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Uterine Arteriovenous Malformation (UAVM)

Overview

Uterine arteriovenous malformation (UAVM) is a rare, abnormal connection between the arteries and veins within the uterine wall. Instead of blood flowing through the normal capillary network, it shunts directly from high‑pressure arteries to low‑pressure veins, creating a tangle of vessels that can bleed heavily when disturbed. UAVM can be either congenital (present at birth) or, more commonly, acquired after a uterine injury such as surgery, trauma, or pregnancy‑related conditions.

Although precise prevalence is uncertain because many cases are under‑diagnosed, studies estimate that UAVM accounts for roughly 1–2 % of abnormal uterine bleeding cases that require intervention in referral centers.<sup>[1] Mayo Clinic</sup> It most often presents in women of reproductive age (20–45 years), but cases have been reported in adolescents and post‑menopausal women.

Symptoms

Symptoms can range from mild to life‑threatening. The most common presentations include:

• Heavy or prolonged vaginal bleeding – often described as “menorrhagia” or bleeding that continues for days after a menstrual period.
• Post‑procedural hemorrhage – sudden, heavy bleeding after a uterine curettage, hysteroscopy, cesarean section, or myomectomy.
• Pain or pelvic pressure – a dull ache or cramping sensation that may be intermittent or constant.
• Spotting or brown discharge between periods.
• Rapid heart rate (tachycardia) and dizziness during a bleeding episode, indicating blood loss.
• Signs of anemia – fatigue, shortness of breath, pallor, or headaches that develop over weeks.
• Fertility concerns – some women discover UAVM while exploring infertility or during early pregnancy work‑up.

In rare cases, the malformation can rupture spontaneously, causing sudden massive hemorrhage that may require emergency surgery.

Causes and Risk Factors

Primary causes

• Congenital UAVM – developmental errors in vascular formation during embryogenesis.
• Acquired UAVM – most cases, resulting from:
  • Uterine surgery (e.g., dilatation & curettage, hysteroscopic polypectomy, myomectomy).
  • Cesarean delivery or other obstetric trauma.
  • Placental invasion disorders such as placenta accreta, increta, or percreta.
  • Uterine infections (e.g., pelvic inflammatory disease).
  • Radiation therapy to the pelvis.

Risk factors

• History of uterine surgery or curettage.
• Multiple pregnancies, especially with complicated deliveries.
• Prior uterine trauma (e.g., abortion, miscarriage management).
• Coexisting vascular anomalies elsewhere in the body.
• Age 20–45 years (peak reproductive years).

Diagnosis

Because UAVM mimics other sources of abnormal uterine bleeding, a systematic approach is essential.

Initial evaluation

• Detailed medical history – focusing on prior uterine procedures, bleeding patterns, and any rapid changes in flow.
• Physical examination – pelvic exam may reveal a pulsatile uterus or active bleeding.
• Laboratory tests – complete blood count (CBC) to assess anemia, type & cross‑match if transfusion may be needed.

Imaging studies

1. Transvaginal color Doppler ultrasound – first‑line test; shows a “tangled” vascular mass with high‑velocity, low‑resistance flow. Sensitivity >85 %.<sup>[2] CDC</sup>
2. Pelvic MRI with contrast – provides detailed anatomy, helps differentiate UAVM from fibroids or retained products of conception.
3. CT angiography – used when planning endovascular therapy; visualizes feeding arteries.
4. Pelvic arteriography (digital subtraction angiography, DSA) – gold standard; directly demonstrates the arteriovenous shunt and allows therapeutic embolization during the same session.

Histopathology (rare)

If a tissue sample is obtained (e.g., after hysterectomy), microscopic examination reveals tangled arterioles and venules lacking an intervening capillary bed.

Treatment Options

Management depends on symptom severity, desire for future fertility, and the size/location of the malformation.

Medical (conservative) management

• Hormonal therapy – combined oral contraceptives, progestin‑only pills, or a levonorgestrel IUD can reduce bleeding but do not eradicate the lesion.
• Tranexamic acid – antifibrinolytic used short‑term to control acute bleeding episodes.
• Iron supplementation – oral or IV iron to correct anemia.

Medical therapy is generally reserved for patients with minimal bleeding who wish to preserve fertility while monitoring the lesion.

Interventional radiology

• Uterine artery embolization (UAE) – the preferred first‑line definitive treatment for most symptomatic UAVMs. Polyvinyl alcohol particles or calibrated microspheres are injected to occlude feeding vessels, achieving hemostasis in >90 % of cases.<sup>[3] Cleveland Clinic</sup>
• Selective arterial embolization – targets only the vessels supplying the malformation, sparing normal uterine tissue and preserving fertility in many cases.
• Complications are rare but can include pelvic pain, transient fever, or non‑target embolization.

Surgical options

• Hysterectomy – definitive cure, recommended for women who have completed childbearing or when embolization fails.
• Laparoscopic or open excision of the malformation – technically demanding; reserved for focal lesions where fertility preservation is essential.
• Myomectomy with concurrent embolization – sometimes performed when a fibroid coexists with UAVM.

Emergent control of hemorrhage

When massive bleeding occurs, immediate steps include:
• Intravenous fluids and blood products (packed RBCs, plasma).
• Rapid uterine artery embolization (if interventional radiology is on‑site).
• If embolization is unavailable, surgical tamponade or hysterectomy may be lifesaving.

Living with Uterine Arteriovenous Malformation

Even after successful treatment, ongoing self‑care helps maintain health and reduces recurrence risk.

• Regular follow‑up imaging – Doppler ultrasound at 3, 6, and 12 months post‑embolization to ensure the lesion has resolved.
• Monitor menstrual patterns – note any return of heavy bleeding or spotting and report promptly.
• Maintain adequate iron stores – diet rich in lean red meat, beans, fortified cereals; consider supplements if labs show low ferritin.
• Exercise wisely – moderate aerobic activity is safe; avoid high‑impact sports that could cause uterine trauma during the first 6 weeks after treatment.
• Pregnancy counseling – most women can conceive after embolization, but discuss timing with your OB‑GYN. Some providers recommend waiting 6–12 months to allow complete vascular remodeling.
• Emotional support – experience of heavy bleeding can be distressing. Consider counseling, support groups, or patient‑advocacy organizations.

Prevention

Because many UAVMs are acquired, certain practices can lower the risk:

• Use gentle techniques during uterine procedures; clinicians should employ ultrasound guidance when possible.
• Limit unnecessary curettage or repeated D&C procedures.
• Manage placental disorders early; multidisciplinary care for placenta accreta reduces vascular injury.
• For women undergoing pelvic radiation, discuss fertility‑sparing options and vascular protective strategies with a radiation oncologist.

There is currently no proven lifestyle measure that prevents congenital UAVM.

Complications

If left untreated or incompletely treated, UAVM can lead to:

• Severe anemia requiring transfusion or iron overload.
• Life‑threatening hemorrhage – rapid blood loss can cause hypovolemic shock.
• Infertility or recurrent pregnancy loss – abnormal uterine vasculature interferes with implantation or placental development.
• Uterine scarring after multiple interventions, potentially leading to adhesion formation (Asherman syndrome).
• Psychological impact – chronic bleeding can cause anxiety, depression, and reduced quality of life.

When to Seek Emergency Care

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References

1. Mayo Clinic. “Uterine arteriovenous malformation.” Updated 2023. mayoclinic.org
2. Centers for Disease Control and Prevention. “Uterine vascular malformations.” 2022. cdc.gov
3. Cleveland Clinic. “Uterine Arteriovenous Malformation: Diagnosis and Management.” 2024. my.clevelandclinic.org
4. World Health Organization. “Guidelines for the management of abnormal uterine bleeding.” 2021.
5. National Institutes of Health. “Uterine Arteriovenous Malformation – Clinical Presentation and Treatment.” 2022.

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