Diagnostic ultrasound ( PDFDrive )

CHAPTER 9 The Kidney and Urinary Tract 351
may also be identiied with RCC (see Fig. 9.51). he lack of
speciicity of imaging features of oncocytomas typically prompts
surgical resection, although as mentioned previously, recent
improvements in immunohistochemistry may prompt imaging
surveillance for patients with biopsy results consistent with benign
oncocytomas.
Angiomyolipoma
AMLs are benign renal tumors composed of varying proportions
of adipose tissue, smooth muscle cells, and blood vessels. AMLs
may occur sporadically or may be found in patients with tuberous
sclerosis. In patients without stigmata of tuberous sclerosis, AMLs
are typically unilateral and discovered in middle-aged women.
Up to 50% of patients with AMLs will have clinical stigmata of
tuberous sclerosis (mental retardation, epilepsy, facial sebaceous
adenomas), and up to 80% of patients with tuberous sclerosis
will have one or more AMLs. 205 AMLs associated with tuberous
sclerosis are usually small, multiple, bilateral tumors, with no
gender predilection. Sporadic AMLs are histologically identical
to those associated with tuberous sclerosis. It is unusual for small
tumors (<4 cm) 206 to be symptomatic; with growth, however,
these tumors may hemorrhage, with symptoms such as hematuria,
lank pain, and palpable lank mass.
At sonography, the echo pattern of AMLs depends on the
proportions of fat, smooth muscle, vascular elements, and
hemorrhage. hese tumors may be located within renal parenchyma
or may be exophytic (Fig. 9.58). If muscle, hemorrhage,
or vascular elements predominate, the tumor may be hypoechoic.
Siegel et al. 152 showed that the multiple fat and nonfat interfaces
in the more typical AMLs, along with the large acoustic impedance
diferences at these interfaces, causes scattering and attenuation
of sound waves. his histology leads to the classic ultrasound
A B C
.
M
.
D
E
F
H
H
G
H
I
FIG. 9.58 Imaging Spectrum of Angiomyolipomas (AMLs). (A) Classic small hyperechoic intraparenchymal tumor. (B) Multiple small echogenic
foci in the anterior cortex of the midpole. (C) Solitary, large, highly echogenic mass in the lower pole. (D) Exophytic echogenic mass involves the
cortex and the perirenal space (arrows). The lat appearance suggests a compliant soft tumor. (E) Large exophytic lower-pole echogenic mass
(arrow). The echogenicity of the mass may be very similar to the perirenal fat. (F) Large, complex intrarenal mass (arrows) is mildly echogenic and
has a hypoechoic component representing myomatous elements (M). (G)-(I) Hemorrhagic AMLs. (G) Exophytic ruptured upper-pole AML with a
perirenal hematoma (H). (H) Echogenic mass with central hypoechoic hemorrhage. (I) Large, predominantly exophytic AML. The kidney below the
mass appears normal. The mass (arrows) shows increased echogenicity from the fat in the AML and a large hypoechoic hemorrhage (H).