Arteriovenous malformations Dr . Reihaneh Pirjani, Peritatologist, Associate Professor, Tehran University Of Medical Sciences

Secondary PPH refers to excessive uterine bleeding occurring between 24 hours and 12 weeks postpartum. Most studies report peak incidence at one to two weeks postpartum

A uterine artery pseudoaneurysm is a very uncommon cause of delayed postpartum hemorrhage.

The most common cause is diffuse uterine atony or subinvolution of the placental site secondary to retained products of conception and/or infection. A bleeding diathesis may also be responsible. Pseudoaneurysm of the uterine artery and arteriovenous malformations are rare causes of secondary PPH described in case reports

Arteriovenous malformations of the uterus are rare lesions although it is likely that hitherto they have been underreported. It was reported the first case in 1926

Arteriovenous malformations arise by definition from an abnormal communication between an artery and a vein. AVMs can be defined as a vascular structural anomaly involving abnormal communication between arteries and veins that bypass the capillary system. Histological examination of these malformations usually reveals a localized proliferation of both arterial and venous vessels with interconnecting fistulae

Pseudoaneurysms differ from true aneurysms in that they are not surrounded by the three layers of the arterial wall; typically, they contain a single loose connective tissue layer. Pseudoaneurysms are a known complication of local trauma with vascular injury

AVMs can be further categorized as 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.

Arteriovenous malformations (AVMs) can be found anywhere in the vascular system, including the uterus.

Uterine AVMs are divided into congenital and acquired AVMs. Congenital AVMs result from a defect in the differentiation of the primitive capillary plexus during fetal angiogenesis. Acquired AVMs are vascular abnormalities usually present after trauma, surgical intervention, or in the setting of a preexisting pathologic uterine process

Some cases are thought to be congenital,and in this situation the lesions may be multiple involving other organs of the body. In most cases the lesions are acquired and have been attributed to trophoblastic disease, previous pelvic surgery or curettage, and cervical or endometrial malignancy.

The most common presenting symptoms of an acquired uterine AVM are menorrhagia and metrorrhagia. Vague pelvic discomfort, urinary symptoms, including polyuria and incontinence, and dyspareunia are common complaints.

Rupture of a uterine artery pseudoaneurysm is an uncommon, but life- threatening, cause of postpartum hemorrhage. 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.

approximately 50% of patients with acquired uterine AVM required blood transfusion secondary to the associated anemia.

uterine artery pseudoaneurysm can occur after vaginal delivery without traumatic procedure Some cases have been reported that had uterine artery pseudoaneurysm rupture after vaginal delivery or complete abortion without an apparent traumatic procedure.

Acquired uterine AVMm rarely affects nulliparous women without a history of uterine trauma secondary to gynecological procedures. A Systematic Review of Acquired Uterine Arteriovenous Malformations:

In fact pregnancy appears to have an important role in the pathogenesis of uterine arteriovenous malformations. It is postulated that these malformations may arise when venous sinuses become incorporated in scars within the myometrium after necrosis of the chorionic villi.

(7.4%) did not have such history; (93%) of them had a history of uterine procedures, such as D&C, cesarean section, or had a history of gestational trophoblastic tumor (7.4%) did not have such history; It seems cesarean delivery is the most common cause. A Systematic Review of Acquired Uterine Arteriovenous Malformations:

A Systematic Review of Acquired Uterine Arteriovenous Malformations: A literature search was performed from 2003 to 2014. In 304 publications 40 articles remained for final inclusion

A diagnosis of pseudoaneurysm of the uterine artery can be established radiologically, such as color Doppler ultrasonography computed tomography. Angiography confirms the diagnosis.

diagnosis Although a definitive diagnosis is usually made by pelvic angiography, transvaginal scanning with color Doppler provides a valuable, noninvasive method of diagnosis

Gray-scale transvaginal sonogram shows the anechoic cyst-like lesion in the cervix.

Color Doppler sonogram shows turbulent blood flow in the lumen of pseudoaneurysm.

Doppler ultrasound scan identified to-and-fro arterial flow.

Duplex Doppler examination shows the typical ‘‘to-and fro’’ pattern at the neck of the pseudoaneurysm Color Doppler will reveal a typical sign for pseudoaneurysm: a swirling blood flow or “to-and-fro”

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treatment Historically, treatment for uterine AVMs required hysterectomy; Transcatheter vascular embolization (TCE) has provided an alternative treatment option for patients wishing to preserve fertility

Nevertheless, acquired uterine AVMs may require repeat embolization for treatment and this should not be considered as a failure of embolization but rather as a requirement for additional treatments

The use of a unilateral or bilateral approach for TCE must be determined in the treatment of a uterine AVM The decision to embolize the contralateral side was largely dependent on the clinical scenario and the preference of the interventional radiologist

fail initial embolization Based on the literature search, there are no definitive treatment guidelines for patients who fail initial embolization. Further, there have been no studies completed comparing the effectiveness of repeat embolization versus medical therapy versus hysterectomy for persistent bleeding after initial embolization.

IN A Systematic Review of Acquired Uterine Arteriovenous Malformations: Of the 21 patients who continued to be symptomatic following the initial embolization: 13 (62%) underwent repeat embolizations 5 (24%) underwent medical treatments with agents such as danazol, progesterone, combination oral contraceptive pills (OCP), implanon therapy, or methotrexate, 2 underwent hysterectomy 1 laparoscopic internal iliac ligation

نکته آخر: It occurs not only after CS, but also after nontraumatic vaginal delivery or abortion, sometimes mimicking retained product of conceptions, and thus leading physicians to perform D&C. Color Doppler will unmask the hidden pseudoaneurysm, a chameleon in obstetric practice.

نکته آخر: D&C should not be performed in this condition. This may cause rupture of the pseudoaneurysm and result in profuse bleeding, Thus, when encountering late PPH, employment of color Doppler is useful