Diagnostic ultrasound ( PDFDrive )

258 PART II Abdominal and Pelvic Sonography
FIG. 8.2 Gut Signature in a Patient With Mild Gut Thickening Caused by Crohn Disease. The muscle layers are hypoechoic. The submucosa
and supericial mucosa layers are hyperechoic. There is a small amount of luid and air in the gut lumen.
may be seen in association with both malignant and benign gut
wall thickening.
Gut wall masses, as distinguished from thickened gut wall,
may be intraluminal, mural, or exophytic, all with or without
ulceration. Intraluminal gut masses and mucosal masses have a
variable appearance on sonography but are frequently hidden
by gas or luminal content. In contrast, gut pathology creating
an exophytic mass (without or with mucosal involvement or
ulceration) may form masses that are more readily visualized.
hese may be diicult to assign to a GI tract origin if typical gut
signatures, targets, or pseudokidneys are not seen on sonographic
examination. Consequently, intraperitoneal masses of varying
morphology, which do not clearly arise from the solid abdominal
viscera or the lymph nodes, should be considered to have a
potential gut origin.
Imaging Technique
Routine sonograms are best performed when the patient has
fasted. A real-time survey of the entire abdomen is performed
with a 3.5- to 5-MHz transducer, and any obvious masses or gut
signatures are observed. he pelvis is scanned before and ater
the bladder is emptied because the full bladder facilitates visualization
of pathologic conditions in some patients and displaces
abdominal bowel loops in others. A routine gut evaluation should
include assessment of all of the small bowel and the colon. In
women, transvaginal sonography is invaluable for evaluation
of the portions of the gut within the true pelvis, particularly the
rectum, sigmoid colon, and, in some patients, the ileum. Further,
oral luid and a Fleet enema may improve localization and
diagnosis of intraluminal or intramural gastric masses and rectal
masses, respectively. Still images in long-axis and cross-sectional
views as well as cine sweeps to show pathologic features allow
for optimal review.
Areas of interest then receive detailed analysis, including
compression sonography 6 (Fig. 8.5). Although this technique
was initially described using high-frequency linear probes, 5- to
9-MHz convex probes and some sector probes work extremely
well. he critical factor is a transducer with a short focal zone,