Saline Infusion Sonohysterography (SIS) is a specialized diagnostic procedure that provides a detailed view of the uterine cavity. This technique combines a standard transvaginal ultrasound with the introduction of sterile saline solution into the uterus. The saline acts as a contrast agent, gently distending the uterine walls and separating the endometrial lining. This fluid-filled environment allows the ultrasound waves to create clearer, more precise images of the inner structures than a conventional ultrasound alone can provide. SIS is a well-tolerated, office-based procedure used to diagnose conditions affecting the shape and health of the uterine lining.
Conditions Diagnosed Using SIS
The primary purpose of SIS is to investigate the internal contours of the uterus when structural abnormalities are suspected. A frequent indication is unexplained abnormal uterine bleeding, including heavy, prolonged, or irregular menstrual flow, or bleeding after menopause. The enhanced visualization helps distinguish benign, focal lesions from diffuse changes in the endometrial tissue.
SIS is highly effective in identifying specific growths that project into the uterine cavity, such as endometrial polyps and submucosal fibroids. Endometrial polyps are localized overgrowths of the uterine lining, while submucosal fibroids are muscular tumors that grow just beneath the lining. These lesions can be the source of abnormal bleeding or contribute to fertility issues by interfering with implantation.
The procedure is also a standard tool in fertility workups, particularly for patients experiencing infertility or recurrent miscarriages. By clarifying the shape of the uterine cavity, SIS can detect congenital abnormalities, like a uterine septum, which is a band of tissue dividing the cavity. It is also used to identify intrauterine scar tissue, known as adhesions or synechiae, which can develop after uterine surgery or infection and compromise the uterine environment.
Patient Preparation and Procedure Steps
SIS timing is carefully selected to ensure the most accurate results. It is typically performed shortly after the menstrual period ends but before ovulation, ideally between day five and day eleven of the cycle. This timing is used because the endometrial lining is thinnest, offering the clearest view of any underlying structural issues. For patients who are postmenopausal or not menstruating, the test can be scheduled at any time.
Patients are advised to empty their bladder immediately before the procedure. To minimize discomfort, taking an over-the-counter pain reliever, such as ibuprofen, about 30 to 60 minutes prior to the appointment is recommended. The procedure itself usually takes less than 30 minutes to complete, with the imaging portion lasting only a few minutes.
The process begins with a standard transvaginal ultrasound to get an initial view of the uterus and ovaries. A speculum is then inserted into the vagina to visualize the cervix, allowing the clinician to gently cleanse the area. A small, flexible, thin tube, known as a catheter, is then threaded through the cervix and positioned inside the uterine cavity.
After the catheter is secured, the speculum is removed, and the transvaginal ultrasound probe is reinserted. The sterile saline solution is then slowly infused through the catheter into the uterus under continuous ultrasound guidance. This creates a temporary fluid pocket that outlines the inner uterine surfaces. Patients may experience mild to moderate cramping or pressure, similar to menstrual cramps, as the fluid distends the cavity.
Understanding Results and Potential Side Effects
Once the images are captured, the catheter and ultrasound probe are removed, and the patient can typically resume normal activities immediately. The saline fluid naturally drains out of the uterus over the next few hours, sometimes resulting in a watery discharge. Mild spotting, which may be red or brown, and persistent cramping are common after-effects that usually resolve within a day.
The images are reviewed by a specialist to identify any irregularities in the contours of the uterine cavity. Clear findings indicate a smooth, normal cavity, while abnormal results may show the presence of polyps, fibroids, or scar tissue. SIS has a high degree of accuracy, which helps guide the next steps, such as whether a more invasive procedure like hysteroscopy or a tissue biopsy is required for confirmation or treatment.
SIS is considered a safe procedure, with serious complications being rare. The most significant, though infrequent, risk is the development of a pelvic infection, which occurs in less than one percent of patients. This risk is slightly higher for individuals with pre-existing conditions like blocked fallopian tubes. Patients should contact their doctor immediately if they develop a fever, severe or worsening pelvic pain, or a foul-smelling vaginal discharge in the days following the procedure.