Postabortal Placental Polyp or Uterine AVM? Saline Instillation Sonohysterography as a Diagnostic Aid

Uterine arteriovenous malformations (AVMs) are rare lesions that can be congenital or acquired. The acquired form is most often associated with trophoblastic disease or uterine surgery. Ginsberg and colleagues¹ described a case following a suction curettage for a missed abortion in which the diagnosis was made by sonography and color Doppler imaging. Recently, we had a case of placental polyp following suction curettage for missed abortion with very similar ultrasound and color Doppler findings in which saline sonohysterography hinted at the true pathology.

Case Report

Our patient is a 36-year-old woman P1021 evaluated for acute pelvic pain. She had had a dilatation and evacuation for a missed abortion at 13 weeks one month prior to presentation, where she described crampy pelvic pain since the procedure. She gave no history of vaginal bleeding, observing that bleeding seemed “unusually light.” Ultrasound was performed, revealing a slightly hyperechoic area in the central uterus with prominent cystic spaces (Figure 1). On power Doppler, these cystic spaces represented increased vascularity with prominent tortuous vessels.

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Because of uterine tenderness on exam, a diagnosis of endometritis was entertained and the patient was given antibiotics. The differential diagnosis of the vascular lesion included an unusual appearance of retained products of conception, acquired uterine arteriovenous malformation or, less likely, trophoblastic disease.

The following week, ultrasound was repeated, again demonstrating hypervascularity. Pulsed Doppler of the lesion revealed a peak systolic velocity of 63.8 cm/sec and resistive index of 0.29. Introduction of saline into the uterine cavity suggested the existence of a plane of cleavage (Figure 2), favoring a diagnosis of a broad-based placental polyp rather than an AVM. Serum beta-HCG was 43 IU/mL, also favoring retained products. A repeat suction dilatation and curettage was performed. The final pathology report confirmed products of conception.

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Discussion

Uterine AVMs involve abnormal vascular connections and usually present as abnormal, sometimes catastrophic bleeding. Because they rarely are found in women who have never been pregnant, pregnancy seems to play a role in their formation. Since the 1990s, color Doppler has supplanted arteriography as the primary diagnostic modality in these cases. Kido et al² reported a case in which the sonographic and Doppler appearance of retained products of conception were identical to that of AVM. Müngen³ opined that arteriography should be more widely utilized prior to definitive therapy.

In our case, because the relationship of the lesion to the uterine cavity was not clearly delineated, we performed saline instillation. The contrast provided by the saline suggested a plane of cleavage, which led to the correct diagnosis and therapy. Moreover, saline instillation is less invasive than arterial catheterization and does not involve ionizing radiation. We would suggest that when the diagnosis of uterine vascular lesions is uncertain, saline instillation sonohysterography should be considered.

References:

1. Ginsberg NA, Hammer R, Parikh S, et al. Arteriovenous malformation of the uterus associated with a missed abortion. Ultrasound Obstet Gynecol. 1994;4:235-237.

2. Kido A, Togashi K, Koyama T, et al. Retained products of conception masquerading as arteriovenous malformation. J Comput Assist Tomogr. 2003;27:88-92.

3. Müngen E. Vascular abnormalities of the uterus: have we recently over-diagnosed them? Ultrasound Obstet Gynecol. 2003;21:529-531.