Saline Infusion – Sonohysterography

Saline infusion sonohysterography (SIS) is a technique in which a catheter is placed into the endometrial cavity and sterile saline is instilled to separate the walls of the endometrium.  SIS is best performed as soon as possible after the cessation of the menses during the follicular phase of the menstrual cycle.  Preferably it is done before day 14 of the cycle.  When the endometrium is thinnest, focal lesions such as polyps are best seen.  In the post-menopausal woman with abnormal bleeding, the examination can be performed at any time.


Patient preparation for the examination is minimal.  A simple analgesic such as Panadeine or Ibuprofen orally one hour before the examination is recommended. The use of prophylactic antibiotics is not necessary.  Complications from SIS are very uncommon. 


An occlusive catheter is placed within the endometrial cavity in order to give a seal so that the saline is retained within the endometrial cavity.  The catheter is primed with saline.  The air within the catheter will be introduced into the endometrial cavity if the catheter is not primed and this may obscure abnormalities during scanning.  The balloon of the catheter is gently inflated and the catheter is retracted to occlude the internal cervical os.  Three dimensional (3D) imaging can be undertaken to give a better global view of the uterine cavity.  Doppler and Colour Doppler examination can be quite helpful in distinguishing blood clots from polyps.  Colour Doppler also is useful in the evaluation of polyps, to outline a feeding vessel, and to enable the accurate placement of the polyp within the endometrial cavity, either on the anterior or posterior wall and also the distance the stalk of the polyp is from the fundus of the cavity or from the internal os. 




Fertility work-up


Uterine anomalies are common in women with infertility and recurrent pregnancy loss.  Therefore it is essential that fertility work-ups include the evaluation for structural uterine anomaly.  Saline infusion sonohysterography is an adjunct to transvaginal scanning.  It is also combined with the use of a contrast agent such as ExEm, to further outline the cavity, looking for filling defects that could be associated with a polyp.  The ExEm is also used to verify the patency of the tubes. 


Anecdotally, at least 50% of woman who have infertility will achieve a pregnancy after a SIS / ExEm study.  This will be achieved with or without ovulation induction therapy.  Often, a lot of echogenic debris will be flushed from the tubes with the installation of the saline.  This has been verified with laparoscopy and dye studies and it seems to be the same with the SIS.  There is a rebound higher pregnancy rate than expected. 


Congenital Anomalies


There is a high incidence of congenital uterine anomalies among patients with recurrent pregnancy loss.  The SIS is able to differentiate a septate or sub-septate uterus from a bicornuate uterus.  In patients with a septate uterus, this can then be managed hysteroscopically with a netroplasty.  Soares evaluated hysteroscopy compared to SIS and found that saline infusion had a higher sensitivity and specificity when compared with hysterography for identification of uterine anomalies. 


Masses and Adhesions


SIS is superior to transvaginal sonography and HSG for identification of polypoid lesions and endometrial hyperplasia.  Identification of a polyp on transvaginal sonography can be very difficult, particularly if the examination is done in the luteal phase of the cycle.  The echo texture of the normal endometrium can obscure the presence of a small polyp. 


Screening before in vitro fertilisations


This is a well-tolerated and less costly procedure than a laparoscopy.  The SIS will give more information regarding the size of location of myomas.  The adnexa can also be evaluated.  I have seen many patients who have had significant endometrial polyps identified on SIS after multiple failed IVF attempts.  Once the polyp or polyps are removed, spontaneous pregnancy is often achieved.  Thus, for these reasons, some authors are recommending screening with SIS before undertaking IVF therapy.


Recurrent pregnancy loss


In patients with recurrent pregnancy loss there is a high incidence of uterine anomalies.  SIS gives an excellent anatomic view of the uterus and is highly accurate in the diagnosis of polyps, endometrial hyperplasia and various uterine anomalies.  It offers several advantages over the traditional HSG.  It uses no ionising radiation and no iodine contrast agent.  The entire uterus is visualised rather than the outline of the endometrial cavity.  As mentioned, it can be combined with a gel such as ExEm to evaluate the patency of the tubes.  If a focal lesion is identified on SIS, that lesion can be treated with hysterography.  The patients who do not have any focal lesions can then be spared a hysteroscopy. 


Post-menopausal bleeding


Post-menopausal bleeding is a common clinical problem.  As many as one in ten women older than 55 have at least one episode of abnormal vaginal bleeding.  Post-menopausal bleeding can occur secondary to many conditions including atrophy, endometrial polyps and endometrial hyperplasia.  However, clinical work up is generally performed to exclude endometrial cancer. 


Transvaginal sonography is a very sensitive means of evaluating the endometrium.  Using a double wall thickness of 5mm, the sensitivity for detecting endometrial cancer is 96% regardless of whether the woman is receiving hormonal replacement therapy.   A thin endometrium of 5mm or less has a high negative predictive value and this finding would support the diagnosis of endometrial atrophy.  If fluid is seen within the endometrial cavity on initial transvaginal scan, the individual wall thickness of the two sides of the endometrium are summed, excluding the intervening fluid. 


Endometrial biopsy in the office can be performed, but this is a blind technique and has inherent limitations particularly in the evaluation of focal lesions.  When the endometrium is found to be thickened, inhomogeneous or indistinct (poorly visualised) on transvaginal scan, further evaluation with SIS can provide additional information.  Saline infusion sonohysterography can determine whether the abnormality is focal or diffuse and thus can direct the next appropriate step in the patient’s work-up. 


Endometrial polyps


Endometrial polyps are a common cause of abnormal vaginal bleeding in both pre-menopausal and post-menopausal women.  In post-menopausal women polyps are found to be the cause of bleeding in approximately 30% of cases.  Most polyps are benign.  The incidence of malignancy in polyps ranges from 0.5% to 1.5%.  Polyps are usually resected for both histological evaluation and symptomatic relieve of the bleeding. 


Cystic components of a polyp can be seen and this may indicate a haemorrhage infarction or inflammation.  Other causes for cysts include dilated glands or mucinous metaplasia, particularly in polyps associated with Tamoxifen use.  Transvaginal sonography cannot distinguish endometrial hyperplasia from benign polyps because both of these conditions can cause thickening of the endometrium.  The saline infusion can help to distinguish focal lesions from diffuse endometrial thickening.  The polyp is a focal lesion which projects into the lumen of the endometrial cavity.  Often with addition of Doppler and Colour Doppler, the feeding vessel can frequently be shown within the stalk of the polyp.  Unfortunately, the Doppler and Colour Doppler does not help in the identification of the polyp which is malignant.  With the saline infusion, information can be given to the clinician as to the precise site of the polyp. 




Fibroids are extremely common and only a small number of these are symptomatic.  When they are symptomatic, the most common symptom is abnormal vaginal bleeding.  Submucosal fibroids are the most likely to cause abnormal bleeding.  Saline infusion sonohysterography can establish the location of the fibroid with respect to the endometrial lining.  The extent to which the fibroid projects into the lumen of the endometrial cavity is of clinical importance.  If the fibroid projects into the lumen by more than 50% of its surface, then it can be resected by hysterography. 


Endometrial hyperplasia


Endometrial hyperplasia is the cause of post-menopausal bleeding in approximately 4% to 8% of cases.  Sonography cannot differentiate among the varyious types of endometrial hyperplasia, they are histologically categorised as simple, complex or atypical.  With atypical hyperplasia, there is a approximately a 23% chance of progression to endometrial carcinoma.  With SIS, endometrial hyperplasia typically appears as a diffuse thickening of the endometrium, although it can occasionally appear as a focal area of endometrial thickening. 


Endometrial carcinoma


Post-menopausal bleeding is the common presenting symptom in a woman with endometrial carcinoma.  Eighty-five percent of endometrial cancers are adenocarcinomas and are associated with endometrial hyperplasia.  Endometrial cancer can be seen as an inhomogeneous focal mass.  There are reports that the endometrial cavity has poor distensibility when saline is infused into the cavity.  Thus the use of a catheter with an occlusive balloon is important for accessing the distensibility of the uterine cavity after the infusion of saline.




Tamoxifen is used as an adjunctive therapy for breast cancer.  It has a weekly oestrogenic effect on the endometrium, resulting in increased incidence of endometrial cavity and endometrial anomalies.  With the use of Tamoxifen, the incidents of endometrial polyps is estimated to be between 8% and 35%.  Tamoxifen related polyps are generally larger and differ from non-Tamoxifen related polyps in their histology.  Endometrial hyperplasia is increased in incidence with Tamoxifen treated woman.  The incidence is 1.3% to 20%.  SIS and transvaginal sonography (TVS) have been advocated as tools for evaluating these women.  Fong found that asymptomatic post-menopausal women being treated with Tamoxifen have endometrial abnormalities in 40% of cases.  Using receiver operated characteristic curves (ROC), Fong found that an endometrial thickness of 6mm should be used as the upper limit of normal in patients who are taking Tamoxifen.  He also found that SIS is more sensitive and specific than TVS alone. 


In post-menopausal woman undertaking Tamoxifen therapy who have had abnormal uterine bleeding, TVS and SIS are useful investigations for assessment of the endometrial thickening, the presence of polyps and the presence of cystic dysplasias within the polyps.  SIS is a useful tool in evaluating these structures within the endometrial cavity.




Saline infusion sonohysterography is a simple technique that yields a large amount of information over transvaginal scanning alone.  There are very few complications.  Because the walls of the endometrium are separated by the saline, they can be evaluated individually.  Focal anomalies are beautifully displayed by this technique.  Saline infusion sonohysterography requires minimal patient preparation and is well tolerated by the patient.