Uterine arterio-venous fistulas are uncommon vascular malformations of the uterus. Some of the other uterine malformations include uterine artery aneurysm, pseudoaneurysms and chorioangiomas of the placenta. The uterine AV fistulae may be congenital or may be acquired due to pelvic surgery, gestational trophoblastic neoplasia and post-partum status.

Most of the women with uterine AV malformation and fistulae present in the reproductive age group with abnormal, unexplained vaginal bleeding. Some of these patients may have a pulsatile mass on examination, audible bruit and palpable thrills.

Ultrasound with color Doppler is a sensitive modality for diagnosing uterine vascular malformations [especially AV fistulae]. Gray scale ultrasound features may be non-specific, demonstrating a hypoechoic mass or multiple anechoic channels within the uterine myometrium. Color and spectral Doppler analysis can be diagnostic and shows -
1. A highly vascular mass which demonstrates a mosaic pattern of color, suggesting turbulence.
2. Intralesional spectral analysis of the artery reveals high velocity flow with a low resistive index.  High flow velocities are also noted in the intralesional veins [due to the abnormal communication with the arteries], resulting in an arterialized venous pattern [as is seen in the case demonstrated here]. 

Management includes conservative management in certain select cases of acquired uterine AV fistulas, selective uterine artery embolization and in severely affected cases hysterectomy may be performed.