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.
     Each new case can be viewed by clicking on one of 
the letters below.  



     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) 
orderliness. 
     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 
haustrations.  
     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 
Volume 3).
     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 
intussusception.





     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) 
orderliness.
     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 
abdomen.  
     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 
view.





	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 
upper quadrant.





	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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Web Page Author:
Loren Yamamoto, MD, MPH
Professor of Pediatrics
University of Hawaii John A. Burns School of Medicine
Loreny@hawaii.edu