Find the Intussusception Target and Crescent Signs
Radiology Cases in Pediatric Emergency Medicine
Volume 7, Case 18
Loren G. Yamamoto, MD, MPH
Kapiolani Medical Center For Women And Children
University of Hawaii John A. Burns School of Medicine
The radiographic signs of intussusception have
been discussed in previous cases (Case 2 of Volume 1,
Case 18 of Volume 3). The purpose of this current
case is to display multiple cases of intussusception to
see if you can identify the radiographic signs of
intussusception on plain abdominal radiographs. The
radiographic signs of intussusception are subtle, so this
case series provides a lot of practice material to
improve diagnistic skills in identifying these signs.
To summarize, the radiographic signs of
intussusception are: 1) target sign, 2) crescent sign, 3)
absent liver edge sign (also called absence of the
subhepatic angle), and 4) a bowel obstruction.
Recall that the target sign is a mass in the right
upper quadrant. It sometimes does not have a target
appearnace and just resembles a solid mass. It is
sometimes called a pseudokidney sign because it may
have the shape of an oval mass in the RUQ.
The crescent sign is caused by the intusscepting
lead point (intussusceptum) protruding into a gas filled
pocket, which often results in a crescent shaped gas
pocket. But if the pocket is large, it may not be
crescent shaped. Thus, it should be more generically
called the intussusceptum protruding into a gas filled
pocket sign, but this is too long and it is not nearly as
catchy as the "crescent" sign. Just realize that the
crescent sign may not be crescent shaped.
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This is a 2 year old month old female. There is a
prominent target sign in the right upper quadrant.
Although this is subtle, this is a very obvious target
sign. Most target signs are even less subtle than this.
There is a crescent sign in the left upper quadrant.
This crescent sign is not really crescent shaped, but it
represents the intussusceptum protruding into a large
gas filled pocket. Note that the direction of the
crescent always points in the direction of normal colon
transit (superiorly if found in the ascending colon, right
to left if found in the transverse colon, and inferiorly if
found in the descending colon). In this case, the
intussusceptum has traversed the ascending colon and
most of the transverse colon as the lead point now
points at the spleenic flexure.
This is a 3 year old female. There is a prominent
crescent sign in the left upper quadrant. In this case,
the crescent sign truly is crescent shaped. Note that it
again points in the direction of normal colon transit. If
the shape of the crescent is pointing the wrong way,
consider the possibility of situs inversus or that this
sign is somehow not due to intussusception.
There is a target sign in the right upper quadrant.
The target is smaller in this case and not as easy to
identify. Once it is pointed out, you should be able to
appreciate the target sign, which is subtle.
This is a 3 year old male. There is a crescent sign
in the right upper quadrant, which is definitely not
crescent shaped. The intussuscepting lead point is
pointing cephalad at the hepatic flexure. The colonic
air pocket is large in this case, so the classic crescent
shape is not seen. This is why it should more
accurately be called the intussusceptum protruding into
a gas filled pocket sign, but this is too long to say.
Note again that the intusscepting lead point always
points in the direction of normal colon transit.
This is a 7 month old male. This radiograph
demonstrates a bowel obstruction. Case 18 of Volume
3 describes the criteria for a bowel obstruction in
children. There are four general criteria: 1) gas
distribution, 2) bowel dilation, 3) air-fluid levels, and 4)
The gas distribution is poor in that there is not much
gas over most of the abdomen.
Bowel dilation may not seem prominent intially, but
the criteria for bowel dilation is not a measured
diameter of the bowel, but rather the loss of plications
and haustrations of the bowel, such that a smooth
hose-like or sausage-like appearance results. This
particular radiograph is tricky because, there is not
much gas anywhere. But look at the upright view on
the right with the two bowel segments seen in the right
upper quadrant. Note that these two bowel segments
are smooth (hose-like) without plications or
Air-fluid levels are not very prominent here since the
entire abdomen is relatively gasless. However,
examine the upright view on the right with two bowel
segments in the right upper quadrant. These are not
very striking, but they are air-fluid levels. Additionally,
these air-fluid levels are not small, but they actually
have the classic candy cane (or upside down J)
appearance where the level in one half of the loop is
different from the level in the other half of the loop.
This is true for one of the bowel segments in the right
upper quadrant. Such air-fluid levels are more
suggestive of a bowel obstruction than small air-fluid
levels which do not have the candy cane or upside
down J appearance.
The last criterion, orderliness, is best appreciated
on a supine view when lots of gas is evident. On this
set of radiographs, there is not much gas present so
that this orderliness criteria is less useful. However,
one could simplify this to whether this view resembles a
bag of sausages or a bag of popcorn. The two bowel
segments in the right upper quadrant look more like two
sausages and it would be hard to find a major
component resembling popcorn here (see Case 18 of
Thus, all four bowel obstruction criteria indicate that
this is a bowel obstruction. Bowel obstructions in
infants and young children generally have this type of
paucity of gas appearance or the appearance of lots of
gas and dilated bowel. This paucity of gas type of
bowel obstruction picture seen in infants and small
children is typically seen in intussusception.
Additionally, there is a mass appearance in the right
upper quadrant of the supine view on the left. This
might be a target sign, but the overlying bowel gas is
obliterating the center of the mass. This is also highly
suggestive of intussception.
This is a 7 month old female. There is an overall
paucity of gas. It would be difficult to definitively
conclude that there is a bowel obstruction here. There
is some evidence of bowel dilation, but it is hard to find
a definite segment where the bowel walls are smooth.
There are a few small air fluid levels in the right upper
quadrant on the upright view (right image), but no
definite candy cane type air fluid levels. The
orderliness is indeterminate.
There is a suspicious mass appearance in the right
upper quadrant and the liver margin is not seen. The
right upper quadrant mass may be a kidney, or it may
be a mass resembling a kidney (the pseudokidney sign)
which is seen in intussusception.
This abdominal series is highly suspicious for
This is an 8 month old female There is a poor
distribution of bowel gas, but no definite bowel dilation
or air fluid levels. There is a faint target sign in the
right upper quadrant. The liver margin is indistinct.
This is frequently seen in conjunction with a target sign,
so whenever the liver margin cannot be easily
identified, look hard for a target sign.
This is a 12 month old male. This is a supine view
which demonstrates a bowel obstruction. Except for
the two dilated bowel segments, there is a paucity of
gas. Recall that this type of paucity of gas bowel
obstruction in an infant or young child is most often due
to intussusception. Examine the four criteria for
determining that this is a bowel obstruction: 1) gas
distribution, 2) bowel dilation, 3) air fluid levels, and 4)
In this radiograph, the gas pattern demonstrates
poor distribution. The bowel dilation is not obvious, but
the only bowel segments which are visible, are the two
bowel segments which look like a pair of sausages.
The bowel walls are smooth (loss of plication and
haustration) indicating that the bowel is distended. Air
fluid levels cannot be assessed on this image since this
is a supine view. The upright view from this patient did
not show much gas except for a small amount of gas in
the left upper quadrant. No air fluid levels were
present. The orderliness criteria appears to favor a
bowel obstruction in this case since this view more
closely resembles a bag of sausages instead of a bag
of popcorn. There are no target signs or crescent signs
visible on this radiograph. However, the liver edge is
not visible. The absence of the subhepatic angle is not
as definitive for intussusception, but it adds to the
suspicion for intussusception.
This is an 8 month old male. The inferior liver
margin is not visible. Now look carefully for a target
sign. There is a target sign in the right upper quadrant
seen on the flat view (left image). There is also strong
evidence for a bowel obstruction. There is an overall
paucity of gas which is poorly distributed. There is
evidence of bowel dilation, especially on the upright
view (right image). Note that most of the bowel is
smooth, resembling hoses. The smooth bowel wall
appearance results when excessive bowel dilation
results in the loss of haustration and plication. There
aren't many air fluid levels, but the degree of
orderliness resembles a bag of sausages more so than
a bag of popcorn. This type of bowel obstruction with a
paucity of bowel gas in an infant or young child is
frequenty associated with intussusception.
This is a 3 year old old male. This series has three
views. The two views on the left are flat views (one is
supine and the other is prone). The view on the right is
the upright view.
The image on the left demonstrates a well defined
inferior liver margin, reducing the suspicion for
intussusception. However, there might still be a target
sign in this area. The middle image shows an absence
of the subhepatic angle and a suspicious target sign in
the right upper quadrant (though somewhat lower than
its usual position).
The upright image on the right shows an outline of a
mass in the shape of a kidney (the pseudokidney sign)
which also raises the suspicion for intussusception.
This is a 2-1/2 year old month old female. This is a
single upright view. The right side of the abdomen is
almost gasless. The inferior liver margin is indistinct.
Looking hard to a target sign in the right upper
quadrant, and there might be one in the lower portion of
the right upper quadrant. There is a general mass
effect in the right upper quadrant which seems to be
displacing any gas filled bowel to the left half of the
The left upper quadrant demonstrates a possible
crescent sign (which again is not crescent shaped).
There is a protrusion into a gas filled pocket near the
spleenic flexure. This is not likely to be a stomach air
bubble. It may be the intussusceptum protruding into a
gas filled spleenic flexure.
This is an 18 month old male. The supine view (left
image) is not very suspicious except for some smoth
bowel segments in the right upper quadrant. The
inferior liver margin is easy to identify. However the
upright view (right image) is almost gasless and there is
a suspicious mass effect in the right upper quadrant.
No definite target or crescent signs can be identified.
This is an 18 month old male. A series of three
radiographs are shown here. The two on the left are
flat views (one is supine and the other is prone). The
view on the right is an upright view. These radiographs
take up a lot of space on the screen, so even when
enlarged, the radiographic signs of intusssuception
may be difficult to identify. Here's a hint. The elusive
crescent sign is present on one of these images. Can
you find it.
These radiographs demonstrate a target sign in the
right upper quadrant in the left left image. The middle
image and the upright image on the right show a right
upper quadrant mass effect, but it would be hard to say
that there is a definite target sign here.
The middle image demonstrates a crescent sign on
the left. In fact there might be two crescent signs here
(but only one of them can be the real thing). The
crescent sign is not very crescent shaped. This is not
uncommon since the shape of this sign is highly
dependent on the size of the air pocket into which the
intussusceptum protrudes. One crescent sign that is
pointed out in the "point" image, is in the transverse
colon. Note that the intussceptum is pointing to the
patient's left. Another possible crescent sign is in the
left lower quadrant with a bulge into the air pocket,
suggestive of a intussceptum pointing inferiorly, down
the descending colon. This middle image also shows a
suspicious mass effect in the right upper quadrant. The
other views show a subtle target sign in this area.
This is a 3 year old male. There is a small
target sign in the right upper quadrant of the upright
This is a 21 month old male. There is a right
upper quadrant mass and obliteration of the liver
margin. There possibly is a faint target sign in the right
This is a 10 month old male. Bowel dilation is
evident. Note the bowel wall is smooth (sausage or
hose like). The liver edge is not visible. A right upper
quadrant mass is present. The center of a target sign
may be present.
This is a 3 year old male. A target sign is
present in the right upper quadrant.
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