PEM Pearls: To Scan or Not to Scan? CT Abdomen in Children with Blunt Torso Trauma

An 18-month-old female with no past medical history is brought in by ambulance after a motor vehicle collision (MVC) at highway speed, restrained in an appropriate car seat. Mom was also brought in after delayed extrication with an obvious femur deformity. EMS reports that the patient had emesis on the scene, was fearful but calm, and has been moving all extremities.

Vitals per EMS: HR 120, BP 100/60, RR 30, SpO2 99%, Temp 36.5 C

Initial Exam:

• General: crying
• Neuro: Glasgow Coma Scale (GCS) of 13 (eyes shut unless talked to, crying spontaneously, moving all extremities)
• MSK: atraumatic chest, erythema on the left leg
• Abdomen: without tenderness

Blunt Torso/Abdominal Trauma

An intra-abdominal injury (IAI) is considered to be any radiographically or surgically apparent injury to an intra-abdominal structure (urinary tract, gastrointestinal tract, spleen, liver, pancreas, gallbladder, adrenal gland, vasculature, and fascia). An intra-abdominal injury requiring intervention (IAI-I) is any IAI that causes death or requires an intervention such as laparotomy, angiographic embolization, blood transfusion, or even admission for intravenous fluids [1].

Despite our curiosity and desire to diagnose all injuries, emergency medicine teams must focus on recognizing IAI-I and tailor their workup accordingly given the negative consequences of excessive workup and treatment of stable IAIs (e.g., unnecessary splenectomies, hepatectomies, increased length of stay, radiation, and increased medical costs/resources).

Although the incidence of pediatric blunt torso trauma in the United States was 110,525 cases in 2016, the prevalence of IAI has been quoted to be as low as 6.3%; more importantly, the prevalence of IAI-I is less than 2% [1]. Non-pediatric level 1 trauma centers were more likely to use computed tomography (CT) in pediatric trauma patients compared to pediatric trauma centers, even after adjusting for injury severity [2].

Clinical Decision Rule

The Pediatric Emergency Care Applied Research Network (PECARN) conducted a prospective study of over 12,000 children ages 0-18 years presenting to pediatric and general EDs with blunt torso trauma. Significant predictors of IAI-I were low GCS, abdominal tenderness, abdominal wall trauma, thoracic wall trauma, decreased breath sounds, and vomiting. The authors developed a prediction rule with a sensitivity of 97% (93.7, 98.9) and a negative predictive value of 99.9% (99.7, 1.00) [1]. External validation had similar sensitivity (99% 96-100%) reinforcing the utility of this clinical decision rule (CDR) in identifying low-risk individuals and decrease the use of CT [4].

In comparison to other CDRs, this rule does not include a gestalt variable but outperforms clinical gestalt with a lower miss rate (6 compared to 23) [5]. Of note, this prediction rule is not a two-way tool and was created only to determine individuals at low risk of IAI-I, rather than to assist providers in deciding who needs a CT scan.

Reviewing the cases missed by the prediction rule in the initial study, possible clinical findings that could be captured with adjuncts, such as labs and imaging, include:

• Gross hematuria
• Microscopic hematuria (Red Blood Cells on Urinalysis)
• Elevated AST/ALT
• Rib fracture

Adjuncts

No single test effectively screens for IAI-I or IAI, but additional testing can increase the index of concern in cases that already have a higher pre-test probability (individuals who have any of the variables factored into the prediction rule). The following adjuncts can be considered for children who are not deemed very low risk.

Labs

• Hematocrit <30% [3,7-8]
• AST>200 U/L, ALT>125U/L [3,7, 9-10]
• Lipase >100 U/L [9,11-12]
• UA Gross hematuria [12-17]

Focused Assessment with Sonography for Trauma (FAST)

• The diagnostic role of a FAST in pediatric trauma is less established than in adult trauma [18].
• Application of FAST increases as provider suspicion for IAI increases [19].
• As an adjunct to the clinical exam, FAST can be incorporated into decision making for selected cases of increased IAI concern [20].

Chest X-ray (CXR)

• Injuries noted on a CXR may contribute to increased concern for IAI depending on location, mechanism, and type of injury [21].

Review of Case

Returning to our case, findings of concern include her GCS of 13 and reported emesis. Although it was a high-speed MVC and may represent a more severe mechanism, this variable was not found to be a predictor of IAI-I and should not in isolation inform your evaluation of her abdominal injury.

Application of the PECARN CDR demonstrates that the patient is not at very low risk for IAI-I. Labs and a FAST are performed and medications are given for symptom control.

The patient’s results are:

Labs:

• HCT 35%
• Lipase 20 U/L
• AST 23 U/L, ALT 30 U/L
• UA: no gross hematuria

FAST: Negative

On re-evaluation after ondansetron and acetaminophen, the patient has a GCS of 15 and is excitedly playing with her new teddy bear from the fire department while sipping apple juice. The patient is safely discharged home with her dad after a very frightening experience without unnecessary costs or radiation.

Take-Home Points

• While blunt pediatric abdominal trauma has a high incidence, the prevalence of IAI-I is rather low.
• The PECARN prediction rule for blunt torso trauma can identify patients that are very-low-risk for an IAI-I.
• Notably, the mechanism of injury is not a predictable factor in determining IAI-I.
• Clinicians should consider the use of labs, FAST, and CXR for risk stratification of patients that are not found to be very-low-risk.

Read more pediatric emergency medicine topics as part of the PEM Pearls Series on ALiEM.

References

1. Holmes JF, Lillis K, Monroe D, et al. Identifying children at very low risk of clinically important blunt abdominal injuries. Ann Emerg Med. 2013;62(2):107-116.e2. doi:10.1016/j.annemergmed.2012.11.009. PMID: 23375510
2. Marin JR, Wang L, Winger DG, Mannix RC. Variation in Computed Tomography Imaging for Pediatric Injury-Related Emergency Visits. J Pediatr. 2015 Oct;167(4):897-904.e3. doi: 10.1016/j.jpeds.2015.06.052. PMID: 26233603
3. Holmes JF, Sokolove PE, Brant WE, et al. Identification of children with intra-abdominal injuries after blunt trauma. Ann Emerg Med. 2002;39(5):500-509. doi:10.1067/mem.2002.122900. PMID: 11973557
4. Springer E, Frazier SB, Arnold DH, Vukovic AA. External validation of a clinical prediction rule for very low risk pediatric blunt abdominal trauma. Am J Emerg Med. 2019 Sep;37(9):1643-1648. doi: 10.1016/j.ajem.2018.11.031. PMID: 30502218.
5. Mahajan P, Kuppermann N, Tunik M, et al. Comparison of Clinician Suspicion Versus a Clinical Prediction Rule in Identifying Children at Risk for Intra-abdominal Injuries After Blunt Torso Trauma. Acad Emerg Med. 2015;22(9):1034-1041. doi:10.1111/acem.12739. PMID: 26302354
6. Nishijima DK, Yang Z, Clark JA, Kuppermann N, Holmes JF, Melnikow J. A cost-effectiveness analysis comparing a clinical decision rule versus usual care to risk stratify children for intraabdominal injury after blunt torso trauma. Acad Emerg Med. 2013;20(11):1131-1138. doi:10.1111/acem.12251. PMID: 24238315
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9. Streck CJ, Vogel AM, Zhang J, et al. Identifying Children at Very Low Risk for Blunt Intra-Abdominal Injury in Whom CT of the Abdomen Can Be Avoided Safely. J Am Coll Surg. 2017;224(4):449-458.e3. doi:10.1016/j.jamcollsurg.2016.12.041. PMID: 28130170
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11. Adamson WT, Hebra A, Thomas PB, Wagstaff P, Tagge EP, Othersen HB. Serum amylase and lipase alone are not cost-effective screening methods for pediatric pancreatic trauma. J Pediatr Surg. 2003;38(3):354-357. doi:10.1053/jpsu.2003.50107. PMID: 12632348
12. Capraro AJ, Mooney D, Waltzman ML. The use of routine laboratory studies as screening tools in pediatric abdominal trauma. Pediatr Emerg Care. 2006;22(7):480-484. doi:10.1097/01.pec.0000227381.61390.d7. PMID: 16871106
13. Mee SL, McAninch JW, Robinson AL, Auerbach PS, Carroll PR. Radiographic assessment of renal trauma: a 10-year prospective study of patient selection. J Urol. 1989;141(5):1095-1098. doi:10.1016/s0022-5347(17)41180-3. PMID: 2709493
14. Morey, Allen F., et al. “Efficacy of Radiographic Imaging in Pediatric Blunt Renal Trauma.” Journal of Urology, vol. 156, no. 6, 1996, pp. 2014–2018., doi:10.1016/s0022-5347(01)65422-3.
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19. Menaker J, Blumberg S, Wisner DH, et al. Use of the focused assessment with sonography for trauma (FAST) examination and its impact on abdominal computed tomography use in hemodynamically stable children with blunt torso trauma. J Trauma Acute Care Surg. 2014;77(3):427-432. doi:10.1097/TA.0000000000000296. PMID: 25159246
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21. Holmes JF, Sokolove PE, Brant WE, Kuppermann N. A clinical decision rule for identifying children with thoracic injuries after blunt torso trauma. Ann Emerg Med. 2002 May;39(5):492-9. doi: 10.1067/mem.2002.122901. PMID: 11973556

Read more pediatric emergency medicine topics as part of the PEM Pearls Series on ALiEM.