A two year old male presents with intermittent episodes of abdominal pain that last for 20 minutes each. In between he is fine – in fact he is tearing up a book in your office/urgent care/ED. He’s probably constipated you think to yourself. But my consulted Dr. Google – plus you can’t get that one kid from last year out of your head. The good news is that you have a low suspicion that this kid has intussusception (the Mississippi of medicine – not to be confused with the Chris Nolan movie). The bad news is two-fold. First, this kid could have intussusception. Second, you don’t have an ultrasonographer available. You can however get an abdominal X-Ray.

This inaugural edition of Briefs is concerned with the following question. In patients with a fairly low suspicion for intussusception can I rule it out with an abdominal X-Ray. Let’s look at three studies that focus on this question.

The diagnostic accuracy of an abdominal radiograph with signs and symptoms of intussusception
In the March, 2012 edition of the American Journal of Emergency Medicine Mendez et. al noted that in their retrospective series that “ultrasound is not needed before an enema for the diagnosis of intussusception for those with a highly suggestive abdominal radiograph, abdominal pain, lethargy, and vomiting.” They defined a highly suggestive abdominal radiograph as

[quote align=”center” color=”#999999″] Having 1 or more of the following: (1) soft tissue mass, (2) bowel obstruction, (3) visible intussusception, or (4) sparse large bowel gas pattern.[/quote]

Furthermore, “a moderately suggestive abdominal radiograph was defined as a nonspecific bowel gas pattern and no sign of mass or obstruction. An abdominal radiograph not suggestive of intussusception was one with a normal gas pattern and no sign of mass or obstruction.”

Of course this study also suggested that you could go straight to air contrast enema if the child was also lethargic and vomiting – which our patient certainly is not. So onto the next study.

Intussusception: clinical presentations and imaging characteristics

In Pediatric Emergency Care from, well now (September 2012) Mandeville et. al endeavored to look at the findings associated with intussusception based on age as well as the test characteristics of air in the ascending colon on plain abdominal radiographs. Recall that if you have air in the ascending colon, then your ileum is less likely to be stuck there. In this retrospective cohort of 219 patients the authors noted that “Children younger than 12 months were more likely to present with emesis, irritability, and guaiac-positive or grossly bloody stools compared with children older than 12 months.” Also, as suspected abdominal pain was present in almost all (96%) of children older than a year.

Of the 219 patients in their study with intussusception 192 had plain belly films. 163 (85%) of these had no air in the ascending colon. Great right… Well, in their institution over the study period ultrasound was performed on 63/219 with 58/63 having findings consistent with intussusception. This is 92%, which if my math is correct is >85%, but what of the low numbers of patients getting sonography? Let’s take a look at the third study.

Accuracy of plain radiographs to exclude the diagnosis of intussusception
Also from the September, 2012 issue of Pediatric Emergency Care (a theme issue methinks) was this study by Roskind et. al. In a prospective cross-sectional study of children 3 months to 3 years suspected of having intussusception they ordered 3 view (supine, prone, and left lateral decubitus) abdominal films on 128 patients. Nineteen (15%) of these patients had intussusception – which paints a more realistic picture than the prior study. If air was present in the ascending colon on all three views they noted the following:

Sensitivity 100% (95% CI

[CI], 79.1-100)
Specificity, 17.4% (95% CI, 11.1-26.1)
NPV, 100% (95% CI, 79.1-100)
Likelihood ratio of a negative test, 0

The test was less sensitive (89.5%) with air in only 2/3 views. Interestingly the test was less sensitive (84%) but more specific (63%) when air was noted in the transverse colon. Ultimately they concluded that when clinical suspicion is low, the presence of air in the ascending colon on 3 abdominal X-Ray views can “obviate the need for further studies.

Back to the patient

Based on these studies, would you now be willing to get a three view abdominal X-ray on this kid. In my mind I’d say yes. Especially if mom was reliable. Nothing is necessarily wrong with sending the kid to the ED for an ultrasound – but you should trust your exam and history, and perhaps save some time and money.