Fallopian tube recanalisation and lipiodol: what the evidence says about tubal-factor infertility

Blocked fallopian tubes are one of the more treatable causes of infertility — and one of the more overlooked, given how much attention IVF receives by comparison. Tubal factors account for an estimated 25–35% of female infertility, and a proportion of these are proximal blockages that can potentially be opened without surgery. This is where fallopian tube recanalisation (FTR) comes in, and where a decades-old contrast agent, lipiodol, has found a genuinely evidence-backed second life.

What is fallopian tube recanalisation?

FTR is a minimally invasive, catheter-based procedure performed under fluoroscopic (X-ray) guidance, usually as a day case with no general anaesthetic required. A fine catheter is passed through the cervix and into the uterine cavity, and a smaller selective catheter is then guided into the opening of the affected fallopian tube. Gentle, controlled pressure and a guidewire are used to clear the proximal blockage — often caused by mucus plugs, debris, or spasm rather than true scarring.

It's typically offered to women who have a confirmed proximal tubal occlusion on hysterosalpingogram (HSG) or HyCoSy, otherwise normal pelvic anatomy, and no other major infertility factor. Success in restoring tubal patency is reported in the order of 85–90% of appropriately selected tubes, with a meaningful proportion of women conceiving naturally afterwards — avoiding, or at least delaying, the need for IVF.

Where lipiodol fits in

Lipiodol (ethiodised poppy seed oil) is an oil-based, iodinated contrast medium. It has been used in the fallopian tubes for close to a century, originally purely as a diagnostic HSG contrast agent to outline the uterine cavity and confirm tubal patency. What's kept it clinically relevant — and brought it back into focus over the last decade — is a separate, therapeutic observation: women who undergo an HSG or tubal flush with oil-based contrast appear to have meaningfully higher pregnancy rates afterwards than women who have the same test with water-based contrast.

In the context of FTR specifically, lipiodol is often used both to confirm successful recanalisation (a tubal spill of contrast on completion imaging) and, in the same sitting, to deliver this therapeutic flushing effect.

The evidence and rationale

The strongest evidence comes from the H2Oil trial, a multicentre randomised controlled trial across 27 centres in the Netherlands, published in the New England Journal of Medicine in 2017. Among 1,119 women undergoing HSG for infertility investigation, ongoing pregnancy within six months occurred in 39.7% of women who had oil-based contrast, compared with 29.1% of women who had water-based contrast — an absolute difference of roughly 10 percentage points, with adverse event rates low and similar between groups. Long-term follow-up of the same cohort has since confirmed the benefit extends to live birth rates, not just short-term pregnancy.

This built on smaller earlier trials and a 2020 Cochrane systematic review of tubal flushing, which likewise found that oil-based contrast was associated with higher rates of clinical pregnancy and live birth than water-based contrast or no flushing, without an increase in serious complications. An Australasian consensus statement (ACCEPT, endorsed by fertility specialist bodies) subsequently supported oil-soluble contrast as a reasonable option for tubal flushing in women with unexplained or mild tubal-factor infertility.

The mechanism isn't fully settled, and several complementary explanations are proposed:

• Mechanical flushing of fine mucus, debris, or endometrial cell clumps that can partially obstruct the tubes without showing up as a fixed occlusion.
• Immunomodulatory effects — lipiodol appears to alter local dendritic and macrophage cell populations in the endometrium, shifting the uterine lining toward a state more receptive to implantation.
• Anti-inflammatory effects on the peritoneal environment, which may be particularly relevant in women with mild endometriosis.

None of these fully explains the effect size on its own, and this is still an area of active research. But the clinical trial evidence for a benefit — independent of the mechanism — is now fairly robust.

Safety considerations

Oil-based contrast has a good safety profile in trials, but it isn't complication-free. The main considerations are:

• Iodine content — lipiodol contains a high concentration of iodine, so it should be used cautiously, or avoided, in women with known thyroid dysfunction, and thyroid function may need monitoring afterwards in at-risk patients.
• Intravasation — if contrast tracks into the venous or lymphatic system (more likely with excessive injection pressure or an already-damaged tube), there's a rare risk of pulmonary oil embolism. This is minimised by controlled, low-pressure technique and fluoroscopic monitoring.
• Iodine allergy — as with any iodinated contrast, prior allergy needs to be screened for.
• Cramping/pelvic discomfort during and shortly after the procedure is common but self-limiting.

Serious complications are uncommon when the procedure is performed by an experienced operator with appropriate patient selection.

Who might be a candidate

FTR with lipiodol is worth discussing for women with:

• A proximal tubal blockage identified on HSG or HyCoSy, with otherwise unremarkable pelvic imaging.
• Unexplained infertility, where tubal flushing alone may improve natural conception rates.
• A preference to try a lower-cost, lower-intervention option before proceeding to IVF.

It isn't a replacement for IVF in women with distal tubal disease, significant male-factor infertility, or other major fertility barriers, and a clear diagnostic workup beforehand is essential to select the right candidates.

The takeaway

Fallopian tube recanalisation is a well-established, minimally invasive option for proximal tubal-factor infertility, and the choice of contrast used during the procedure isn't incidental — it's backed by randomised trial evidence showing a genuine improvement in pregnancy and live birth rates when oil-based (lipiodol) contrast is used. For the right patient, it's a low-risk step worth considering before, or alongside, other fertility treatment.

• Dreyer K, et al. Oil-Based or Water-Based Contrast for Hysterosalpingography in Infertile Women. N Engl J Med. 2017;376:2043-2052.
• Wang R, et al. Tubal flushing for subfertility. Cochrane Database Syst Rev. 2020.
• van Rijswijk J, et al. Tubal flushing with oil-based or water-based contrast at hysterosalpingography for infertility: long-term reproductive outcomes of a randomized trial. Fertil Steril. 2020.
• Australasian CREI Consensus Expert Panel on Trial evidence (ACCEPT). The use of oil-soluble contrast media for tubal flushing in infertility: a consensus statement. Aust N Z J Obstet Gynaecol. 2020.
• Fatum M, et al. Pregnancy outcomes after fallopian tube recanalization: oil-based versus water-soluble contrast agents. J Vasc Interv Radiol. 2002.