When is saline infusion sonography (sonohysterography) indicated?

When is Saline Infusion Sonography (Sonohysterography) Indicated?

Saline infusion sonohysterography (SIS) is indicated when transvaginal ultrasound shows abnormal or equivocal findings in the endometrial cavity, particularly for evaluating intrauterine adhesions, endometrial polyps, and submucosal leiomyomas in patients with infertility or abnormal uterine bleeding. 1

Primary Indications

Infertility Evaluation

• SIS is particularly useful for assessing potential causes of infertility, including intrauterine adhesions, endometrial polyps, and leiomyomas that may impact the uterine cavity 1
• The American College of Radiology recommends SIS when evaluating uterine cavity abnormalities in infertility workup, as it provides superior assessment compared to transvaginal ultrasound alone 1
• SIS demonstrated 75% sensitivity and 93% specificity for detecting intrauterine adhesions, far superior to transvaginal ultrasound 1

Abnormal Uterine Bleeding

• When transvaginal ultrasound demonstrates focal endometrial abnormalities or thickening that requires further characterization, SIS should be performed as a second-line diagnostic procedure 2, 3, 4
• SIS achieved 92.9% sensitivity and 89.7% specificity for detecting endometrial abnormalities in women with abnormal bleeding, compared to only 71.4% sensitivity and 67.7% specificity for transvaginal ultrasound alone 5
• The diagnostic accuracy is particularly high for submucosal myomas, where SIS reaches 100% sensitivity and specificity 5

Distinguishing Focal from Diffuse Lesions

• SIS excels at differentiating between endometrial polyps and submucosal fibroids, with 97% accuracy according to the American College of Radiology 2
• When transvaginal ultrasound findings are equivocal or show thickened endometrium without clear characterization, SIS provides definitive assessment 6, 7
• SIS reduces the post-test probability of missing polyps or submucous myomas from 0.18 (after TVS alone) to 0.02 (after combined TVS and SIS) 7

Specific Clinical Scenarios

Submucosal Fibroid Assessment

• SIS accurately depicts the percentage of intracavitary component of submucosal fibroids, which directly impacts treatment planning 1
• Three-dimensional SIS shows good agreement (kappa 0.80) with diagnostic hysteroscopy for classifying submucosal fibroids 1

Postmenopausal Bleeding

• When postmenopausal women present with endometrial thickness ≥5 mm and bleeding, SIS can characterize focal lesions before proceeding to tissue sampling 2, 4
• SIS achieved 94.1% sensitivity and 88.5% specificity in perimenopausal and postmenopausal women with abnormal bleeding 4

Premenopausal Abnormal Bleeding

• In premenopausal patients with abnormal bleeding, SIS combined with transvaginal ultrasound is superior to TVS alone (McNemar test, P = 0.008) 7
• SIS missed only 2% of abnormalities compared to 18% missed by transvaginal ultrasound alone 7

When SIS is NOT Indicated

Endometriosis Evaluation

• There is no relevant literature supporting isolated SIS in patients with suspected endometriosis 1
• Transvaginal ultrasound, MRI, or transrectal ultrasound are the appropriate modalities for endometriosis assessment 1

Tubal Patency Assessment

• Isolated SIS without tubal contrast agent is not indicated for evaluating tubal occlusion, though incidental fluid in the posterior cul-de-sac may suggest patency 1
• For tubal assessment, hysterosalpingo-contrast sonography (HyCoSy) with echogenic contrast is required 1

Antibiotic Prophylaxis Considerations

• Antibiotic administration is at the discretion of the referring physician if there is prior history of pelvic inflammatory disease or if hydrosalpinx is noted at the time of study 1

Common Pitfalls to Avoid

• Do not assume SIS can differentiate benign from malignant endometrial pathology with certainty—tissue diagnosis remains mandatory when malignancy is suspected 2
• The presence of leiomyomas and adenomyosis can obscure complete visualization of the endometrium, potentially masking coexistent pathology 2
• SIS cannot replace endometrial sampling or hysteroscopy with biopsy when focal endometrial abnormality is identified, regardless of whether fibroids are also present 2

Diagnostic Algorithm

1. Start with transvaginal ultrasound for initial endometrial assessment 3
2. Proceed to SIS when:
   • Focal endometrial abnormality is detected 3
   • Endometrial thickness is abnormal but etiology unclear 4, 5
   • Infertility workup requires uterine cavity assessment 1
   • Submucosal fibroid characterization is needed 1, 5
3. Consider 3D SIS for improved classification of uterine anomalies and better delineation of endometrial versus myometrial lesions 1, 6
4. Follow with tissue sampling or hysteroscopy when any abnormality is confirmed on SIS 2