Vomiting in the infant is a common and nonspecific symptom, but some cases of vomiting are medical emergencies that require surgery. The authors review 4 surgical causes of vomiting in the infant. With attention to the clinical presentation and imaging evaluations, it is possible to quickly diagnose or exclude common problems and address rarer conditions. Radiologists can develop a work-up algorithm with an understanding of the pathologies, the patterns, and the pitfalls in these very young patients.
is an Assistant Professor of Radiology and Pediatrics, and
is an Associate Professor of Radiology, Department of Radiology,
Wake Forest University School of Medicine, Winston-Salem,
Vomiting in the infant is a common and nonspecific symptom. Most
causes of vomiting in this age group are benign and self-limited,
including gastroesophageal reflux, milk allergies, and
gastroenteritis. However, several causes constitute medical
emergencies and require surgical intervention. In this article, we
will explore 4 surgical causes of vomiting in the infant, giving
attention to clinical presentation, imaging evaluation, and
management, where applicable. The goal is the creation of a work-up
algorithm through an understanding of the pathologies, the
patterns, and the pitfalls.
Hypertrophic pyloric stenosis
Hypertrophic pyloric stenosis (HPS) is a form of gastric outlet
obstruction related to overgrowth of the circular muscle of the
pyloric channel. It typically presents in infants in the first 3 to
6 weeks of life as nonbilious vomiting, which has become projectile
in character, leading to dehydration as the obstruction becomes
complete. The incidence is higher in firstborn males, and those
with a positive family history are predisposed.
The diagnosis may be evident based on the patient's medical
history and physical examination alone. If an olive-sized mass is
palpable in the midepigastrium, the surgeon often will not request
a radiographic study.
That notwithstanding, since gastroesophageal reflux can masquerade
as HPS, most clinicians want imaging confirmation.
All imaging evaluations for HPS should begin with a radiograph
of the abdomen. If the stomach is distended and fluid-filled, even
after 2 hours of fasting, the diagnosis should be suspected,
particularly if little gas is seen in the bowel (Figure 1). A
normal radiograph does not exclude HPS, however.
Further evaluation can be accomplished with either an ultrasound
or an upper gastrointestinal series (UGI). In our practice, we
advocate ultrasound as the initial imaging approach, since it
allows direct visualization of the pyloric channel and measurement
of channel length and muscle thickness.
Studies vary as to appropriate upper normal measurements; we denote
as abnormal a muscle thickness >3.2 mm and a channel length
>16 mm, as these limits provide an acceptable positive
predictive value without a significant number of false-positive
Pitfalls do exist in obtaining the necessary images for diagnosis.
The gastric antrum can be mistaken for the pylorus if the stomach
is not distended. This issue can be overcome by allowing the infant
to ingest Pedialyte (Ross Products, Columbus, OH) during the
examination. Not only does the Pedialyte distend the stomach, it
also provides a sonographic window that makes the anatomic
landmarks more apparent. The improved window also minimizes the
second pitfall, which is overestimating muscle thickness by
scanning in an oblique plane. Finally, pylorospasm can cause
temporary thickening of the pyloric muscle; therefore, real-time
observation should be of adequate duration.
If measurements change and if fluid is observed passing through the
channel, the examination is normal.
Diagnosis of HPS can be accomplished by a UGI as well. While it
provides only an indirect assessment of the pyloric channel, it has
the added benefits of offering fuller anatomic evaluation of the
stomach and duodenum and functional assessment for gastroesophageal
reflux. We recommend passing a nasogastric tube for this
examination-for aspirating gastric contents, which can be
substantial, and for better control of the contrast medium.
Approximately 5 to 10 mL of barium are injected via the enteric
tube, followed by 60 to 120 mL of air. A small amount of contrast
passing through a narrowed, elongated pyloric channel constitutes
the string sign, the most specific and helpful radiographic finding
by this technique (Figure 3). The shoulder sign, the impression of
the hypertrophied pyloric muscle on the distended gastric antrum,
is also helpful and is more readily generated (Figure 4). Other
suggestive findings include the caterpillar sign of the
hyperperistaltic stomach (Figure 5) and the olive pit sign, which
is formed from the pyloric muscle impression upon the antrum seen
en face with a tiny amount of contrast at the orifice. As with
ultrasound imaging, pylorospasm can be a pitfall; findings must
remain constant to diagnose HPS.
Malrotation with midgut volvulus
Malrotation is an error of embryologic development. In the
normal course of events, the bowel of the developing embryo
herniates into the extraembryonic coelomic cavity, where it makes a
90˚ cephalocaudal rotation before returning into the
intra-abdominal cavity and completing a 270˚ counterclockwise
rotation. The resulting relationship of small bowel and colon
creates a wide mesenteric root, fixed in the left upper quadrant
and in the right lower quadrant. Deviation from this developmental
pathway may result in a narrow mesenteric attachment, predisposing
the patient to midgut volvulus and bowel ischemia or necrosis.
Bilious vomiting is the hallmark of malrotation with midgut
volvulus, either intermittent or fixed.
Although any obstruction distal to the sphincter of Oddi can lead
to bilious vomiting, malrotation is the diagnosis to exclude
because of the issue of vascular compromise to the bowel. The
question of malrotation requires an emergent answer, and a UGI is
the examination of choice. A normal abdominal radiograph does not
exclude the diagnosis.
The UGI is performed via an enteric tube with the tip positioned
in the antropyloric region. Five to 10 mL of barium contrast medium
are injected, followed by adequate air to push the contrast through
the pylorus and duodenum. This technique limits the amount of
contrast used in an infant who may require an emergent laparotomy.
Fluoroscopic spot images are obtained in the right anterior
oblique, anteroposterior, and left lateral projections to show the
duodenal C-loop, duodenojejunal junction (DJJ), and retroperitoneal
course of the duodenum, respectively. The duodenum should pass
posterior to the stomach with the DJJ lateral to the left pedicles
at the level of the duodenal bulb. The DJJ can be as much as 1
vertebral body height inferior to the duodenal bulb and still be
In the case of malrotation with midgut volvulus, the small bowel
twists around the axis of the superior mesenteric artery and vein
because of its abnormal fixation. The duodenum will not cross the
midline, but instead it corkscrews in the right aspect of the
abdomen (Figure 6). Classically, the contrast column will terminate
in a beaked configuration if the obstruction is complete (Figure
7). Alternative patterns of malrotation exist if the volvulus is
intermittent or if the obstruction is related to peritoneal bands
(so-called Ladd's bands) crossing anterior to the bowel because of
a malpositioned cecum. Ladd's bands create extrinsic compression
upon the duodenum.
Sometimes the findings on the UGI are equivocal. For example,
the apparent DJJ may lie to the left of the midline but lower than
1 vertebral body height; the DJJ may be in the midline (Figure 8A);
or contrast may fill jejunal loops that are not clearly to the left
of the midline. If a normal interpretation of the examination is in
doubt, the contrast should be followed to the cecum with a series
of abdominal radiographs obtained over time (Figure 8B). A normally
positioned cecum in the face of borderline findings on the
fluoroscopic examination does not usually warrant the risks of
surgery, as the mesenteric attachment remains adequate.
Two other particular situations in the evaluation of suspected
malrotation deserve focused consideration, and both stem from the
interpretation of the initial abdominal radiograph. First is the
abdomen radiograph that shows diffusely dilated bowel loops. This
pattern can be seen with complete midgut volvulus and bowel
ischemia, but it can also be seen with low intestinal obstructions
of other etiologies, including volvulus around an omphalomesenteric
duct remnant. With such radiographic findings, the initial
fluoroscopic study should be an enema using isosmolar water-soluble
contrast medium to determine the position of the cecum and/or the
level of obstruction (Figure 9). If this examination is
inconclusive, evaluation of the upper gastrointestinal tract should
be performed using barium suspension as the contrast medium. The
barium is denser and should be distinguishable from any
water-soluble contrast remaining in the colon, allowing assessment
of the course of the duodenum and the position of the DJJ. The
second situation relates to an abnormal feeding tube course as
shown by abdominal radiography. Since the tube itself can distort
the course of the duodenum, bowel rotation should be assessed with
the tube retracted to the duodenal bulb followed by contrast
injection (Figures 10 and 11). This practice should prevent
unnecessary surgeries for presumed malrotation.
Intussusception is a bowel obstruction that results when 1 bowel
loop telescopes into another, usually beginning at the ileocecal
valve. In the vast majority of cases, a lead point is never
discovered. However, given the epidemiological correlation of viral
infections with intussusception incidence, the theory is that
activated Peyer's patches in the terminal ileum function as lead
Infants with intussusception typically present with episodes of
crampy abdominal pain separated by periods of lethargy. They may
vomit frequently, leading to dehydration, and bloody stools are
Imaging evaluation will begin with abdominal radiographs in the
anteroposterior and left lateral decubitus projections.
Air within the cecum effectively excludes the diagnosis. In
positive cases, a paucity of gas is seen in the right lower
quadrant and sometimes within the entire lower abdomen and pelvis.
A complete obstruction of at least several hours' duration may
yield the classic pattern of dilated bowel loops and stacked
air-fluid levels (Figure 12). The identification of a soft tissue
mass that silhouettes the inferior liver edge in this clinical
setting is pathognomonic (Figure 13).
The infant with presumed intussusception should undergo
immediate image-guided enema reduction. The only contraindications
to the procedure are severe dehydration, shock, peritonitis, and
pneumoperitoneum, any of which make the case a purely surgical one.
The enema can be performed with positive oral contrast or with air,
with fluoroscopy or ultrasound serving as the imaging modality. Of
these choices, we advocate pneumatic reduction under fluoroscopy
for its speed, its clarity, and its ease. Additionally, if the
intussusceptum cannot be fully reduced, an air-filled colon rather
than a barium-filled colon is more desirable at surgery. Moreover,
in the rare event of an intraprocedural bowel perforation, the
volume of fecal contents may be less with air as the reduction
agent than with barium.
The air reduction technique utilizes a Foley catheter (of the
largest caliber that is appropriate for the patient), a pneumatic
kit (GRI Medical Products, Inc., Cave Creek, AZ) (which is composed
of an adapted sphygmomanometer with pressure gauge and tubing), and
Christmas tree adapters (Figure 14). The apparatus is assembled,
and the catheter is taped securely in the patient's rectum. Air is
then insufflated into the colon, where it encounters the
intussusceptum and, it is hoped, pushes the mass back through the
ileocecal valve (Figure 15). Resting pressures should be maintained
<120 mm Hg with the patient quiet. Of note, the patient is not
sedated for this procedure because the child can offer some
resistance to the insufflation, which serves as another check
against overinflating the colon. Reduction is complete when air has
refluxed into the distal ileum, as evidenced by fluoroscopy. If the
mass is no longer movable, even after 2 or 3 more attempts, that
situation also serves as the end point of the examination;
completion of the reduction will occur in the operating room.
Finally, bowel perforation will also terminate the examination and
lead to surgery. In the rare event of bowel perforation, an
18-gauge needle can be placed approximately 2 cm below the
umbilicus to obviate the risk of pneumoperitoneum.
Fewer than 5% of cases of intussusceptions recur. Most of those
recurrences are within the first 24 hours after the initial
reduction, supporting the practice of a 24-hour hospital stay after
successful therapeutic enema.
Recurrences, especially more than 1, are suggestive of a lead
point. These can include a Meckel's diverticulum, a duplication
cyst, a polyp, or a bowel or mesenteric neoplasm, such as Burkitt's
lymphoma. In infants, Meckel's diverticulum would be the most
Incarcerated inguinal hernia
Incarcerated inguinal hernia is one of the most common causes of
bowel obstruction in infancy. These occur much more commonly in
boys than in girls, generally being of the indirect type via a
patent processus vaginalis. Premature infants have a greater risk
for this event than do term infants.
As with malrotation and intussusception, bilious vomiting can be
the presenting sign.
The role of the radiologist in diagnosing incarcerated inguinal
hernia is variable. Patients present with signs of obstruction,
such as vomiting and abdom-inal distention, plus an
inguinal-scrotal mass or fullness. If the clinician cannot reduce
the hernia sac, the diagnosis is made. Sometimes, however, the
diagnosis is equivocal, and imaging is indicated.
The abdominal radiograph will confirm a mechanical bowel
obstruction and a thickened inguinal-scrotal fold (with or without
bowel gas within the hemiscrotum) if incarcerated hernia is the
etiology of the patient's symptoms. It may also direct the care
team to another diagnosis. Ultrasound can provide important
additional information through its ability to assess vascular flow
to the involved bowel loop within the inguinal ring (Figure 16).
Pneumatosis intestinalis can affect incarcerated bowel if the
degree of vascular compromise is sufficient, but this finding
should be visible on the accompanying radiographs (Figure 17).
The vomiting infant can present a diagnostic challenge. The
first question to answer is whether the problem is medical or
surgical. The history and physical examination coupled with the
abdominal radiograph should direct the next step in management.
While the plain radiograph examination cannot fully exclude any of
the discussed causes of infantile vomiting, it is crucial for
choosing further imaging options, for excluding contraindications
to subsequent studies, and for assessing for any unexpected
findings. If the initial radiographs suggest an obstruction, but
the level is indeterminate, the first fluoroscopic examination
should be an enema. If intussusception is in the differential
considerations, then the enema should be performed with appropriate
technique for an anticipated reduction, whether with air or with
positive contrast. If the abdominal radiograph is nonspecific, high
obstruction or gastro-esophageal reflux could still explain the
symptom profile, making a UGI in order-with the caveat that
ultrasound is a more specific test for hypertrophic pyloric
Other, rarer causes of vomiting in infants that are related to
obstruction include antral and duodenal webs, small bowel stenosis,
complicated Meckel's diverticulum, and appendicitis. The former are
generally apparent on fluoroscopic examination with careful
attention to technique and spot compression. Complicated Meckel's
diverticulum and appendicitis may require abdominal ultrasound or
computed tomography for diagnosis. Nevertheless, with an orderly
approach in obtaining imaging studies, we can diagnose or exclude
the common problems readily and move on to other tools in our
arsenal to identify the rare conditions.