Saline infusion sonohysterography (SIS) or saline ultrasound uterine scan is a test where a small volume of saline (salt solution) is inserted into the uterus (or womb). This allows the lining of the uterus (endometrium) to be clearly seen on an ultrasound scan. It is also known as a saline ultrasound uterine scan. “Ultrasound” is the term used for an imaging test that uses high frequency soundwaves. SIS helps to see if there is any thickening of the endometrium of the uterus, or if there are polyps. Polyps are small growths of the endometrium. The scan can also be performed in the assessment of post menopausal endometrium or possible Asherman’s Syndrome (a condition caused by the presence of scars in the uterine cavity).