A Shadowed Endometrium and a Request for Saline Infusion Sonography
A 42-year-old G2P2 with 8 months of heavy, irregular menses and secondary infertility has a transvaginal scan showing an anteverted, normal-sized uterus. A 2.5 cm densely calcified intramural fibroid in the anterior fundal myometrium produces a broad, clean acoustic shadow that completely obscures the endometrium on the sagittal view. Endometrial thickness cannot be measured reliably; on one off-axis frame it appears 12 mm and heterogeneous. Both ovaries are normal and urine beta-hCG is negative. The referring clinician has requested saline infusion sonohysterography to evaluate the cavity.
1. How do you deal with the shadowing? Give specific maneuvers, what each accomplishes, and the limits of the examination.
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Dense calcific shadowing represents missing information, not an artifact to be filtered out. The endometrium can never be reported as normal through a shadow.
Maneuvers
- Change the angle of insonation: tilt and rotate the transvaginal probe, and reposition the patient (roll her, or place her fists under the hips) so the fundus tips away from the fibroid. Frequently the endometrium becomes visible from an off-axis or coronal window.
- Transabdominal approach with a full bladder: the beam enters the fundus from a different direction and may clear or sidestep the calcification; useful for anterior/fundal lesions.
- Machine optimization: move the focal zone to the depth of the endometrium, narrow the sector, adjust gain, and use tissue harmonic imaging - harmonic helps with beam-width and side-lobe artifacts but will not penetrate dense calcific shadowing.
- 3D coronal reconstruction if available; the coronal plane can show the cavity around the calcification.
Limits
- If the endometrium cannot be seen on any view, state that explicitly in the report and recommend MRI or office hysteroscopy.
- A 12 mm heterogeneous measurement taken from one off-axis frame through a shadow should not be reported as the endometrial thickness - that number will drive unnecessary or inappropriate management.
2. Describe the timing, technique, and contraindications for saline infusion sonohysterography, including how to avoid artifacts that mimic pathology.
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Timing
- Days 5–10 of the menstrual cycle - early proliferative, menses finished, endometrium thin.
- Confirm a negative pregnancy test, screen for pelvic infection and active bleeding, and treat suspected cervicitis or pelvic inflammatory disease first.
- Contraindications: pregnancy, active pelvic infection, and unexplained active bleeding until it has been evaluated.
Technique
- Lithotomy position, speculum, cleanse the cervix; stabilize with a tenaculum if needed.
- Insert a 5–7 French balloon catheter through the os so the balloon sits just beyond the internal os and inflate with 1–2 mL; a straight catheter works if the cavity is small or the cervix is tight.
- Remove the speculum, insert the transvaginal probe, then instill sterile saline slowly, typically 5–20 mL, under real-time guidance while sweeping sagittally and coronally from fundus to cervix.
- Document cavity distensibility, lesion location, size, base, and the endometrium away from the lesion.
Avoiding artifacts
- Air is the main trap: purge the tubing and catheter, use a syringe free of bubbles, and inject gently. Air produces brightly echogenic foci with ring-down or twinkling artifact that mimic polyps, stones, or adhesions - and it moves with continued infusion.
- Overdistension can flatten a polyp against the wall; underdistension can mimic synechiae.
Risks: cramping, vasovagal reaction, rare infection or perforation. Routine prophylactic antibiotics are not standard.
3. At sonohysterography the cavity distends well and a smooth, echogenic, broad-based filling defect arising from the anterior wall is outlined by saline without shadowing; the endometrium elsewhere measures 4 mm and is regular. What is your interpretation, and is anything further required?
Read the worked answer
Most likely an endometrial polyp.
- Polyps: smooth, echogenic, broad-based or stalked filling defects outlined by saline, without internal shadowing, and without distortion of the myometrial–endometrial junction.
- Submucosal fibroid: usually hypoechoic, broad-based, often shadowing, may distort the junctional zone and show a "double contour" where it meets the myometrium.
- Synechiae: thin echogenic bands, often with a tethered, poorly distensible cavity.
- Air bubbles: mobile, associated with ring-down artifact, and resolve with continued infusion.
What still has to happen
- Endometrial sampling is required. Sonohysterography is a morphological test, not a tissue diagnosis. A 42-year-old with 8 months of heavy irregular bleeding needs Pipelle biopsy or hysteroscopic resection regardless of how benign the cavity looks; age, chronic anovulation, obesity, hypertension, and unopposed estrogen all raise the risk of hyperplasia or carcinoma.
- Hysteroscopy is the definitive way to assess the deep margin of the lesion and to treat it.
- The calcified intramural fibroid does not distort the cavity and does not explain the bleeding - it only limited the initial examination, which is why the sonohysterogram was the right next step.