Gastrointestinal (GI) complaints are among the most frequent causes of pediatric emergency department visits. This article describes the clinical presentation, epidemiology, and imaging findings of five GI emergencies that require surgical intervention: Malrotation and midgut volvulus; intussusception; hypertrophic pyloric stenosis; appendicitis; and Meckel’s diverticulum. Radiologists are at the critical front line of diagnosis for surgical decision making and also have a vital therapeutic role in cases of intussusception.
is a Radiology Resident, University of Washington Medical Center,
is an Assistant Professor of Radiology, University of Washington
Medical Center, and a Staff Radiologist, Children's Hospital
& Regional Medical Center, Seattle, WA.
Gastrointestinal (GI) complaints are among the most frequent
causes for emergency department visits in the pediatric population.
Radiology plays an ever-increasing role in the diagnosis and
treatment of these emergencies. This article describes the clinical
presentation, epidemiology, and imaging findings of 5 GI
emergencies that require surgical intervention: Malrotation and
midgut volvulus; intussusception; hypertrophic pyloric stenosis;
appendicitis; and Meckel's diverticulum.
Malrotation and midgut volvulus
Malrotation is any deviation from the normal 270º
counterclockwise rotation of the bowel that occurs during
embryogenesis. The resultant shortened mesenteric pedicle
predisposes to midgut volvulus, a clockwise rotation around the
superior mesenteric artery axis that can lead to bowel ischemia. A
mnemonic for remembering the direction of rotation of volvulus and
surgical devolvulus is: "the surgeon turns back the hands of
The incidence of malrotation is 1 in 500.
The male-to-female ratio is 2:1. Malrotation with midgut volvulus
may become rapidly life-threatening. The previously healthy infant
with bilious emesis is one of the few "drop everything else"
presentations in pediatric imaging, as the stopwatch of ischemic
bowel may be ticking. The older the child, however, the more
atypical the symptoms; the teenager with chronic abdominal pain or
malabsorption may be suffering from recurrent bouts of volvulus and
Conventional radiographs are neither sensitive nor specific for
malrotation. On the upper GI series, it is crucial to locate the
position of the duodenal-jejunal junction (DJJ). The DJJ must be at
least over (but more reassuringly lateral to) the left vertebral
pedicle and at the same height as the duodenal bulb on a
well-centered view. If the DJJ does not meet these two criteria,
then malrotation is diagnosed (Figure 1). Signs of midgut volvulus
include an abrupt termination, or beak, of the contrast column
(Figure 2) and the corkscrew (apple peel, or barber pole
) sign (Figure 3).
On ultrasound (US) and computed tomography (CT), the superior
mesenteric artery (SMA) and superior mesenteric vein (SMV)
relationship may be reversed (Figure 4). Normally the SMV is to the
right of the SMA; with malrotation, the SMV may occupy a position
directly anterior or to the left of the SMA. Of critical
importance, a normal SMA/SMV relationship does not exclude
malrotation, and the upper GI remains the imaging gold standard.
Conversely, some children without malrotation may have a vertical
or inverted SMA/SMV relationship.
Several other US signs of midgut volvulus include: Hyperdynamic
; distal SMV dilation
; whirlpool sign
(Figure 5); and a truncated SMA sign
(Figure 6). Two technical points should be kept in mind when
evaluating the SMA/SMV relationship. First, scan as caudally as
possible; at the portal confiuence, the SMV occupies the most
ventrally vertical position with respect to the SMA and may
erroneously suggest malrotation. Second, place the transducer over
the midline and not over the liver; rightward deviation will
falsely "move" the SMV to the left and possibly ventral to or left
of the SMA.
Intussusception is the telescoping of a segment of bowel into an
adjacent segment; the great majority of cases are ileocolic. In
only 5% of cases is a pathologic lead point identified.
Lymphoid hyperplasia is the cause in the vast majority of the
remaining 95%. The classic clinical triad is abdominal pain,
currant-jelly stool, and palpable abdominal mass. However, in our
experience, lethargy and drawing up of the legs are the most
commonly reported signs, and a significant percentage of patients
may be pain-free at presentation.
Most patients are between the ages of 6 months and 2 years.
Conventional radiographs are neither specific nor sensitive.
Findings include the meniscus (Figure 7) and target signs. The most
important use for radiographs is excluding pneumoperitoneum. A
gas-filled cecum on a left lateral decubitus film is a good
negative predictor for intussusception. However, determination of
cecal position can be difficult; in 45% of children ≤5 years of
age, a gas-/stool-filled sigmoid colon is positioned in the right
lower quadrant and may mimic a normal-appearing cecum.
One less well-known sign that the authors have found to be
predictive of intussusception is "ileization" of the right lower
quadrant, ie, visualization of gas-filled small-bowel loops in the
right lower quadrant, filling the "vacuum" left by the
intussuscepted cecum and ascending colon (Figure 7).
Several studies have reported 100% diagnostic accuracy rate for
US, and US may be used to guide hydrostatic and air reduction.
A clear advantage is the lack of ionizing radiation. The technique
is more widely used in Europe and Asia, but is gradually being
adopted in the United States. Several US signs have been described:
Doughnut; pseudokidney; crescent in doughnut (Figure 8A); sandwich
(Figure 8B); and hayfork
CT findings for intussusception are characteristic. The
telescoping nature of the pathology is seen on axial images as an
eccentric fat and soft-tissue density mass surrounded by bowel wall
(Figure 9). The typically crescentic fat represents the mesentery
drawn into the intussuscipiens, and the soft tissue is a
combination of bowel, lymph nodes, and mesenteric vasculature.
In most institutions, a contrast enema remains the standard for
diagnosis and initial treatment. Peritonitis and perforation are
absolute contraindications. The major complication is perforation
with potential tension pneumoperitoneum. Prior to performing the
enema, a surgical consult is required, the patient must have an
intravenous (IV) line in place (for emergency resuscitation), and a
large-bore needle (eg, 14-g catheter needle) should be within close
reach to decompress a tension pneumoperitoneum. If the patient
cries during the procedure, it is expected and beneficial; crying
simulates the Valsalva maneuver and protects against bowel
perforation by reducing the transmural gradient.
Explaining this to the parents both reassures and defiects requests
for sedation. Whether air or liquid is used to perform the enema is
a matter of personal preference. The rates of reduction of
intussusception are not statistically different when using air
versus liquid contrast
; however, air is faster, uses less radiation, causes significantly
smaller perforations, and results in less peritoneal contamination
if perforation does occur.
Those who favor liquid point to the slightly lower perforation rate
in large studies, superior visualization of pathologic lead points,
and greater control over the lead pressure.
The authors favor the air enema for speed, decreased radiation
dose, and cleanliness, reserving the contrast enema for children
with a higher pretest probably of a pathologic lead point based on
age (<1 month old or >4 years old). A negative study goes
quickly, with rapid filling of the colon and refiux into the
terminal ileum. In a positive study, the intussusceptum is usually
encountered in the transverse colon, and the initial reduction
proceeds rapidly to the ileocecal valve (Figures 10A and 10B).
Disappearance of the cecal mass and free refiux of air into the
terminal ileum indicates successful reduction (Figure 10C). How
long to persist is controversial, with some advocating 3 attempts,
a maximum pressure of 120 mm Hg, and limiting the duration of
maximal pressure to <3 minutes.
Others will try longer, reasoning that both perforation and
incomplete reduction will result in surgery. We have had excellent
success with delayed attempts after initial incomplete reduction;
after waiting 15 to 20 minutes (to allow the edematous bowel and
ileocecal valve to decrease in size), a subsequent reduction
attempt may be successful.
If tension pneumoperitoneum occurs, insert a large-bore needle (eg,
14-g catheter needle) in the midline abdomen through the avascular
linea alba, 2 cm above the umbilicus.
Hypertrophic pyloric stenosis
Several hypotheses have been proposed for hypertrophic pyloric
stenosis (HPS), including those focused on the pyloric muscle and
its innervation, hormones, and a molecular etiology.
The typical patient is a male infant with a previously normal
feeding history who presents with nonbilious, projectile emesis. In
the premature infant, the diagnosis may be made at an older age.
Palpation may reveal an "olive" in the right upper quadrant;
however, in 15% of cases, even highly experienced pediatricians and
surgeons cannot make this diagnosis on physical examination.
The incidence of HPS is 1 to 4 cases per 1000 live births, with a
2:1 to 5:1 male/female ratio.
Patients usually present between the ages of 2 and 8 weeks, with
peak incidence at 3 to 5 weeks.
With delayed diagnosis, the infant shows signs of dehydration,
lethargy, and a hypochloremic alkalosis due to loss of stomach
Ultrasound is the imaging modality of choice because it enables
direct visualization of the pyloric muscle and avoids ionizing
radiation. The pylorus is a hypoechoic structure with echogenic
mucosa/ submucosa and serosa on either side (Figure 11). Although a
narrow range of diagnostic measurement criteria have been
published, the authors use the mnemonic π (3.14) to remember 3-mm
thickness and 14-mm channel length. Practically, the appearance of
HPS is characteristic, independent of measurements. A
high-frequency linear transducer should be used. Allowing the
infant to bottle-feed with glucose solution (NOT echogenic formula)
will provide an acoustic window through the antrum and facilitate
evaluation for liquid shuttling across the pylorus. A right
posterior oblique position may displace air into the fundus and
liquid against the pylorus, which will now lie in a more dependent
position. An important component of the complete US evaluation is
inclusion of the SMA/SMV relationship and the kidneys to assess the
possibility of malrotation or renal pathology as the cause of the
Although once the diagnostic standard for HPS, the upper GI
series is now virtually never performed as an initial study for
this indication; the diagnosis may be revealed during a
fiuoroscopic examination for another indication, such as possible
malrotation. In a positive study, one may observe "shouldering" of
the hypertrophic pyloric muscle at the antrum and the string or
double-track sign, representing barium squeezed between folds of
mucosa pressed together by the hypertrophied muscularis layer
Luminal obstruction is the usual initial insult in appendicitis.
Obstruction may be caused by a fecolith, appendicolith, lymphoid
follicle, or foreign body. Lifetime risk in males is approximately
9% and in females 7%.
It has been estimated that 1% to 8% of children who present to the
emergency department with abdominal pain will be diagnosed with
Appendectomy is the most common emergency surgical procedure
performed in children.
Abdominal radiographs are frequently normal in appendicitis.
However, one or more of the following signs may be present:
Calcified appendicolith (occurs in <10% of cases) (Figure 13);
obliteration of the right psoas margin; splinting leading to a
lumbar dextroscoliosis; and right lower quadrant air-fiuid levels
(localized ileus). A perforated appendix may produce
There is significant and ongoing controversy over which imaging
modality, US or CT, should be used for initial evaluation in
children with suspected appendicitis. Ultrasound advantages include
low cost, lack of ionization radiation, and ability to evaluate
compressibility and vascularity. A sensitivity of 85% and a
specificity of 92% have been reported for US using meta-analysis of
all studies published between 1986 and 1994.
Ultrasound evaluation using graded compression is performed with a
high-frequency linear array transducer. Gentle pressure is applied
to the right lower quadrant to compress and displace normal bowel
loops. Technically adequate studies can be achieved in >95% of
An abnormal appendix measures ≥6 mm in maximal outer diameter, is
not compressible, reveals adjacent infiammatory changes, and is
hyperemic with Doppler imaging. Other US findings include:
Echogenic submucosa in early acute appendicitis; a target sign if
the appendix is fiuidfilled (hypoechoic fiuid layer, echogenic
mucosa/submucosa, and hypoechoic muscularis); an appendicolith;
pericecal or periappendiceal fiuid; increased periappendiceal
echogenicity (from infiamed fat); and enlarged mesenteric nodes
Advantages of CT over US include: Reduced operator dependence;
enhanced visualization of soft tissues, bones, gas, and fiuid; and
superior evaluation for complicating phlegmon and abscess
formation. CT is also superior in obese patients. Sivit et al
showed that CT had a significantly higher sensitivity (95% versus
= 0.009) and accuracy (94% versus 89%,
= 0.05) than that of graded compression US for the diagnosis of
appendicitis in children, adolescents, and young adults.
Specificity was 93% for both. CT was especially useful when the US
examination was normal.
The optimal CT technique is controversial. The highest reported
diagnostic efficacy has been with rectal contrast only and thin
collimation through the lower abdomen and pelvis, with
sensitivities of 97% to 100% and specificities of 94% to 98%.
We prefer IV contrast without oral or rectal contrast to decrease
preparation time and for enhanced evaluation of infiammatory
changes, complicating abscesses, and evaluation of other
intra-abdominal and pelvic structures. CT features of acute
appendicitis include: Appendix diameter >6 mm; appendiceal wall
thickening and enhancement; an appendicolith; apical cecal
thickening; periappendiceal or pericecal fat stranding; mesenteric
lymphadenopathy; phlegmon or abscess (Figure 15).
Meckel's diverticulum occurs in 2% to 3% of the population and
is the most common developmental anomaly of the GI tract.
The diverticulum occurs at the antimesenteric border of the distal
ileum and is caused by incomplete obliteration of the
omphalomesenteric duct. The diverticulum often contains ectopic
gastric and pancreatic mucosa. Complications include peptic
ulceration with hemorrhage, intestinal obstruction from
diverticular inversion, diverticulitis, and intussusception.
Conventional radiographs may reveal calcified stones in a
lamellated pattern in the lower right quadrant. Meckel's
diverticulum is notoriously difficult to detect with fiuoroscopy,
and a barium study to evaluate for Meckel's diverticulum is usually
performed only if clinical suspicion remains high after negative
Hemorrhage is the most frequent complication. Technetium-99m
(Tc-99m) pertechnetate scintigraphy is the imaging study of choice
when a child presents with GI bleeding and a Meckel's diverticulum
is suspected. After IV administration of the radiotracer, ectopic
gastric mucosa in the diverticulum will appear as a focus of
increased activity, usually within 30 minutes of injection (Figure
Normal activity will occur concurrently in the stomach. In
children, the sensitivity, specificity, and accuracy of Tc-99m
pertechnetate scintigraphy is 85%, 95%, and 90%, respectively.
Causes of a false-positive scan include: Gastric or small intestine
duplication, heterotopic gastric mucosa in an otherwise normal
small intestine, and infiammatory bowel disease that causes
A false-negative scan will result if the diverticulum contains too
few or no gastric mucosa.
The second most common complication is intestinal obstruction,
but identifying a Meckel's diverticulum as the cause is often
difficult preoperatively. The most useful radiographic finding that
suggests Meckel's diverticulum as the cause of obstruction is
lamellated calcification in the right lower quadrant.
When the diverticulum causes obstruction, it is usually secondary
to inversion that causes luminal obstruction or forms an
intussusception lead point.
CT is a superb modality for diagnosing bowel obstruction, but
identification of a Meckel's diverticulum is often difficult. A
third presentation is right lower quadrant pain and fever mimicking
appendicitis. The US findings of a tubular, hyperemic structure can
mimic appendicitis; however, a Meckel's diverticulum will typically
be larger, have more irregular mucosal layers, and have associated
anomalous vessels (Figure 17).
Gastrointestinal emergencies continue to be a frequent cause of
morbidity in the pediatric population, and several diseases
requiring surgical intervention can lead to mortality if not
rapidly diagnosed and treated. Radiologists are at the critical
front line of diagnosis for surgical decision making and, in the
case of intussusception, have a vital therapeutic role as well.