AVMs can be defined as a vascular structural anomaly
involving abnormal communication between arteries and veins that bypass the capillary
system. AVMs can be further categorized as 1) high-flow
vascular malformations as typified by a high-pressure gradient
across the arterial and venous system that enables a high vascular flow through
the nidus, the intervening network of vessels communicating the arteries to the
veins. 2) fistulous connectionà a direct communication may exist in the absence
of a nidus representing a fistulous connection of the arteries and venous
structures. Though AVMs involving the uterus are rare, if present, they can be
a serious cause of recurrent and intermittent menorrhagia.
Classification of AVM of uterus: Uterine AVMs are divided into A) congenital and B) acquired AVMs. Congenital
AVMs result from a defect in the differentiation of the primitive capillary
plexus during fetal angiogenesis.
Etiology of AVM:-In
contradistinction, acquired AVMs are vascular abnormalities usually present after trauma, surgical
intervention, or in the setting of a preexisting pathologic uterine process.
Case reports have described acquired AVM formation following
uterine dilation and curettage (D&C), cesarean section, and myomectomy. Pathologic
processes such as infection, trophoblastic disease, and malignancies involving
the uterus have also been described as associated with acquired AVMAn acquired uterine AVM is a rare cause of life-threatening bleeding that may be the
result of trauma, surgical intervention, or in the setting of a preexisting
pathologic uterine process. Historically, treatment for uterine
AVMs required hysterectomy however,
transcatheter vascular embolization (TCE) has provided an alternative treatment
option for patients wishing to preserve fertility. Nevertheless, the method and
approach of transcatheter treatment and the embolic agent utilized varies in
the literature
An
acquired uterine AVM is characterized by a single Arteriovenous communication
between the branches of the uterine artery and the myometrial
venous plexus. Indeed, terms, including “arteriovenous fistula,”
“traumatic uterine arteriovenous malformation,” and “arteriovenous shunt” are
interchangeably used in the literature, despite their differences, to describe
such acquired pathology which may be difficult to differentiate. ( AJP Rep. 2016 Mar; 6(1): e6–e14.
.
Acquired AVM was defined as a uterine AVM pertaining to or diagnosed following
trauma, surgical intervention, or in the setting of a preexisting pathologic
uterine process. Included articles described the uterine AVM as acquired and
included a description of the underlying pathology.
The
broad initial search using the search heading “uterine
Acquired
uterine AVMs are typically identified in symptomatic, multiparous women of childbearing
age. \
NO D & C once sonologically AV
malformation isd suspected by Doppler:-That may be fatal!!! The differential diagnosis for a woman of childbearing age
presenting with menorrhagia and metrorrhagia is broad .Although rare, acquired
uterine AVM should be considered in patients with appropriate history and
presenting symptoms. Notably, the typical treatment options for uterine
bleeding, such as D&C, can cause uterine trauma and paradoxically worsen
the bleeding in the presence of an acquired AVM. D&C is therefore contraindicated
in acquired uterine AVM or those patients with suspected acquired AVM.. If
there is increased bleeding during a D&C performed for abnormal uterine
bleeding, then a uterine AVM should be suspected and the appropriate
precautions taken for the possibility of ongoing severe hemorrhage.
Historically,
acquired uterine AVM was diagnosed by pathology after hysterectomy Recently,
less invasive imaging studies have been utilized for diagnostic purposes to
guide therapeutic options.
How to diagnose AV malformations?? The most common presenting symptoms of an acquired
uterine AVM are menorrhagia and metrorrhagia. Bleeding is often intermittent
and torrential. This is secondary to the high vascular flow across the involved
lesion due to the differential pressure gradient across the arterial and venous
systems. These patients may also present with anemia and hypotension, secondary
to acute blood loss. Ans: TVS & Doppler : Transvaginal ultrasound is
the initial imaging study of choice for abnormal uterine bleeding. As a
definitive diagnosis based on grayscale ultrasound imaging is difficult alone. A history of recurrent spontaneous abortion
may also place a patient at higher risk for acquired uterine AVM formation,
possibly due to the increased vascularization and resultant physical alteration
of the embryo's implantation site. Despite these common presenting
symptoms, patients may alternatively remain asymptomatic despite the presence
of a uterine AVM. Asymptomatic patients may later develop symptoms following
uterine trauma or secondary to hormonal changes related to pregnancy or the
menstrual cycle.
What does Doppler informs us?? Ans: Doppler imaging is imperative to the
diagnosis. The presence of a tubular, hypoechogenic structure in the myometrium
by grayscale ultrasound imaging, although common, is not specific for uterine
AVM. The identification of uterine high velocity blood flow with low impedance
by Doppler ultrasound is highly suggestive for a uterine AVM). Subinvolution of
the placental bed and adenomyosis in the setting of menorrhagia also can have
similar ultrasound findings such as hypervascularity and turbulent flow. There
are no firm criteria to differentiate between an AVM and the subinvolution of
the placenta by ultrasound. This raises a concern for the overdiagnosis of
uterine AVM.
How
relevant is MRI??
Magnetic resonance imaging (MRI) is recommended for the evaluation
beyond ultrasound for uterine AVM when indicated, particularly in cases when
the acoustic windows are limited by body habitus or technique. MRI findings
include serpiginous signal voids in
the uterus and enhancement of the signal voids on rapid data acquisition during
infusion of contrast. MRI provides better tissue contrast and
helps delineate the surrounding pelvic organ involvement. Acquired AVM primarily involves the myometrium while retained products
of conception primarily involve the endometrium The diagnosis can be
confirmed when these imaging findings are coupled with maternal serum hCG,
which has a slower decline in retained products of conception.
How important is CT
in picking up AV malformations?? Computed
tomography (CT) can assess the degree of involvement of the surrounding
visceral structures. however, utilizes ionizing radiation, which
should be avoided in women of childbearing age and does not contribute
additional information beyond that garnered by MRI. Characteristic CT findings
include the presence of a soft-tissue density mass with enhancement pattern
resembling adjacent vessels. Angiography should be offered in
consideration for a possible therapeutic option following diagnostic
confirmation. There are typical findings of a uterine AVM by
angiography include high arterial flow with early venous filling 
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