The Saline Infusion Sonohysterogram (SIS), also known as a Sonohysterogram (SHG), is a standard diagnostic procedure used early in the investigation of infertility. It allows specialists to gain a detailed look at the internal structure of the uterus, which is crucial for successful conception and implantation. While primarily designed to identify structural barriers, a common question is whether performing the test might also have a secondary therapeutic effect. This article examines the procedure and addresses whether the saline flush itself can increase the chances of achieving pregnancy.
What is a Saline Infusion Sonohysterogram?
A Saline Infusion Sonohysterogram is a specialized, minimally invasive imaging technique that provides a clearer view of the uterine cavity than a traditional transvaginal ultrasound. The procedure involves inserting a thin, flexible catheter through the cervix and into the uterus. A sterile saline solution is then gently instilled into the uterine cavity.
The fluid expands the uterine walls, separating them and creating an anechoic (echo-free) environment. This expansion allows the sonographer to visualize the endometrial lining and the cavity’s contours with exceptional clarity. The saline acts as a contrast agent, outlining any structures or abnormalities that might otherwise be difficult to see on a conventional ultrasound. This high-resolution assessment is essential for evaluating the environment where an embryo would implant.
The Diagnostic Role of SIS in Fertility Workups
Fertility specialists rely on the SIS procedure to structurally evaluate the reproductive tract, as uterine cavity issues can impede implantation or lead to recurrent pregnancy loss. The test identifies physical conditions interfering with conception, including endometrial polyps and submucosal fibroids that bulge into the uterine cavity.
The SIS is also highly effective at finding intrauterine adhesions (scar tissue or synechiae), which can distort the cavity and interfere with implantation. Furthermore, it helps assess for congenital uterine abnormalities, such as a uterine septum. By determining if a structural issue is present, the SIS guides the next steps in a fertility treatment plan, ensuring the uterus is a receptive environment for pregnancy.
Does the Saline Flush Improve Conception Rates?
Although the Saline Infusion Sonohysterogram is designed purely as a diagnostic tool, some studies indicate a small, temporary increase in spontaneous conception rates immediately following the procedure. This observation is similar to a phenomenon noted after a hysterosalpingogram (HSG), another diagnostic test involving fluid flushing. This beneficial side-effect is thought to result from the physical action of the saline flush itself.
The hypothesized mechanism is that the pressure of the fluid passing through the uterine cavity and potentially through the fallopian tubes may clear minor obstructions. This flushing action could dislodge small mucus plugs, debris, or inflammatory substances hindering sperm transport or early implantation. This temporary improvement may create a more favorable pathway for conception. This transient effect is usually seen within the first three to six cycles after the SIS is performed, after which conception rates return to the baseline rate.
Interpreting Results and Subsequent Treatment Options
After the Saline Infusion Sonohysterogram is complete, the results determine the path forward. If the SIS reveals a normal, smooth uterine cavity without structural anomalies, the focus shifts to other potential causes of infertility, such as hormonal or male factors. The couple may be encouraged to attempt conception naturally in the following cycles to take advantage of the temporary flushing effect.
When the SIS identifies a structural abnormality, such as a polyp, submucosal fibroid, or significant scar tissue, it leads directly to therapeutic intervention. The next step is typically a hysteroscopic surgery, such as a polypectomy or myomectomy, to remove the obstruction. This targeted surgical treatment provides a significant increase in fertility by restoring the normal anatomy of the uterine cavity. The SIS serves as a map, guiding the specialist to a corrective procedure that improves the chances of a successful pregnancy.