Diagnostic ultrasound ( PDFDrive )

274 PART II Abdominal and Pelvic Sonography
A
B
C
D
FIG. 8.19 Intramural Sinus Tract in Active Crohn Disease of the Neoterminal Ileum. (A) and (B) Long-axis views of the terminal ileum
show wall thickening and surrounding abundant inlammatory fat. The luminal surfaces are in apposition and are central within the thickened loop.
(B) Bright echogenic line running parallel to the serosa, an intramural sinus tract illed with air. (C) and (D) Axial images show two bright echogenic
linear streaks suggesting air dissected within the layers of the bowel, deep to the echogenic submucosal layer.
segments of gut most oten appear to be in ixed constant apposition,
with the lumen appearing as a linear echogenic central area
within a thickened gut loop (Fig. 8.20). his is in contrast to
thickened sections, where the luminal diameter may be maintained
(Fig. 8.21). Fixed acute angulations are frequent associations
with advanced strictures (Video 8.8). Incomplete mechanical
obstruction may be inferred if dilated, hyperperistaltic segments
are seen proximal to a stricture (Fig. 8.21C and D, Videos 8.9
and 8.10). Peristaltic waves from the obstructed gut, proximal
to a narrowed segment, may produce visible movement through
the strictured segment. Less oten, involved segments of gut show
luminal dilation with sacculation, as well as narrowing, and the
retained lumen is of variable caliber. Concretions and bezoars
may develop in gut between strictured segments.
Parente et al. 31 showed that bowel ultrasound is an accurate
technique for detecting small bowel strictures, especially in
patients with severe disease who are candidates for surgery.
Management of strictures in Crohn disease is challenging.
Diferentiating between patients who have a predominantly
inlammatory versus a mainly ibrotic component of their stricture
is imperative to improve selection between medical therapy and
surgery. Investigations using only gray-scale ultrasound features
are frequently inconclusive.
However, bowel ultrasound has been shown to detect
ibrosis using a variety of elastographic techniques. Shear wave
elastography uses acoustic radiation force impulse technology to
assess elastic properties of tissue through an acoustic ultrasound
force that propagates a shear wave through tissue. Measurements
of the velocity in meters per second (m/sec) of this shear wave
traversing through the tissue are made. Shear wave elastography
provides an objective and reproducible quantitative measurement
of tissue stifness. 32 Early investigations assessing ibrosis in
animal models with elastography show some promising results. 33
Our recent experience combines both CEUS and point shear
wave elastography. Our results suggest CEUS parameters relect
inlammation and elastography values relect the chronic features
of ibrosis and smooth muscle hypertrophy, improving greatly
our contributions to patient management. 34
Incomplete Mechanical Bowel Obstruction
Obstructive symptoms of bloating abdominal pain and abdominal
distention are frequently associated with stricture in IBD. On
sonography, distended prestenotic loops of bowel are luid
distended and show dysfunctional and excess peristalsis (see
Fig. 8.21C and D, Videos 8.9 and 8.10).
Localized Perforation
Although free perforation of the bowel is rare in Crohn disease,
localized perforation with phlegmonous masses contained within
the surrounding perienteric inlammatory fat is common