Tubal flushing: A fertility boost or just a flush?

The therapeutic potential of tubal flushing has been debated for over seven decades and remains a topic of considerable interest today.

The concept of tubal flushing dates back to the early 20th century. The procedure was first used by Rindfleisch in 1910 to evaluate the uterine cavity to detect abnormalities of the uterus such as fibroids, polyps and adhesions. By 1914, Cary had expanded its use to assess whether or not the fallopian tubes were open using collergol, a silver-based contrast medium. Although widely used for diagnostic purposes, the idea that tubal flushing might enhance natural conception rates wasn't seriously explored until the mid-20th century, when it was suggested it could potentially improve conception rates in the months proceeding.

Today, tubal flushing is performed using several techniques, including hysterosalpingography (X-ray dye test), hysterosalpingo-contrast sonography (ultrasound dye test using contrast), hysterosalpingo-foam sonography (ultrasound dye test using foam)and laparoscopy with dye testing. Different contrast media are employed, either water-based or oil-based but the primary aim is to assess for tubal patency.

Numerous studies have compared the effects of different contrast media for tubal flushing. Notably, the Water versus Oil (H2Oil) study, published in the New England Journal of Medicine in 2017, remains one of the largest randomised controlled trials (see BioNews 904). This multicentre trial found that hysterosalpingography with oil-based contrast medium (Lipiodol® Ultra-Fluid) resulted in a ten percent higher ongoing pregnancy rate within six months compared to water-based contrast. Subsequent systematic reviews with meta-analyses confirmed the benefits of oil-based contrast media on pregnancy and live birth rates, while water-based media did not show similar effects.

At this year's annual meeting of the European Society of Human Reproduction and Embryology (ESHRE) in July 2024, we heard two presentations on the therapeutic potential of tubal flushing. The first, from the H2Oil Timing study, investigated whether tubal flushing with oil-based contrast shortens the time to pregnancy in women with unexplained infertility, potentially reducing the need for invasive fertility treatments. This multicentre trial conducted in the Netherlands involved 577 women randomised to immediate or delayed hysterosalpingography by six months (see BioNews 1247). With a median age of 30 and a median infertility duration of 17 months in both groups, the study found no difference in clinical pregnancy rates.

Researchers concluded that early tubal flushing with oil-based contrast does not shorten the time to ongoing pregnancy in women with unexplained infertility and a favourable prognosis for natural conception. The differing results between the H2Oil trial and H2Oil Timing may be due to the latter's focus on low-risk, high-prognosis women with shorter infertility durations and no risk factors for tubal disease such as endometriosis and previous pelvic infections. Thus participants in the H2Oil Timing study already had  a high likelihood of spontaneous conception.

The second study presented by Dr Yan compared the effects of oil-based and water-based contrast agents on fertility outcomes in low-risk women with unexplained infertility and high-risk women with ovulatory dysfunction, such as anovulatory PCOS or tubal disease. This large single-centre study with 1187 participants found that, among low-risk women with unexplained infertility, oil-based contrast was associated with a significantly higher clinical pregnancy rate compared to water-based contrast. However, this difference was not observed in the high-risk population.

These studies have contributed valuable insights into the therapeutic potential of tubal flushing, though many questions remain. If tubal flushing with oil-based contrast enhances fertility, which specific subgroups of women benefit most, and when is the optimal time to perform the procedure? The forthcoming H2Oil2 study aims to address these questions by evaluating the effectiveness of oil-based versus water-based contrast agents in three subgroups: women aged 39 and over, those with ovulatory disorders, and those at high risk for tubal pathology. This international multicentre study, conducted in the Netherlands and the UK, hypothesises that oil-based contrast will improve ongoing pregnancy rates in all three subgroups.

Tubal flushing has evolved from a purely diagnostic tool to one with significant therapeutic potential in reproductive medicine. The growing body of evidence supporting the fertility-enhancing effects of tubal flushing, especially with oil-based contrast media, highlights its value as a treatment option for women with unexplained infertility and other reproductive challenges. In an era when IVF is sometimes considered the only therapeutic option for infertility, it is important for us to remember that many patients will value an intervention that could improve their chances of natural conception.