Diagnostic ultrasound ( PDFDrive )

CHAPTER 6 The Biliary Tree and Gallbladder 203
A
B
FIG. 6.44 Segmental Adenomyomatosis. (A) Fundal adenomyoma. (B) Hourglass adenomyomatosis. In both cases, note the constricted
contour of the gallbladder and thickening of the wall with hypertrophy of the smooth muscle. On sonography, the exaggerated Rokitansky-Aschoff
sinuses may appear as cystic spaces or as echogenic foci with comet-tail artifact, possibly caused by cholesterol crystals (depicted here as yellow
particles) lodged in them.
Polypoid Masses of Gallbladder
Diferentiation of benign and malignant polyps is essential because
benign masses are common and malignant polyps require early
intervention to improve outcome. Current evidence suggests that
risk of malignancy in polyps less than 6 mm in size is negligible
and they require no further follow-up. 100-102 More recent data
suggest that gallbladder adenomas form a small fraction of 6- to
10-mm polyps and because they may have a risk of malignant
transformation, imaging follow-up is recommended. 101,103 Whether
such practice, based on retrospective surgical series, is justiied
through a cost-beneit analysis remains unknown, especially in
a Western population where gallbladder cancer is rare. 104 Malignancy
has been documented in 37% to 88% of resected polyps
greater than 10 mm and therefore resection of these larger polyps
is advised. 105
Apart from size, research from both endoscopic and highresolution
ultrasound has identiied additional features that help
diferentiate nonneoplastic from neoplastic polyps. he presence
of hypoechoic foci centrally within the polyp has been shown
to be a signiicant predictor of neoplastic polyps with sensitivity/
speciicity of 85%/67% on high-resolution transabdominal
ultrasound and 91%/89% on endoscopic ultrasound. 106,107 Also
the presence of a central vessel within the polyp (vascular core)
and hypoechoic appearance are suggestive of a neoplastic polyp.
Cholesterol Polyps
Approximately one-half of all polypoid gallbladder lesions are
cholesterol polyps. hese represent the focal form of gallbladder
cholesterolosis, a common nonneoplastic condition of unknown
origin. Cholesterolosis results in accumulation of lipids within
macrophages. he difuse form, commonly known as “strawberry
gallbladder,” is not visible on imaging. Cholesterolosis has the
same risk factors as gallstone disease, but the two conditions
rarely coexist. 98 Cholesterol polyps usually are 2 to 10 mm,
although lesions up to 20 mm have been described. 105 On
pathologic series, one-ith are solitary, but the mean number
of polyps is eight. 98
Common Polypoid Masses of the Gallbladder
Cholesterol polyps a (50%-60%)
Inlammatory polyps a (5%-10%)
Adenoma a (<5%)
Focal adenomyomatosis
Gallbladder adenocarcinoma
Metastases (especially melanoma)
a Data from Bilhartz LE. Acalculous cholecystitis, cholesterolosis,
adenomyomatosis, and polyps of the gallbladder. In: Feldman M,
et al., editors. Sleisenger and Fordtran’s gastrointestinal and liver
disease. 7th ed. New York: Elsevier Science; 2002. pp. 1123-1125. 98
he sonographic appearance of cholesterol polyps is multiple
ovoid, nonshadowing lesions attached to the gallbladder wall
(Fig. 6.47). Unlike small, nonshadowing stones, polyps are not
mobile. Larger lesions may contain a ine pattern of echogenic
foci. 108
Adenomas, Adenomyomas, and
Inlammatory Polyps
Adenomas are true benign neoplasms of the gallbladder, with
a premalignant potential much lower than for colonic adenomas.
Adenomas represent less than 5% of gallbladder polyps and occur
as solitary lesions. hey have a propensity to occur in patients
with primary sclerosing cholangitis and polyposis syndromes. 109
Adenomas are usually pedunculated, and larger lesions may
contain foci of malignant transformation. 98 Adenomas tend to
be homogeneously hyperechoic but become more heterogeneous
as they increase in size 105 (Fig. 6.48). hickening of the gallbladder
wall adjacent to an adenoma should suggest malignancy. Central
hypoechoic foci, representing central vessels or microscopic cysts
are quite suggestive. 107 On occasion, an adenomyoma may appear
as a sessile, polypoid gallbladder lesion. Imaging features,
especially hyperechoic foci with or without comet-tail artifact
and microcysts, should allow diferentiation. 106 Inlammatory