Sonohysterography (SIS)

Sonohysterography (SIS) is an imaging method in which sterile saline (physiological serum) is given into your uterine cavity while a transvaginal ultrasound is performed, to assess the inner surface of your uterus and findings that affect the cavity. The saline separates the walls of the uterus from one another and allows the structures in the cavity to be seen more clearly on ultrasound. The information below offers a general framework and does not replace a diagnosis or treatment recommendation specific to you.

What is sonohysterography (SIS)?

On a routine transvaginal ultrasound, the uterine cavity looks like a closed slit. In SIS, saline is given into the cavity through a thin catheter; the cavity widens with this fluid, and bulges on the inner surface or changes in shape in the walls become visible. No X-ray is used and no contrast material is given. In this respect SIS is a form of ultrasound done with saline.

In which situations is SIS requested?

SIS may be requested if you are having difficulty conceiving, to assess your uterine cavity, and to investigate abnormal uterine bleeding. When a polyp, a fibroid extending into the uterine cavity, adhesions or a septum is suspected on ultrasound, clarifying this impression is also a reason. In the assessment of unexplained infertility, current guidelines recommend ultrasound (three-dimensional if possible) as the first method for the uterus, and state that no additional assessment is needed if the cavity looks normal on ultrasound. SIS is a method your doctor turns to, according to you, in situations not clarified by ultrasound.

How do you prepare for SIS, and how is the timing determined?

Your SIS appointment is mostly given for the days after your menstrual bleeding has ended; if you come on a day with bleeding, your doctor may postpone the procedure. If there is a possibility that you are pregnant or you have signs of an active pelvic infection, the procedure is postponed. During preparation you need to tell your doctor about the possibility of pregnancy, the medicines you use and your allergies; in particular, mention a latex allergy before the procedure, because part of the material used may contain latex. Your doctor decides whether a painkiller is needed and the other preparations.

What happens during and after the procedure?

You lie in the gynaecological examination position and a speculum is used during the examination. While saline is given through a thin catheter passed through your cervix, your uterine cavity is watched live with the ultrasound probe in the vagina; as the cavity fills with fluid, the walls and the bulges inside are scanned on the screen. No X-ray image is taken, so the focus is the ultrasound sections on the screen. You may feel a cramp similar to period pain; the pain varies from person to person. The duration varies with the findings seen and with the person.

On leaving, mild cramp and light spotting are common.

What does SIS show, and what does it not show?

SIS can show findings in your uterine cavity such as a polyp, a fibroid extending into the cavity, adhesions and a septum. SIS is counted among the methods used to detect lesions inside the uterus. Even so, your doctor interprets what the imaging finding is, and the distinction between a polyp, a fibroid or adhesions may not be clear in the image. Very fine adhesions may be missed. SIS has a high predictive value in detecting findings inside the uterus; even so, SIS does not make a definitive diagnosis on its own, and for lesions in the uterine cavity the definitive diagnosis and treatment method is hysteroscopy.

SIS is not the main method for showing tubal patency; other methods are used for this purpose. SIS is not done for the purpose of treatment, and it has not been shown to increase the likelihood of pregnancy.

What is the difference between SIS, HSG and hysteroscopy?

The choice is made according to your complaint, your history, your allergies, your access and your doctor's preference. None automatically takes the place of another.

What are the risks of SIS, and in whom is it not done?

SIS is generally a well-tolerated procedure, but it cannot be said to have no risks. The main problems are pain and cramp, a temporary feeling of dizziness, light spotting and, rarely, pelvic infection; if you have a history of pelvic infection, your doctor may plan an additional precaution. If the dizziness does not pass once you leave the room, gets worse or leads to fainting, it counts as urgent. A latex allergy is an important point. The procedure is not done if there is a possibility that you are pregnant or you have an active pelvic infection. A normal SIS result does not mean you will become pregnant.

How is the SIS result interpreted, and what is the next step?

A normal result shows that no structural problem is seen in your uterine cavity; the remaining assessment turns to the other possible causes of your difficulty in conceiving. If there is an abnormal finding, your doctor decides, according to you, whether it needs to be confirmed by hysteroscopy or whether treatment needs to be planned.