Sonographers are generally reluctant to examine the esophagus,
stomach, and intestinal tract because of the presumed technical
challenges. However, it has been found that sonography often is
useful in evaluating gastrointestinal wall disorders in the
pediatric population. This pictorial essay demonstrates the
sonographic appearance of selected pediatric gastrointestinal
disorders. These entities are presented in order of anatomic
position, from cranial to caudal. The advantages and limitations of
sonography, as compared to contrast studies, will be discussed, as
well as examination techniques and common pitfalls.
Sonography may be more sensitive than a contrast study for
detecting small hiatal hernias.1 The preferred method for scanning
is to place the transducer in the subxiphoid area in order to scan
the distal esophagus and the gastroesophageal junction in
longitudinal and transverse planes (figure 1). Demonstration of the
stomach often can be improved after the oral ingestion of water, as
it will provide a sonolucent window. Sonography also may be used to
detect gastroesophageal reflux, though this examination can be
quite labor intensive.2 Reflux occurs when there is retrograde flow
of fluid or gas from the stomach into the distal esophagus. If
fluid refluxes forcefully from the stomach into the distal
esophagus, the sonographic appearance of this fluid may be seen as
ranging from anechoic to mildly echogenic or "cloudy", due to the
Gastric wall thickening
There is a broad differential diagnosis for gastric wall
thickening. It includes (but is not limited to) lymphoma,
carcinoma, hypertrophic gastritis, Crohn's disease, peptic ulcer
disease, prosta- glandin-induced antral foveolar hyperplasia, and
chronic granulomatous disease of childhood. Additionally, diffuse
gastric rugal hypertrophy is a hallmark of Menetriers' disease
(figure 2), though this appearance is nonspecific.
During the sonographic exam, it is helpful to use the left lobe
of the liver as an acoustic window, although the ante-rior
abdominal wall can serve this purpose as well. Left coronal imaging
is useful in studying the gastric fundus as it is juxtaposed with
the splenic hilum. Examining the fundus with the patient in the
left lateral decubitus position also can be helpful, as this will
cause intraluminal gas to shift towards the gastric antrum.
Normal gastric wall thickness generally ranges between 2.5 and
3.5 mm.3,4 However, one must be aware that apparent thickening of
the gastric wall may be seen when the stomach is collapsed.
Furthermore, retained intraluminal debris may be present and should
not be mistaken for a focal lesion.
Hypertrophic pyloric stenosis/gastric outlet
Sonography is the procedure of choice for the diagnosis of
hypertrophic pyloric stenosis. It is preferred over an upper
gastrointestinal examination because the abnormal pyloric muscle
mass that is the hallmark of this condition is able to be directly
visualized. In this disorder, thickening of the antropyloric muscle
and elongation of the antropyloric canal are the two most important
diagnostic criteria. A pyloric muscle thickness of 4 mm or greater
was originally considered to be diagnostic,5 but more recent work
3 mm as the upper limit.6 An antropyloric canal length of 12 mm
or greater is currently considered to be diagnostic.
Pyloric stenosis manifests sonographically on transverse images
with a typical "donut" or "bulls-eye" appearance (figure 3).7 The
outer hypoechoic layer of the "bulls eye" consists of the pyloric
muscle mass, whereas the inner hyperechoic layer corresponds to the
mucosal layer. Longitudinal imaging will reveal the typical
elongated antropyloric canal, as well as any thickening of the
antropyloric muscle. Sonography will detect any fluid that may be
trapped between the mucosal folds of the antropylorus and these
findings should correspond to the classic "string" or
"double-track" signs of contrast radiography.
In patients suspected of having pyloric stenosis, sonography is
best performed with the patient in the right posterior oblique
position. This maneuver allows intraluminal fluid to fill the
antrum, providing more of an acoustic window. One should be careful
not to overfill the stomach with fluid, however, because the
distended stomach may prevent optimal measurement of pyloric length
and thickness.8 In this situation, the antropylorus is displaced
posteriorly, and transverse imaging may underestimate its length.
If the stomach is too distended, excess fluid can be aspirated
through a nasogastric tube. Once the stomach is emptied, the
hypertrophied pyloric muscle mass may become more palpable, and its
maximum longitudinal dimension will be in line with the transverse
plane of imaging.
Patients with classic hypertrophic pyloric stenosis are treated
surgically with pyloromyotomy. However, some symptomatic patients
will present with minimal pyloric muscle thickening that does not
meet the criteria for this diagnosis. In these patients, the
pyloric muscle usually measures between 2 to 3 mm. These patients
are treated initially with an antispasmodic agent, such as
metoclopramide. If symptoms persist, a reexamination should be
performed, as some of these patients eventually may progress to
fulfill the criteria for hypertrophic pyloric stenosis. One should
not be overzealous in diagnosing hypertrophic pyloric stenosis in
these transitional cases. If it is missed on the initial
ultrasound, it will likely be detected during a follow-up
ultrasound or during an upper gastrointestinal examination.
However, if pyloric stenosis is misdiagnosed, a surgical procedure
may be performed unneccesarily.
The most common cause of gastric outlet obstruction in an infant
is pylorospasm, often caused by milk allergy. Sonography will
reveal elongation of the antropyloric canal and thickening of the
contracted pyloric muscle. The pyloric muscle thickening is
generally less than 3 mm in these cases. Further observation should
eventually show relaxation of the pylorus and passage of fluid into
Other less common causes of gastric outlet obstruction also can
be detected with sonography. Gastric diaphragms are hyperechoic
congenital membranes that extend across the gastric antrum, either
partially or completely obstructing the stomach. Gastric antral
thickening and/or edema due to peptic ulcer disease,
prostaglandin-induced antral foveolar hyperplasia, eosinophilic
gastritis, and other causes (see preceding section) also may cause
gastric outlet obstruction.
Enteric duplication cyst
Presence of gastric duplication cysts is another possible cause
of gastric outlet obstruction. These cysts may clinically mimic
hypertrophic pyloric stenosis, though they have a completely
different sonographic appearance. The normal bowel wall typically
demonstrates an inner echogenic mucosal layer and an outer
hypoechoic muscular layer. Therefore, the presence of a cystic
lesion with this type of wall architecture is virtually
pathognomonic for an enteric duplication cyst (figure 4). However,
one should be aware that a similar appearance may be present in any
cyst in which bleeding has occurred, with resultant fibrin
deposition along the cyst wall. In some duplication cysts,
peristalsis may be observed in the cyst wall, thus confirming the
Bowel hematomas generally manifest as eccentric intramural
thickening of the bowel wall. The sonographic appearance varies,
depending on the age of the lesion. Fresh hematomas often are
hyperechoic, but they eventually become hypoechoic as liquefaction
occurs (figure 5). During its evolution, the hematoma may have
either a unilocular or multilocular appearance.10 In cases of blunt
abdominal trauma, the duodenum is the most commonly injured segment
of the gastrointestinal tract due to its relatively fixed position
and its juxtaposition to the lumbar vertebrae.
Two common scenarios that can lead to a duodenal hematoma are
seat belt injuries sustained during a motor vehicle accident and
the battered child syndrome. Duodenal hematomas also may develop
spontaneously in coagulopathic patients.11 If a duodenal hematoma
is detected in a patient without a plausible history of
non-accidental abdominal trauma or a known coagulopathy, the
possibility of child abuse should be raised. Obtaining a skeletal
survey would be a reasonable first step in determining a possible
abusive cause of the hematoma. However, when a suspected child
abuse victim presents with a low hematocrit or symptoms of gastric
outlet obstruction such as vomiting, the possibility of a duodenal
hematoma with or without concomitant solid organ injury should be
Duodenal stenosis and duodenal atresia are common causes of
intrinsic congenital duodenal obstruction. Plain abdominal
radiographs may be diagnostic in patients with duodenal atresia,
demonstrating a characteristic "double-bubble" sign which
represents the dilated and gas-filled stomach and duodenal bulb. In
patients with combined duodenal and esophageal atresia, plain films
may not display these diagnostic signs because air can not enter
the stomach or duodenum unless there is an associated
tracheoesophageal fistula. Sonography can be useful in these rare
cases, as it is able to directly visualize the distended and
fluid-filled proximal duodenum, stomach, and distal
Sonography may in some cases have the ability to directly
visualize the site and/or cause of duodenal obstruction. In
addition, if bowel perforation distal to a proximal obstruction is
present, plain radiographs may not demonstrate free intraperitoneal
air. In these cases, sonography may demonstrate free
intraperitoneal fluid, raising the suspicion for bowel perforation,
thus making it a better choice as a screening examination.
Another cause of duodenal obstruction that can be detected
sonographically is a duodenal diaphragm (figure 6). In this entity,
the distal duodenum is stretched into a "windsock" configuration.
Extrinsic causes of duodenal obstruction such as an annular
pancreas or a mesenteric mass also may be seen with ultrasound.
Reversal of the normal relationship between the superior
mesenteric artery and vein suggests the diagnosis of midgut
malrotation, with or without migdgut volvulus (figure 7). However,
some patients with midgut volvulus may have a normal relationship
between the superior mesenteric artery and vein.13 It has been
reported that the presence of mesenteric vessels swirling in a
clockwise direction (the so-called "whirlpool" sign) is highly
specific for midgut volvulus,14 but not all patients will display
this finding. Because of this, an upper gastrointestinal
examination remains the gold standard for detecting midgut
volvulus. However, sonography may suggest the possibility of midgut
volvulus in patients for whom this diagnosis is unsuspected. If an
ultrasound examination reveals a reversed relationship between the
superior mesenteric artery and vein, then confirmation should be
achieved with an upper gastrointestinal examination.
Small bowel wall thickening
The differential diagnosis of small bowel wall thickening is
extensive and includes (but is not limited to) Crohn's disease,
tuberculosis, lymphoma, Henoch-Schönlein purpura, and
graft-versus-host disease. With sonography, the thickened bowel
wall can be visualized directly, rather than inferred indirectly as
with plain abdominal radiographs or contrast studies. Normal small
bowel wall thickness should not exceed 3 mm.15 Although a specific
diagnosis often may not be possible based on the ultrasound
findings alone, in conjunction with the clinical history, physical
exam, and laboratory findings, sonography may be quite
Classically, patients with Crohn's disease manifest
sonographically with thickening of the wall of the terminal ileum.
There usually is increased blood flow to this region, which can be
detected with color-flow Doppler imaging. These findings are
nonspecific, however, and can be seen with other entities such as
tuberculosis, Yersinia enterocolitica infection, and lymphoma.
Henoch-Schönlein purpura is an idiopathic systemic vasculitis,
with bowel involvement usually limited to the duodenum and jejunum
(figure 8), although ileal and colonic involvement also can be
seen. The bowel may be the initial site of presentation, prior to
any vessel or skin abnormalities. Circumferential echogenic small
bowel wall thickening often is present, resulting from intramural
hemorrhage. In addition, Henoch-Schönlein purpura may be associated
with intussusception and, therefore, examination of the entire
intestinal tract can be extremely helpful. Significant ascites may
be present and other organ systems may also be affected. For
example, the kidneys may demonstrate increased echogenicity as a
result of hemorrhagic nephritis.
In patients with graft-versus-host disease, diffuse
circumferential thickening of the bowel wall can be seen (figure
9). The bowel loops are often fluid-filled and, unlike in
Henoch-Schönlein purpura, there is no bowel wall nodularity or
active peristaltic activity. Contrast studies characteristically
demonstrate a bland, tubular, "toothpaste-like" pattern.
Intestinal lymphangiectasia is associated with diffusely nodular
bowel wall thickening (figure 10). The appearance is nonspecific,
however, as other disorders such as giardiasis, strongyloidiasis,
and cystic fibrosis can give a similar picture.
When searching for appendicitis, a graded-compression method
should be used.16 Normal gas-filled bowel loops can be displaced
from the right lower quadrant with steady compression on the
transducer, allowing visualization of the inflamed appendix which,
unlike the normal appendix, is not compressible. The demonstration
of an appendicolith is not necessary to make the diagnosis of
appendicitis, though it is a suggestive sign (figure 11). If
perforation has occurred, the appendix becomes decompressed and may
be more difficult to detect. The presence of an abscess in the
right lower quadrant, which will manifest sonographically as a
complex fluid collection, can be a clue that the appendix has
perforated. However, a small amount of free fluid can be seen
around the appendix in the absence of perforation.
Sonography is the initial imaging modality of choice in the
evaluation of suspected appendicitis. However, exclusion of
appendicitis requires visualization of the entire length of a
normal appendix, which may not always be possible. For example,
patient discomfort may prevent a satisfactory examination. The
maximal outer diameter of the appendix should not exceed 6 mm.16,17
If the clinical question of appendicitis persists despite an
apparently normal sonogram, other imaging modalities such as
computed tomography or a contrast enema may be required.
Mesenteric adenitis is a common cause of abdominal pain in
children, symptoms of which may be similar to those of
appendicitis. The etiology usually is viral, though it also can be
seen with Yersinia enterocolitica infections. Mesenteric adenitis
is a diagnosis of exclusion and should be made only when other
entities such as appendicitis have been ruled out. Sonographically,
it manifests as multiple enlarged mesenteric lymph nodes (figure
12) which often show increased blood flow on color Doppler imaging.
Mild bowel wall thickening also may be associated with this
Prior to the advent of ultrasound, the primary diagnosis of
mesenteric adenitis could only be made intraoperatively or
histologically, as appendicitis could not be excluded with
confidence radiographically or clinically. However, with
ultrasound's current capabilities, the diagnosis of appendicitis
and other entities can be excluded, and the presence of multiple
enlarged mesenteric lymph nodes can suggest mesenteric adenitis as
a primary diagnosis. In this situation, the patient can be safely
observed without the fear of ongoing appendicitis or appendiceal
perforation. If the patient's symptoms persist or worsen, a repeat
sonogram can be performed.
A patient with an intussusception classically presents with
crampy abdominal pain, "currant jelly" stools, vomiting, and a
palpable abdominal mass. Those presenting in this manner can most
likely proceed to enema reduction for diagnosis and therapy,
bypassing an ultrasound examination altogether. Not all patients
with intussusception will present in this manner, however, and
therefore sonography is an important diagnostic tool, demonstrating
both a high sensitivity and specificity for this disorder.18 In the
hands of an experienced sonographer, a meticulously-performed
ultrasound exam which is normal, combined with a normal abdominal
plain film, may obviate the need for a contrast enema. Abdominal
radiographs of patients with suspected intussusception may
demonstrate an obstructive pattern, with gas-filled loops of bowel
filling the abdomen. This appearance should not discourage the use
of sonography, as the retroperitoneum can be used as an acoustic
window in order to examine the colon.
Classically, longitudinal imaging of an intussusception reveals
a hypoechoic mass with bright central echoes, the so-called
"pseudo-kidney" sign. Trans-verse imaging reveals a characteristic
"donut" configuration. The bright central echoes correspond to
trapped intestinal contents, as well as mucosa and mesentery, while
the hypoechoic outer layer corresponds to the edematous wall of the
intussusception. On occasion, an enlarged mesenteric lymph node can
be seen within the lumen of the intussuscipiens (figure 13). If
there is a pathologic lead point such as a cyst or tumor, it also
may be demonstrated sonographically.19 With the current generation
of high resolution scanners, longitudinal scanning may show the
telescoping of one bowel loop into another as multiple parallel
layers of varying echogenicity, while transverse imaging may reveal
multiple concentric rings.
As mentioned previously, if an intussusception is strongly
suspected, the study of choice is an enema examination rather than
sonography because an enema examination can be both diagnostic and
therapeutic. An enema reduction can be performed using barium,
gastrografin, saline, or air. Currently, air reduction is the most
popular method, though these agents all are effective. However, if
perforation occurs during attempted reduction, using barium as the
contrast agent may result in barium peritonitis, whereas this
complication would not occur with any of the other agents.
Sonography may play a greater role in the management of patients
with intussusception when ultrasound-guided reduction with a normal
saline enema becomes a more accepted practice.
An enema reduction is contraindicated if there are clinical
signs of peritonitis or radiographic signs of free intraperitoneal
air. Patients with these signs will require surgical management.
Sonography can sometimes be helpful in predicting whether
non-surgical reduction of an intussusception will be successful.
The finding of excessive free fluid and/or diminished or absent
perfusion in the intussusception by color Doppler imaging suggest
that attempts at non-surgical reduction will fail.
Large bowel wall thickening
The differential diagnosis of large bowel wall thickening is
extensive and there is considerable overlap with the differential
diagnosis for small bowel wall thickening. Included in the list are
inflammatory bowel disease, infectious colitis, neutropenic colitis
(typhlitis), necrotizing enterocolitis, pseudomembranous colitis,
lymphoma, Henoch-Schönlein purpura, and hemolytic-uremic syndrome.
These diseases often are indistinguishable from each other based on
the sonographic appearance alone and all can manifest with colonic
wall thickening. The normal colonic wall should not exceed 5 mm in
The sonographic manifestations of necrotizing enterocolitis are
varied and include bowel wall thickening, aperistaltic bowel loops,
and portal venous gas (figure 14). Intramural bowel gas can
sometimes be directly visualized, and sonography may be more
sensitive than plain films in this regard. After bowel perforation,
ascites with a fluid/debris level may be present. It has been
reported that detecting increased flow velocity in the celiac and
superior mesenteric arteries with Doppler sonography is an early
sign of necrotizing enterocolitis.21 Abdominal radiographs in
patients with this disorder range from an ileus pattern to a
complete absence of bowel gas. Sonography can be especially useful
in patients with a gasless abdomen, as the fluid-filled loops of
bowel act as a natural acoustic window.
The ultrasound appearance of typhlitis is marked edematous
thickening of the cecal wall associated with polypoid thickening of
the mucosa (figure 15).22 In the clinical setting of neutropenia,
the results are consistent with typhlitis. Sonography is preferred
over contrast examinations in neutropenic patients because of the
risk of bacteremia during a contrast enema. Furthermore, sonography
is superior to a contrast enema in distinguishing typhlitis from
pathology in adjacent organs (e.g., appendicitis). While a contrast
enema may not be able to distinguish typhlitis from appendicitis,
these entities have completely different sonographic features.
Hemolytic-uremic syndrome is a disease of unknown etiology
characterized by microangiopathic hemolytic anemia, renal failure,
and thrombocytopenia. It manifests sonographically as marked
colonic wall thickening (figure 16). The appearance is nonspecific,
and sonography is useful primarily as an adjunct to the history,
physical examination, and laboratory studies.
While sonography is not necessary in order to make the diagnosis
of imperforate anus, it can be helpful to further characterize the
nature of the anomaly (figure 17). Sonography can directly
visualize the location of the distal end of the hindgut, which can
be important for surgical planning. The distance from the rectal
pouch to the perineum is measured with longitudinal midline images
through the perineum, usually obtained while the patient is in the
lithotomy position. A perineum-to-pouch distance of less than 1.5
cm suggests a low imperforate anus.23
Alternatively, the "M" line of Cremin can be drawn.24 This line
roughly corresponds to the level of the puborectalis muscle.
Hindgut termination above this line suggests that the patient has a
high imperforate anus, whereas termination below this line suggests
a low imperforate anus. The "M" line of Cremin is drawn through the
junction of the lower third and the upper two thirds of the ischia
and parallels the pubococcygeal line (a line drawn from the
midpubic bone to the sacrococcygeal junction).
Patients with imperforate anus have an increased risk of
associated genitourinary tract and spinal cord abnormalities and
ultrasound can be useful in their detection as well. It should be
emphasized that a radiographic study of the rectum can
underestimate or overestimate the true location of the most distal
aspect of the rectal pouch: straining may make a high pouch appear
to be low, and a mucous plug may make a low pouch appear to be
Sonography in conjunction with plain abdominal radiographs often
is useful in the evaluation of suspected bowel pathology in the
pediatric population. In many cases, it may obviate the need for
contrast examinations. We recommend initial evaluation with
sonography rather than a contrast study in the following cases:
• Gasless abdomen on plain abdominal radiograph.
• Physical examination or abdominal radiograph suspicious for
• Debilitated patient condition such that contrast examination
may be dangerous (e.g., risk of bacteremia in a neutropenic patient
or intubated neonate who can not be transported to the radiology
• Initial evaluation of suspected appendicitis.
However, there are situations in which we recommend a contrast
study for definitive diagnosis, such as suspected midgut
malrotation and volvulus, for which an upper gastrointestinal study
should be performed immediately, or for treatment of
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Dr. Chang, Dr. Lim-Dunham, and Dr. Yousefzadeh are with the
Department of Radiology at the University of Chicago Hospitals in