AJR 2002; 179:145-147
© American Roentgen Ray Society
Color-Flow Doppler Sonography of Pseudoaneurysms in Patients with Bleeding Renal Angiomyolipoma
M. Lapeyre1,
J. M. Correas1,
N. Ortonne2,
C. Balleyguier1 and
O. Hélénon1
1 Department of Radiology, Necker Hospital, 149 rue de Sèvres, 75743
Paris Cedex 15, France.
2 Department of Pathology, Necker Hospital, 75743 Paris Cedex 15, France.
Received May 29, 2001;
accepted after revision November 30, 2001.
Address correspondence to O. Hélénon.
Introduction
A renal angiomyolipoma is typically recognized as a fat-containing tumor on
CT [1,
2]. Although vascular
complication is unusual, the risk of complication—especially when lesion
is large—is the main indication for treatment of angiomyolipoma
[1,
3,
4]. Clinically significant
hemorrhaging has occurred in as many as 51% of angiomyolipomas larger than 4
cm that were surgically removed
[1]. However, it is unusual to
find intratumoral pseudoaneurysms within hemorrhagic angiomyolipomas.
We report two cases of hemorrhagic angiomyolipomas associated with
intratumoral pseudoaneurysms.
Case Reports
In our first case, a 42-year-old woman presented with sudden onset of right
flank pain. Physical examination was remarkable for right flank tenderness,
but her vital signs were normal. Laboratory studies disclosed a hemoglobin
level of 10.6 g/dL and hematocrit of 35%. CT was performed before and after
administration of contrast material (5-mm section thickness, 7-mm
collimation). A 3.5-cm heterogeneous tumor associated with a subcapsular
hematoma was seen in the upper pole of the right kidney and had negative
attenuation (-20 H). No evidence of retroperitoneal hemorrhage or intrarenal
pseudoaneurysm was found.
The patient was referred to the intensive care unit for observation. Six
days later, she again had minor right flank pain. No biologic or physical
abnormalities were found. Sonographic examination revealed a round hypoechoic
intratumoral mass measuring 2.5 cm in diameter within a hyperechoic solid mass
in the right kidney (Fig. 1A).
Color-flow Doppler sonography was used to code the flow within the mass
(Fig. 1B). Spectral
investigation using pulsed Doppler sonography showed the typical to-and-fro
flow pattern in the neck that connected the pseudoaneurysm to the injured
artery. Subsequent CT was performed using 5-mm section thickness and 7-mm
collimation on one unenhanced and two enhanced studies (delays, 20 and 80
sec). An obvious pseudoaneurysm filled with contrast medium was seen on early
arterial phase CT after contrast administration
(Fig. 1C). A partial
nephrectomy was performed, and the diagnosis of hemorrhagic angiomyolipoma
with intratumoral pseudoaneurysm was confirmed by pathologic examination.
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Fig. 1B. —42-year-old woman with renal angiomyolipoma. Color Doppler
sonogram shows color-flow signal (straight arrows) in hypoechoic
intratumoral area. Neck of pseudoaneurysm (curved arrow) is also seen
arising from cortical renal artery.
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|
In our second case, a 40-year-old man with von Hippel-Lindau disease
presented with left flank pain and gross hematuria. Multiple angiomyolipomas
were found in both kidneys on CT using a standard protocol with a delayed (60
sec) contrast-enhanced study (5-mm section thickness, 7-mm collimation). A
heterogeneous mass with negative attenuation (-35 H) was also identified in
the left kidney and was associated with a marked perirenal hemorrhage
(Fig. 2A). The patient's vital
signs were normal, and he was admitted for medical observation. Fifteen days
later, sonography showed a 2-cm hypoechoic mass on the upper part of the
hemorrhagic angiomyolipoma. The mass was color-flow filled, and spectral
analysis obtained from the neck of the pseudoaneurysm revealed a to-and-fro
flow pattern (Fig. 2B). Renal
arteriography confirmed the diagnosis of intratumoral pseudoaneurysm
(Fig. 2C) and enabled
successful transluminal embolization, which was performed using coils.
Follow-up CT and sonography at 6 months after embolization showed no pattern
of recurrence.
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Fig. 2A. —40-year-old man with hemorrhagic renal angiomyolipoma.
Unenhanced CT shows heterogeneous mass in lower pole of left kidney with
negative attenuation associated with perirenal hemorrhage.
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Fig. 2B. —40-year-old man with hemorrhagic renal angiomyolipoma. Color
Doppler image shows intratumoral pseudoaneurysm filled with bidirectional
color-flow signal, and spectral analysis obtained from pseudoaneurysm neck
shows typical to-and-fro flow pattern.
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Discussion
Renal angiomyolipomas are benign neoplasms composed of mature adipose
tissue, thick-walled blood vessels, and smooth muscle in varying proportions
[4]. The treatment of these
lesions depends on whether there is risk of acute hemorrhage or suggestion of
renal cell carcinoma in patients with angiomyolipomas that have no detectable
intratumoral fat [1,
3,
4]. Follow-up imaging has been
proposed to manage patients asymptomatic neoplasms and symptomatic lesions
smaller than 4 cm whose symptoms resolve promptly, whereas asymptomatic tumors
of 4 cm or larger and symptomatic tumors smaller than 4 cm should be treated
by surgery or embolization [1].
The risk of hemorrhage correlates with the size of the tumor and is
significantly greater in angiomyolipomas of more than 4 cm
[1,
3]. Oesterling et al.
[1] reported that hemorrhage
prompted surgery in 51% of resected angiomyolipomas larger than 4 cm in
diameter, whereas only 10% of small resected angiomyolipomas bled. Despite the
presence of blood vessels with thicker walls than those of normal vessels,
hemorrhage is not uncommon in an angiomyolipoma. The characteristic lack of
normal elastic layers predisposes intratumoral vessels to aneurysm formation
and hemorrhage. Although intrarenal or perinephric hemorrhage is the usual
complication of angiomyolipomas, pseudoaneurysm appears to be unusual,
because, to our knowledge, this development has been reported in only one case
[5]. Intrarenal pseudoaneurysm
is also a well-known complication of penetrating renal injuries, renal
surgery, and percutaneous renal procedures
[6,7,8].
Color-flow Doppler sonographic patterns have been well described in the
literature. Sonography shows a round hypoechoic mass in the renal parenchyma
that fills with color signal on color-flow Doppler imaging. Spectral analysis
performed at the level of the communicating channel shows a typical pattern
known as the to-and-fro sign, which signifies both systolic feeding arterial
flow and diastolic draining arterial flow.
Angiomyolipomas with intratumoral hemorrhage are often difficult to
characterize, because the intratumoral fat component or even the tumor itself
can be obscured by blood. However, in most cases of massive hemorrhage, the
tumor is large (
4 cm) and can be identified as a poorly marginated mass
arising from the renal cortex, exhibiting contrast enhancement and a fat
component [9]. Such a
heterogeneous appearance of the tumor may prevent detection of an intratumoral
pseudoaneurysm.
In our two cases, no pseudoaneurysms were found on initial CT, whereas the
diagnosis was established by color Doppler sonography. However, no early
contrast-enhanced CT studies were performed. Arterial phase CT has the
potential to provide information similar to that of color-flow Doppler
sonography.
We believe that pseudoaneurysm formation increases the risk of bleeding
recurrence associated with hemorrhagic angiomyolipomas, although spontaneous
thrombosis remains possible, as has been observed in iatrogenic femoral
pseudoaneurysms [10].
Selective transluminal embolization of pseudoaneurysms in this setting is an
efficient treatment that could obviate partial or radical nephrectomy in
patients with lesions smaller than 4 cm.
In conclusion, arterial pseudoaneurysm is a vascular complication that can
be associated with hemorrhage within an angiomyolipoma. Color-flow Doppler
sonography appears to be the modality of choice to determine whether a
hemorrhagic angiomyolipoma is at risk of early recurrent bleeding associated
with an intratumoral pseudoaneurysm. The detection of such a vascular lesion
should prompt appropriate treatment based on the size of the
angiomyolipoma.
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Introduction
Case Reports
