Published on:
March 20, 2026
When couples face difficulties conceiving, one of the most important investigations involves checking whether the fallopian tubes are open and functioning correctly. Fallopian tube patency — the term used to describe whether the tubes are unblocked and allow free passage of eggs and sperm — is a critical factor in natural conception. Impaired tubal patency accounts for up to 35% of all cases of subfertility and infertility, making it one of the most common causes of difficulty conceiving.
The fallopian tubes serve as the vital passageway where fertilisation occurs. Each month, an egg released from the ovary travels through the fallopian tube, where it may encounter sperm and become fertilised before moving into the uterus for implantation. If one or both tubes are blocked — whether by scar tissue, adhesions, endometriosis, or previous infection — this natural process is disrupted, significantly reducing the chances of pregnancy.
For anyone undergoing an infertility investigation, assessing fallopian tube patency is typically one of the first-line tests recommended. Early detection of tubal problems allows clinicians to advise on the most appropriate treatment pathway, whether that involves further intervention to clear a blockage or proceeding directly to assisted reproduction techniques such as IVF.
There are several methods available to assess whether the fallopian tubes are patent (open). The two most widely used outpatient procedures are hysterosalpingography (HSG) and hysterosalpingo-contrast sonography (HyCoSy). Both tests aim to determine whether contrast material can pass freely through the tubes, indicating they are unblocked, but they differ significantly in how they achieve this.
HSG has been the traditional method for assessing tubal patency for decades. During an HSG, a thin catheter is inserted through the cervix into the uterus, and an iodine-based contrast dye is injected. X-ray fluoroscopy is then used to capture real-time images as the dye fills the uterine cavity and, if the tubes are open, spills out through the ends of the fallopian tubes. While HSG provides useful information about the shape of the uterine cavity and the patency of the tubes, it does come with several notable drawbacks, including radiation exposure and a reputation for being quite uncomfortable.
HyCoSy is a more modern, ultrasound-based alternative. During a HyCoSy procedure, a small catheter is placed through the cervix, and a contrast agent — either a specially designed echogenic solution or a saline and air mixture — is gently introduced into the uterus. Using transvaginal ultrasound, the clinician observes the flow of contrast through the uterine cavity and along the fallopian tubes in real time. If the tubes are patent, the contrast is seen flowing through and spilling from the ends of the tubes near the ovaries.
Both procedures are typically performed in the first half of the menstrual cycle, after the period has ended but before ovulation, to avoid disrupting a potential early pregnancy. The appointment usually takes between 15 and 30 minutes, and patients can generally return to their normal activities shortly afterwards.
While both HSG and HyCoSy are recognised as effective first-line tests for evaluating fallopian tube patency, there is a growing body of evidence — and clinical preference — favouring HyCoSy for several compelling reasons. If you are exploring which test is right for you, understanding these advantages can help you make an informed decision in consultation with your gynaecologist.
Perhaps the most significant advantage of HyCoSy is that it is entirely radiation-free. HSG relies on X-ray fluoroscopy, which exposes the pelvic region — including the ovaries — to ionising radiation. While the dose from a single HSG is relatively low, any unnecessary radiation exposure is best avoided, particularly in women of reproductive age who are actively trying to conceive. HyCoSy uses ultrasound, which has an excellent safety profile and no known harmful effects at diagnostic levels.
One of the most frequently cited benefits of HyCoSy is that it is significantly less painful than HSG. Research has consistently shown that patients find HyCoSy more comfortable, with studies from institutions such as Aminu Kano Teaching Hospital confirming that HyCoSy was preferred by patients due to its reduced pain and better tolerance, with minimal adverse effects. The iodine-based contrast used in HSG can cause cramping and discomfort, whereas the contrast agents used in HyCoSy tend to be better tolerated.
The iodinated contrast dyes used in HSG carry a small but real risk of allergic reaction, which can range from mild skin rashes to more serious anaphylactic responses. HyCoSy contrast agents have a considerably lower incidence of allergic reactions, making the procedure safer for a wider range of patients, including those with known iodine sensitivities or contrast allergies.
Because HyCoSy is performed using transvaginal ultrasound, it offers a valuable opportunity to assess other pelvic structures simultaneously. During the same appointment, the clinician can evaluate the uterus for fibroids, polyps, or structural abnormalities, examine the ovaries for cysts or signs of conditions such as polycystic ovary syndrome, and assess the overall pelvic anatomy. HSG, by contrast, is limited to providing information about the uterine cavity and tubal patency through X-ray images and does not visualise the ovaries or surrounding structures with the same detail. For a thorough pelvic evaluation, a gynaecology ultrasound provides an excellent foundation, and HyCoSy can build upon this assessment seamlessly.
HyCoSy is generally a quicker procedure than HSG. There is no need for the X-ray suite, no fluoroscopy setup, and no waiting for radiographic images to develop. The real-time nature of ultrasound means the clinician can observe contrast flow immediately, often completing the assessment in under 15 minutes. Most patients experience only mild, short-lived cramping and can resume normal activities almost immediately.
A natural concern for patients and clinicians alike is whether HyCoSy is as reliable as HSG. The evidence is reassuring. A meta-analysis evaluating multiple comparative studies found that HyCoSy demonstrated over 93% sensitivity and over 97% specificity in detecting tubal patency when compared against laparoscopy — the gold standard for tubal assessment. These figures are comparable to, and in some studies superior to, the accuracy of HSG.
Research published in Fertility and Sterility has reported an observed concordance between HyCoSy and HSG of approximately 90% for assessing the endometrial cavity. While the concordance for fallopian tube patency was reported at around 72% in some studies, this discrepancy often reflects the limitations of HSG rather than HyCoSy, as ultrasound-based methods can sometimes provide additional information that X-ray cannot capture, such as the presence of peritubal adhesions or hydrosalpinges.
Furthermore, the use of dedicated positive contrast agents (rather than simple saline solution) has been shown to improve the diagnostic accuracy of HyCoSy, bringing it closer to — or matching — the performance of iodinated contrast used in HSG. A study published in Ultrasound in Obstetrics & Gynecology concluded that positive ultrasound contrast agents appear to be more efficient than saline solution alone at determining fallopian tube patency, and as efficient as iodinated contrast agents used in HSG.
If you have been advised to undergo a HyCoSy, knowing what to expect can help ease any anxiety about the procedure. Here is a step-by-step overview of what typically happens during the appointment.
Your clinician will usually schedule the HyCoSy for between day 5 and day 12 of your menstrual cycle — after your period has finished but before ovulation. You may be advised to take a mild painkiller such as ibuprofen about an hour before the appointment to minimise any discomfort. It is also advisable to bring a sanitary pad, as some light spotting or watery discharge is normal afterwards. If you have any concerns about gynaecological symptoms beforehand, a gynaecological scan and consultation can help address these ahead of your HyCoSy appointment.
You will be asked to lie on an examination couch, similar to a standard ultrasound appointment. A speculum is gently inserted to visualise the cervix, and a thin, flexible catheter is passed through the cervical canal into the uterus. The speculum is then removed, and a transvaginal ultrasound probe is inserted. The contrast agent is slowly injected through the catheter while the clinician watches the ultrasound screen in real time.
As the contrast fills the uterine cavity, the clinician assesses the shape and lining of the uterus. The contrast is then observed flowing along each fallopian tube. If the tubes are patent, the contrast will be seen spilling freely from the ends of the tubes. The entire imaging process typically takes between 10 and 20 minutes.
Most patients experience mild cramping during or immediately after the procedure, similar to period pain, which usually resolves within 30 minutes. Light spotting or watery discharge may continue for a day or two. Serious complications are extremely rare. Your clinician will typically discuss the results with you immediately after the procedure, which is a significant advantage over HSG, where you may need to wait for a radiologist's report.
Despite the many advantages of HyCoSy, there are certain circumstances where HSG may still be the preferred option. HSG provides excellent visualisation of the uterine cavity architecture and can be particularly useful when detailed assessment of uterine abnormalities such as a septate or bicornuate uterus is required. In some clinical settings, HSG may be more readily available or covered by certain insurance plans.
Additionally, some fertility specialists may prefer HSG when they require very detailed images of the tubal architecture — for instance, to assess the precise location and nature of a tubal blockage before considering surgical intervention. There is also some evidence to suggest that the flushing effect of HSG with oil-based contrast may have a modest therapeutic benefit, potentially improving fertility rates in the months following the procedure, although this remains an area of ongoing research.
Ultimately, the choice between HyCoSy and HSG should be made in consultation with your gynaecologist or fertility specialist, taking into account your individual medical history, symptoms, and preferences. Both tests are valuable tools in the fertility investigation toolkit, and the best choice depends on your specific clinical situation.
Understanding whether your fallopian tubes are open is a fundamental step in any fertility investigation. Tubal factor infertility is one of the most treatable causes of difficulty conceiving, and early diagnosis allows for timely and targeted treatment. For some women, knowing that the tubes are patent provides reassurance and allows the clinical focus to shift to other potential factors. For others, identifying a blockage early can save months of fruitless trying and guide them towards the most effective treatment pathway — whether that is tubal surgery, intrauterine insemination (IUI), or in vitro fertilisation (IVF).
It is worth noting that tubal patency testing is just one piece of the fertility puzzle. A comprehensive fertility assessment will typically also include hormone blood tests, semen analysis for the male partner, assessment of ovarian reserve, and evaluation of the uterine cavity. Your specialist will use the results of all these investigations together to build a complete picture and recommend the most appropriate next steps.
For women who have a history of pelvic inflammatory disease, previous ectopic pregnancy, endometriosis, or pelvic surgery, the risk of tubal damage is higher, and early tubal patency testing is particularly important. Even in the absence of known risk factors, tubal assessment is considered a standard part of the infertility work-up and is recommended by the National Institute for Health and Care Excellence (NICE) for couples who have been trying to conceive for 12 months or more.
Most women report only mild discomfort during HyCoSy, similar to period cramps. Studies consistently show that HyCoSy is significantly less painful than HSG. Taking a mild painkiller such as ibuprofen an hour before the procedure can help minimise any discomfort. The cramping typically subsides within 30 minutes of the procedure being completed.
HyCoSy has been shown to be highly accurate, with sensitivity exceeding 93% and specificity over 97% when compared to laparoscopy, which is considered the gold standard. When performed with a dedicated positive contrast agent, HyCoSy is comparable in accuracy to HSG and provides the added benefit of simultaneous assessment of the ovaries and uterus.
There is some evidence that the flushing effect of contrast through the fallopian tubes during tubal patency tests — both HyCoSy and HSG — may have a mild therapeutic benefit by clearing minor debris or mucus plugs from the tubes. Some studies have reported modestly improved conception rates in the months following the procedure, although this is not the primary purpose of the test.
The entire appointment, including preparation and the scan itself, typically takes between 20 and 30 minutes. The actual imaging portion — where contrast is injected and observed on ultrasound — usually lasts only 10 to 15 minutes. Results are generally available immediately, as the clinician interprets the images in real time during the procedure.
In most private clinic settings, you can self-refer for a HyCoSy procedure, although it is often performed as part of a broader fertility investigation recommended by a GP or fertility specialist. If you are experiencing difficulty conceiving or have risk factors for tubal disease, speaking to a gynaecologist first can help ensure you receive the most appropriate investigations for your situation.
The information provided in this article is for educational purposes only and is based on NHS recommendations. It is not a substitute for professional medical advice. Always consult your doctor or a qualified healthcare provider for advice on medical conditions or treatments.
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