Diagnostic ultrasound ( PDFDrive )

CHAPTER 53 The Pediatric Gastrointestinal Tract 1857
Sonographic Signs of Appendicitis
Noncompressible, blind-ended, tubular structure
Diameter of tube ≥6 mm
Fluid trapped within nonperforated appendix
Target appearance of echogenic mucosa around luid
center surrounded by hypoechoic muscle
Fecalith: echogenic focus with pronounced posterior
acoustic shadowing
Hypervascular appendix on color Doppler ultrasound
Gangrenous appendix: lack of low on color Doppler
ultrasound
Sonography of a child with acute abdominal pain is a procedure
that requires patience and experience. he examination is
facilitated by clinically localizing the pain, and even young
children can help to guide the examination if asked to point
with one inger to the site of maximal tenderness. Posterior
manual compression and let lateral decubitus positioning may
help to identify the appendix in patients whose appendix is not
initially seen with graded-compression technique. 131 he ascending
colon can be used as a helpful landmark, following the lateral
border identiied by haustrations to identify the cecum, then
localizing the terminal ileum as the appendix, which arises 1 to
2 cm below the origin of the terminal ileum. he appendix is
retrocecal in position in up to 68% of cases and within the pelvis
in up to 53%. 132,133 hus the examination should include the
paracolic gutter, and a larger curvilinear probe may be needed
to assess a low-positioned pelvic appendix. he normal appendix
is easily compressible and smaller than the inlamed appendix,
usually measuring less than 6 mm in diameter (Fig. 53.41). When
the appendix cannot be found sonographically, the study indings
are generally considered indeterminate. Standardized interpretive
schemes that evaluate integrity of the appendix and assess inlammatory
changes of the right lower quadrant have been shown
to improve diagnostic accuracy. 134,135
Sonographically, the acute, inlamed appendix appears as a
blind-ending tubular structure that is noncompressible and
measures 6 mm or greater in diameter 136 (Fig. 53.42). Size of the
appendix can vary signiicantly in patients with both normal
and abnormal appendices, and the 6-mm criterion is more useful
for excluding appendicitis than for conirming it. 137 Viralassociated
lymphoid hyperplasia thickens the hypoechoic
appendiceal wall and can increase the maximum outer diameter
of the appendix but should have no intraluminal luid and no
periappendiceal fat because the serosa is not involved (Fig. 53.43).
However, there can be mural hyperemia and recurrent pain,
sometimes leading to surgical intervention, although typically
the lymphoid hyperplasia spontaneously resolves. 105 It is interesting
to note that this was described by Symmers in JAMA in 1919. 138
Careful examination of the appendiceal tip should be performed
in the presence of lymphoid hyperplasia, because the lymphoid
tissue can predispose to appendicitis of the tip in some cases. 139
Fecal material impacted within the appendix, a nonsurgical
condition treated with a bowel cleansing regimen, also increases
the outer diameter, but the wall stratiication of the appendix
should be preserved and there should be no inlammatory change
or hyperemia. 140
Demonstration of other, associated sonographic abnormalities
improves conidence in the diagnosis of appendicitis. Fluid is
oten seen trapped within a nonperforated appendix, and the
surrounding echogenic mucosal layer and hypoechoic muscular
layer of the appendiceal wall, combined with the central anechoic
luid, give the appendix a target appearance in cross section.
Fecaliths, even those not calciied, can oten be identiied,
appearing as echogenic foci with pronounced posterior acoustic
shadowing (see Fig. 53.42D). A small amount of luid may be
seen adjacent to the appendix, even in the absence of perforation.
Mesenteric lymphadenopathy frequently accompanies appendicitis,
but alone is a nonspeciic inding seen with other types of
abdominal inlammation. 141 hickening and increased echogenicity
of the periappendiceal mesenteric fat is a valuable secondary
inding, and the presence of more than one ultrasound sign of
inlammation should be considered strong evidence of appendicitis,
even if other deinitive signs are absent. 142-144
An advantage of sonography over other imaging modalities
is the ability to correlate the pain of appendicitis with the imaging
indings. Pinpoint tenderness with compression over the appendix
is diagnostic in many children. 136 In cases of perforated appendicitis,
the appendix itself is oten more diicult to identify than
in acute nonperforated appendicitis. 145 With perforation, the
appendix becomes decompressed, and increasing intestinal gas
from adynamic ileus and functional obstruction can interfere
with the ultrasound examination Nevertheless, a careful, gradedcompression
technique may allow detection of focal aperistaltic
bowel in the right lower quadrant, or a complex luid collection
representing an abscess 146 (Fig. 53.44A). Loss of the normal
echogenic mucosal integrity suggests a gangrenous appendix
(Fig. 53.44B-C), oten associated with signs of perforation including
echogenic periappendiceal luid, abscess, interloop luid
collections, marked periappendiceal fat thickening, and aperistaltic
bowel loops (Fig. 53.44D-E).
he risk of appendiceal perforation is greater in children
younger than 4 years, because of many factors including limited
verbal skills and lower incidence and thus less suspicion at younger
ages. 147 he omentum is also poorly developed and almost devoid
of fat in young children and thus is unable to contain a perforation.
Diarrhea is a common presenting sign in young children and
oten confused with gastroenteritis, leading to a delay in diagnosis
and the greater incidence of perforation. 148,149 Ater perforation,
increasing low may be seen in the sot tissues surrounding the
appendix, and widespread abdominal luid collections may be
present at time of diagnosis owing to the lack of omental
containment. 150,151
Sonographic Signs of
Appendiceal Perforation
Abscess formation
Loss of integrity of mucosal layer of the appendix
Presence of a fecalith in children younger than 8 years
Large amount of periappendiceal echogenic fat