DOI: 10.1148/rg.25si055510
RadioGraphics 2005;25:S99-S117
© RSNA, 2005
Uterine Fibroid Vascularization and Clinical Relevance to Uterine Fibroid Embolization1
Jean-Pierre Pelage, MD, PhD,
Julien Cazejust, MD,
Etienne Pluot, MD,
Olivier Le Dref, MD,
Alexandre Laurent, MD, PhD,
James B. Spies, MD,
Sophie Chagnon, MD and
Pascal Lacombe, MD
1 From the Department of Radiology, Hôpital Ambroise Paré, 9 ave Charles-de-Gaulle, 92104 Boulogne Cedex, France (J.P.P., J.C., E.P., S.C., P.L.); Departments of Body and Vascular Imaging (O.L.D.) and Neuroradiology (A.L.), Hôpital Lariboisière, Paris, France; and Department of Radiology, Georgetown University Medical Center, Washington, DC (J.B.S.). Recipient of a Certificate of Merit award for an education exhibit at the 2004 RSNA Annual Meeting. Received February 15, 2005; revision requested March 25 and received June 7; accepted June 27. J.P.P. is a consultant with Biocompatibles, Biosphere Medical, and Boston Scientific, from which he has received research funding; J.B.S. is a consultant with Biosphere Medical and Boston Scientific, from which he has received research funding; and all remaining authors have no financial relationships to disclose.
Address correspondence to J.P.P. (e-mail: jean-pierre.pelage{at}apr.aphp.fr).
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Abstract
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Embolization has become a first-line treatment for symptomatic uterine fibroid tumors. Selective catheterization and embolization of both uterine arteries, which are the predominant source of blood flow to fibroid tumors in most cases, is the cornerstone of treatment. Although embolization for treatment of uterine fibroid tumors is widely accepted, great familiarity with the normal and variant pelvic arterial anatomy is needed to ensure the safety and success of the procedure. The uterine artery classically arises as a first or second branch of the anterior division of the internal iliac artery and is usually dilated in the presence of a uterine fibroid tumor. Angiography is used for comprehensive pretreatment assessment of the pelvic arterial anatomy; for noninvasive evaluation, Doppler ultrasonography, contrast material–enhanced magnetic resonance (MR) imaging, and MR angiography also may be used. After the uterine artery is identified, selective catheterization should be performed distal to its cervicovaginal branch. For targeted embolization of the perifibroid arterial plexus, injection of particles with diameters larger than 500 µm is generally recommended. Excessive embolization may injure normal myometrium, ovaries, or fallopian tubes and lead to uterine necrosis or infection or to ovarian failure. Incomplete treatment or additional blood supply to the tumor (eg, via an ovarian artery) may result in clinical failure. The common postembolization angiographic end point is occlusion of the uterine arterial branches to the fibroid tumor while antegrade flow is maintained in the main uterine artery.
© RSNA, 2005
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Introduction
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Embolization has become a first-line treatment for symptomatic uterine fibroid tumors (1) and is currently offered as an alternative to hysterectomy and multiple myomectomy (2–4). Although there is widespread acceptance of embolization for treatment of uterine fibroid tumors, this treatment method requires great familiarity with the pelvic arterial anatomy. Variations in the vascularization of uterine fibroid tumors may account for treatment failures and complications, including uterine necrosis and amenorrhea (1–5). The uterus and uterine fibroid tumors are mainly supplied by the uterine artery, but ovarian arteries and round ligament arteries also may play a role (6–8). Angiography is useful for comprehensive assessment of the anatomy of the internal iliac artery, its pattern of division, and its branches (6–8). Doppler ultrasonography (US), contrast material–enhanced magnetic resonance (MR) imaging, and MR angiography also may be useful for evaluation of the arterial supply to the fibroid tumor before embolization (7). The authors have performed more than 2000 embolization procedures for treatment of uterine fibroid tumors. The purpose of this article is to provide a comprehensive review of the arterial anatomy of the female pelvis for diagnostic radiologists interested in women’s imaging and for interventional radiologists who wish to learn more about uterine fibroid embolization. The normal arterial anatomy is reviewed because it is the key to the procedure. Anatomic variants that may result from uterine fibroid tumor vascularization also are presented because such variants help to determine the outcome of embolization. The clinical relevance of the arterial anatomy for the selection of patients and of the technique to be used in catheterization and embolization, as well as for the possibility of complications, also is discussed.
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Normal and Variant Arterial Supply to the Uterus
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Internal Iliac Artery (Hypogastric Artery)
The internal iliac artery (also called the hypogastric artery) supplies the pelvic walls and the pelvic viscera (6–8). The internal iliac artery terminates in two main stems (bifurcation), one anterior and one posterior, in 57%–77% of the general population (Fig 1) (6,8). The anterior branches (visceral and parietal) of the internal iliac artery include the inferior gluteal, obturator, internal pudendal, vesical, middle hemorrhoidal, and genital (uterine and vaginal) arteries (6,8). The posterior branches (parietal only) include the superior gluteal, iliolumbar, and lateral sacral arteries (6,8). In individuals with bifurcation of the internal iliac artery, the contralateral anterior oblique (25°–40° angle) projection is best for identification of the uterine artery (Fig 1) (6). Absence of the internal iliac artery is rarely observed (Fig 2).
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Figure 1. Digital subtraction angiogram (right anterior oblique projection) obtained with selective injection via the left internal iliac artery shows the division of the artery into two main stems (anterior stem, A; and posterior stem, P) and three branches (inferior gluteal artery, 1; uterine artery, 2; and superior gluteal artery, 3).
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Figure 2. Digital subtraction angiogram obtained with selective injection via the right common iliac artery shows the absence of the right internal iliac artery and the origin of all pelvic branches, including the uterine artery (UA), in the common iliac artery (arrow). (Courtesy of Jean-Louis Bertrand, MD, Centre Hospitalier de Perpignan, Perpignan, France.)
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Uterine Artery
Uterine fibroid tumors derive their main peripheral blood supply almost exclusively from the uterine arteries (9). The origin of the uterine artery is well identified on the contralateral oblique projection in most patients (Fig 1) (6). The uterine artery is the first or the second branch of the anterior division of the internal iliac artery (from the inferior gluteal artery) in 51% of cases (Fig 1) (6,7). In 6% of cases, the uterine artery is the first branch of the internal iliac artery above the level of the inferior gluteal and superior gluteal arteries (Fig 3) (6). In the presence of this anatomic variant, or when the internal iliac artery terminates in trifurcation (15%–40% of the general population), the ipsilateral anterior oblique projection is used (Fig 3) (6). The uterine artery has a characteristic U shape, with a descending segment that parallels the lateral pelvic wall, a transverse segment that crosses the distal ureter at the level of the cervix, and an ascending segment that courses along the uterine margin at the medial edge of the broad ligament (Figs 1, 3, 4) (6–8). The uterine artery may have a common trunk with the vesical or vaginal artery (Fig 5) (6). The uterine artery has several branches: the cervicovaginal artery, which arises from the transverse segment and which should be spared during embolization, and the intramural (arcuate) arteries, which course through the outer third of the myometrium (Fig 4) (6,8). The uterine artery may be replaced by small arterial branches (Fig 6) or may be absent; it is often replaced by the ipsilateral ovarian artery. The congenital absence of both uterine arteries is encountered in less than 1% of cases (Fig 7). The presence of aberrant uterine vessels that originate in the abdominal aorta also has been reported (10).
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Figure 3a. (a, b) Digital subtraction angiograms obtained with selective injection via the right internal iliac artery show, in left anterior oblique projection (a) and right (ipsilateral) oblique projection (b), the origin of the uterine artery (UA), which is best depicted in b (arrow) because of its location closer to the origin of the hypogastric artery. (c) Right anterior projection obtained with digital subtraction angiography shows superselective catheterization achieved by using a microcatheter and a guidewire with 90° angulation.
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Figure 3b. (a, b) Digital subtraction angiograms obtained with selective injection via the right internal iliac artery show, in left anterior oblique projection (a) and right (ipsilateral) oblique projection (b), the origin of the uterine artery (UA), which is best depicted in b (arrow) because of its location closer to the origin of the hypogastric artery. (c) Right anterior projection obtained with digital subtraction angiography shows superselective catheterization achieved by using a microcatheter and a guidewire with 90° angulation.
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Figure 3c. (a, b) Digital subtraction angiograms obtained with selective injection via the right internal iliac artery show, in left anterior oblique projection (a) and right (ipsilateral) oblique projection (b), the origin of the uterine artery (UA), which is best depicted in b (arrow) because of its location closer to the origin of the hypogastric artery. (c) Right anterior projection obtained with digital subtraction angiography shows superselective catheterization achieved by using a microcatheter and a guidewire with 90° angulation.
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Figure 4. Digital subtraction angiogram obtained with selective uterine artery injection shows the characteristic arterial course, with an initial descending segment (D), a transverse segment (T) from which the cervicovaginal artery (CV) originates, and an ascending segment (A). Numerous intramural arteries (arrows) also are visible.
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Figure 5. Digital subtraction angiogram obtained with selective injection via the right genitourinary artery trunk shows right cervicovaginal (CV), vesical (V), and uterine (UA) arteries that arise from the anterior division of the internal iliac artery via a common genitourinary artery trunk (GU).
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Figure 7a. (a) Flush pelvic aortogram shows no flow through the uterine arteries from the internal iliac artery, while both ovarian arteries, which arise from the infrarenal aorta, are visible (arrows). (b, c) Digital subtraction angiograms obtained with selective injection via the right (b) and left (c) ovarian arteries confirm ovarian arterial supply to the uterus.
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Figure 7b. (a) Flush pelvic aortogram shows no flow through the uterine arteries from the internal iliac artery, while both ovarian arteries, which arise from the infrarenal aorta, are visible (arrows). (b, c) Digital subtraction angiograms obtained with selective injection via the right (b) and left (c) ovarian arteries confirm ovarian arterial supply to the uterus.
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Figure 7c. (a) Flush pelvic aortogram shows no flow through the uterine arteries from the internal iliac artery, while both ovarian arteries, which arise from the infrarenal aorta, are visible (arrows). (b, c) Digital subtraction angiograms obtained with selective injection via the right (b) and left (c) ovarian arteries confirm ovarian arterial supply to the uterus.
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Ovarian Artery
The ovarian artery arises anteromedially from the abdominal aorta a few centimeters below the renal arteries in 80%–90% of cases and has a characteristic corkscrew appearance (6,8,11–13). Rarely, the ovarian artery arises from the renal, lumbar, adrenal, or iliac artery (Figs 8, 9) (11–13). Identification of the normal ovarian artery is not usually possible with angiography because of the small diameter of the artery (usually, less than 1 mm) (6,11,12). The ovaries are supplied by ovarian arteries in 40% of cases, by both uterine and ovarian arteries in 56% of cases, and by uterine arteries alone in 4% of cases (12,13).
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Figure 8. Anatomic variants. Flush pelvic aortogram depicts two moderately enlarged ovarian arteries (arrows): a left ovarian artery that arises from the aorta, and a right ovarian artery that arises from the right renal artery (*).
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Figure 9. Anatomic variants. Flush pelvic aortogram shows a right ovarian artery that arises from the right common iliac artery and supplies a large fundal fibroid tumor (F). (Courtesy of Gerald Zemel, MD, Miami Cardiac and Vascular Institute, Miami, Fla.)
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Round Ligament Artery
The round ligament artery, which arises from the external iliac artery or from the inferior epigastric artery, plays a minor role in uterine vascularization in normal physiologic conditions (Fig 10) (6,14).
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Figure 10. Digital subtraction angiogram obtained with selective injection via the left external iliac artery (*) shows a left round ligament artery (arrow) that arises from the inferior epigastric artery and supplies the left side of the uterus. (Reprinted, with permission, from reference 13.)
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Arterial Anastomoses
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The interventional radiologist should be aware of two different types of arterial anastomosis between the uterine arteries and the ovarian arteries: left-to-right anastomosis (between the left and the right uterine arteries) and utero-ovarian anastomosis (between the uterine artery and the ovarian artery) (6,8). Left-to-right anastomosis is visible in about 10% of cases (Fig 11) (6,8), and utero-ovarian anastomosis is identified in 10%–30% of cases (Figs 11, 12) (6,8,15). Retrograde filling of the ovarian artery is sometimes observed when contrast material is selectively injected via the ipsilateral uterine artery (6). The ovary itself is occasionally depicted (Fig 13). The usual diameter of the utero-ovarian anastomosis has been estimated to be less than 500 µm (Fig 14) (9). Anastomosis may not be present at the beginning of the procedure and may become obvious only with flow redistribution after embolization of the main arterial supply to the fibroid tumor (11,12).
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Figure 11. Digital subtraction angiogram obtained with selective injection via the left uterine artery (LUA) shows transverse anastomosis (arrow) between that artery and the right uterine artery (RUA) and retrograde opacification of the left artery via a utero-ovarian anastomosis (OA).
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Figure 12. Digital subtraction angiogram obtained with selective injection via the left uterine artery (UA) depicts reflux into the ovarian artery (OA), a sign of anastomosis between the uterine and ovarian arteries.
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Figure 13. Digital subtraction angiogram obtained with selective injection via the right uterine artery shows reflux into the ovarian artery, with resultant opacification of the ovary (arrow). Ut = uterus.
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Figure 14. Anatomic drawing shows the arterial blood supply (short arrows) to the uterus and three fibroid tumors (F). The perifibroid plexus is composed of arteries with diameters of 500–1000 µm in most cases. The diameter of the utero-ovarian anastomosis (long arrow) is usually less than 500 µm. (Reprinted, with permission, from reference 7.)
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Arterial Supply to Uterine Fibroid Tumors
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The presence of uterine fibroids usually results in distortion and enlargement of the uterine arteries (Figs 1, 4) (9,16,17), which supply both normal myometrium and the fibroids (Fig 14) (9,16–18). Usually, the flow to the fibroid tumor is substantially increased; perifibroid arteries are larger in diameter than are those that supply normal myometrium (Figs 14, 15) (9,17,18). The tumor itself is relatively hypovascular, and its interior is supplied by small centripetal arteries that originate in a rich perifibroid arterial plexus (16–19). In the presence of multiple fibroid tumors, diffuse uterine hypervascularity is usually visible at angiography (Fig 16). In a few cases, a separate arterial supply to the fibroid may be observed (Fig 17).
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Figure 15. Photomicrograph (hematoxylin-safran-eosin stain; magnification, x200) of a specimen from the periphery of an intramural fibroid tumor (F), which was resected immediately after embolization, shows targeted occlusion of the perifibroid arterial plexus with 500–700-µm-diameter calibrated microspheres (arrows).
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Figure 17. Late arterial phase flush pelvic aorto-gram in a woman with three intramural fibroid tumors shows three separate areas of localized hypervascularity with dimensions that correspond to those of the fibroid tumors.
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Even in the presence of two apparently normal uterine arteries, an additional supply to the fibroid may come from another source, such as the ovarian artery. This occurs in about 5%–10% of cases (Figs 9, 18, 19) (6–8,11,12,20,21). Ovarian artery supply to uterine fibroids is more frequently found in women who have undergone pelvic surgery and those with previously diagnosed tubal or ovarian disease and/or large fundal fibroids (Figs 19, 20) (12). In women with one or more of these predisposing factors, the extent of ovarian artery supply to the fibroid tumor should be assessed with flush pelvic aortography (11). This may be done before or after uterine artery embolization (10,11). Since only residual blood flow to the fibroid tumor may be of clinical relevance, aortography is generally advocated after uterine artery embolization (10,11). Other sources of supply may be the round ligament artery and the lumbar artery (Figs 10, 21) (6,15).
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Figure 19. Digital subtraction angiogram obtained with selective injection via a left ovarian artery with origin in the aorta shows enlargement of the artery and a large hypervascular fundal fibroid tumor (F).
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Figure 20a. (a) Sagittal T2-weighted MR image shows a large fundal fibroid tumor (F) in a patient who previously underwent myomectomy. (b) Flush pelvic aortogram in the same patient depicts an enlarged right ovarian artery (OA) that originates from the aorta and supplies the fundal fibroid. Both uterine arteries (arrows) are also visible.
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Figure 20b. (a) Sagittal T2-weighted MR image shows a large fundal fibroid tumor (F) in a patient who previously underwent myomectomy. (b) Flush pelvic aortogram in the same patient depicts an enlarged right ovarian artery (OA) that originates from the aorta and supplies the fundal fibroid. Both uterine arteries (arrows) are also visible.
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Figure 21. Flush pelvic aortogram in a patient with a pedunculated subserosal fibroid tumor shows a large left lumbar artery that supplies the fibroid (*). (Courtesy of Woodruff Walker, MBBS, FRCR, Royal Surrey Hospital, Guildford, England.)
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Unlike other types of fibroid tumor, pedunculated susbserosal fibroid tumors may have a specific feeding artery that corresponds to the arterial pedicle (Fig 22). A fibroid tumor located in a bicornate uterus may be supplied by one uterine artery only (Fig 23).
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Figure 22a. (a) Contrast-enhanced sagittal MR image in a patient with a left-sided pedunculated subserosal fibroid tumor (F) shows the arterial pedicle (arrow). (b) Digital subtraction angiogram obtained with selective injection via the left uterine artery in the same patient depicts the same arterial pedicle (arrow) and tumor (F).
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Figure 22b. (a) Contrast-enhanced sagittal MR image in a patient with a left-sided pedunculated subserosal fibroid tumor (F) shows the arterial pedicle (arrow). (b) Digital subtraction angiogram obtained with selective injection via the left uterine artery in the same patient depicts the same arterial pedicle (arrow) and tumor (F).
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Figure 23a. (a) Axial T2-weighted image shows a bicornate uterus with a single intramural fibroid tumor (F) on the left side. (b) Early arterial phase flush pelvic aorto-gram in the same patient shows exclusive supply to the fibroid tumor from the left uterine artery (arrow) and a small right uterine artery. (c) Late phase digital subtraction angiogram depicts hypervascularity of the fibroid (F). (Courtesy of Woodruff Walker, MBBS, FRCR, Royal Surrey Hospital, Guildford, England.)
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Figure 23b. (a) Axial T2-weighted image shows a bicornate uterus with a single intramural fibroid tumor (F) on the left side. (b) Early arterial phase flush pelvic aorto-gram in the same patient shows exclusive supply to the fibroid tumor from the left uterine artery (arrow) and a small right uterine artery. (c) Late phase digital subtraction angiogram depicts hypervascularity of the fibroid (F). (Courtesy of Woodruff Walker, MBBS, FRCR, Royal Surrey Hospital, Guildford, England.)
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Figure 23c. (a) Axial T2-weighted image shows a bicornate uterus with a single intramural fibroid tumor (F) on the left side. (b) Early arterial phase flush pelvic aorto-gram in the same patient shows exclusive supply to the fibroid tumor from the left uterine artery (arrow) and a small right uterine artery. (c) Late phase digital subtraction angiogram depicts hypervascularity of the fibroid (F). (Courtesy of Woodruff Walker, MBBS, FRCR, Royal Surrey Hospital, Guildford, England.)
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Preembolization Imaging
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Imaging is very important in preprocedural planning for uterine fibroid embolization because it allows assessment of uterine fibroids and of concurrent conditions that may imitate or exacerbate the symptom complex. Deciding who is an appropriate candidate for the procedure involves careful evaluation of uterine fibroid tumors, particularly their number, size, and location and the degree of their vascularization (22–27).
Gray-scale and Color Doppler US
US is the primary imaging modality used to evaluate patients in whom the presence of uterine fibroid tumors is suspected (22,23,26,27). Trans-abdominal and transvaginal US are used in conjunction with color and pulsed Doppler US (22,23,26). Doppler US can be used to assess fibroid and uterine vascularity and flow patterns (22,23). Typically, uterine fibroid tumors have a marked peripheral blood flow (perifibroid plexus) and decreased central flow (Fig 24) (22,23). The resistance index is usually decreased in the perifibroid plexus, compared with that in the surrounding normal myometrium (Fig 24) (23). Doppler US also may be helpful for distinguishing an endometrial polyp with a single feeding vessel from an intracavitary submucosal fibroid tumor (26).
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Figure 24a. (a) Power Doppler US image in a patient with a 5-cm-diameter intramural fibroid tumor shows characteristic peripheral arterial flow that corresponds to the perifibroid plexus (arrows). (b) Pulsed Doppler US image in the same patient shows a low resistance index (0.50) in the periphery of the fibroid tumor.
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Figure 24b. (a) Power Doppler US image in a patient with a 5-cm-diameter intramural fibroid tumor shows characteristic peripheral arterial flow that corresponds to the perifibroid plexus (arrows). (b) Pulsed Doppler US image in the same patient shows a low resistance index (0.50) in the periphery of the fibroid tumor.
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The diagnosis of adenomyosis is usually made with gray-scale US, but Doppler US may be helpful for differentiating adenomyosis from fibroid tumors (Figs 24, 25) (24). In adenomyosis, multiple scattered vessels or intratumoral vascularity are depicted, whereas peripheral vessels and outer feeding vessels are visible in uterine fibroid tumors (Fig 25) (24).
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Figure 25a. (a) Color Doppler US image in a woman with diffuse adenomyosis shows dense intramural vascularity. (b) Flush pelvic aortogram shows multiple small abnormal intramural arteries and patchy uterine vascularization, findings that are consistent with adenomyosis.
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Figure 25b. (a) Color Doppler US image in a woman with diffuse adenomyosis shows dense intramural vascularity. (b) Flush pelvic aortogram shows multiple small abnormal intramural arteries and patchy uterine vascularization, findings that are consistent with adenomyosis.
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US plays a vital role also in the exclusion of associated pathologic conditions in the pelvic region, such as adnexal masses and endometrial carcinoma (26). Adnexal masses may mimic subserosal fibroid tumors, but the two entities usually have very different vascular features (26). Because a pedunculated subserosal fibroid tumor has only one feeding artery, it may separate from the uterus and drift into the peritoneal cavity after embolization (Fig 22) (3,5). Pedunculated subserosal fibroid tumor is therefore considered a contraindication to embolization (2–4). Preprocedural identification of the pedicle is crucial to separate broad-based fibroid tumors from pedunculated ones (3,27).
Contrast-enhanced MR Imaging and MR Angiography
MR angiography may help the physician to obtain a better understanding of the arterial anatomy before embolization (Figs 26, 27) and may enable detection of an ovarian artery supply to the tumor (26,27). The majority of uterine fibroid tumors are markedly enhanced after the administration of a gadolinium-based contrast material (Fig 28) (26,27). Hypervascular uterine fibroid tumors may decrease more in size after embolization than do iso- or hypovascular fibroid tumors (27).
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Figure 26a. (a) MR angiogram before uterine fibroid embolization nicely depicts trifurcation of the right internal iliac artery and a kink at the origin of the uterine artery (UA). (b) Digital subtraction angiogram obtained with selective injection via the right internal iliac artery in the same patient demonstrates good correlation between MR angiography and digital subtraction angiography.
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Figure 26b. (a) MR angiogram before uterine fibroid embolization nicely depicts trifurcation of the right internal iliac artery and a kink at the origin of the uterine artery (UA). (b) Digital subtraction angiogram obtained with selective injection via the right internal iliac artery in the same patient demonstrates good correlation between MR angiography and digital subtraction angiography.
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Anatomy and Angiographic End Points of Embolization
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Complete occlusion of the uterine arteries with stasis of contrast material is the usual angiographic end point when embolization is performed with nonspherical polyvinyl alcohol particles (1–4). Embolization is stopped when a standing column of contrast material is observed in the uterine artery or when reflux of contrast material toward the uterine artery origin or into the hypogastric artery is observed (Fig 29) (1,3). Complete embolization of both uterine arteries (to stasis) may lead to myometrial and/or endometrial ischemia, with potentially disastrous consequences, such as endometrial atrophy or extensive uterine necrosis (3,28–30).
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Figure 29a. (a, b) Digital subtraction angiograms obtained with injections in the right (a) and left (b) uterine arteries after embolization with 355–500-µm-diameter nonspherical polyvinyl alcohol particles show an area of stasis and myometrial devascularization (arrow). (c) Postembolization contrast-enhanced MR image shows the same area of devascularization (arrows) and helps confirm the infarction of all fibroids (F).
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Figure 29b. (a, b) Digital subtraction angiograms obtained with injections in the right (a) and left (b) uterine arteries after embolization with 355–500-µm-diameter nonspherical polyvinyl alcohol particles show an area of stasis and myometrial devascularization (arrow). (c) Postembolization contrast-enhanced MR image shows the same area of devascularization (arrows) and helps confirm the infarction of all fibroids (F).
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Figure 29c. (a, b) Digital subtraction angiograms obtained with injections in the right (a) and left (b) uterine arteries after embolization with 355–500-µm-diameter nonspherical polyvinyl alcohol particles show an area of stasis and myometrial devascularization (arrow). (c) Postembolization contrast-enhanced MR image shows the same area of devascularization (arrows) and helps confirm the infarction of all fibroids (F).
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Recently, the use of a different angiographic end point was investigated at microsphere embolization (18). Since the target of embolization is the perifibroid arterial plexus, the main uterine artery should be spared (18). With calibrated microspheres, it is appropriate to stop embolization when the fibroid branch arteries have become occluded, even if antegrade flow is still present in the main uterine artery (the so-called "pruned-tree" appearance). Additional angiographic criteria to identify the proper end point also include identification of uterine artery–to–ovarian artery or left-to-right anastomoses, which are usually not present initially (18). Limited embolization of the uterine arteries should be performed to reduce ischemic injury to normal myometrium and/or endometrium as a result of complete occlusion of collateral vessels (Figs 14, 29). When calibrated microspheres with diameters of more than 500 µm are used, a limited embolization, with targeted devascularization of the perifibroid plexus, is recommended (Figs 14, 29) (18,31).
With the gradual shift over time both in technique and in end point, from the achievement of complete stasis of uterine arterial flow to the maintenance of persistent flow in the main uterine artery, the risk to normal tissue has decreased; sufficient blood flow is left to sustain portions of the myometrium (Figs 29 , 30) (26,31).
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Figure 30a. (a, b) Digital subtraction angiograms obtained with selective injection via the left uterine artery before (a) and after (b) limited embolization with 500–700-µm-diameter tris-acryl microspheres. The postembolization image shows patency of the main uterine artery (arrow) and cervicovaginal branches (CV). (c, d) Contrast-enhanced sagittal MR images obtained before (c) and 24 hours after (d) embolization. The postembolization image shows normal perfusion of the myometrium and infarction of the three fibroid tumors (F).
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Figure 30b. (a, b) Digital subtraction angiograms obtained with selective injection via the left uterine artery before (a) and after (b) limited embolization with 500–700-µm-diameter tris-acryl microspheres. The postembolization image shows patency of the main uterine artery (arrow) and cervicovaginal branches (CV). (c, d) Contrast-enhanced sagittal MR images obtained before (c) and 24 hours after (d) embolization. The postembolization image shows normal perfusion of the myometrium and infarction of the three fibroid tumors (F).
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Figure 30c. (a, b) Digital subtraction angiograms obtained with selective injection via the left uterine artery before (a) and after (b) limited embolization with 500–700-µm-diameter tris-acryl microspheres. The postembolization image shows patency of the main uterine artery (arrow) and cervicovaginal branches (CV). (c, d) Contrast-enhanced sagittal MR images obtained before (c) and 24 hours after (d) embolization. The postembolization image shows normal perfusion of the myometrium and infarction of the three fibroid tumors (F).
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Figure 30d. (a, b) Digital subtraction angiograms obtained with selective injection via the left uterine artery before (a) and after (b) limited embolization with 500–700-µm-diameter tris-acryl microspheres. The postembolization image shows patency of the main uterine artery (arrow) and cervicovaginal branches (CV). (c, d) Contrast-enhanced sagittal MR images obtained before (c) and 24 hours after (d) embolization. The postembolization image shows normal perfusion of the myometrium and infarction of the three fibroid tumors (F).
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Normal Post-embolization Imaging Findings
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In the initial studies about uterine fibroid embolization, US was used to evaluate the uterus and the fibroids after treatment (1,3,27). A marked 35%–60% reduction in uterine volume and 40%–80% reduction in fibroid volume have been observed at 3–6 months after embolization (2–4). The disappearance of fibroid vascularization is usually observed at Doppler US after successful embolization (25–27).
Given the limitations of US, most investigators currently use MR imaging for follow-up of patients who have undergone embolization for uterine fibroid tumors (3,4,25,26). After embolization, fibroid tumors usually show signal intensity changes that are consistent with hemorrhagic infarction, including increased signal intensity on T1-weighted images and homogeneous decreased signal intensity on T2-weighted images (25,26). In addition, the immediate reduction in perfusion after embolization in a fibroid tumor correlates well with the clinical response (25).
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Common Causes of Treatment Failure and Recurrence
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Abstract
Introduction
