Abdominal Pain and the Peritoneal Fat Margins
Radiology Cases in Pediatric Emergency Medicine
Volume 3, Case 19
Loren G. Yamamoto, MD, MPH
Kapiolani Medical Center For Women And Children
University of Hawaii John A. Burns School of Medicine
     This is a 4-year old female with a history of 
abdominal pain for 3 days.  She was seen by her 
private physician in the morning and then referred to the 
emergency department for further evaluation because 
of tenderness in the right lower quadrant.
     Exam:  VS T37.0 (oral), P122, R24, BP 108/73, 
oxygen saturation 99% in room air.  Alert, cooperative, 
uncomfortable, but no acute distress.  Oral mucosa 
sticky.  Neck supple.  Heart regular without murmurs.  
Lungs clear.  Abdomen flat.  Guarding on the right.  She 
points to the epigastrium as the site of her pain.  
However, most of the tenderness is elicited in the right 
lower quadrant.  Bowel sounds are hypoactive.  Color 
and perfusion are good.
     An abdominal series is ordered.

View abdominal series:  Flat (supine) view.

Abdominal series:  Upright view.

     The following laboratory results are obtained:
CBC  WBC 17.5, 51% segs, 23% bands, 21% lymphs,
     4% monos, Hgb 12.8, Hct 37, platelets 405,000.
ESR 43
UA SG 1.033, 3+ ketones, no WBC's, 0-2 RBC's per

     Her abdominal series shows diffuse gaseous 
distention of the colon and small bowel compatible with 
an ileus or an early obstruction.  The distribution of gas 
is good.  No free air is visible under the diaphragm.  No 
appendicolith is visible. 
     Compare the radiographic appearance of the left 
lower quadrant with the right lower quadrant.  Can you 
appreciate any differences?  Look at the peritoneal fat 
stripe on the left and on the right.  The bowel should 
generally lie very close to this fat stripe.  This is true 
on the patient's left (right on image), but note that this is 
not the case on the patient's right (left on image).  In the 
right lower quadrant, the bowel is about 1 cm from the 
peritoneal fat stripe.  In the left lower quadrant, the 
bowel is about 1-2 mm from the fat stripe.  This can be 
best visualized in the magnified focused view of the 
lower abdomen.

View close-up of lower abdomen.

     Look at the peritoneal fat stripes on both sides just 
above the iliac crests (white arrows).  Note that on the 
patient's left, there is a very narrow space between the 
fat stripe and the bowel.  However, on the patient's 
right, the bowel is farther away from the fat stripe 
suggesting that there is fluid, a mass, or thickened 
tissue pushing the bowel aside.
     The black arrow points to a small gas pocket that 
does not appear to be within bowel.  These findings 
together are highly suggestive of a ruptured appendix.

     The patient is taken to surgery where a ruptured 
appendix is found.  There is exudate extending from the 
right paracolic gutter to the liver and diaphragm.  She 
recovers and is discharged in good condition on the 
sixth post-operative day.
     The radiographic findings in appendicitis are 
infrequent and diverse.  Radiographic findings highly 
suggestive of an acute appendicitis include an 
appendicolith, free air, RLQ sentinal loops (dilated 
bowel loop(s) in the RLQ in an otherwise nearly gasless 
abdomen), and absence or indistinctness of the right 
psoas margin.  Free air may not always be present 
under the diaphragm since it may be loculated.  Less 
specific findings include diminished intestinal gas, a 
scoliosis to the left (concavity to the right, due to 
splinting), or a bowel obstruction.  

     Swischuk LE.  Emergency Radiology of the Acutely 
Ill or Injured Child, second edition.  Baltimore, Williams 
and Wilkins, 1986, pp 191-209.

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