What is the purpose and procedure of Hysterosalpingoscintigraphy (HSS) in diagnosing infertility or uterine abnormalities?

Hysterosalpingoscintigraphy (HSS) in Diagnosing Infertility

Hysterosalpingoscintigraphy (HSS) is a functional imaging test that evaluates the transport function of the uterus and fallopian tubes by tracking radionuclide movement, and can serve as a predictive test for IVF success in patients with idiopathic infertility who have patent fallopian tubes but impaired transport function. 1

Purpose of HSS

• HSS assesses the functional transport capability of the female reproductive tract, specifically the directed transport of radionuclides from the uterus toward the fallopian tubes, mimicking sperm transport at ovulation 1
• Unlike structural tests like hysterosalpingography (HSG) or hysterosalpingo-contrast sonography (HyCoSy), HSS evaluates the physiological function rather than just anatomical patency 2, 1
• HSS can identify patients with "idiopathic infertility" who have patent tubes but impaired transport function, potentially guiding treatment decisions toward IVF 1

Procedure of HSS

• The procedure involves administering radionuclides into the uterus during the late follicular phase of the menstrual cycle 1
• In normal functioning, there is quick uptake of radionuclides into the uterus and transport to the side bearing the dominant follicle in approximately 70% of patients 1
• The test is considered positive when there is appropriate directional transport of particles toward the fallopian tubes 1
• A negative HSS result shows uptake of particles without transport toward the fallopian tubes, indicating impaired transport function despite anatomical patency 1

Clinical Significance and Outcomes

• Patients with negative HSS results (27% in one study) showed significantly lower pregnancy rates with timed intercourse or insemination (8.4%) compared to those with positive HSS (15%) 1
• Importantly, patients with negative HSS had significantly higher pregnancy rates with assisted reproductive technologies (ART) like IVF (57% vs. 25%), suggesting that HSS can identify candidates who would benefit from proceeding directly to IVF 1
• HSS may be particularly valuable in cases of unexplained infertility where standard structural tests like HSG show normal results 1

Comparison with Other Diagnostic Methods

• HSG remains the more common first-line test for evaluating tubal patency with 65% sensitivity and 85% specificity compared to laparoscopy 2
• HSG provides structural information about tubal patency, size, irregularity, and peritubal disease, but not functional transport capability 2, 3
• HyCoSy is another alternative with similar accuracy to HSG for determining tubal patency 2
• MRI has high accuracy (75.6%) for detecting hydrosalpinges but is not typically used as a first-line test for tubal patency 4
• Diagnostic hysterolaparoscopy is considered the gold standard but is more invasive than HSS, HSG, or HyCoSy 5

Clinical Applications

• HSS is particularly valuable for patients with unexplained infertility who have normal HSG results showing patent tubes 1
• A negative HSS result (impaired transport function) should be considered an indication for proceeding directly to IVF treatment rather than continuing with timed intercourse or insemination 1
• HSS provides functional information that complements the structural information obtained from HSG or HyCoSy 2, 1

Limitations and Considerations

• HSS is less commonly used than HSG or HyCoSy in routine infertility workups 2
• The test requires nuclear medicine facilities and expertise in interpreting the results 1
• While HSS evaluates transport function, it does not provide detailed anatomical information about uterine abnormalities that might be detected with HSG, MRI, or hysteroscopy 6