Sonohysterography, also called saline-infusion sonohysterography (SIS), is an immensely useful but cost-effective procedure which maximizes the utility of ultrasound imaging of the uterine cavity in women with suspected intrauterine anomalies.
The indications for this procedure typically include:
- Abnormal vaginal bleeding in premenopausal women – to exclude endometrial thickening (generalized or localized), endometrial polyps, submucosal fibroids
- Abnormal vaginal bleeding in postmenopausal women to locate areas of endometrial hyperplasia or focal malignancy
- Women with infertility – to exclude endometrial adhesions (places where the front and back walls of the uterus are stuck to each other, which may prevent the gametes from moving freely across the uterine cavity to achieve fertilization), as well as small growths or congenital anomalies such as uterine septa, bicornuate uterus (two uterine horns) and unicornuate uterus (one uterine horn)
- Preoperative evaluation of uterine fibroids and polyps
- Postoperative confirmation of complete removal of these structures
- Confirmation of potential abnormalities seen by ultrasound scanning of the uterus
- Failure to obtain a clear view of the endometrial cavity by transvaginal scanning
The primary reasons to avoid this procedure include:
- Pelvic infection
- Abnormal and excessive vaginal bleeding
The SIS should be timed for the 4th to 11th day of the menstrual cycle (provided the flow has ceased) because this helps to visualize the thin endometrium with maximum clarity. The thinness of the inner layer of the uterine wall helps to instill saline more easily, and to pick out disturbances in the uterine contour quite accurately. Later on the endometrium begins to grow thicker under the influence of estrogen, which may wrongly appear to be endometrial polyps or hyperplastic areas of the endometrium.
The patient is usually offered a nonsteroidal anti-inflammatory drug (NSAID) to help prevent uterine cramps during the infusion of saline. The pregnancy test done just before the SIS starts should be negative.
The lithotomy position is used and the cervix is brought into the field of view. Upon adequate cleaning, a thin small catheter is passed gently through the cervical canal and into the uterine cavity, after removing the air inside it by a stream of saline.
Once it is properly located, its tip is inflated to help it remain in the right position. A transvaginal ultrasound probe is put in position beside the catheter in the vagina, and about 40 milliliters of saline (which has been prewarmed) is instilled via a large syringe attached to the catheter.
The uterine cavity is scanned in two different directions and the whole of the area is visualized. The normal findings are those of a dark central area which represents the non-echo-producing (anechoic) part of the uterus, surrounded by a hyperechoic white endometrial stripe.
Problems may arise during the procedure, such as abnormal positions of the uterus making catheter placement difficult, cervical stenosis or extreme narrowing, the accidental insertion of air, and the leakage of saline into the vagina without distending the uterine cavity (which leads to non-detection of some endometrial lesions).
Patients should be both reassured and comforted. A pre-SIS ultrasound is crucial to help detect and avoid conditions such as pelvic inflammation, tubal defects, and tenderness around the adnexa, which could potentially lead to complications worsening the condition of the patient.