Diagnostic ultrasound ( PDFDrive )

1314 PART IV Obstetric and Fetal Sonography
A
B
FIG. 38.13 Meconium Peritonitis. (A) Transverse image at 34 weeks shows ascites (A) surrounding the liver with associated calciications
(arrowheads) on the liver surface; a inding typical of meconium peritonitis. St, Stomach. (B) Abdominal radiograph in the neonate conirms peritoneal
calciications (arrowheads). See also Video 38.7.
A
B
FIG. 38.14 Meconium Pseudocyst. (A) Oblique sagittal view of the torso shows multiple calciications on the peritoneal surface of the liver
in a fetus with a meconium pseudocyst (arrowhead), with an irregularly calciied wall. (B) Meconium pseudocyst in another fetus. Note cyst with
debris with calciied rim (arrows). (With permission from McNamara A, Levine D. Intraabdominal fetal echogenic masses: a practical guide to
diagnosis and management. Radiographics. 2005;25[3]:633-645. 32 )
or greater than that of adjacent bone, such as the iliac bone. 106
To avoid a false-positive diagnosis due to artifacts and image
processing, the diagnosis of echogenic bowel requires that the
lowest level of ultrasound gain at which bones still appear white
be used and that all image enhancement algorithms be disabled
(Fig. 38.15, Video 38.8). he use of a high-frequency probe
(8 MHz) can lead to overdiagnosis of echogenic bowel 107 ; therefore
the diagnosis of echogenic bowel should always be conirmed
using a low-frequency (≤5 MHz) probe. Despite these attempts
to standardize the diagnosis of echogenic bowel, it should be
recognized that there is a signiicant subjective component in
the diagnosis of echogenic bowel, which can lead to signiicant
interobserver variability. 108
When strict diagnostic criteria are used, the incidence of
echogenic bowel in the general obstetric population is 0.2% to
0.7%. 79,106 Because the echogenicity of normal bowel increases
throughout pregnancy, the inding of echogenic bowel becomes
normal in the third trimester. In particular, meconium in the
colon can be seen normally as echogenic material in the third
trimester.