Diagnostic ultrasound ( PDFDrive )

CHAPTER 8 The Gastrointestinal Tract 261
FIG. 8.5 Schematic of Compression Sonography. Left, Normal gut is compressed. Middle, Abnormally thickened gut, or right, an obstructed
loop, such as that seen in acute appendicitis, will be noncompressible.
change in the patient with acute abdominal pain. Teefey et al. 7
examined 35 patients and found absent or barely visible blood
low on color Doppler and absence of arterial signal to be suggestive
of ischemia. In contrast, readily detected color Doppler
low was consistent with inlammation.
Contrast-Enhanced Ultrasound and
Elastography of the Bowel
Two exciting new applications of ultrasound of the bowel include
contrast-enhanced ultrasound (CEUS) and elastography. he
former provides objective repeatable measures of mural blood
low, which may change in response to inlammation and neoplasia,
and the latter measures bowel wall stifness. 9 Although
these investigations are still in their infancy, their additional
beneit over routine gray-scale ultrasound with Doppler is evident.
heir great contribution to the evaluation of those with inlammatory
bowel disease will be discussed in that section. CEUS is
also useful in the assessment of mass lesions to determine the
presence of vascularity analogous to the role of contrast enhancement
on CT or MRI scan.
GASTROINTESTINAL
TRACT NEOPLASMS
he role of sonography in the evaluation of GI tract neoplasms
is similar to that of CT. Visualization is limited in cases of early
mucosal lesions or with small intramural nodules, whereas tumors
growing to produce an exophytic mass, a thickened segment of
gut, or a sizable intraluminal mass are more easily detected (Fig.
8.7, Video 8.1). Sonograms are frequently performed early in
the diagnostic workup of patients with GI tract tumors, oten
before their initial identiication. Vague abdominal symptomatology,
abdominal pain, a palpable abdominal mass, and anemia
are common indications for these scans. Appreciation of the
typical morphologies associated with GI tract neoplasia may
lead to accurate recognition, localization, and even staging of
disease, with the opportunity for directing appropriate further
investigation, including sonography-guided aspiration biopsy.
Adenocarcinoma
Adenocarcinoma is the most common malignant tumor of the
GI tract. Grossly, it has variable growth patterns (see Fig. 8.7),
including iniltrative, polypoid, fungating, and ulcerated tumors.
Most GI tract mucosal cancers are not visualized on sonography.
However, large masses, either intraluminal or exophytic, and
annular tumors create sonographic abnormalities. 10,11 Tumors
of variable length may thicken the gut wall in either a concentric
symmetrical or an asymmetrical pattern. A target or pseudokidney
morphology may be created (see Fig. 8.4). Air in mucosal
ulcerations typically produces linear echogenic foci, oten with
ring-down artifact, within the bulk of the mass. Tumors are
usually, but not invariably, hypoechoic. Annular lesions may
produce gut obstruction with dilation, hyperperistalsis, and
increased luminal luid of the gut proximal to the tumor site. 11
Evidence of direct invasion, regional lymph node enlargement,
and liver metastases should be sought.
Adenocarcinoma accounts for 80% of all malignant gastric
neoplasms, where iniltration may be supericial or transmural,
the latter creating a linitis plastica, or “leather bottle,” stomach.
Adenocarcinoma occurs much less frequently in the small bowel
than in the stomach or large bowel. It accounts for approximately