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EDUCATION EXHIBIT |
1 Department of Radiology, Georgetown University Hospital, Washington, DC
I am pleased to have the opportunity to comment on the excellent article by Ghai et al in this issue of RadioGraphics (1). The authors present a comprehensive review of the use of US in the assessment of patients treated with uterine embolization for fibroids. The article is particularly timely because, in recent years, embolization has become accepted into practice as an effective therapy for women with fibroids (2–5) and the number of procedures performed has been steadily increasing. Embolization has even been recognized by the American College of Obstetricians and Gynecologists as effective (6).
The authors present the imaging aspects from the perspective of a center that relies primarily on US. This is a common circumstance both in the United States and in countries with limited access to MR imaging, such as that of the authors. From my perspective as an interventionalist who performs UAE, it may be helpful for the reader to understand the clinical needs for patient evaluation both before and after the procedure.
Preprocedural imaging of the uterus and adnexa is essential for patient selection, both to confirm the diagnosis and to assess the extent of the fibroids. The imaging findings are combined with the clinical evaluation to provide the basis for the decision on whether UAE is an appropriate choice for the patient. In most cases, a US examination can provide sufficient detail to determine a patient’s suitability for embolization. However, in a study by Omary et al (7), MR imaging resulted in a change in management in 22% of cases, thereby providing evidence that MR imaging increases the diagnostic certainty of the treatment decision. Thus, although US is certainly helpful in preprocedural imaging, it is best used when access to or resources for the more definitive MR imaging technology are not available.
The anatomic criteria used by most interventionalists for selecting patients for embolization are similar to those described by Ghai et al (1). In our practice, we have found that the women who have the best symptomatic and anatomic improvement have an overall uterine size less than that at 24 weeks gestation. Furthermore, we have shown that, in general, the larger the fibroid at baseline examination, the slower it will shrink over time and the less the amount of overall shrinkage (8). The same study showed that the rate and eventual degree of shrinkage of a fibroid also depends on its position in the uterus. Sub-mucosal fibroids shrink the fastest and the most, followed by intramural fibroids and then serosal fibroids (8). In addition, we share the concern expressed by Ghai et al (1) that very large pedunculated serosal fibroids with small attachments to the uterus may in fact detach after embolization. Furthermore, we are concerned that these very large, bare pedunculated fibroids projecting into the lower and midabdominal cavity may be more prone to adhesion formation than other fibroids. We can also state from prior experience that pedunculated fibroids may indeed be more likely to parasitize blood supply from sources other than the uterine arteries.
For all these reasons, quality imaging prior to embolization is needed and must be complete enough to characterize the size and location of the important fibroids (ie, those that are largest or that might affect the endometrial cavity). Fibroids that distort or directly abut the endometrial cavity are the most likely to cause heavy menstrual bleeding (9). Although this type of detailed anatomic characterization is perhaps most easily achieved with MR imaging, it certainly can also be achieved with US, but only with a careful and complete study. Because the quality of imaging in the radiology community is quite variable, it may be necessary in some cases to perform repeat imaging at the center where the embolization is going to be performed to ensure that a proper decision on therapy can be reached.
My greatest departure from the authors on the role of US in the treatment of uterine embolization patients is with regard to postprocedural assessment, both when a complication is suspected and in the context of routine confirmatory imaging. In terms of complications, the most common symptom manifesting late after this procedure is pain, which may be due to self-limited cramping related to excess activity by the patient, cramping related to fibroid passage (with or without associated infection), or uterine injury. My colleagues and I agree with the authors as to the findings that may be present at US, but in our experience, none of these findings is well characterized with US. As interventionalists, we need to answer the following questions: Are the fibroids infarcted? Are any fibroids migrating toward the cervix (a sign of impending fibroid passage)? Is there an ischemic injury to the normal myometrium of the uterus? Are there any adnexal findings that would explain the symptoms? In our experience, the answers to these questions will allow differentiation between fibroid passage, myometrial injury, and simple benign cramping from residual uterine inflammation. These questions can be adequately answered only with contrast-enhanced MR imaging. When US is performed in this circumstance, it often reveals amorphous artifact in the uterine cavity, a finding that suggests possible tissue mixed with air but that may, as the authors mentioned, be the normal appearance of a postembolization intracavitary fibroid. It is often difficult to determine whether a fibroid has become deformed, with a portion pointing toward the cervix. US cannot reliably help determine if there are areas of myometrium that are not perfused, making it a poor means of assessing uterine injury or the success of fibroid devascularization.
A similar problem exists with the routine use of US to document the anatomic success of embolization. We have found that the amount of fibroid and uterine shrinkage does not correlate with the degree of symptomatic improvement at 1 year after embolization (8). Although the patient is often interested in the degree of shrinkage, we are much more interested in whether the fibroids have successfully been completely devascularized. This is the one parameter that we believe will best correlate with long-term success. In our small study of long-term imaging outcome that Ghai et al quoted, we found that three of 20 patients did not have complete fibroid infarction 3 months after undergoing embolization (10). We subsequently obtained serial contrast-enhanced MR images in these three patients at 1, 2, and 3 years after embolization. In each of these patients, the residual viable portions of fibroid regrew, and eventually all of these fibroids caused symptoms that required therapy. None of the other 17 patients had recurrent symptoms. There were some patients (n = 4) who developed new fibroids, but none of these fibroids had yet caused symptoms. Thus, the contrast-enhanced MR imaging appearance of the fibroids 3 months after treatment could be used to predict long-term outcome at 3 years.
This important finding now guides our follow-up imaging protocol. We do not believe there is an advantage in obtaining routine serial post-embolization images, and we now limit ourselves to performing a single contrast-enhanced MR imaging study 3 months after embolization. Our primary interest is not in the degree of shrinkage of the fibroids, but in the degree of devascularization. The latter cannot currently be assessed to the same degree of accuracy with US.
We use the imaging findings as a guidepost for managing symptom outcome. If MR imaging shows complete fibroid infarction and the patient’s symptoms have improved, he or she does not need additional follow-up studies. If the symptoms have not improved but the fibroids are infarcted, we counsel that the patient wait for a few more months, since most patients will have symptomatic improvement. At that point, if there is still no improvement, we usually discuss with the gynecologist a plan to investigate other potential causes for the symptoms.
If the fibroids are not completely infarcted, the degree of infarction is important in the timing of recurrence of symptoms. In our experience, even a limited degree of fibroid infarction can relieve symptoms, but if there is substantial residual viable tissue, recurrence of symptoms within the first 12–18 months is likely. Lesser degrees of residual viable fibroid tissue will likely recur 2–3 years after treatment. Up to this point in our practice, every reembolization procedure has been performed to treat fibroids that were originally incompletely infarcted. In some cases, there were also small new fibroids, and it is difficult to be certain to what degree they contributed to new symptoms. We have not yet re-treated any patients with only new fibroids, although we anticipate that this will happen in some patients 4–5 years after therapy. In our practice, the basis for distinguishing new fibroids from old fibroids is a contrast-enhanced MR imaging study performed at the time of recurrence, the results of which are compared with those of the baseline study and the 3-month postembolization study. With MR imaging, it is easy to distinguish new fibroids from old ones. It would certainly be difficult to do so with US; it is much more difficult to characterize new, perfused fibroids from older adjacent infarcted fibroids with this modality, particularly as uterine shrinkage distorts the relationship of fibroids over time.
What role, then, does US have in a uterine embolization practice? If MR imaging is not available, a decision on preprocedural therapy may be made on the basis of a high-quality US examination with a relatively low error rate. On occasion, a misdiagnosis may be made that will affect the success of the procedure, but this is likely to occur in only a minority of patients.
On the other hand, from my perspective, there is little use for US in postembolization management. Because US cannot be used for complete assessment of either the adequacy of embolization or the patient with a possible complication, I would not use it for follow-up.
If resources for and access to MR imaging were not an issue, I would think it evident that this modality has clear and demonstrable advantages over US in uterine embolization patients. However, the low cost and ready availability of US make it the only tool available to some practitioners. In this circumstance, careful and thorough imaging with US is important to ensure that patient treatment needs are met.
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2 Division of Vascular and Interventional Radiology, Department of Medical Imaging, Toronto General Hospital, University Health Network–Mount Sinai Hospital, University of Toronto Toronto, Ontario, Canada
We welcome the informative and educational commentary written by Dr Spies regarding our article in RadioGraphics (1). Although we agree that MR imaging may have an important future role in the assessment of patients undergoing uterine embolization for fibroids, in places were MR imaging resources are limited, US can still play an important front-line role in the assessment of these patients.
In our country, MR imaging resources remain largely unavailable for routine assessment of UAE patients. This situation likely also exists in other countries. US is readily available due to its lower cost compared with MR imaging, and US examinations can be performed within a short period of time. The purpose of our article is simply to provide an overview of US findings in UAE patients that are helpful for clinicians involved in the care of these patients. Where US is the primary imaging modality, recognizing potential findings in UAE patients will aid in proper clinical management in most cases.
One discrepancy we noted is in regard to the study by Omary et al (2), which suggested that MR imaging increased the diagnostic certainty of treatment and resulted in change in management in 22% of cases of UAE. Dr Spies infers on the basis of this study that MR imaging is more definitive than US; however, no comparison between US and MR imaging was performed, nor was any US evaluation mentioned in the Materials and Methods or Results section of this study.
Contrast-enhanced MR imaging following UAE has demonstrated initial promise in determining the success of embolization for fibroid revascularization (3). We acknowledge that MR imaging may have future potential in helping to determine long-term clinical outcome on the basis of findings that suggest incomplete infarction of fibroids following UAE. The information provided by US is not as comprehensive as that provided by MR imaging, and further studies directly comparing US with MR imaging are needed to determine the differences in the clinical value of the two modalities.
We make no claims of the superiority of US over MR imaging, nor was it our intent to do so. Because of the potential advantages of MR imaging over US, we have changed our clinical practice and now routinely evaluate our patients with MR imaging. However, when MR imaging resources are not available, US can play an important front-line role in the treatment of UAE patients, as demonstrated in multiple large series examining the efficacy of UAE (4–8). US is also commonly used in our practice in patients who present to their primary care physician or obstetrician-gynecologist or to the emergency department with signs and symptoms that suggest a post-UAE complication.
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