An HSG — hysterosalpingography — is an X-ray test in which dye is pushed through the cervix into the uterus and watched as it spills out of the fallopian tubes. It is usually the first test done when a couple is not conceiving, and its report is one of the most misread documents in fertility care.
It answers two questions: what shape is the inside of your uterus, and does dye pass through your tubes. Both matter. But the second one is answered far less reliably than the confident wording of most reports suggests.
Seven things to know before you act on it
- HSG is a screening test, not a final answer. Laparoscopy with dye is the reference standard, not this.
- It misses about a third of genuinely blocked tubes — pooled sensitivity is 65%.
- And it calls some open tubes blocked — specificity is 83%, so roughly one in six patent tubes is misreported.
- Blockage right at the uterus is often spasm, not obstruction. The tube can clamp shut simply because dye is being pushed into it.
- One blocked tube is not half a problem. If the other is open and you ovulate from both ovaries, the practical impact is much smaller than it sounds.
- The test is also a treatment. Flushing with oil-based contrast raised ongoing pregnancy from 29.1% to 39.7% in a trial of 1,119 women.
- A normal HSG does not mean normal tubes. It cannot see endometriosis, adhesions around the tube, or whether the tube actually works.
What the test actually does
A thin tube is passed just inside the cervix, contrast dye is injected, and X-ray images are taken as the dye fills the cavity and moves outwards. If the tubes are open, dye spills into the abdomen and the radiologist sees it scatter. If it does not spill, the report says blocked.
It is done in the first half of the cycle — usually between day 6 and day 11, after bleeding has stopped and before ovulation — so that there is no chance of an early pregnancy in the uterus, and the lining is thin enough to see the cavity clearly.
How accurate is it, really?
This is the part that is almost never explained, and it changes how the report should be read.
A meta-analysis pooling 19 studies and 3,964 women compared HSG against laparoscopy with dye, which is the reference standard. It found:
- Sensitivity 65% (95% CI 50–78%). Of tubes that are genuinely blocked, HSG identifies about two-thirds. It misses the rest.
- Specificity 83% (95% CI 77–88%). Of tubes that are genuinely open, about one in six is reported as blocked.
The reviewers' own conclusion was that HSG is "of limited use for the detection of tubal patency because of its low sensitivity." That is a long way from how the result is usually delivered.
None of this makes HSG a bad test. It is quick, widely available, needs no anaesthetic, and it shows the uterine cavity at the same time. It is a good first test and a poor last word, and the mistake is treating it as the second.
Why "blocked at the cornu" is so often wrong
Where the tube leaves the uterus it is extremely narrow — a fraction of a millimetre. It is also muscular. Push dye against it under pressure, in a woman who is tense and in pain, and it can simply clamp shut. On the film that looks identical to a blockage.
This is called tubal spasm, and it is why a proximal block — a blockage right at the corner of the uterus, rather than out at the far end — carries far less weight than a blockage at the fimbrial end. A great many proximal blocks turn out to be patent when the tube is tested again, or looked at directly at laparoscopy.
A proximal block on a single HSG is a reason to test again, not a reason to plan IVF. If that is the only abnormal finding on your report, ask what the next confirming step is before anything irreversible is decided.
Reading the tube findings
Both tubes blocked
The result that frightens people most, and the one that most deserves a second look — particularly if the blockage is proximal on both sides, because bilateral spasm is common. Confirmation is usually by laparoscopy with dye, sometimes by repeating the HSG. If genuine bilateral blockage is confirmed, IVF bypasses the tubes entirely and is the logical route.
One tube blocked, one open
Much less serious than it sounds. Eggs are released from alternate ovaries in most cycles, and the open tube can often collect an egg from the opposite side. Pregnancy is entirely possible naturally. In this situation the sensible next step is usually to look at everything else — ovulation, sperm, age, how long you have been trying — rather than to focus on the blocked side.
A swollen, fluid-filled tube
A hydrosalpinx — a tube blocked at its far end and distended with fluid. This one genuinely matters, and not only because the tube does not work: the fluid can leak back into the uterus and substantially reduce the chance of an embryo implanting. Where IVF is planned, removing or clipping such a tube first is standard advice, because it measurably improves success.
Free spill on both sides
Good news, and the commonest result. It means dye passed through. It does not mean the tubes are healthy — see below.
The half of the report nobody reads
An HSG shows the shape of the uterine cavity, and that half is often skimmed past on the way to the tube result. Things it can show:
- Filling defects — a polyp, a fibroid pushing into the cavity, or adhesions. These are followed up by hysteroscopy, which both confirms and treats.
- A small or irregular cavity with a ragged outline — a possible sign of intrauterine adhesions, particularly after a D&C.
- A cavity divided or unusually shaped — a septum or another congenital variation, which can matter for miscarriage as well as conception.
What genital tuberculosis looks like on an HSG
Genital TB is an uncommon cause of tubal infertility in most of the world and a genuinely important one here. It is worth knowing the vocabulary, because these phrases appear on Indian reports and are rarely explained to the patient:
- Beaded or rigid "lead-pipe" tubes — irregular narrowing along the tube.
- Golf-club appearance — a blocked, clubbed end.
- A small, shrunken or "tobacco-pouch" cavity with a distorted outline.
- Calcification in the pelvis on the plain film.
None of these proves TB, and none of them should be treated on their own. But they are a reason to raise the question specifically rather than to accept "blocked tubes" as the whole explanation.
The finding that surprises people: the test can help you conceive
This is real, it is from a proper randomised trial, and it is almost never mentioned when the test is booked.
In a trial of 1,119 women having an HSG, the type of dye used was randomised to oil-based or water-based contrast. Over the following months:
- Ongoing pregnancy: 39.7% with oil, 29.1% with water (relative risk 1.37, 95% CI 1.16–1.61).
- Live birth: 38.8% with oil, 28.1% with water (relative risk 1.38, 95% CI 1.17–1.64).
- About 10 women need the oil version for one additional pregnancy.
Nobody is entirely sure why. Flushing debris out of the tube, an effect on the lining, an effect on the local immune environment — all are proposed. What is not in doubt is the size of the effect, which is comparable to some fertility treatments.
The practical point: if you are having an HSG anyway and you are trying to conceive, it is worth asking which contrast will be used. The months immediately after the test are a genuinely favourable window.
What HSG cannot tell you
Worth being explicit, because a normal report is often over-read as reassurance:
- Whether the tube works. A tube is not a pipe. It has delicate hair-like cilia and muscular movement that carry the egg. Dye passing through says the channel is open, not that the mechanism functions.
- Endometriosis. HSG is blind to it entirely.
- Adhesions around the outside of the tubes and ovaries, which can prevent an egg being picked up even when the tube is perfectly open inside.
- Anything about eggs or sperm. It is one part of an assessment, never the whole of it.
What it feels like, and how to make it easier
Honestly: uncomfortable, and occasionally properly painful, usually for under a minute as the dye goes in. Most women describe strong period-like cramping. A few find it barely troubling; a few find it much worse than they were led to expect, and being told beforehand that it "is nothing" is not kind or useful.
What helps:
- A painkiller about an hour beforehand — an anti-inflammatory such as ibuprofen, if it suits you, taken before the test rather than after.
- Not going alone, if you can arrange it.
- Telling the person doing the test to slow down. Dye pushed hard and fast hurts more, and it also makes spasm more likely — so it is worse for the result as well as for you.
- Expecting some spotting and cramping afterwards for a day or so. Pads, not tampons.
Fever, heavy bleeding, worsening pain or a foul discharge in the days afterwards is not normal and needs to be seen — infection after HSG is uncommon but it does happen.
The alternatives, and when they are better
- HyCoSy / HyFoSy — the same idea using ultrasound and a foam or saline contrast instead of X-ray. No radiation, comparable information about the tubes, and often better information about the ovaries and uterine wall at the same time.
- Laparoscopy with dye — the reference standard. It sees the tubes from the outside, finds endometriosis and adhesions, and can treat what it finds in the same sitting. It needs anaesthesia, so it is not a first test, but it is the right answer when HSG findings are being questioned or when endometriosis is suspected.
- Hysteroscopy — for the cavity rather than the tubes, when HSG has shown a filling defect or a suspicious outline.
What should happen next
An HSG result should change the plan only in the context of everything else — your age, how long you have been trying, whether you ovulate, and a semen analysis. A tube report in isolation is not a treatment plan.
- Both tubes open — attention moves to ovulation, sperm and time. If you are not ovulating regularly, our page on PCOS is usually the next thing to read.
- One blocked — usually carry on, with everything else optimised.
- Proximal block, one or both sides — confirm before you act. This is the single most important sentence on this page.
- Confirmed bilateral blockage or a hydrosalpinx — a fertility specialist conversation, with IVF the usual route and the hydrosalpinx dealt with first.
What happens at the clinic
Consultation, going through your HSG report and films with you, the rest of the fertility assessment, blood tests, and treatment such as ovulation induction where that is what is needed, all happen at the clinic. The HSG itself is done at an imaging centre or hospital and is arranged by referral, as are all scans, since we do not run imaging here. Hysteroscopy and laparoscopy are hospital procedures.
If you are holding a report that says blocked and you have been told IVF is the only option, that is a reasonable thing to want a second opinion on. Bring the report and, if you can, the films or the CD.
Dr. Anam Ghani, MBBS, MS (OBGY)
Obstetrician & Gynaecologist in Gurugram with 12+ years of clinical experience and 8000+ deliveries. Trained at Lady Hardinge Medical College with senior residencies at GTB, Kasturba and DDU Hospitals. Practises at Sector 51 (Mayfield Garden) and Sector 56, Gurugram, with a special focus on fertility assessment, PCOS, high-risk pregnancy and laparoscopic gynae surgery.
To book a consultation, contact us here, WhatsApp +91 84472 59265, or call either clinic directly.
This article is for general education and does not replace an individual assessment. An HSG report is interpreted alongside your age, your history, your ovulation and a semen analysis, and treatment decisions belong with the doctor seeing you. Do not delay or change fertility treatment on the basis of anything written here.