Saline Infusion Sonohysterography (SIS) is a specialized diagnostic imaging technique that provides a detailed view of the uterine cavity and the endometrium (the lining of the uterus). This procedure enhances a standard transvaginal ultrasound by utilizing sterile saline to gently distend the uterine walls, creating a clear contrast for sound waves. This minimally invasive method allows healthcare providers to accurately visualize the internal structure of the uterus. SIS helps diagnose conditions that might be missed with conventional ultrasound alone and is typically performed in an outpatient setting.
Diagnostic Applications of SIS
Physicians often recommend SIS to investigate the cause of abnormal uterine bleeding, such as heavy or irregular periods. The test is effective at differentiating between normal endometrial thickening and structural abnormalities. SIS helps identify issues like endometrial polyps or submucosal fibroids (muscle tumors that grow into the uterine cavity).
SIS is also a standard part of the workup for infertility or recurrent miscarriage, as structural issues can impede implantation or cause pregnancy loss. It allows for precise mapping of the cavity to check for scar tissue, known as intrauterine adhesions or Asherman’s syndrome. SIS also helps evaluate congenital uterine abnormalities, such as a uterine septum. The improved visualization provides an accurate assessment of the cavity’s shape and contour, which is necessary before planning corrective surgical procedures.
Performing the Saline Infusion Sonohysterography
The SIS procedure begins with a standard transvaginal ultrasound to get a baseline view of the uterus and surrounding pelvic structures. Once this initial scan is complete, a speculum is inserted into the vagina to visualize the cervix, similar to a routine pelvic exam. The cervix is then often cleansed with an antiseptic solution to minimize the risk of infection.
A very thin, flexible plastic tube, called a catheter, is gently threaded through the opening of the cervix and positioned inside the uterine cavity. The speculum is then removed, and the transvaginal ultrasound transducer is reinserted into the vagina. The sterile saline solution is slowly and steadily infused through the catheter into the uterus.
The purpose of the saline is to separate the front and back walls of the uterine cavity, which normally rest against each other, thus allowing the ultrasound to clearly outline the endometrial lining. This fluid-filled cavity enables the medical professional to accurately assess the texture, thickness, and any protrusions from the lining in real-time. The procedure is relatively quick, with the imaging portion typically lasting only a few minutes once the catheter is in place.
Patient Preparation and Recovery
Patients are typically advised to schedule the SIS procedure during the follicular phase of their menstrual cycle, usually between cycle day five and day twelve, shortly after their period has ended. This timing ensures that the endometrial lining is at its thinnest, which provides the clearest view of any abnormalities, and also confirms the patient is not pregnant. To reduce potential discomfort, patients are often instructed to take an over-the-counter pain reliever, such as ibuprofen, about 30 to 60 minutes before the appointment.
Following the procedure, most patients can resume their normal daily activities immediately, as there is no required downtime. Mild cramping, similar to menstrual cramps, is common and typically resolves quickly. Patients should also expect watery vaginal discharge or light spotting for a few hours as the saline naturally drains. Although rare (less than one percent of cases), patients should contact their doctor immediately if they experience new or worsening pain, a fever, or heavy bleeding, as these may indicate a pelvic infection.