Reference: Arnold CG, et al. Performance of individual criteria of the Pediatric Emergency Care Applied Research Network (PECARN) intraabdominal injury prediction rule. Acad Emerg Med. Jan 2025

Date: May 7, 2025

Dr. Sandi Angus

Guest Skeptic : Dr. Sandi Angus is a Paediatric and Adult Emergency Medicine Registrar in the Shrewsbury and Telford Hospital NHS Trust. She is passionate about paediatric EM, wellbeing and medical education.

Case: A ten-year-old boy presents to your emergency department (ED) after being involved in a motor vehicle collision at high speed. Emergency Medical Service (EMS) tells you that he was properly restrained. His parents were also in the vehicle and are currently being brought to the ED as well. He appeared a bit dazed initially, but he has had a Glasgow Coma Scale (GCS) score of 15 throughout transport. Your primary survey is unremarkable. He complains of some abdominal pain, although you note a soft abdomen on exam and no seatbelt sign. As you complete your secondary survey, he vomits once, which is non-bloody. A medical trainee working with says to you, “He says his stomach hurts and threw up. Do you think we need to CT scan his abdomen?”

Background: Intra-abdominal injury (IAI) in children is a significant concern for emergency physicians. This is particularly true in cases of blunt trauma. Although relatively uncommon compared to adults, IAIs in children can be life-threatening. We have to identify them early and manage them appropriately.

The organs most frequently injured include the spleen, liver, and kidneys, but any abdominal organ can be affected​. Diagnosing IAIs in pediatric patients poses a unique challenge. Children often present with subtle clinical findings, and the physical examination can be unreliable due to factors such as altered mental status, distracting injuries, or the child’s inability to articulate their symptoms​.

Imaging modalities like computed tomography (CT) are the gold standard for diagnosis, but CT use must be balanced against the risks of ionizing radiation. Traditionally, clinicians relied heavily on their clinical gestalt, but this approach can miss injuries or lead to unnecessary imaging. The risks of CT imaging are not inconsequential. Children are more radiosensitive than adults, and for each  abdominal or pelvic scan, the lifetime risks of cancer are 1 per 500 scans, irrespective of the age at exposure. However, this is actually very small compared with the background risk of developing cancer in a lifetime, which is 1 in 3, so if your scan is clinically justified, the benefit is likely to outweigh the potential harm [1].

To improve diagnostic accuracy and minimize unnecessary CT scans, clinical decision rules (CDRs) or “tools” have been developed. One such tool, the Pediatric Emergency Care Applied Research Network (PECARN) clinical prediction rule for intra-abdominal injuries, identifies children at very low risk of clinically important IAIs, aiming to safely reduce CT utilization​ [2-3]. This rule was composed of seven variables, all of which could be collected on history and physical exam. There was no need for labs or imaging in this decision rule.

These seven variables were:

If all seven variables were negative, the child was at very low risk of having intra-abdominal injury requiring intervention and the decision rule recommended against a CT scan.

Despite the benefits of existing decision rules, the question remains how best to apply these tools when only one or two PECARN criteria are positive—a clinical gray zone not well characterized in earlier validation studies. Understanding the individual performance of PECARN rule components in predicting IAI is crucial for refining decision-making in pediatric trauma care.

Reference: Arnold CG, et al. Performance of individual criteria of the Pediatric Emergency Care Applied Research Network (PECARN) intraabdominal injury prediction rule. Acad Emerg Med. Jan 2025

Authors’ 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 IAI.”

Quality Checklist for Clinical Decision Rules:

Results: The original study included 7,542 children with blunt torso trauma across six emergency departments. Of those children, 2,986 (39.6%, 95% CI 38.5 to 40.7) had one or two PECARN positive variables. The median age was 9.8 years and slightly over half (56%) were male. CT scans were obtained in 1236 (41%) of the patients.

Primary Outcome: Of the 1,639 patients who had one variable positive, 21 (1.3%, 95% CI 0.8-2) had intra-abdominal injuries undergoing acute intervention. Of the 1347 who had two variables positive, 27 (2%, 95% CI 1.3-2.9) had intra-abdominal injuries undergoing acute intervention.

Secondary Outcome: Of those 2986 patients enrolled, 227 (7.6%, 95% CI 6.7-8.6) had intra-abdominal injuries.

They also broke it down by each individual variable and how many patients were diagnosed with intra-abdominal injury and intra-abdominal injury undergoing acute intervention. GCS≤14 was the most important individual predictor variable for intra-abdominal injury undergoing acute intervention.

Inclusion Criteria:

It’s important to review the inclusion criteria from the original study because we do not think this clinical decision rule should be applied indiscriminately to every child with abdominal trauma.

A large proportion of the children included in the original study had some pretty severe mechanisms of injury (32% from motor vehicle collisions, 19% were struck by a vehicle, and 13% due to fall from height. Be careful in applying this clinical decision tool to less severe mechanisms.

They excluded patients who had injury that occurred over 24 hours ago. Many of us may have encountered a patient in the emergency department who complains of belly pain from a blunt abdominal injury a day ago and were perhaps seen at an urgent care facility or tried to wait it out. Although they were not part of the patient population in this study, would it be inappropriate to use this clinical decision tool on those patients?

Partial Verification Bias:

In this secondary analysis, only around 40% of patients included had CT scans. What about those who did not?

In the original derivation study, there was one patient with a splenic laceration who returned after being discharged from the ED without imaging who underwent splenic artery embolization. It is possible that some of these patients who did not undergo CT scan still had intra-abdominal injuries that were missed.

This does highlight the primary outcome that they defined as IAI undergoing acute intervention. It is arguably more patient oriented, they missed some IAI but maybe it was not clinically significant. I’ve admitted low grade splenic or liver laceration to the hospital who were observed without any intervention except a repeat hemoglobin before being sent home.

Spectrum Bias:

Subpopulations with only 1–2 rule variables may not fully represent all blunt trauma presentations​. This study only looked at the risk of IAI if one or two variables were positive. Table 5 demonstrates the proportion of children with IAI with two positive variables. Be cautious in that some combinations of these two variables included very few patients.

What happens as you add more variables (>2), and does it matter which variables are positive?

They excluded 2,357 (31%) of patients in the original study because they had more than one positive variable. In that study, 203 children had intra-abdominal injuries undergoing acute interventions. We know there is a proportion of children who can have more variables present and still not have intra-abdominal injury requiring acute intervention.

It is also important to remember that not all variables are created equal. In this study, no patients with the positive single variable of: abdominal pain, vomiting, abnormal breath sounds, or abdominal tenderness had intra-abdominal injury undergoing acute intervention.

Comparison to Clinical Gestalt:

Our FOAMed friend, Dr. Justin Morgenstern, at First10EM thinks clinical decision rules are ruining medicine. Is this clinical decision rule too obvious? Would you be thinking about performing a CT scan if all seven predictor variables were negative without the decision rule? How does this compare to clinical gestalt?

There was another secondary analysis of the same original PECARN study that compared the decision rule with clinicians recorded suspicion of IAI (<1, 1-5, 6-10, 11-50, >50%). The CDR had higher sensitivity 97% compared to clinicians 82.8%, but the clinicians had higher specific 78.7% vs 42.5% [4].

A third of low-risk patients by clinical suspicion still got CT scans, so we see that suspicion for intraabdominal injury did not correlate with the ordering of CTs. We are unsure of the reasons why clinicians chose to obtain the CT even if the suspicion was low.

Adjunct Workup for Intra-abdominal Injury:

One of the strengths of this PECARN clinical decision tool is that all of these variables are things you get from the history and physical examination alone. But are there other things we can use to help risk-stratify children with blunt abdominal injury?

Blood tests, including hemoglobin, lipase, and liver enzymes? The evidence for the use of lab tests is mixed. Hemoglobin measurement is not particularly reliable in the setting of acute blood loss. The sensitivity, specificity, PPV, and NPV of these lab tests are quite variable.

The evidence for FAST is mixed as well [5-9]. It is dependent on operator skill. Unfortunately, a negative FAST scan in pediatrics does not necessarily mean that there’s no significant intra-abdominal injury, just as in adults. The specificity of it is better- so if you see free-fluid in the context of trauma and hemodynamic instability, it’s blood until proven otherwise. However, the sensitivity is poor – Children can still have abdominal injuries without free fluid, although it can be improved by doing serial scanning [10].  There’s still a lot of ongoing research on this topic.

And finally, there is the option of observation in the ED or hospital for serial exams as well.

Comment on Authors’ Conclusion Compared to SGEM Conclusion: We agree with the authors’ conclusion.

Case Resolution: During the boy’s stay in the ED, you and the trainee assessed him multiple times. His reported abdominal pain seems to improve, and he does not have any further episodes of emesis. Your repeat examinations reassure you that the chances of him having a clinically significant intra-abdominal injury are low. His aunt arrives at the ED. You fill her in on the patient’s ED course, and she takes the patient home.

Clinical Application: The PECARN clinical decision tool can be used to risk-stratify children presenting with blunt intra-abdominal injury. If the child is negative for all seven variables, there is a very low chance of them having an intraabdominal injury that requires urgent intervention. Even if one or two of the variables are positive, this does not necessarily mean that the child needs to undergo a CT scan. Use this decision tool in conjunction with your clinical judgement.

What Do I Tell My Trainee? I’m glad you asked that question. There are several ways a child presenting with blunt intra-abdominal injury can be evaluated. Those include lab tests, ultrasound, CT scans, serial exams and observation. The PECARN clinical decision tool risk stratifies these children based on seven variables from the history and physical examination. Even if one or two of these variables are positive, this doesn’t mean we automatically need to put the child through the scanner. Let’s continue to re-evaluate him while he is under our care in the emergency department.

References:

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