The Stomach Flu? - The Target, Crescent, and Absent Liver Edge Signs
Radiology Cases in Pediatric Emergency Medicine
Volume 1, Case 2
Lynette L. Young, MD
Loren G. Yamamoto, MD, MPH
Kapiolani Medical Center For Women And Children
University of Hawaii John A. Burns School of Medicine
An 11 month old male with history of "stomach flu"
symptoms two weeks ago that had resolved, now
presents to the ED with emesis five times the night
prior, without blood or bilious material. In the morning
he had three loose stools with blood but no mucous.
There are no URI symptoms, and no history of fever.
He cries intermittently in cycles of 10 to 20 minutes.
His past medical history is unremarkable.
Exam: Vital signs T36.5Ax, P118, RR40, Wt
50%ile. He is alert, smiling, and not toxic appearing.
Skin exam shows good perfusion (capillary refill time 2
seconds). Pupils reactive. Tympanic membranes no
erythema. Oral mucosa moist. Heart regular, no
murmur. Lungs clear breath sounds, good aeration.
Abdomen soft, flat, active bowel sounds, no mass
palpated. Testes descended bilaterally, nontender. No
anal fissure, stool heme-positive. Pulses were good.
A stool culture was sent and an abdominal series
View abdominal series: Supine (Flat) view
View abdominal series: Upright view
There is a suspicion of a soft-tissue mass in the right
upper quadrant. There is some distention of a single
loop of small bowel in the mid-abdomen and gaseous
distention of the transverse colon and proximal left
colon. No peritoneal free air. The liver edge is not
easily identified in these views (the absent liver edge
sign). There is a paucity of bowel gas.
A barium enema demonstrated an intussusception
at the hepatic flexure which was successfully reduced.
Teaching points and Discussion:
1. Intussusception is a common abdominal
emergency in young children. A delay in establishing
the diagnosis leads to a delay in treatment, bowel
ischemia, and bowel infarction. An early diagnosis is
2. The most common is ileocolic, with the lead point
proximal to the ileocecal valve. Bloody mucousy stool
(currant-jelly stool) is a late sign, resulting from
engorgement of the intestine, edema, and then bleeding
from the mucosa. Although this finding is known as
currant jelly stools, it can resemble blood mixed with
stool as in dysentery. This can easily be dismissed as
being caused by gastroenteritis due to shigella or
salmonella. This pitfall can be avoided by considering
the diagnosis of intussusception in all cases of bloody
diarrhea and bloody stools.
3. Males outnumber females 2:1. The 3 - 12 month
old age group is the most common.
4. The triad of symptoms: a) intermittent crampy
abdominal pain (episodic pain, child may appear
comfortable in between episodes); b) emesis, and c)
passage of bloody, mucousy stools. Most patients with
intussuception do not present with this triad, therefore it
is not useful to use this set of findings to rule out
5. An abdominal mass is not part of the triad, but
this finding, that represents the leading head of the
intussusception, may be helpful in establishing the
diagnosis. The mass may be present in any part of the
abdomen depending on where the intussuception
originates and where it ends. This mass is usually
palpated in the right abdomen, but in severe cases, it
may be present in the left abdomen if the
intussusception has passed the splenic flexure and has
entered the descending colon.
6. Plain abdominal films may be normal. There may
be evidence of bowel obstruction after 6-12 hours of
symptoms. Thus, plain abdominal films cannot be used
to rule out intussusception. However, plain films may
be used to add to the body of clinical evidence
prompting one to do a barium enema.
7. Radiographic signs on plain abdominal films
include the target sign, the crescent sign, the absent
liver edge sign, and other signs that are less specific for
Target sign: Two approximately concentric circles of
fat density to the right of the spine, due to layers of
peritoneal fat surrounding and within the
intussusceptum alternating with layers of mucosa and
muscle. This sign resembles a very faint target, or
bull's eye, or doughnut appearance.
View a target sign example.
This radiograph shows a classic target sign in the
right upper quadrant just below the liver. It resembles a
chubby doughnut with a puffy center. It is very subtle.
You may need to adjust the contrast control on your
monitor to appreciate it. This radiograph also shows
the absent liver edge sign and the crescent sign. A
paucity of bowel gas is also noted.
Crescent sign: Soft-tissue density mass of the
intussusceptum projecting into the colon (leading
edge). If the head of the intussusceptum is projecting
into a gas filled pocket, it will show itself. It often takes
on a crescent shape; however, it may also merely
resemble a protruding head into a gas filled pocket.
View a crescent sign example.
This radiograph shows a classic crescent sign in the
left upper quadrant. This radiograph indicates that the
head of the intussuception is in the distal transverse
colon. Also note that this radiograph demonstrates the
target sign and the absent liver edge sign. The target
sign is again subtle and less noticeable in this film. You
may need to adjust the contrast control on your monitor
to appreciate it.
Go back to the target sign radiograph to see
if you can appreciate the crescent sign on this
radiograph (left upper quadrant). In this case, the
crescent is not as crescent shaped, because the
colonic air pocket surrounding the intussusceptum is
larger than in the crescent sign film.
View an atypical crescent sign.
This radiograph shows an atypical crescent sign in
the right upper quadrant just below the liver. The head
of the intussusception is coming up the ascending
colon. It can be seen protruding upward into the gas
filled transverse colon at the hepatic flexure.
Other non-specific radiographic signs that may
suggest an intussusception are as follows:
a. Abdominal mass: An absence of bowel gas in
the area suggesting indirectly that something is pushing
normal bowel out of the way.
b. Small bowel obstruction: Dilated bowel loops
and air-fluid levels. Examine the flat plate (supine view
of this case
Notice the dilated bowel segments. They exhibit
smooth bowel walls lacking normal haustrations.
This is suggestive of a small bowel obstruction.
c. Paucity of gas: Distal to obstruction.
d. Loss of subhepatic angle: The absent liver edge
The target and crescent signs are the most accurate
in making the diagnosis of intussusception on a plain
film. The target sign is seen twice as often as the
crescent sign. An abdominal mass is most commonly
seen on radiographs, but it is non-specific.
8. Barium enema is the gold standard of diagnosis.
It often results in a successful reduction of the
intussusception as well. Ultrasound and air contrast
enemas have also been used to diagnose
intussusception. The two contraindications to
performing a barium enema include shock and/or
radiographic or clinical evidence of bowel perforation.
Patients with hypovolemic shock should first have their
intravascular volume restored before undergoing a
barium enema. Any patient with evidence of bowel
perforation should be taken immediately to surgery.
9. Vomiting is a common reason to seek emergency
or acute care. It is usually the result of a benign cause.
However, it may be difficult to distinguish serious
causes from benign causes if the evaluation is
superficial. Whenever the chief complaint is vomiting,
the diagnosis of intussusception should be considered.
The history and examination should be directed at
determining whether intussusception is possible based
on clinical grounds. The chart should include
comments in the history regarding the frequency of
vomiting, the color of the emesis, the presence or
absence of abdominal pain, the frequency of abdominal
pain, and the activity level of the child. Intussusception
is more likely if the emesis is bilious and/or frequent.
Intussusception is more likely if the pattern of the pain
is colicky in nature (intermittent and severe in regular
cycles 5-20 minutes apart). Intussusception is more
likely if the child exhibits lethargy. The absence of
these symptoms does not rule out intussusception.
Patients with intussusception may have all, some, or
none of these symptoms. The physical exam portion of
the chart should document the presence or absence of
lethargy and an abdominal mass. The exam should
include the testes (in males) and the inguinal region
looking for incarcerated hernias. The rectal exam and
stool guaiac results should also be recorded. Ideally,
the chart should comment on whether the examiner has
noted a colicky abdominal pain pattern observed during
the evaluation period.
10. Infants presenting purely with lethargy (no
vomiting) have often been evaluated for possible
sepsis. However, lethargy is a common presentation
for intussusception despite the absence of all the other
signs of intussusception.
1. Waisman Y. Intussusception. In: Barkin RM
(ed). Pediatric Emergency Medicine Concepts and
Clinical Practice. Chicago, Mosby Year Book, 1992, pp.
2. Schnaufer L, Mahboubi S. Intussusception. In:
Fleisher GR, Ludwig S (eds). Textbook of Pediatric
Emergency Medicine, third edition. Baltimore,
Williams and Wilkins, 1993, pp. 1314-1316.
3. Ratcliffe JF, Fong S, Cheong I. O'Connell P. The
Plain Abdominal Film in Intussusception: The Accuracy
and Incidence of Radiographic Signs. Pediatric
Radiology 1992; 22:110-111.
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