Diagnostic ultrasound ( PDFDrive )

CHAPTER 8 The Gastrointestinal Tract 295
A
B
C
FIG. 8.45 Closed-Loop Obstruction. (A) Plain ilm is unremarkable.
(B) Sonogram shows grossly dilated, gasless, luid-illed,
small bowel loops. (C) Single loop shows a suggestive C or U
shape.
Paralytic Ileus
Paralytic ileus is a type of bowel obstruction related to adynamic
function of the bowel wall. Paralysis of the intestinal musculature,
in response to general or local insult, may impede the progression
of luminal contents. Although the lumen remains patent, no
progression occurs. Sonography is usually of little value because
these patients characteristically have poor-quality sonograms
resulting from large quantities of gas in the intestinal tract.
However, on rare occasions, the sonogram may demonstrate
dilated, luid-illed, very quiet, or aperistaltic loops of intestine.
A luid-luid level in a dilated loop is characteristic of paralytic
ileus, relecting lack of movement of the intestinal contents (see
Fig. 8.43).
Gut Edema
Patients with acute vasculitis of various causes may present with
acute abdominal pain and ascites, with massive edema of the
small bowel wall seen as the major abnormality on imaging.
Hypoalbuminemia, congestive heart failure, and spontaneous
venous thrombosis may also show difuse edema of the gut wall.
Prominent, thickened, hypoechoic valvulae conniventes (Fig.
8.47) and gastric rugae are relatively easy to recognize on the
sonographic study, which should also include Doppler evaluation
of the mesenteric and portal veins.
Gastrointestinal Tract Infections
Although luid-illed, actively peristaltic gut may be seen with
infectious viral or bacterial gastroenteritis, most afected patients
do not demonstrate a sonographic abnormality. However, some
pathogens, notably Yersinia enterocolitica, Mycobacterium
tuberculosis, and Campylobacter jejuni, produce highly suggestive
sonographic abnormalities in the ileocecal area, as described
earlier. Certain high-risk populations, such as those with AIDS
and neutropenia, 64 appear to be susceptible to acute typhlitis
and colitis, which also have a highly suggestive sonographic
appearance.