Hysterosalpingography

Hysterosalpingography (HSG) is a fluoroscopic study of the uterine cavity and fallopian tubes after water soluble iodinated contrast (usually 5 to 10 mL, up to 20 mL when the tubes are open) is injected slowly through a catheter in the cervical canal.

Images are taken during filling of the cavity, as the tubes fill, when contrast spills from the fimbrial ends into the peritoneal cavity, and on a delayed film after 10 to 20 minutes, which shows the pattern of peritoneal spill and any loculation.

An oil based contrast agent has been used in some centres and is associated with higher pregnancy rates in the months after the study in women with unexplained infertility, but it carries a small risk of oil embolism and granuloma formation.

The study is timed in the first half of the cycle, after menstrual bleeding has stopped and before ovulation (days 6 to 11), to avoid pregnancy and to avoid a thickened endometrium that mimics polyps. The effective dose is about 1 to 3 mSv, mainly to the ovaries, and pulsed fluoroscopy with few exposures keeps it low.

Infertility affects about 10 to 15% of couples, and a tubal factor is present in 20 to 30% of infertile women. HSG is the first line test for tubal patency and the uterine cavity. Sonohysterosalpingography (hysterosalpingo contrast sonography) and laparoscopy with dye test are alternatives, and MR gives a three dimensional view of the uterine shape but not tubal patency.

Indications. Primary or secondary infertility (tubal patency and cavity). Recurrent miscarriage (uterine anomalies, cervical incompetence, adhesions). Assessment after tubal surgery, sterilisation (before reversal), or tubal reanastomosis. Suspected congenital uterine anomaly. Suspected intrauterine adhesions (Asherman syndrome) after curettage or infection.

Assessment of a uterine scar defect after caesarean section. Before assisted reproduction when tubal status is unknown. Not during pregnancy, active pelvic infection or heavy bleeding.

Contraindications and precautions. Pregnancy or possible pregnancy (the study is timed in the first half of the cycle after a negative pregnancy test or barrier contraception). Active pelvic inflammatory disease, endometritis or untreated cervicitis (risk of spreading infection; delay until treated). Heavy uterine bleeding.

Recent uterine or tubal surgery or curettage (wait about 2 weeks). Allergy to iodinated contrast. Thyroid disease (iodine load is small, but thyroid function is checked in at risk women). A history of previous pelvic infection, hydrosalpinx or tubal disease: antibiotic prophylaxis is given. Pain is common and analgesia (an oral non-steroidal analgesic taken beforehand) is given.

A vasovagal reaction can occur. The woman is asked to inform staff if she is breastfeeding, though no interruption is needed.

Preparation and technique. The woman is in the lithotomy position, a speculum is inserted, the cervix is cleaned with antiseptic, and a catheter with a balloon or a cannula with a cervical cup is placed in the cervix. Contrast is injected under fluoroscopy at a slow, constant rate, with images of the cavity (early, before overfilling), the tubes, and the peritoneal spill.

Traction on the cervix straightens an anteverted uterus. The tubes are filmed in each oblique position as required.

Normal appearances. A triangular, smooth walled uterine cavity with a symmetrical outline and a straight or slightly concave fundus; a cavity length of 6 to 8 cm and a capacity of 3 to 5 mL.

Two thin fallopian tubes: the narrow isthmus (1 to 2 mm) running from the cornua, then the wider ampulla (up to 5 to 8 mm) with fine longitudinal folds, then the funnel shaped infundibulum and fimbriae. Contrast spills freely from each tube into the pelvis, outlining loops of bowel and the peritoneal surfaces, and spreads smoothly on the delayed film with no collections.

The cervical canal is fusiform with a feathery pattern of folds.

Interpretation.

• Tubal occlusion: proximal occlusion (at the cornua, either from spasm, debris, or true obstruction, shown by a failure of contrast to enter the tube beyond the uterotubal junction) and distal occlusion (contrast fills the tube but does not spill, with dilatation of the ampulla in hydrosalpinx).
• Hydrosalpinx: a dilated, sometimes sausage shaped tube with loss of the fine mucosal folds, a "cobblestone" outline in the ampulla, and failure of spill or a delayed film that shows retained contrast. Fimbrial phimosis and peritubal adhesions cause loculated spill, with contrast pooling around a tube or ovary.
• Salpingitis isthmica nodosa: multiple small diverticular outpouchings of the isthmus (a "honeycomb" pattern), which is associated with infertility and ectopic pregnancy.
• Tuberculous salpingitis: a beaded, rigid, "pipe stem" tube with multiple constrictions, calcification, and a "golf tee" deformity of the tubal ends, and a contracted, deformed cavity with intrauterine adhesions (synechiae).
• Pelvic inflammatory disease sequelae: tubal damage, pelvic adhesions and intrauterine adhesions.
• Intrauterine filling defects: submucous fibroids (a smooth, round filling defect with a bulge of the cavity), polyps (a smooth, small filling defect on a narrow base, which changes with the volume of contrast), adhesions (irregular, angular, "bandlike" defects that do not change with the fill), air bubbles (round, move with positioning, and are avoided by purging the catheter), and retained products of conception.
• Congenital uterine anomalies: unicornuate (a single, banana shaped cavity with one tube), didelphys (two separate cavities and two cervices), bicornuate (two cavities joined at the lower part, with an intercornual angle over 105 degrees and a fundal cleft over 1 cm), septate (two cavities with an intercornual angle under 75 degrees and a fundal outline that is flat or slightly convex), and arcuate (a mild fundal indentation). HSG shows the cavity and not the fundal outer contour, so a septate and a bicornuate uterus are not reliably separated without ultrasound or MR.
• Cervical incompetence: a wide internal os (more than 8 mm) or a funnel shaped canal.
• Caesarean scar defect (niche): a contrast filled pouch at the anterior lower uterine segment.
• Adenomyosis: tiny diverticula extending from the cavity into the myometrium, with an irregular outline.
• Ectopic and unusual features: contrast intravasation (veins or lymphatics fill with contrast, a "reticular" pattern, caused by high pressure, endometrial damage or tubal obstruction), and uterine perforation by the catheter.

Critical values and findings needing immediate action.

• Anaphylaxis or severe contrast reaction: stop the injection, give intramuscular adrenaline, oxygen, intravenous fluids and call for resuscitation support.
• Pelvic infection after the study (fever, pelvic pain, discharge within days): antibiotics, with urgent review and ultrasound to exclude a tubo ovarian abscess.
• Uterine perforation with bleeding or peritonitis: resuscitation and gynaecological review.
• Intravasation of oil based contrast with respiratory or neurological symptoms (embolism): oxygen and supportive care.
• Pregnancy found at the time of study: stop the procedure.
• Findings of a hydrosalpinx before assisted reproduction: gynaecology referral, as surgical removal or occlusion of the tube improves results of in vitro fertilisation.

Limitations and artefacts.

• Spasm of the uterotubal junction produces false proximal occlusion, and a repeat injection, a smooth muscle relaxant (hyoscine butylbromide), or a delay and re-injection after a few minutes reduces false findings; the false positive rate for proximal occlusion is about 10 to 15% in some series.
• The test shows only the tubal lumen and not the tubal wall, the ovaries, the outer uterine contour, or pelvic organs. Endometriosis and peritoneal disease are not shown. Normal HSG with tubal patency does not prove normal tubal function.
• Pain (moderate to severe in about a fifth), vasovagal reactions (about 1 in 10 to 20), pelvic infection (about 1 to 3%, higher with tubal disease), contrast reactions (rare), and radiation exposure of the ovaries are the main risks.
• Air bubbles, mucus, menstrual blood, a thick endometrium, and over distension mimic or hide lesions. Too rapid injection causes spasm and pain.
• A late film is needed to assess peritoneal spill and loculation, and a single early film may miss adhesions.
• The test cannot prove that the tubes are normal in function, and pregnancy may still be difficult after a patent HSG.
• A pregnancy rate rise is seen in the months after HSG (a flushing effect), especially with oil based contrast.
• Radiation dose to the ovaries requires that the study be justified clinically and kept short.

Special groups.

• Women with previous pelvic infection, ectopic pregnancy or tubal surgery: higher risk of infection, so antibiotic cover is given.
• Women with iodine allergy or thyroid disease: sonohysterosalpingography with saline or foam and ultrasound avoids iodinated contrast and radiation.
• Women with uterine anomalies: HSG shows the cavity, and MR or three dimensional ultrasound shows the fundal shape.
• Women who have had a sterilisation: HSG before reversal shows the length of the remaining tube.
• Adolescents and virgo intacta: avoid unless essential, and use ultrasound or MR.
• Pregnancy: do not perform.
• Regions: pelvic inflammatory disease, genital tuberculosis and previous unsafe abortion are common causes of tubal infertility, and HSG may be the first line test for the fallopian tubes where laparoscopy is not available.

Follow up tests. Pelvic ultrasound (transvaginal, with three dimensional views of the uterus), sonohysterosalpingography, hysteroscopy for intrauterine lesions and septum resection, laparoscopy and dye test for tubal disease and endometriosis, MR of the pelvis for uterine anomalies and adenomyosis, ovarian reserve tests (anti-Mullerian hormone, follicle stimulating hormone, antral follicle count),

semen analysis, thyroid function and prolactin, chlamydia and gonorrhoea testing, tests for genital tuberculosis (endometrial biopsy, polymerase chain reaction), and referral to gynaecology or a fertility service.