Evaluating the PECARN Abdominal Trauma Rule in the grey zone….

By / / #FOAMed, Emergency Medicine, Paediatrics, Trauma & Orthopaedics

Background

One of my many jobs, and one that i really enjoy is woking in a large tertiary Paeds ED here in Virchester. We are one of the busiest in the country and have a huge catchment area for trauma. Thankfully major trauma in kids is not that common, but when it all gets concentrated in one spot, we see a fair number and I like to think I make reasonable decisions about imaging. One group that is a little tricky are those children presenting with blunt abdominal trauma. On the one hand, we want to detect serious intra-abdominal injuries requiring acute intervention (IAIAI); on the other, we want to avoid unnecessary radiation exposure from CT imaging. We have guidelines which have recently been updated (you may want to read more about them here), but even then a lot comes down to clinical judgement in the resus room.

The PECARN (Pediatric Emergency Care Applied Research Network) abdominal trauma prediction rule was developed to identify children at very low risk of IAIAI. It seems to perform well in derivation with a score of more than 3 being significant (a rate of 4.5% and above for IAIAI), but what about those with just one or two concerning features? This study by Arnold et al., explored precisely that—the risk of IAIAI in children who didn’t pass the rule cleanly but were not entirely negative either (the ones who scored 1 or 2).

As a reminder head over to MDCALC to review the rule here, and/or look at the included factors below.

  1. Evidence of abdominal wall trauma or seatbelt sign
  2. GCS <14 and blunt abdominal trauma
  3. Abdominal tenderness
  4. ≥1 of the following:
    • Thoracic wall trauma
    • Complaint of abdominal pain
    • Decreased breath sounds
    • Vomiting

The authors build on earlier work that demonstrated PECARN’s 100% sensitivity in ruling out IAIAI when none of the seven clinical variables were present. But we frequently encounter children with just one or two of these variables. This study focused on those patients in the grey zone, not ruled in and not ruled out.

The abstract is below and you can (and should) also read the JC on this in Annals from Stanford Schor (links below).

Abstract.

Objective: The Pediatric Emergency Care Applied Research Network (PECARN) derived and externally validated a clinical prediction rule to identify children with blunt torso trauma at low risk for intraabdominal injuries undergoing acute intervention (IAIAI). Little is known about the risk for IAIAI when only one or two prediction rule variables are positive. We sought to determine the risk for IAIAI when either one or two PECARN intraabdominal injury rule variables are positive.

Methods: We performed a planned secondary analysis of a prospective, multicenter study that included 7542 children (<18 years old) with blunt torso trauma evaluated in six emergency departments from December 2016 to August 2021. Patients with only one or two PECARN rule variables positive were included. The outcome was IAIAI (IAI undergoing therapeutic laparotomy, angiographic embolization, blood transfusion, or two or more nights of intravenous fluids).

Results: Among the 7542 children enrolled, 2986 (39.6%, 95% confidence interval [CI] 38.5%-40.7%) had one or two PECARN variables positive and were included. Of this subpopulation, 227 (7.6%, 95% CI 6.7%-8.6%) had intraabdominal injuries. In the 1639 patients with only one rule variable positive, 21 (1.3%, 95% CI 0.8%-2.0%) had IAIAI. In the 1347 patients with two rule variables positive, 27 (2.0%, 95% CI 1.3%-2.9%) had IAIAI. Risk for IAIAI for each variable was highest for Glasgow Coma Scale (GCS) score <14 (16/291, 5.5%, 95% CI 3.2%-8.8%) and abdominal wall trauma (three of 321, 0.9%, 95% CI 0.2%-2.7%). Risk for IAIAI when two variables were present was highest when decreased breath sounds (three of 44, 6.8%, 95% CI 1.4%-18.7%) and GCS <14 (10/207, 4.8%, 95% CI 2.3%-8.7%) were present with one other variable.

Conclusions: Few children with blunt torso trauma and one or two PECARN predictor variables present have IAIAI. Those with GCS score <14, however, are at highest risk for IAIAI.

What is PECARN?

The Pediatric Emergency Care Applied Research Network (PECARN) was the first federally funded research network in the United States dedicated to emergency care research in children. Founded in 2001 and funded by the Emergency Medical Services for Children (EMSC) programme of the Health Resources and Services Administration (HRSA), PECARN is a collaboration among children’s hospitals, academic centres, and general hospitals across the US. The UK/Ireland equivalent, albeit on a very different model would be the awesome PERUKI team. Both organisations have done incredible work to improve children’s emergency care. PERUKI have a conference coming up in Scotland – you should think about going 🙂

What Kind of Study Is This?

This was a planned secondary analysis of a large, prospective, multicentre observational cohort conducted across six US tertiary paediatric trauma centres between 2016 and 2021. Children under 18 (always remember that the North Americans consider under 18 to be paediatric, in the UK it’s under 16), with blunt torso trauma were eligible, provided they had one or two positive PECARN variables. The parent study, which enrolled over 7,500 patients, had previously validated the PECARN rule. This analysis focused on the 2,986 children who had exactly one or two predictor variables. So it’s really a sub-group analysis and we always have to be a bit cautious about those.

The main outcome was IAIAI: intraabdominal injuries that led to death, therapeutic laparotomy, angiographic embolisation, blood transfusion, or a hospital stay of at least two nights for intravenous fluids due to pancreatic or GI injury. That seems pretty reasonable and inclusive. Those are not the patients I would want to delay CT on, or worse send home!

Tell Me About the Patients

Out of the 7,542 children in the parent cohort, 2,986 had either one or two positive PECARN variables and made up the study sample. Their median age was around 9.8 years, with a slight male predominance (56%). These were kids who, by virtue of having only one or two PECARN flags, sat in a grey zone, not clearly high-risk but not safely low-risk either.

Mechanisms of injury were as expected: road traffic collisions, followed by falls from height, pedestrian-versus-vehicle injuries, and bicycle-related trauma. CT imaging was performed in 41.4% of this cohort, and nearly half were admitted.

What Were the Measured Outcomes in This Study?

The primary outcome was IAIAI, injuries that demanded immediate action. Secondary outcomes included any intraabdominal injury (IAI), even if no acute intervention was required.

Crucially, the study didn’t just look at the overall rates but broke the data down by which specific PECARN variables were present—whether in isolation or in combination with one other variable. This granular approach helps identify which signs are most predictive of serious injury.

What Are the Main Results?

  • Of 2,986 children with one or two predictor variables:
    • 227 (7.6%) had any IAI.
    • 48 (1.6%) had IAIAI.
  • In children with only one PECARN variable (n=1,639):
    • 89 (5.4%) had any IAI.
    • 21 (1.3%) had IAIAI.
  • In children with two variables (n=1,347):
    • 138 (10.2%) had any IAI.
    • 27 (2.0%) had IAIAI.
  • Importantly, no IAIAI were observed in children who had only abdominal pain, vomiting, or abdominal tenderness.
  • The variable most predictive of IAIAI was a Glasgow Coma Scale (GCS) <14:
    • As a single finding: 5.5% had IAIAI.
    • In combination with another: up to 15% had IAIAI depending on the pairing.

This suggests that certain isolated findings, especially those not associated with abnormal consciousness, may not warrant immediate CT, but that a period of observation may be more appropriate, and in reality that is a technique I se a lot in PEM. The overall findings are in keeping with the original study, but that subset of IAIAI in patients with altered consciousness could be clinically important

What about the Methodology

It’s a large(ish) database, with a reasonable number of patients with positive findings,, but still a small percentage of those positive findings which will affect how precise we can be about the findings. That said the 95% confidence are fairly tight for most variables, though low GCS, the most interesting finding isn quite wide (risk of 5.5%, 95%CI 3.2-8.8%).

It is a prospective study that should give us good documentation on a single assessment. In reality single assessments are something I avoid, one of the most important things we do in paeds practice (not just trauma) is to use time and repeated assessment to guide our decision making. I will almost always do multiple assessments in any patient who I have concerns about, and I’m very happy to change my mind if my initial impression turns out to be wrong.

That said, this study still provides insight into a more nuanced approach to PECARN-positive patients, particularly if you were someone who applied the rule without much thought. Top tip – thought is really important in medicine! Don’t just follow rules all the time. Great clinicians know when to use/adjust/revise them.

Should We Change Practice Based on This Study?

Perhaps, but probably not though that may depend on what your practice is now, and what options are available to you. I find that a lot of clinicians are really anxious about assessing these kids and will frequently refer back to tertiary centres. That’s OK from a patient safety perspectivce, but it may be that tools such as this PECARN tool can assist your decision making and potentially help with referral pathways too. Whether we divide PECARN further on the basis of this study would require external validation.

This study suggests that those children with isolated vomiting, abdominal pain, or tenderness can likely avoid CT and instead be observed with appropriate safety nets. GCS <14, on the other hand, remains a red flag and in fact would make me happier with my decision to CT if the GCS is low. I’m still exercising judgement though, using the score as a decision aid and not a rule.

As always this may be locality specific, and it does include a different age group to that in the UK, and so I’d like to see data from departments and populations more like my own.

Summary

I like this paper. It gives me a bit more objective information to guide my decision making, but it also (perhaps paradoxically) reinforces my belief that assessing these patients takes, skill, experience, time, repeated assessment and patience.

vb

Simon Carley

References

  1. Holmes JF, Lillis K, Monroe D, Borgialli D, Kerrey BT, Mahajan P, Adelgais K, Ellison AM, Yen K, Atabaki S, Menaker J, Bonsu B, Quayle KS, Garcia M, Rogers A, Blumberg S, Lee L, Tunik M, Kooistra J, Kwok M, Cook LJ, Dean JM, Sokolove PE, Wisner DH, Ehrlich P, Cooper A, Dayan PS, Wootton-Gorges S, Kuppermann N; Pediatric Emergency Care Applied Research Network (PECARN). Identifying children at very low risk of clinically important blunt abdominal injuries. Ann Emerg Med. 2013 Aug;62(2):107-116.e2. doi: 10.1016/j.annemergmed.2012.11.009. Epub 2013 Feb 1. PMID: 23375510.
  2. Arnold CG, Ishimine P, McCarten-Gibbs KA, Yen K, Atigapramoj N, Badawy M, Ugalde IT, Chaudhari PP, Upperman JS, Kuppermann N, Holmes JF. Performance of individual criteria of the Pediatric Emergency Care Applied Research Network (PECARN) intraabdominal injury prediction rule. Acad Emerg Med. 2025 Jun;32(6):643-649. doi: 10.1111/acem.15084. Epub 2025 Jan 13. PMID: 39804061; PMCID: PMC12173795.
  3. Schor S. Tummy Aches, Tummy Tenderness, and Throwing Up: Low-Risk Patients in the Pediatric Emergency Care Applied Research Network Abdominal Trauma Validation Study: August 2025 Annals of Emergency Medicine Journal Club. Ann Emerg Med. 2025 Aug;86(2):204-205. doi: 10.1016/j.annemergmed.2025.05.004. PMID: 40685218.
  4. Matthew Gray, “Imaging decisions in paediatric trauma – RCR update 2024,” in St.Emlyn’s, December 16, 2024, https://www.stemlynsblog.org/imaging-decisions-in-paediatric-trauma-rcr-update-2024/.
  5. https://www.rcr.ac.uk/our-services/all-our-publications/clinical-radiology-publications/major-paediatric-trauma-radiology-guidance/
  6. https://pecarn.org/about/
  7. https://www.peruki.org/

Cite this article as: Simon Carley, "Evaluating the PECARN Abdominal Trauma Rule in the grey zone….," in St.Emlyn's, August 1, 2025, https://www.stemlynsblog.org/evaluating-the-pecarn-abdominal-trauma-rule-in-the-grey-zone/.

Thanks so much for following. Viva la #FOAMed

Scroll to Top