Renal angiomyolipoma with bleeding
M Muttarak*,1, MD,
N Pattamapaspong1, MD,
B Lojanapiwa2, MD,
B Chaiwun3, MD
1 Department of Radiology, Chiang Mai
University, Chiang Mai, Thailand
2 Department of Surgery, Chiang Mai University, Chiang Mai, Thailand
3 Department of Pathology, Chiang Mai University, Chiang Mai, Thailand
A 47-year-old woman was referred to our hospital for the
management of her large abdominal mass. She had a history of right flank pain
off and on for 2-3 years. She was admitted to the provincial hospital in the
previous four days due to right flank pain and nausea. She had no history of
trauma. Abdominal computed tomography (CT) was performed and liposarcoma was
suspected in the right flank. She was pale and was found to have an ill-defined
14x17 cm mass with mild tenderness in the right flank. Her blood pressure and
pulse was 130/80 mm Hg and 80/minute, and body temperature was 36.5oC.
Laboratory investigations were: haemoglobin 6.2 g/dL, haematocrit 20.3%, white
blood cell count 9.6x103/mm3 and creatinine 1 mg/dl. Urinalysis
revealed red blood cell 1-2 while white blood cell 8-12 in the high power
Abdominal CT showed a large predominantly fat-containing
mass arising from the lateral aspect of the right kidney with compression of
the liver, enlarged vessels within the mass, intratumoural and perinephric haematoma
Symptomatic treatment with blood transfusion was given but
she still had anaemia and flank pain. An elective simple right neprectomy was
performed. She made an uneventful recovery.
On gross examination, there was a large circumscribed
fat-containing mass with hemorrhage, and compression of the renal parenchyma
(Figure 2). Microscopic examination revealed tortuous thick-walled blood vessels,
sheets of mature fat cells and bundles of muscle fibres (Figure 3), consistent
with angiomyolipoma (AML).
AMLs are uncommon benign tumours of the kidney composed of
varying amounts of fat, smooth muscle and abnormal thick-walled blood vessels. AMLs
may occur as isolated lesions or are associated with tuberous sclerosis (TS).
Isolated or sporadic AMLs account for 80 to 90% of reported cases and commonly
occur in women aged 40 to 70. The lesions in this group are usually unilateral
and focal. AMLs associated with TS� are usually bilateral and multifocal, and
can occur at any age and in either sex. Most patients are asymptomatic and the tumour
is often incidentally detected during ultrasonography (US) or CT [1,2]. When
symptoms do occur, common presenting symptoms are flank or abdominal pain,
palpable mass and haematuria related to spontaneous intramural or extramural hemorrhage.
The main complication of AMLs is hemorrhage, which is related to the tumour
size, increased vascularity and abnormal thick-walled vessels that are
predisposed to the formation of microaneuryms and bleeding. AMLs larger than 4
cm in diameter increase the risk for hemorrhage . Although AMLs are
considered a benign lesion, reports of growing lesions, invasion into the
inferior vena cava and regional lymph nodes have been noted .
Preoperative diagnosis of AMLs was difficult in the past and
rarely made. Today, with the widespread use of US and CT, more AMLs are
diagnosed preoperatively. With US, AMLs appear as a marked hyperechoic mass
(Figure 4) due to high fat content and multiple tissue interfaces produced by fat
and multiple vessels . However, this high echoic mass is not pathognomonic
for AMLs. Other renal tumours including renal cell carcinoma, liposarcoma,
atypical Wilms� tumour, lymphoma, lipoma, oncocytoma, and cavernous haemangioma
may be hyperechoic. CT is highly specific to fatty tissue in the lesion and is
often performed to confirm the diagnosis [1,2]. Although there have been a few
reports of fat occurring in renal cell carcinomas, calcification has also been
detected . Whereas, AMLs rarely contain calcification , therefore a
diagnosis of AMLs should not be made if a lesion contains fat and
calcification. Rarely, renal tumours including lipoma, liposarcoma, Wilms� tumour,
teratoma, oncocytoma, and xanthogranulomatous pyelonephritis contain sufficient
quantities of fat to be detected at CT . A large exophytic renal angiomyolipoma
may be difficult to differentiate from a well-differentiated perirenal liposarcoma
because they both contain fat. Careful evaluation for a defect in the renal
parenchyma and a presence of enlarged vessels can help differentiate angiomyolipoma
from liposarcoma .
Some AMLs may contain very small amounts of fat that can be
overlooked if they are not carefully evaluated. If a small amount of fat is
suspected in a renal mass, unenhanced CT scan with thin sections combined with
a small area for attenuation analysis is recommended. A small number of AMLs
contain predominantly muscle and blood vessels with scanty fat component. These
AMLs appear as non-fatty renal mass and the imaging differentiation from renal
cell carcinoma seems impossible.
Treatment of AMLs depends on the size of the lesion. If an
isolated AML is less than 4 cm in diameter, conservative follow-up with either
US or CT is recommended. If the AML is larger than 4 cm, it has a greater
tendency to bleed. Therefore, patients with AMLs greater than 4 cm and bleeding
or uncontrollable pain should undergo renal-sparing or renal arterial embolisation
if it is available . The case presented in this paper did not have
preoperative embolisation because angiography service was not available at that
In summary, this case is a large solitary renal AML with
spontaneous bleeding. Clinical course, diagnosis and management of renal AMLs
Figure 1 Enhanced-CT images at (A) upper pole (B) middle pole, and (C) lower pole of the right kidney (K) show a 13x15x20 cm fat-containing mass arising from the lateral aspect of the kidney with sharp defect (arrows) in renal parenchyma, enlarged vessels (arrowheads), intratumoural and perinephric hemorrhage (H), and compression of the liver (L).
Figure 2 Photograph of an excised specimen reveals a large circumscribed mass (black arrows) with variegated cut surface, showing predominance yellowish areas of fat admixed with intratumour hemorrhage and necrotic foci. The normal renal parenchyma (white arrows) is compressed.
Figure 3 Photomicrograph shows admixture of tortuous thick-walled blood vessels (black arrows), sheets of mature adipose tissue (F) and bundles of smooth muscle fibres (M) (hematoxylin and eosin stain; x40).
Figure 4 Oblique coronal US scan of the kidney of another patient with uncomplicated AML shows a hyperechoic mass (cursors) in the upper pole.
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|Received 15 December 2006; received in revised format 12 February 2007; accepted 23 February 2007
Correspondence: Department of Radiology, Chiang Mai University, Chiang Mai, Thailand. Tel.: +66 53 945450; Fax: +66 53 217144; E-mail: firstname.lastname@example.org (Malai Muttarak).
Please cite as: Muttarak M, Pattamapaspong N, Lojanapiwat B, Chaiwun B,
Renal angiomyolipoma with bleeding, Biomed Imaging Interv J 2007; 3(4):e8
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