Introduction
Blunt abdominal trauma (BAT) is one of the most common scenarios in the emergency department (ED). The prevalence of intra-abdominal injury in patients with blunt abdominal trauma among is 13% [
1]. Motor vehicle accident is one of the major causes of BAT. Other causes include fall injury, physical assault, sports, and crush injury [
2]. The liver is the second most injured organ following BAT after the spleen [
3]. The clinical diagnosis of liver injury in BAT is a major challenge for emergency physicians and trauma surgeons.
Focus Assessment with Sonography for Trauma (FAST) scan is one of the useful radiological investigations of BAT but has low sensitivity in diagnosing the liver injury and is user-dependent. Therefore, computed tomography (CT) scan is considered as the gold standard for diagnosing liver injury in BAT [
4,
5]. CT scan will help to access not only the liver but also other associated organ injuries. Not all the health facilities will have access to the CT scan. In these centers, the elevation of liver enzymes, i.e., aspartate transaminase (AST) and alanine transaminase (ALT), may provide valuable guidance to the emergency physician to suspect liver trauma. Also, the CT scan is expensive and has exposure hazards. It is also difficult to maintain the resuscitation of the hemodynamically unstable patient in the CT scan suite. This might be an extra burden for patients not only in developing countries like Nepal but also for the health system in a developed country. Previous studies have shown that these parameters may assist in the prediction of liver trauma and their severity [
6‐
10]. Patients will be greatly benefitted from on timely referral of the patient to the tertiary trauma center.
So, the objective of this study was to evaluate the role of AST and ALT in patients with BAT and its significance in predicting the severity of the liver injury.
Methods and material
The study was conducted in Chitwan Medical College Teaching Hospital (CMCTH) which was established in 2006. Since then, CMCTH has developed as a multi-specialty tertiary care center in Nepal. The ED receives a huge number of trauma casualties from all over central Nepal. It was a prospective observational study from February 2019 to May 2020.
Exclusion criteria
-
Patients with penetrating abdominal trauma
-
Patients who died in the emergency department during resuscitation
-
Patients who presented late after 24 h of the trauma
-
Patients with a history of liver disease
-
Patients positive for hepatitis B and hepatitis C surface antigen
Study method
All the patients with BAT were received by on-duty surgical residents in the emergency department. The patient was initially evaluated in the triage, and necessary resuscitation was done according to the Advanced Trauma Life Support (ATLS) protocol. Then, blood samples were sent for hemoglobin, hematocrit, WBC (white blood cell) count, serum AST, and ALT. FAST scan was done and patients with hemodynamic instability were taken for laparotomy. CT scans were done in the rest of the stable patients. The on-duty surgical residents inform the attending surgeon on duty. The first author or the attending surgeon further evaluated the patient and appropriate history with age, gender, mode of injury, and time of trauma of the patient were recorded. Based on the imaging and operative finding, patients with liver injury and without liver injury were noted with the associated injury. The grade of liver injury was done according to the Organ injury Scale by the American Association of Surgery for Trauma (AAST) (2018 version) (Additional file
1: Supplementary Table) [
11]. The datasheet was completed by the first author on the same day of admission or within 24 h of the admission. All the patients with BAT were included in the study as they are received and managed by the surgeons of the Department of Surgery of CMCTH. On discharge, the length of total hospital stay, length ICU stay (if admitted in ICU), re-admission in ICU, any blood transfusion, morbidity, and mortality were also recorded.
Data analysis
All statistical analyses and graphics were performed with the SPSS for Windows, version 16.0., Chicago, SPSS Inc. For comparisons of clinical and grading characteristics between the two groups (liver injury and no liver injury), the chi-squared test was used for categorical variables as appropriate, and the Mann-Whitney
U test used for quantitative variables (AST and ALT). The comparisons between more than two groups (grade of injury) were performed using the Kruskal-Wallis test. Results were expressed as median (IQR). All
p values are two-sided with
p values < 0.05 considered statistically significant. The receiver operating characteristic (ROC) was used to calculate the optimal cut-off value of AST and ALT, and using the optimal cut-off value, the sensitivity, specificity, positive predictive value, and negative predictive value were obtained [
12].
Ethics statement
The institutional review committee of CMCTH approved this prospective observational study. Written consent was given by patients for the information to be used for the research.
Discussion
Before CT scans were introduced, surgeons use to proceed for laparotomy when they suspected parenchymatous organ injury in BAT [
13]. The availability of a modern multi-detector CT scan has helped today’s surgeons tremendously in managing BAT with liver injury conservatively. It not only helps to establish the grade of injury but also helps to detect delayed complications of the high-grade liver in injury [
14,
15]. The diagnosis of liver injury is challenging in peripheral centers all over the world where CT is not available. This even applies to developed countries like Japan. To establish the severity of the liver injury is beyond the reach of those emergency physicians and surgeons.
The development of the FAST scan is useful in diagnosing hemoperitoneum, but because of its low sensitivity and specificity, its role in BAT is limited [
4,
16]. The role of elevated liver enzymes in predicting the severity of liver injuries is still a matter of dispute. Liver enzymes AST and ALT are present in hepatocytes in high concentration, and following BAT, they leak into blood circulation. Their main function is to catabolize amino acids, permitting them to enter the citric acid cycle. AST is typically found in the liver only but ALT is also found in the heart skeletal muscle, kidney, brain, and RBC [
17]. The alteration of ALT and AST in chronic liver injury and drug-induced liver has been extensively studied [
18]. Few studies have demonstrated their role as a marker in predicting the severity of liver injury [
6‐
10].
In this prospective observational study, we investigate the role of AST and ALT in the diagnosis of liver injury and its severity. In the recent study, Koyoma et. al. reported the optimal cut-off value of AST and ALT was 109 U/l and 97 U/l respectively for the patients with liver injury in blunt abdominal trauma. They suggested the optimal cut-off value as a predictor and also screening tool for CT scans for the presence of liver injury. Even in a developed country like Japan, they have pointed out the significance of AST and ALT levels for early CT scans and if not available, transfer to the patient to tertiary center [
10]. Similar results were reported by Tian et al., Chang et al., Shrivastava et al., and Lee et al. [
6‐
9]. Shrivastava et al. only compared ALT level whereas other studies included both AST and ALT values.
Our study results also demonstrate that the increased level of AST and ALT predicts the underlying liver injury in patients with blunt abdominal trauma. The median level of grade II liver injury was less than grade I liver injury. This may be because of very few patients with grade I liver injury. The median level of grade III and grade IV was much higher than grades I and II (Table
3). In countries like Nepal where there are few tertiary centers, patients with a high level of AST and ALT should be stabilized and immediately shifted to tertiary care centers. The median of AST and ALT of patients requiring blood transfusion was more than that of the patient not requiring blood transfusion (
p < 0.05). This shows that the AST and ALT level is not only important for the prediction of liver injury but also alerts the surgeons about the possible need for blood transfusion. Similarly, the median of AST and ALT in patients with mortality was significantly higher than patients without mortality (
p < 0.05). Since only 2 patients expired due to liver injury, the significance of AST and ALT in mortality cannot be suggested. One study reported elevated WBC counts together with elevated AST and ALT are strongly associated with liver injury [
19]. But in our study, there was no association between WBC count and liver injury. Overall, the sensitivity, specificity, and positive and negative predictive value of AST and ALT for predicting liver injury were low, so we suggest not using these liver enzymes as a diagnostic tool but to use as a screening tool for possible liver injury. There were some limitations during the study. This was a single institute study and the number of patients with liver injury was relatively small particularly grade I liver injury.
Conclusion
In conclusion, we report the optimal cut-off value of AST and ALT for liver injury in BAT as ≥ 106 U/l and 80 U/l, respectively. In countries like Nepal, where CT scan is not available in every center, the elevated level of AST and ALT might assist the surgeons to timely refer the suspected patients with the liver injury to a tertiary center. In tertiary centers, it might help the surgeons to go for conservative management for minor liver injuries in BAT preventing the exposure hazards of CT scans.
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