clinicians should strive to reduce the risks to fertility and ensure patient safety. Perflubutane-based HyCoSy is an excellent option for this purpose.

During the preparation of this work, the authors did not use generative AI or AI-assisted technologies in the writing process. The authors take full responsibility for the content of this publication.

The fallopian tubes play a pivotal role in natural conception, including sperm transport, oocyte pick-up, fertilization, and embryo transport. Tubal factors are estimated to account for approximately 30%–40% of female infertility. As tubal obstruction is often asymptomatic, it is commonly diagnosed only after infertility is identified. Therefore, early tubal patency evaluation is crucial for women desiring pregnancy. Hysterosalpingography (HSG) is widely used as the first-line method for tubal patency evaluation. In addition to detecting tubal stenosis or hydrosalpinx, HSG enables assessment of intrauterine abnormalities, such as endometrial polyps, uterine septa, and intrauterine adhesions as well as peritubal adhesions based on the intraperitoneal spread of contrast media. However, the oil-based and water-soluble contrast agents utilized in HSG are iodine-based, raising concerns about iodine hypersensitivity reactions and potential adverse effects on maternal and fetal thyroid function. Furthermore, exposure of the gonads to radiation is unavoidable. To achieve a safe and simple approach for tubal patency evaluation, we performed hysterosalpingo-contrast sonography (HyCoSy) using perflubutane as the ultrasound contrast agent. This study introduces the HyCoSy procedure using perflubutane, reports the clinical outcomes at our institution, and evaluates the safety of the examination.

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.