Uterine Artery Embolization: Technique and Complications

Uterine bleeding has always been a major concern when talking about women’s health - whether it occurs during or after childbirth, as part of overly heavy menstruation, or following surgery on the uterus. Uterine fibroids have contributed to a large share of this condition.

For this reason, millions of hysterectomies and myomectomies are done across the world for women with fibroid-related abnormal uterine bleeding, either following failed medical management or as a primary treatment. Even then, the surgery was accompanied by excessive hemorrhage in many cases.

In the latter part of the 1980s, Jacques Ravina began to explore the theoretical and practical aspects of uterine artery embolization (UAE) as a pre-operative measure to reduce the hemorrhagic complications of surgical management of uterine bleeding - especially due to fibroids.

Since this measure was already in use for the postoperative management of such hemorrhage, the technology existed, and progress was correspondingly rapid. To his surprise, UAE often served as a definitive primary treatment making surgery unnecessary for the control of symptoms.

What to Expect

Before performing a UAE, the patient should be evaluated with respect to the signs and symptoms, as well as her desire to conceive following the procedure. Imaging of the uterus and other pelvic organs utilizing an ultrasound and MRI scanning, a Pap smear, and an endometrial biopsy, are all recommended to rule out other disease. A careful medical history should be taken.

Following routine pre-operative preparation, an intravenous line is placed and various drugs are given including anesthetics, antibiotics, and analgesics. Various protocols have been described for this procedure, stemming from classic epidural anesthesia to patient-controlled analgesia (often in combination with paracetamol and non-steroidal anti-inflammatory drugs).

The common femoral artery is used for insertion of the catheter, through a single small groin incision. Contrast agent is injected, commonly an iodine-containing one, which outlines the uterine arteries on both sides with their branches, and the fibroid-supplying network of vessels. A technique called fluoroscopy is used to see these images using a pulsed X-ray beam.

A thin slender tube, called a catheter, is used to gain access to the uterine arteries. The type of catheter used is one which can be used for insertion into the uterine arteries, such as the Robertson uterine catheter or the Cobra glidecath.

The interventional radiologist injects the embolic agent into the identified branch of the uterine artery. The contrast injection is repeated, and the image is viewed to make sure that the vessels to the fibroids are blocked completely. The other side is then visualized and treated similarly.

Following UAE, the patient is asked to lie prone in order to help clot form at the femoral artery puncture site. In about 24 hours, the patient is encouraged to move around and the urinary catheter is taken out. The patient is commonly discharged with oral analgesic prescription as required (for a few days up to a few weeks).

Positioning the Catheter and Preventing Collateral Flow

The tip of the catheter is currently recommended to be placed, if possible, beyond the place where the branch of the uterine artery supplying the cervix and upper vagina begins, in order to spare these regions from the results of the embolization. This is due to their proposed role in normal sexual experience.

The ovarian arteries provide several branches to the uterus in about 5% of women, which can result in the partial failure of the procedure due to this collateral supply. When faced with such situation, the embolization should include the uterine artery to the point beyond which the ovarian artery branches join those of the uterine artery, in order to supply the fundus (the upper part) of the uterus.

Care should be taken not to compromise the ovarian flow. Gelatin sponge pledgets or other particles above 500-600 micrometers are ideal for proximal injection into the ovarian artery. This is because the ovarian vasculature is too small to allow them to enter the vessels, and they will therefore embolize the uterine vessels instead through the anastomotic points. In addition, the artery of the round ligament is also embolized if found to supply the uterus.

Agents Used

Different agents are used according to the indication for the procedure. The earliest UAE procedures for fibroid embolization used polyvinyl alcohol (PVA) particles, after which a gelatin sponge pledget was used to block the proximal end of the embolized vessel and to prevent backflow of the embolic particles.

This was confirmed by iliac artery injection which showed a small stump of uterine artery filling followed by a stationary column of contrast material within the vessel. Although highly effective in reducing fibroid size, more fibroids may grow in the future, thus the stump of the main vessel should be preserved. This is difficult with the use of PVA, which is of uneven size producing a more proximal occlusion than intended.

The next option to emerge was the use of calibrated microspheres which offered ease of use due to predictable flow, and reduced clogging of the catheters. In turn, this means a much-reduced dose of the embolic agent is used to achieve blockage of the arteries supplying the fibroid rather than the main uterine artery.

This is apparently made easier by the low-resistance nature of the vessels around the fibroid, compared to normal myometrial vessels, and to the increased vulnerability of the fibroid to an interruption in the oxygen supply. The signs of this end-point are:

• new collateral vessels appear after the UAE
• there is increased difficulty in injecting the contrast after a successful UAE
• the main uterine artery is blocked on a post-operative angiogram

Both agents are equally safe and effective, however. In case UAE is performed for postpartum or vaginal hemorrhage, other options include gelatin foam, n-butyl cyanoacrylate which is like a glue, and even coils in some circumstances.

UAE Outcomes

UAE is associated with successful occlusion in up to 99% of cases, but symptomatic relief is confirmed in a slightly lower percentage of patients. Thus, menorrhagia and uterine size is reduced in 85-95% and 80-90% of cases, respectively. The percentage of decrease in uterine volume is not directly related to relief in pressure symptoms and menorrhagia, however.

In all the available reports, UAE patients require less hospitalization, return to work sooner, and are capable of returning to normal activity within a shorter time. Moreover, the return of fertility following UAE is comparable to that after myomectomy.

Complications

The rate of complications following UAE is about 1-3%. The most common among these are:

• Pain: this is the most common side effect, and is usually due to the interruption of the blood flow, as well as the temporary lack of oxygen in the normal myometrium as well. It is worst during the first 24 hours, and necessitates adequate pain medication.
• Postembolization syndrome: this is a syndrome characterized by low fever, nausea, pain, vomiting and (most commonly) tiredness. It occurs at about 48 hours following the procedure, and rarely lasts beyond a week with conservative management. Symptoms persisting longer than this should be separately evaluated.
• Fibroid expulsion: the expulsion of a detached fibroid may be quite distressing, associated with pain in the lower abdomen, infection and (very commonly) the need for surgical removal of the fibroid through the vagina – especially if antibiotics and analgesics fail to provide relief and control of infection.
• Excessive vaginal discharge: this may be due to the sloughing of necrotic tissue from a fibroid, and is seen in up to a fourth of patients who had submucosal fibroids. This may last for up to a month after the procedure. Conservative management is the rule but occasionally the uterus may require to be emptied surgically of the dead tissue.
• Uterine artery dissection or rupture: the catheter may accidentally creep between the layers of the uterine artery wall, weakening it (this is termed dissection), or may even break through the wall (rupture). This may require open surgery for repair. Luckily, this is a rare complication.
• Complications of angiography: these include hypersensitivity to the contrast agent, extravasation (the exit of contrast agent from the cannulated vessel), as well as the impairment of renal function

What to watch for during follow-up period

Any high fever, chills and severe pain may signal an infection and should be reported to the healthcare provider. The patient is commonly asked to return after three months for an MRI imaging test to evaluate any uterine and fibroid changes in size.