DOI:10.2214/AJR.05.0629
AJR 2006; 187:762-768
© American Roentgen Ray Society
Ethanol and Polyvinyl Alcohol Mixture for Transcatheter Embolization of Renal Angiomyolipoma
Uri Rimon1,2,
Mordechai Duvdevani2,3,
Alexander Garniek1,2,
Gil Golan1,2,
Paul Bensaid1,2,
Jacob Ramon2,3 and
Benyamina Morag1,2
1 Department of Diagnostic Imaging, Sheba Medical Center, Tel-Hashomer, Israel
52621.
2 Sakler School of Medicine, Tel-Aviv University, Tel-Aviv, Israel.
3 Department of Urology, Sheba Medical Center, Tel-Hashomer, Israel 52621.
Received April 12, 2005;
accepted after revision July 25, 2005.
Address correspondence to U. Rimon
(rimonu{at}sheba.health.gov.il).
Abstract
OBJECTIVE. The purpose of this study was to assess the immediate and
midterm effects of embolization of the angiogenic component of renal
angiomyolipoma in which a mixture of ethanol and polyvinyl alcohol is used as
a permanent obliterator.
MATERIALS AND METHODS. Seventeen patients with 18 renal
angiomyolipomas (size range, 5.5-20 cm; mean size, 10 cm) were treated with
transcatheter embolization over an 8-year period. Embolization was performed
with a mixture of 96% ethanol and polyvinyl alcohol particles. Follow-up with
CT (mean follow-up period, 22.4 months) and one (mean, 14 months) or two
(mean, 27 months) angiographic examinations were conducted to evaluate changes
in the size of the tumor and to look for recurrence of the angiogenic
component.
RESULTS. All initial angiograms showed the characteristic tortuous,
hypervascular, and aneurysm-forming angiogenic component. Immediate complete
obliteration was achieved in 17 tumors (94.4% technical success rate). There
was one partial technical failure. Mean tumor size was reduced to 7.6 cm (mean
size reduction, 24%). Fourteen patients with 15 tumors underwent one
angiographic follow-up examination (mean time after treatment, 14 months), and
four patients underwent two angiographic follow-up examinations (mean time
after treatment, 27 months). Reduction of the angiogenic component occurred in
10 (66.6%) of the tumors and complete obliteration in five (33.3%) of the
tumors. No retroperitoneal hemorrhage or tumor growth was seen during the
follow-up period. No complications were encountered.
CONCLUSION. We found a mixture of ethanol and polyvinyl alcohol an
efficient embolizing agent with a sustained midterm effect in the management
of renal angiomyolipoma. Repeated embolization was needed in tumors with a
large angiogenic component. Tumor shrinkage after embolization was
minimal.
Keywords: CT digital subtraction angiography embolization kidney
Introduction
Renal angiomyolipoma (AML) is a benign hamartomatous tumor that contains
fat, smooth muscle, and abnormal blood vessels in varying proportions. Two
types of AML are commonly recognized. The sporadic type, a single tumor,
occurs mainly in the older population (50-80 years), is predominant among
women, and constitutes 80% of all cases of AML. The second type of AML is
associated with tuberous sclerosis (TS) and other types of phakomatosis and
also is predominant among women. The TS type usually is symptomatic with
multiple bilateral lesions and constitutes 20% of all cases of renal AML
[1-3].
The main complication of AML is retroperitoneal bleeding, which can be life
threatening [1,
3,
4]. The bleeding tendency
originates from the irregular, aneurysmal, tortuous blood vessels that
constitute the angiogenic component of the tumor
[5-7].
The larger the tumor, the greater is the risk of bleeding; 4 cm is the usually
accepted cutoff size [3,
8-10].
It is generally agreed that patients with asymptomatic AML larger than 4 cm
should be treated, as should those with symptomatic lesions of any size
[5,
11]. Nephron-sparing
procedures such as tumorectomy and selective embolization are the procedures
of choice for preserving the renal parenchyma
[1]. Absolute ethanol with or
without lipiodol [4,
7,
12-14],
coils [6,
13], polyvinyl alcohol (PVA)
[6,
13], or gelatin sponge
(Gelfoam) [13] has been used
successfully as an embolization material. Ethanol is superior to other
materials because of its liquidity and high occlusion potential
[4,
7,
15].
We made a mixture of the smallest PVA particles available and 96% ethanol
to achieve better immediate and long-term occlusion. The purpose of this study
was to show the immediate and midterm effects of embolization with a mixture
of ethanol and PVA as a permanent obliterator of the angiogenic component of
renal AML.

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Fig. 1A 35-year-old man with intrarenal bleeding in large
angiomyolipoma of left kidney. Early phase anteroposterior digital subtraction
angiogram before embolization shows hypervascular angiogenic component
(short arrows) with 4-cm aneurysm (star) with single feeder
vessels (long arrow).
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Fig. 1B 35-year-old man with intrarenal bleeding in large
angiomyolipoma of left kidney. Late phase of A shows hypervascular
angiogenic component (arrows) and 4-cm aneurysm (star).
Complete embolization was achieved (not shown).
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Fig. 1C 35-year-old man with intrarenal bleeding in large
angiomyolipoma of left kidney. Angiogram shows selective catheterization of
aneurysm feeder. Minicoil embolization was performed (not shown).
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Fig. 1D 35-year-old man with intrarenal bleeding in large
angiomyolipoma of left kidney. Anteroposterior angiogram 18 months after
embolization shows new aneurysm (star) and recurrence of
hypervascular but smaller angiogenic component (arrows). Second
embolization was performed.
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Fig. 1E 35-year-old man with intrarenal bleeding in large
angiomyolipoma of left kidney. Anteroposterior angiogram after third
embolization (29 months after first embolization) shows marked reduction in
angiogenic component.
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Materials and Methods
Patients
Institutional review board approval was obtained, and informed consent was
waived for this retrospective study, although informed consent had been
obtained from each patient before the procedures. From January 1992 to
December 2004, 29 patients were referred for angiography and possible
embolization of symptomatic or large (> 4 cm) renal AML; there was only one
patient from 1992-1996. After embolization, that patient had an elective
nephrectomy of the treated kidney because the urologists did not trust the
longevity of the embolization. As a result, the actual study follow-up period
was 8 years. Among this group, 23 patients underwent therapeutic transcatheter
embolization with the technique described later. Seventeen of these patients
completed at least 10 months of CT or angiographic follow-up, and they
constituted the study group.

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Fig. 1F 35-year-old man with intrarenal bleeding in large
angiomyolipoma of left kidney. Contrast-enhanced axial CT scan shows large
(largest diameter, 13 cm) angiomyolipoma (arrows) before
embolization.
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Fig. 1G 35-year-old man with intrarenal bleeding in large
angiomyolipoma of left kidney. Unenhanced axial CT scan at same level as
F after three embolizations shows reduction in tumor size
(arrows) and coil artifacts 41 months after first embolization.
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The subjects were 13 women and four men 24-82 years old (mean age, 55
years). Twelve (71%) of the patients (eight women and four men; age range,
35-82 years; mean age, 61 years) had the sporadic form of AML. Five (29%) of
the patients (all women; age range, 24-59 years; mean age, 41 years) had the
TS form. One of these patients also had pulmonary lymphangiomatosis. The 17
patients had 18 AML tumors. In one patient with TS, two tumors were found in
the same kidney. Symptoms were present in 13 patients and included
retroperitoneal hemorrhage (n = 8), hematuria, (n = 1), and
flank pain (n = 4). The other four patients had no symptoms, and the
tumors were incidental findings. All five patients with TS presented with
retroperitoneal bleeding. Only three of the eight patients with
retroperitoneal bleeding were treated during the acute bleeding phase. They
were inpatients at our hospital. The other five patients were treated on an
ambulatory basis several weeks to months after the hemorrhagic episode. These
patients were referred from other institutions after they had been given
supportive treatment and the diagnosis had been made.
In all patients, the diagnosis was made with unenhanced and enhanced CT on
the basis of the presence of lipomatous components in the tumor
[1,
16]. Tumor size ranged from
5.5 to 20 cm (mean, 10 cm) measured in the largest of the x-,
y-, or z-axis diameter on CT scans obtained before
angiography. Tumor size was 5-18 cm (mean, 11.7 cm) in the group with the TS
type of AML and 5.5-20 cm (mean, 9.3) in the group with the sporadic type.
Embolization Technique
Two interventional radiologists performed all procedures. One of them
participated in all procedures. Transarterial catheter embolization was
performed through the common femoral artery with 5-French angiographic
catheters. All diagnostic digital subtraction angiographic examinations
started with a flush aortogram for evaluation of extrarenal arterial feeders
to the tumor. After aortography, selective renal artery catheterization was
performed. After careful review of the arteries feeding the tumor, small
coaxial catheters (2.5 French, Tracker, Boston Scientific, or 2.7 French,
Leggiero, Terumo) were used for selective catheterization of each feeding
artery as far distally as possible to prevent arterial spasm and reflux of the
embolization material to normal parenchymal arteries. With this superselective
injection, arteriovenous shunting and the amount of embolization mixture were
evaluated. Embolization was performed with a mixture containing 20 mL of
absolute ethanol and 1 mL (1 bottle) of 45- to 150-µm (Contour, Target) or
47- to 90-µm (Cook) PVA particles. To prevent dilution of the ethanol, no
opacifying agent was added. Balloon occlusion was not used.
The embolization mixture was carefully injected with a 1-mL syringe in 0.3-
to 0.5-mL doses, which were gently pushed with 1 mL of contrast material for
verification of arterial occlusion. When embolization neared the occlusion
point, the radiologist obtained a selective control angiogram. If reflux to
normal arteries was seen, the radiologist considered, according to his
experience, whether to continue or to stop embolizing the vessel. Once
complete occlusion of one feeder artery was achieved, another feeding branch
was catheterized, investigated for shunting and amount of contrast material,
and embolized in the same manner as the first until all arterial feeders were
occluded. An effort was made to achieve complete tumor devascularization.
Control renal or segmental angiograms were obtained during the procedure for
evaluation of changes in tumor vascularity during the embolization procedure,
especially to find extrarenal feeder vessels and arteriovenous shunts. Control
renal angiography was performed at the end of each procedure.
Minicoils with a diameter range of 2-5 mm (Tracker, Boston Scientific) were
used in two situations, either to occlude single aneurysm feeders (two
aneurysms in one patient [Fig.
1C]), or in follow-up embolizations, to occlude hypertrophic
capsular arterial feeders that had been of normal size on the previous
angiogram and only after the ethanol-PVA mixture was used and stasis
achieved.
The mean embolization procedure time was 70 minutes (range, 45-160
minutes). Conscious sedation with midazolam and meperidine was administered on
an individual basis according to the decision of the radiologist in charge.
Antibiotic prophylaxis was not given.
After groin hemostasis was achieved, patients were transferred to the
urology department for an overnight stay and were usually discharged the day
after the procedure. Patients with postembolization syndrome were given
supportive treatment until symptoms resolved.
Follow-up
The patients underwent outpatient follow-up examinations by the urology
team 3-6 months after the procedure and once a year thereafter. Follow-up CT
was performed 10-66 months (mean, 23 months) after the procedure on all
patients, including the patients who were later lost to follow-up.
Conventional unenhanced and enhanced axial scans were obtained at different
institutions with different equipment and protocols. The interventional
radiologists reviewed for tumor size the CT scans obtained before the
procedure as well as the follow-up CT scans.

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Fig. 2A 44-year-old woman with bleeding angiomyolipoma of upper pole
of left kidney. Anteroposterior digital subtraction angiogram obtained before
embolization shows moderate tumor vascularity (arrows).
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Fig. 2B 44-year-old woman with bleeding angiomyolipoma of upper pole
of left kidney. Follow-up anteroposterior angiogram 16 months after
embolization shows obliteration of angiogenic component.
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Fig. 2C 44-year-old woman with bleeding angiomyolipoma of upper pole
of left kidney. Contrast-enhanced axial CT scan in acute bleeding phase shows
tumor (arrows) with maximum diameter of 12 cm.
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Fig. 2D 44-year-old woman with bleeding angiomyolipoma of upper pole
of left kidney. Contrast-enhanced axial CT scan 37 months after embolization
shows mainly lipomatous well-defined tumor (arrows). Maximum diameter
decreased to 6.5 cm.
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Follow-up angiograms were obtained for evaluation of the durability of
embolization and for embolization of recurrent angiogenic components. This
follow-up angiographic examination was part of a continuous treatment strategy
to show that planned-interval embolization is successful in obliteration of
the angiogenic component and prevention of bleeding and rupture. The end point
of this treatment strategy was obliteration of the vascular component as seen
on digital subtraction angiograms 12 months after the last embolization.

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Fig. 3A 24-year-old woman with tuberous sclerosis who had undergone
right nephrectomy because of uncontrolled bleeding angiomyolipoma. Preventive
embolization of angiomyolipoma in left kidney was performed. Angiogram before
embolization.
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Fig. 3B 24-year-old woman with tuberous sclerosis who had undergone
right nephrectomy because of uncontrolled bleeding angiomyolipoma. Preventive
embolization of angiomyolipoma in left kidney was performed. Angiogram after
embolization.
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Fig. 3C 24-year-old woman with tuberous sclerosis who had undergone
right nephrectomy because of uncontrolled bleeding angiomyolipoma. Preventive
embolization of angiomyolipoma in left kidney was performed. Follow-up
angiogram 60 months after first embolization shows hypertrophic capsular
artery (arrow) supplying angiomyolipoma. Lesion was embolized with
ethanol-polyvinyl alcohol mixture and minicoil.
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Fig. 3D 24-year-old woman with tuberous sclerosis who had undergone
right nephrectomy because of uncontrolled bleeding angiomyolipoma. Preventive
embolization of angiomyolipoma in left kidney was performed. Angiogram after
second embolization.
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Fourteen patients with 15 tumors underwent one follow-up angiographic
examination 9-60 months (mean, 12 months) after the first embolization and
after clinical evaluation. Four patients underwent a second follow-up
angiographic examination 22-29 months (mean, 27 months) after the first
embolization.
One TS patient with bilateral tumors underwent embolization of the left
kidney and 9 months later underwent embolization of the right kidney. At the
second embolization, follow-up digital subtraction angiography was performed
on the left kidney. The patient was lost to further follow-up, so there was
follow-up on one kidney only. The patient later was found to have died of
gastric carcinoma 5 years after embolization.
Results
Aortography revealed only one extrarenal feeder from a right intercostal
artery in a huge right renal tumor (20 x 18 x 12 cm). Angiography
showed the tumors had the characteristic features of AML
[17]: large tortuous vessels
with aneurysm formation of different sizes (largest, 4 cm) (Figs.
1A,
1B,
1C,
2A, and
3A). These vessels were easily
differentiated from the normal renal vasculature. No arteriovenous shunting
was found in any tumor. Vascular fragility was seen in four cases: During
manipulation of the coaxial catheter, rupture of small vessels occurred with
stable contrast extravasation without pain or signs of acute hemorrhage. The
amount of ethanol used was 0.5-35 mL (mean, 7.5 mL per procedure). Five
minicoils (one 5 mm/3 cm and four 3 mm/3 cm) were used in two tumors for
embolization of aneurysm feeder vessels. Complete immediate devascularization
of the angiogenic components was achieved in 17 tumors, a 94.4% technical
success rate. The one technical failure was incomplete tumor embolization due
to the presence of a small difficult-to-catheterize, tortuous arterial feeder.
The patient later underwent two successful embolization procedures 22 months
apart (the second procedure was performed 9 months after the first and the
third procedure, 13 months after the second), and reduction of the tumor size
and the angiogenic component was achieved.
Follow-up CT scans obtained 10-66 months (mean, 22.4 months) after
treatment were available for all 17 patients. No tumor had grown; two had not
changed in size; and 16 were smaller. The largest diameter of the tumors had
decreased to 1.5-8 cm (mean, 7.6 cm; mean reduction, 24%) (Figs.
1F,
1G,
2C, and
2D). In the TS group,
follow-up CT was performed a mean of 24.7 months (range, 10-66 months) after
treatment, and tumor size was 1.5-18 cm (mean, 9.2 cm; mean reduction, 21.4%).
In the sporadic group, follow-up CT was performed a mean of 21.3 months
(range, 10-41 months) after treatment, and tumor size was 2.8-13 cm (mean, 6.9
cm; mean reduction, 25.8%).
Fourteen patients with 15 tumors underwent their first angiographic
follow-up examination 9-60 months (mean, 14 months) after treatment. No new or
recurrent angiogenic component was seen in four patients (Figs.
2A and
2B), one of them with TS. These
patients thus had reached the treatment end point. In 11 tumors (five TS type,
six sporadic type), the vascular component was smaller than before the first
embolization, and embolization was repeated
(Fig. 1D). In three of these
patients a hypertrophied renal capsular artery supplying the tumor was found.
These capsular arteries were embolized with the ethanol-PVA mixture, and after
complete stasis was achieved, one 2 mm/3 cm minicoil was placed to prevent
recurrence in each of these vessels (Figs.
3A,
3B,
3C, and
3D).
Four patients underwent a second angiographic follow-up examination 22-29
months (mean, 27 months) after treatment. One of these patients had TS; two
had large masses occupying most of the kidney (Figs.
1A,
1B, and
1F), and one had evidence of
partial failure of the first embolization. In the patient with TS, no
recurrence of the angiogenic component was seen, so she had reached the
treatment end point. In the other three patients, vascularity was reduced, and
embolization was repeated (Fig.
1E). Follow-up angiography and embolization were performed in the
same manner as the first procedures with the ethanol-PVA mixture and minicoils
as deemed necessary.
Five patients (two with TS), who had five (33.3%) of the tumors, arrived at
the treatment goal, which was absence of angiogenic components at digital
subtraction angiography, 12 months after the last embolization. In 10 (66.6%)
of the tumors, the angiogenic component had become smaller, and further
digital subtraction angiography was planned. Three patients did not undergo
follow-up angiography. One patient, who had no symptoms, refused further
intervention. The other two (one with bleeding in the renal sinus and one with
pain) did not undergo further treatment because of advanced age and poor
general health and after a thorough discussion with the urologist. All three
of these patients underwent follow-up CT.
No complications occurred during or after the procedures, and there was no
rupture of a tumor or retroperitoneal hemorrhage after embolization or during
the follow-up period. No nontargeted embolization was documented. One tumor
had liquefied 1 month after embolization. The patient had no symptoms, so
intervention was not needed. Two patients had postembolization syndrome of
nausea, low-grade fever, headache, and flank pain on the treated side. These
patients were treated with IV fluids and nonsteroidal antiinflammatory
medication until symptoms subsided, and they were discharged from the hospital
after 3 and 4 days. All other patients were discharged 24 hours after the
procedure. Of the four patients with flank pain, in three, the pain resolved
during the first year of clinical follow-up. In one patient, the pain did not
resolve despite successful embolization.
Discussion
Treatment of patients with symptomatic renal AML is definitely indicated,
but there is debate regarding the size criteria for treatment of patients with
asymptomatic AML. Most published data indicate that asymptomatic tumors larger
than 8 cm should be treated because of high bleeding risk
[1,
2,
5,
6,
8,
18]. Some clinicians favor
treatment even for asymptomatic tumors when they are larger than 4 cm
[5,
8,
14]. At our institution, we
offer embolization to every patient with an asymptomatic tumor larger than 4
cm and to all patients with symptomatic tumors
[4,
5,
9].
With conventional unenhanced and enhanced CT in the follow-up period after
embolization, we found only 24% mean reduction in tumor size, as have other
investigators [4,
11,
12]. We did not wait for
clinical recurrence. We performed the first diagnostic angiographic
examination a mean of 14 months and a second examination a mean of 27 months
after embolization to evaluate the remains of the angiogenic component and to
look for regrowth, which is the source of renewed bleeding in these tumors
[5-7].
Embolization was repeated when growth of new vessels was seen. That reduction
or obliteration of the angiogenic component occurred even without marked
change in tumor size showed that size should not be considered a risk factor
for bleeding after embolization and that surgical removal is not necessary (as
it would be with the size criterion).
Transarterial catheter embolization of renal AML is a documented treatment
option [3,
4,
6,
10,
12-14].
Most investigators use absolute ethanol as the main embolization material,
with or without iodized oil [4,
12,
13,
14,
19] because it is easily
administered, diffuses through the entire tumor vasculature, permanently
occludes the arteries at the capillary level, and causes tumor infarction and
necrosis [7,
15]. Han et al.
[13], Lee et al.
[12], and Kothary et al.
[14] reported their experience
with a mixture of ethanol and iodized oil in relatively large patient series.
Han et al. treated five patients with this mixture and another nine patients
with different embolic material. After imaging follow-up examinations at least
12 months after embolization, the 14 patients had a mean reduction in tumor
size of 70.2%, and no vascularity seen on CT or sonography. The investigators
did not perform digital subtraction angiography to evaluate the angiogenic
components, and they did not report separately on follow-up of the patients
who underwent ethanol and iodized-oil embolization. Lee et al. treated 15
patients with 21 tumors, all with a mixture of ethanol and iodized-oil. The
mean follow-up period was 35.6 months. These investigators reported decreased
size in 12 tumors and no change in eight. Two of the patients had bleeding
during the follow-up period. Lee et al. also did not perform follow-up digital
subtraction angiography. Kothary et al. treated 19 patients with 30 tumors
with a mixture of ethanol and iodized-oil. The mean follow-up period was 51.5
months. The recurrence rate was 42.9% with recurrence only in the TS group of
nine tumors. Recurrence manifested as tumor growth, pain, and bleeding. The
authors treated the recurrence by the same method of embolization as the first
procedure.
We used an approach different from that of the foregoing investigators.
First, we added the smallest PVA particles available (45-150 µm) to
ethanol, surmising that the particles would augment the effect of ethanol on
the vascular bed by producing stasis in the small arteriolar bed and
prolonging the effect on the arterioles. This mixture may not directly affect
the tumor capillary bed, but it has the advantage of being a combination of
two permanently occlusive materials, each of which may augment the influence
of the other. Because no intratumoral arteriovenous shunting was seen, it was
deemed safe to use small particles without allowing embolization through the
lesions to nontargeted areas. We used coaxial systems and superselective
catheterization of all tumor feeders, as did Lee et al.
[12] in most of their cases.
We also embolized the feeding vessels with a very small amount of ethanol-PVA
mixture in each injection (0.3-0.5 mL) to avoid reflux to normal renal
parenchyma. By using this technique we did not find it necessary to opacify
the ethanol-PVA mixture as other investigators have
[4,
12,
14,
19], allowing us to introduce
more ethanol to a given vessel. Other authors have used occlusion balloons
with ethanol embolization [4,
7,
12,
13,
14], but these balloons can be
used only in fairly large feeders, and not as precisely as with the coaxial
technique.
Second, we made an effort to perform follow-up digital subtraction
angiography 1 year after embolization to evaluate and, if needed, to repeat
embolization of the angiogenic component of the tumor. We assumed that if no
vascularity was seen after 1 year, the possibility of future bleeding was very
low, an assumption proved with continuous follow-up.
In this series, our treatment goal of complete obliteration of the
angiogenic component was met in five (33.3%) of 15 tumors. The vascular
component was reduced in 10 (66.6%) of the tumors, and follow-up was continued
for these patients. These results suggest that embolization with the
ethanol-PVA mixture has a durable midterm effect. It is significant that we
did not see retroperitoneal hemorrhage or tumor growth in any of the treated
patients during the 8 years of the study, which is a better result than that
reported by others [12,
14].
Four patients were treated for flank pain. This symptom is not specific and
was not the indication for treatment but only for further investigation with
CT, which showed tumors of the size that is an indication for treatment.
Nevertheless, in three patients the pain resolved during the first year after
embolization, which may suggest the AML was the cause of the pain. One patient
continued to have abdominal pain of unknown cause after successful
embolization.
The most important limitation of our study was the small series of patients
with relatively short follow-up, which made statistical analysis impossible.
The small size of the study group was due to the rarity of the lesions; unless
a worldwide registry is formed, this limitation will not be solved. For the
same reason, it was impossible to conduct a comparative prospective study, the
results of which may have been statistically significant. The follow-up period
in this study, although fairly long, must be lengthened to obtain further
confirmation of the results. Another limitation was that we did not use CT
angiography protocols for all patients, and the findings may have been
predictive of the angiogenic component of the tumors. Most of the follow-up CT
scans were obtained at institutions other than ours with CT equipment
different from ours, and we did not have control over the protocols. That is
why we used CT to evaluate the size and general structure of the tumors and
not for evaluation of the angiogenic component. Fast acquisition helical CT
and power Doppler sonography may obviate the use of angiography as the
follow-up technique. This issue can be addressed in future studies comparing
CT angiography and conventional angiography in the evaluation of renal
AML.
In conclusion, on the basis of these results we favor embolization with an
ethanol-PVA mixture as the primary treatment to obliterate or reduce the
angiogenic component of renal AML, minimizing the risk of bleeding, even
without reduction in tumor size. Tumors with a rich angiogenic component
should be managed with several embolization procedures.
Acknowledgments
We are grateful to M. Hertz for assistance in the preparation of the
manuscript.
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