Uterine AVMs: Morphologic Patterns
The available evidence does not describe uterine arteriovenous malformations (AVMs) as forming distinct "clusters" or "sheets" as specific morphologic patterns. Uterine AVMs are characterized on imaging as areas of enhanced myometrial vascularity with numerous abnormal vascular channels, rather than discrete clustered or sheet-like formations 1.
Imaging Characteristics of Uterine AVMs
Grayscale Ultrasound Findings
- Thickening of the uterine wall with numerous cystic lesions representing dilated vascular spaces 2
- These appear as multiple anechoic or hypoechoic tubular structures within the myometrium 2
Doppler Ultrasound Features
- Doppler imaging is essential for diagnosis, showing low-resistance arterial flow patterns within the myometrium 1
- Color Doppler demonstrates hypervascular lesions with turbulent flow 2
- The vascular channels show direct arteriovenous connections without an intervening capillary bed 3
MRI Appearance
- Inhomogeneous signal void on T1- and T2-weighted sequences 4
- Dynamic MRI and magnetic resonance angiography reveal hypervascular lesions 2
- May show hemosiderin deposits suggesting prior hemorrhage 4
Important Diagnostic Considerations
Terminology Evolution
- The terminology for these lesions is evolving, with many not representing true AVMs 1
- Alternative terms include "vascular lesions" and "enhanced myometrial vascularity" 1
- Many of these lesions will resolve spontaneously, particularly acquired forms 1, 5
Critical Diagnostic Pitfalls
- Exercise caution when diagnosing uterine AVMs in the postpartum period, as similar ultrasound findings can occur with retained products of conception (RPOC) and gestational trophoblastic disease (GTD) 1
- Low-resistance arterial flow in the myometrium may also result from subinvolution of the placental bed, which can occur after first trimester pregnancy loss and simulate an AVM 1
- In stable patients, follow-up ultrasound should be performed before definitively diagnosing or treating a potential AVM 1