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Uterine Leiomyoma (Fibroid) Imaging

  • Author: Philip Thomason, MD; Chief Editor: Eugene C Lin, MD  more...
 
Updated: Feb 21, 2015
 

Overview

Leiomyomas of the urterus (or uterine fibroids) are benign tumors that arise from the overgrowth of smooth muscle and connective tissue in the uterus. Histologically, a monoclonal proliferation of smooth muscle cells occurs. A genetic predisposition to leiomyoma growth exists. The radiologic characteristics of these neoplasms are shown in the images below.

Transabdominal sagittal sonogram shows a heterogen Transabdominal sagittal sonogram shows a heterogeneous but predominately hypoechoic posterior uterine fibroid.
Sagittal T2-weighted MRI shows a large heterogeneo Sagittal T2-weighted MRI shows a large heterogeneous fundal uterine fibroid.
CT scan shows a subserosal, 2.3- to 2.5-cm, right CT scan shows a subserosal, 2.3- to 2.5-cm, right anterior fundal uterine fibroid.

Rarely, uterine leiomyomas may undergo malignant degeneration to become a sarcoma. The true incidence of malignant transformation is difficult to determine, because leiomyomas are common, whereas malignant leiomyosarcomas are rare and can arise de novo. The incidence of malignant degeneration is less than 1.0% and has been estimated to be as low as 0.2%.

Preferred examination

The preferred imaging modality for the evaluation of uterine fibroids is ultrasonography (US), specifically, transabdominal and transvaginal US.

Calcified fibroids are often depicted on conventional radiographs of the pelvis. In some patients, magnetic resonance imaging (MRI) provides additional information. The role of computed tomography (CT) scanning is limited. Calcifications may be more visible on CT scans than on conventional radiographs because of the superior contrast differentiation achieved with CT scanning.[1, 2]

Limitations of techniques

In the detection of uterine fibroids, CT scanning is limited by the similar attenuation characteristics of fibroids and healthy myometrium, although some fibroids may be hypoattenuating. Fibroid calcifications can be depicted on CT scans.

For excellent patient education resources, visit eMedicineHealth's Women's Health Center. Also, see eMedicineHealth's patient education article Uterine Fibroids.

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Radiography

Conventional radiographs have a limited role in the diagnosis of uterine fibroids, because only heavily calcified fibroids are depicted on these scans. Extreme enlargement of the uterus resulting from fibroids may be seen as a nonspecific soft-tissue mass of the pelvis that possibly displaces loops of bowel.

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Computed Tomography

Like radiography, CT scanning also has a limited role in the diagnosis of uterine fibroids. On CT scans, fibroids are usually indistinguishable from healthy myometrium unless they are calcified or necrotic. Calcifications may be more visible on CT scans than on conventional radiographs because of the superior contrast differentiation in CT scanning. A fibroid has been identifed on the image below.

CT scan shows a subserosal, 2.3- to 2.5-cm, right CT scan shows a subserosal, 2.3- to 2.5-cm, right anterior fundal uterine fibroid.
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Magnetic Resonance Imaging

MRI has an important role in defining the anatomy of the uterus and ovaries, as well as in assessing disease in patients in whom US findings are confusing. MRI also may be helpful in planning myomectomy, or selective surgical removal of a fibroid.

Fibroids appear as sharply marginated areas of low to intermediate signal intensity on T1- and T2-weighted MRI scans. (A coronal, T2-weighted MRI fibroid scan appears below.)

Coronal T2-weighted MRI shows an enlarged uterus w Coronal T2-weighted MRI shows an enlarged uterus with multiple fibroids.

One third of fibroids have a hyperintense rim on T2-weighted images (as demonstrated in the image below) as a result of dilated veins, lymphatics, or edema.

Sagittal T2-weighted MRI shows a fibroid located i Sagittal T2-weighted MRI shows a fibroid located in the lower uterus that has a partially hyperintense rim. A smaller discrete fibroid is depicted in the fundus.

An inhomogeneous area of high signal intensity (seen in the image below) may be depicted on T2-weighted images; this results from hemorrhage, hyaline degeneration, edema, or highly cellular fibroids.

Sagittal T2-weighted MRI shows a large heterogeneo Sagittal T2-weighted MRI shows a large heterogeneous fundal uterine fibroid.

The intravenous administration of gadolinium-based contrast material usually is not required; however, if it is administered, fibroids usually enhance later than does the healthy myometrium. Fibroid enhancement can be hypointense (65%), isointense (23%), or hyperintense (12%) in relation to that of the myometrium.

Gadolinium-based contrast agents (gadopentetate dimeglumine [Magnevist], gadobenate dimeglumine [MultiHance], gadodiamide [Omniscan], gadoversetamide [OptiMARK], gadoteridol [ProHance]) have been linked to the development of nephrogenic systemic fibrosis (NSF) or nephrogenic fibrosing dermopathy (NFD). For more information, see the Medscape Reference topic Nephrogenic Systemic Fibrosis. The disease has occurred in patients with moderate to end-stage renal disease after being given a gadolinium-based contrast agent to enhance MRI or magnetic resonance angiography (MRA) scans.

NSF/NFD is a debilitating and sometimes fatal disease. Characteristics include red or dark patches on the skin; burning, itching, swelling, hardening, and tightening of the skin; yellow spots on the whites of the eyes; joint stiffness with trouble moving or straightening the arms, hands, legs, or feet; pain deep in the hip bones or ribs; and muscle weakness. For more information, see Medscape.

The primary limitation of MRI is the high cost. Its availability in terms of time and location is another factor that determines its usefulness. Additionally, patients with pacemakers or certain metallic foreign bodies cannot undergo MRI. Claustrophobia is a relative contraindication.

Degree of confidence

MRI has a sensitivity of 86-92%, a specificity of 100%, and an accuracy of 97% in the evaluation of probable fibroids.

In one study, MRI findings were assessed in helping predict early posttherapeutic response after uterine artery embolization (UAE) in 15 patients with 52 fibroids. The signal intensity ratios (SIRs) on T1-weighted images and gadolinium-enhanced images were useful for the prediction of the changes in size of fibroids responding to UAE. The sensitivity, specificity, and area under the ROC curve (AUC) in the prediction of the affected lesions were 92%, 50%, and 0.712 with SIR on T1-weighted images, and 85%, 62%, and 0.731 with SIR on gadolinium-enhanced images, respectively.[3]

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Ultrasonography

US is the imaging modality of choice in the detection and evaluation of uterine fibroids.[4, 5, 6]

Most fibroids are intramural, that is, located in the myometrium (as seen in the first image below); however, they can be submucosal or subserosal (as demonstrated in the second image below).

Sagittal sonogram shows a posterior, fundal, 4.2 X Sagittal sonogram shows a posterior, fundal, 4.2 X 3.5-cm intramural uterine fibroid.
Sonogram shows a subserosal, 2.3- to 2.5-cm, right Sonogram shows a subserosal, 2.3- to 2.5-cm, right anterior fundal uterine fibroid.

Uterine fibroids most often appear on ultrasonograms as concentric, solid, hypoechoic masses. This appearance results from the prevailing muscle, which is observed at histologic examination. These solid masses absorb sound waves and therefore cause a variable amount of acoustic shadowing. A hypoechoic fibroid is seen in the images below.

Transabdominal sagittal sonogram shows a heterogen Transabdominal sagittal sonogram shows a heterogeneous but predominately hypoechoic posterior uterine fibroid.
More midline image obtained in the same patient as More midline image obtained in the same patient as in the previous image shows 2 markers that delineate the margins of the endometrial stripe.

Fibroids may vary in their degree of echogenicity; they can be heterogeneous or hyperechoic, depending on the amount of fibrous tissue and/or calcification. Fibroids may have anechoic components resulting from necrosis.

If fibroids are small and isoechoic relative to the uterus, the only ultrasonographic sign may be a bulge in the uterine contour. Fibroids in the lower uterine segment may obstruct the uterine canal, causing fluid to accumulate in the endometrial canal.

The echogenic endometrial stripe may be displaced by a fibroid. Calcifications are hyperechoic, with sharp acoustic shadowing. Diffuse leiomyomatosis appears as an enlarged uterus with abnormal echogenicity.

Magnetic resonance-guided high-intensity focused ultrasound has been shown to be successful in reducing the size of fibroids.[7]

Vascular density, ischemic necrosis, and histological cellular activity score have been found to be statistically significantly associated with some 3D power Doppler ultrasound indices. A high histological cellular activity score, combining hypercellularity, a fibrosclerosis rate less than 25%, and positive Ki-67 staining, was found in one study to be statistically related in multivariate analyses to high 3D power Doppler VI in spherical samples and vascularization flow index (VFI). Positive CD31 staining was statistically related to high 3D power Doppler VI in spherical samples. In contrast, ischemic necrosis was statistically related to low 3D power Doppler VI in the total volume and VFI.[8]

Of 280 women who underwent magnetic resonance-guided focused ultrasound (MRgFUS), the rate of minor complications was 3.9%, and there were 3 serious complications (1.1%), including one skin burn, a fibroid expulsion, and one case of persistent neuropathy. According to the authors of the study, the nonperfused volume (NPV) achieved following MRgFUS have increased as the experience with this treatment has grown. In a 5-year follow-up study of 162 women, the overall reintervention rate was 58.64%, but in those treatments with greater than 50% NPV, the re-intervention rate was 50%.[9]

Degree of confidence

US has a sensitivity of 60%, a specificity of 99%, and an accuracy of 87%.

False positives/negatives

Although the ultrasonographic appearance of fibroids usually is diagnostic, in fewer than 5% of patients, fibroids (especially when necrotic) may mimic normal pelvic structures (particularly the ovaries) and pathologic pelvic conditions, including uterine variants and pregnancy-related conditions. MRI results often clarify confusing pelvic ultrasonographic findings.

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Angiography

Although angiography has no role in the diagnosis of uterine fibroids, it is used to guide uterine arterial embolization (UAE) of fibroids.

UAE is a minimally invasive procedure performed by an interventional radiologist. Typically, UAE is carried out via a percutaneous femoral arterial approach. Both of the uterine arteries are individually selected with angiographic guidance and are embolized with 300-500 µm polyvinyl alcohol (PVA) foam particles.[10, 11]

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Contributor Information and Disclosures
Author

Philip Thomason, MD Director of Diagnostic Radiology, Department of Radiology, Beverly Hospital

Philip Thomason, MD is a member of the following medical societies: American College of Radiology, Massachusetts Medical Society, Radiological Society of North America

Disclosure: Nothing to disclose.

Specialty Editor Board

Bernard D Coombs, MB, ChB, PhD Consulting Staff, Department of Specialist Rehabilitation Services, Hutt Valley District Health Board, New Zealand

Disclosure: Nothing to disclose.

Karen L Reuter, MD, FACR Professor, Department of Radiology, Lahey Clinic Medical Center

Karen L Reuter, MD, FACR is a member of the following medical societies: American Association for Women Radiologists, American College of Radiology, American Institute of Ultrasound in Medicine, American Roentgen Ray Society, Radiological Society of North America

Disclosure: Nothing to disclose.

Chief Editor

Eugene C Lin, MD Attending Radiologist, Teaching Coordinator for Cardiac Imaging, Radiology Residency Program, Virginia Mason Medical Center; Clinical Assistant Professor of Radiology, University of Washington School of Medicine

Eugene C Lin, MD is a member of the following medical societies: American College of Nuclear Medicine, American College of Radiology, Radiological Society of North America, Society of Nuclear Medicine and Molecular Imaging

Disclosure: Nothing to disclose.

References
  1. Dahnert W. Dahnert's Radiology Review Manual. 4th ed. Baltimore, Md: Williams & Wilkins; 1996. 884-5.

  2. Weissleder R, Wittenberg J. Primer of Diagnostic Imaging. St Louis, Mo: Mosby-Year Book; 1994. 302.

  3. Noda Y, Kanematsu M, Goshima S, Kondo H, Watanabe H, Kawada H, et al. Prediction of early response to uterine artery embolization in fibroids: value of MR signal intensity ratio. Magn Reson Imaging. 2015 Jan. 33(1):51-5. [Medline].

  4. Callen PW, ed. Ultrasonography in Obstetrics and Gynecology. 5th ed. Philadelphia, Pa: Saunders Elsevier; 2007.

  5. Kurtz AB, Middleton WD. Ultrasound. St Louis, Mo: Mosby; 1996.

  6. Sauerbrel EE, Nguyen KT, Nolan RL. A Practical Guide to Ultrasound in Obstetrics and Gynecology. 2nd ed. Philadelphia, Pa: Lippincott-Raven; 1998. 52-8.

  7. Kim YS, Kim JH, Rhim H, Lim HK, Keserci B, Bae DS, et al. Volumetric MR-guided High-Intensity Focused Ultrasound Ablation with a One-Layer Strategy to Treat Large Uterine Fibroids: Initial Clinical Outcomes. Radiology. 2012 Mar 9. [Medline].

  8. Minsart AF, Ntoutoume Sima F, Vandenhoute K, Jani J, Van Pachterbeke C. Does three-dimensional power Doppler ultrasound predict histopathological findings of uterine fibroids? A preliminary study. Ultrasound Obstet Gynecol. 2012 Dec. 40(6):714-20. [Medline].

  9. Quinn SD, Vedelago J, Gedroyc W, Regan L. Safety and five-year re-intervention following magnetic resonance-guided focused ultrasound (MRgFUS) for uterine fibroids. Eur J Obstet Gynecol Reprod Biol. 2014 Nov. 182:247-51. [Medline].

  10. Siskin GP, Beck A, Schuster M, et al. Leiomyoma infarction after uterine artery embolization: a prospective randomized study comparing tris-acryl gelatin microspheres versus polyvinyl alcohol microspheres. J Vasc Interv Radiol. 2008 Jan. 19(1):58-65. [Medline].

  11. Kim HS, Paxton BE, Lee JM. Long-term efficacy and safety of uterine artery embolization in young patients with and without uteroovarian anastomoses. J Vasc Interv Radiol. 2008 Feb. 19(2 Pt 1):195-200. [Medline].

 
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Transabdominal sagittal sonogram shows a heterogeneous but predominately hypoechoic posterior uterine fibroid.
More midline image obtained in the same patient as in the previous image shows 2 markers that delineate the margins of the endometrial stripe.
Sagittal T2-weighted MRI shows a large heterogeneous fundal uterine fibroid.
Sagittal sonogram shows a posterior, fundal, 4.2 X 3.5-cm intramural uterine fibroid.
Coronal T2-weighted MRI shows an enlarged uterus with multiple fibroids.
Sagittal T2-weighted MRI shows a fibroid located in the lower uterus that has a partially hyperintense rim. A smaller discrete fibroid is depicted in the fundus.
Axial MRI shows the cross section of a fibroid in the lower uterus. Note the mass effect on the bladder, which is located anteriorly.
CT scan shows a subserosal, 2.3- to 2.5-cm, right anterior fundal uterine fibroid.
Sonogram shows a subserosal, 2.3- to 2.5-cm, right anterior fundal uterine fibroid.
 
 
 
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