Compartmental anatomical classification of traumatic abdominal injuries from the academic point of view and its potential clinical implication

Trauma is a leading cause of hospitalization, long-term disabilities and mortality worldwide [1]. Traumatic abdominal injury (TAI), whether blunt or penetrating trauma is the third common type of injury (10%) after head (30%) and chest (20%) [2]. In respect to the mechanism of injury (MOI), Motor Vehicle Crash (MVC) is a common cause of admission to the emergency department, accounts for 50-75% of TAI cases [1, 3, 4]. Moreover, the mechanism and outcome of TAI varies from country to country depending upon the socioeconomic status and culture [5]. In Europe, blunt TAI is more frequent than the penetrating TAI [6]. However, the true frequency of blunt TAI as well as its incidence among out-of-hospital deaths is not well-known. In spite of using advanced imaging and invasive procedures, blunt TAI remains a diagnostic and therapeutic challenge in clinical practice [2, 7]. Therefore, adopting a stepwise approach in the evaluation of TAI patients is important to initiate efficient management. Hence, the classic initial step is to consider the mechanism of injury and the vector of force to predict the most likely injury pattern to be assessed [2]. This step should be followed by simultaneous physical examination and bedside imaging. Herein, we hypothesized that in addition to these steps, approaching TAI differently in relation to the abdominal compartments may add new insights for the diagnosis and risk stratification. There are four arbitrary anatomical compartments of the abdomen such as intrathoracic abdomen (ITC) (or upper abdomen), retroperitoneal abdomen (RPC), true abdomen (TAC) (or central abdomen), and pelvic abdomen (PAC) [8]. As data describing the epidemiology of TAI in each abdominal compartment is lacking worldwide, we thought to study the mechanism, patterns and outcome of TAI in relation to the four arbitrary abdominal compartments which have not been reported yet.

During the period from January 2008 to December 2011, 6,888 cases were admitted to the section of trauma at HGH; of them 1036 (15%) cases had abdominal injuries with mean age of 30.6 ± 13 years and median of 29(1–84) years. Males represented the majority of patients (93%). Details for the 4 intra-abdominal compartments injuries were available for 927 patients. Expatriates (84%) were the most injured population in comparison to the nationals (16%). Table 1 demonstrates the main characteristics in the 2 groups.

The classification of abdominal injuries based on the four arbitrary anatomical compartments is shown in Figure 1. The vast majority of injuries were depicted in the ITC (65%). Blunt trauma (95%) was the most common MOI in the entire study population. Figure 2 shows the anatomical abdominal compartments based on the mechanism of injury. MVC was the main MOI in the all groups except for PAC, in which fall dominated. Table 2 defines the 4 intra-abdominal compartments according to method of diagnosis, organs involved and mechanism of injury. Tables 3 and 4 summarize the overall descriptive profiles of the study population, in addition to the pattern, mechanism and outcomes of injuries in each compartment.

Up to the best of our knowledge, description of the TAI in relation to the four arbitrary anatomical compartments of the abdomen is not known. This anatomical approach may help better understanding of the pattern and outcome of TAI. Classically, TAI has been tackled from different aspects including mechanism of injury (blunt vs. penetrating), organ function (solid vs. hollow) or peritoneum-organ relationship. Yet, the injury classification according to anatomical proximity of organs has not been addressed. Moreover, the peculiar association between anatomical compartments and variables such as age, MOI, pattern of injury, associated extra-abdominal injuries and outcomes is not well-defined.

In the current study, majority of patients who sustained abdominal injuries were young in their most productive age and were predominantly males. Similar findings were also reported by earlier studies [5, 9]. The most common mechanism of injury in this study was blunt trauma (95%), this finding puts our study as the largest series with 1,036 TAI cases which exceeds the earlier published report on blunt TAI in the literature [9‐11]. Moreover, the MOI explains the higher incidence of associated extra-abdominal injury in our analysis. This high incidence of blunt abdominal injuries could be attributed to high frequency of MVCs and falls from height (mainly workplace-related injuries). Furthermore, MVC was the commonest mechanism of injury among all the injured compartments except pelvic abdominal compartment (PAC) injury, in which fall from height dominated. Expatriates in Qatar constitute around 80% of the population; this explains the involvement of large number of expatriates (84%) in our study. Vast majority of expatriates had PAC and TAC injuries. The main abdominal injuries included liver (35%; ITC), spleen (32%; ITC) and kidneys (18%; RPC). Hollow viscus injuries were identified as small and large bowel injures (12% and 5% respectively) in TAC and urinary bladder injury (4%) in PAC injuries. The rate of hematomas (pelvic and retroperitoneal) was higher in PAC and TAC injuries. The main extra-abdominal injuries involved the head in RPC and ITC (31% and 28%, respectively), lung and heart in ITC (33% and 2%, respectively) and RPC (22% and 0.7%, respectively). The rate of extremity injuries was observed in 21% in PAC injuries. Although blood loss is a common complication with solid organ injuries (i.e., ITC and RPC), our study demonstrated paradoxically that the need for transfusion was higher in TAC and PAC injuries. This finding could be explained in part by the higher rate of surgery (i.e., Exploratory Laparotomy, long bone, and spinal fixation) and associated retroperitoneal and pelvic hematomas in these compartments. Hospital length of stay was prolonged among PAC patients, a finding that could be related to higher incidence of extremities injuries, higher rate of surgery, sepsis and lower mortality.

The overall mortality rate, in the current analysis, was 10%; the peak mortality was seen in patients with RPC and TAC (15% and 11%) followed by 9.4% in ITC injuries, while the lowest rate was 1.5% in patients with PAC injury.

In the present study, associated TBI was reported in a quarter of the cases and its presence was associated with 5 fold increase in the mortality rate. The median head AIS was highest in TAC and RPC patients and matched up their high mortalities. Our finding is consistent with previous data which demonstrated TBI to be the most frequent cause of mortality in patients with blunt trauma [12]. Moreover, after adjustment for relevant co-variates the associated TBI was a strong independent predictor of mortality in our cohort (adjusted OR = 5.3). In addition, the need for blood transfusion was also an important independent predictor for mortality, showing a 3 fold increased risk of mortality (adjusted OR = 3.0). The multivariate logistic regression analysis also demonstrated other predictors of mortality in TAI such as age (OR 1.03; p = 0.03), mean ISS (OR 1.1; p = 0.001), and serum lactate (OR 1.03; p = 0.04). Serum lactate level was higher in patients with TAC in comparison to other compartments.

An Indian study by Lone et al. [13] reported 144 TAI cases (53% penetrating and 47% blunt trauma) and found that the mortality rates were 9.2% and 8.2% among patients with penetrating and blunt injuries, respectively. The cause of death was mainly related to hemorrhagic shock. Gad et al. [9] analyzed TAI in 248 Egyptian cases (69% blunt and 31% penetrating) and reported 26% overall mortality rate in terms of 58% in penetrating and 12% in blunt trauma . The higher mortality rate was due to delay in treatment, a factor that was not measured in our study. Lund et al. [14] from Denmark reported higher mortality (up to 56%) in hemodynamically unstable patients with abdominal injuries undergoing emergency laparotomy. Smith et al. [11] from Australia studied 1,224 TAI cases (79% were blunt injury) over 8 yrs and reported an overall mortality rate between 7-9%. Our findings showed that the mortality rate increased from 7% to reach 15% in those who presented with higher abdominal AIS. Particularly, the median abdominal AIS was higher in TAC injuries compared to other compartments (P = 0.001). However, abdominal AIS was not identified as an independent predictor of mortality in our study.

Traumatic abdominal injury is a common clinical challenge that varies according to the mechanism and site (abdominal region) of injury. The anatomical approach of TAI may be of academic interest as a re-visit of the basic medicine. Also, it could be a complementary tool for better understanding and diagnosis of TAI and therefore further studies are needed to outline these compartments preoperatively.