Case 2 - The Stomach Flu ? - The Target, Crescent, and Absent Liver Edge Signs

Volume 1, Case 2
Lynette L. Young, MD
Loren G. Yamamoto, MD, MPH
Kapiolani Medical Center For Women And Children
University of Hawaiʻi 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 was obtained.

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 essential.
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 intussusception.
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 intussusception.

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:

1. Abdominal mass: An absence of bowel gas in the area suggesting indirectly that something is pushing normal bowel out of the way.
2. 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.
3. Paucity of gas: Distal to obstruction.
4. Loss of subhepatic angle: The absent liver edge sign.

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.

References

1. Waisman Y. Intussusception. In: Barkin RM (ed). Pediatric Emergency Medicine Concepts and Clinical Practice. Chicago, Mosby Year Book, 1992, pp. 784-786.
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.