Based upon mechanism, location of injuries identified on physical examination, screening radiographs, and the patient’s overall condition, additional diagnostic studies may be indicated. Selective radiographs are done early in the patient’s ED evaluation. For patients with severe blunt trauma, chest and pelvic radiographs should be obtained. Historically, a lateral cervical spine radiograph was also obtained, hence the reference to the big three films, but currently patients preferentially undergo CT scanning of the spine rather than plain film radiography. Since its initial use in the early 1980s, CT scanning has become a routine part of the trauma evaluation for abdominal injury. With multi-slice helical scanning, the entire torso can be scanned in under 5 min. Patients with a positive FAST, who do not have immediate indications for laparotomy and are hemodynamically stable, undergo CT scan to quantify their injuries. Additionally, patients with persistent abdominal tenderness, significant abdominal wall trauma, distracting injuries, or altered mental status should undergo CT imaging. Although the majority of abdominal penetrating injuries that violate the peritoneum require laparotomy, the exception is penetrating trauma isolated to the right upper quadrant. In hemodynamically stable patients with the trajectory of penetrating trauma confined to the liver by CT scan, nonoperative observation is an option [7, 8].

CT scanning is excellent for identifying injuries of the solid organs (liver, spleen, kidney). If a diaphragmatic injury is not clearly identified on ED radiograph, CT scan can also be used to delineate these injuries, particularly with sagittal or coronal reconstructions (Fig. 9.3). Despite the increasing diagnostic accuracy of multi-slice CT scanners, CT still has limited sensitivity for identification of intestinal injuries. Bowel injury is suggested by findings of thickened bowel wall, “streaking” in the mesentery, free fluid without associated solid organ injury, or free intraperitoneal air [9].

The American Association for the Surgery Trauma (AAST) developed a grading scale to provide a uniform definition of solid organ injuries based upon the magnitude of anatomic disruption (Table 9.1) [10]. Solid organ injury grading permits effective transfer of information between treating physicians, and predicts failure rates and complication rates of nonoperative management (NOM). In addition to grading the injury, specific findings that should be noted on CT scan include contrast extravasation (i.e., a “blush”), the amount of intraabdominal hemorrhage, and the presence of pseudoaneurysms (Fig. 9.4).

The diagnostic approach differs between penetrating and blunt abdominal trauma. As a rule, minimal evaluation is required prior to laparotomy for gunshot or shotgun wounds that violate the peritoneal cavity, because over 90 % of patients have significant internal injuries. Anterior truncal GSWs between the fourth intercostal space and the pubic symphysis, whose trajectory by x-ray or entrance/exit wound indicates peritoneal penetration, should undergo operative exploration (Fig. 9.5). GSWs to the back or flank are more difficult to evaluate because of the retroperitoneal location of the injured abdominal organs. Triple-contrast CT scan can delineate the trajectory of the bullet and identify peritoneal violation or retroperitoneal entry, but may miss specific injuries [11]. Similarly, in obese patients if the GSW is thought to be tangential through the subcutaneous tissues, CT scan can delineate the tract and exclude peritoneal violation. Laparoscopy is another option to assess peritoneal penetration, and is followed by laparotomy to repair injuries if found. If in doubt, it is always safer to explore the abdomen than to equivocate, but a period of close observation in the patient with a reliable examination and hemodynamic stability may be considered.

In contrast to GSWs, SWs that penetrate the peritoneal cavity are less likely to injure intraabdominal organs. Anterior abdominal SWs (from costal margin to inguinal ligament and bilateral mid-axillary lines) should be explored under local anesthesia in the ED to determine if the fascia has been violated. Injuries that do not penetrate the peritoneal cavity do not require further evaluation, and the patient is discharged from the ED. Patients with fascial penetration must be further evaluated for intraabdominal injury, as there is up to a 50 % chance of requiring laparotomy. The optimal diagnostic approach remains debated between serial examination, diagnostic peritoneal lavage (DPL), and CT scanning; the most recent evidence supports serial examination and laboratory evaluation [12].

Abdominal SWs of three body regions require a unique diagnostic approach: thoracoabdominal SWs, right upper quadrant SWs, and back/flank SWs. Occult injury to the diaphragm must be ruled out in patients with SWs to the lower chest. Diagnostic laparoscopy or DPL can be used to exclude diaphragmatic injury. Patients undergoing DPL evaluation have different laboratory value cut-offs than those traditional values formerly used for abdominal stab wounds (Table 9.2). A RBC count of more than 10,000/μL is considered positive, and an indication for laparotomy while patients with a DPL RBC count between 1,000/μL and 10,000/μL should undergo laparoscopy or thoracoscopy. A RBC count of less than 1,000/μL is considered negative; that is, the red cells are due to the procedure itself. Alternatively, laparoscopy may be preferred in those who cannot tolerate a DPL or those with evidence of a hemothorax or pneumothorax on chest radiograph. SWs to the flank and back should undergo triple-contrast CT to assess for retroperitoneal injuries of the colon, duodenum, and urinary tract [11] (Fig. 9.6).

Although not universally embraced, selected patients with penetrating injuries to the right upper quadrant may be candidates for NOM [13–16]. Patients must have a CT scan that documents confinement of the injury to the liver (Fig. 9.7). Additionally, the patient must be hemodynamically stable, have a reliable physical examination without evidence of peritonitis (i.e., cannot have depressed mental status), and not require blood products. Patients should be admitted for serial examination and hemoglobin monitoring; any alteration should prompt laparotomy. Violation of the diaphragm has the risk of a biliopleural fistula. An alternative approach is to perform laparoscopy to confirm trajectory of the missile or knife, and to repair the diaphragm. In addition to avoiding the morbidity of a laparotomy, the success of NOM for penetrating trauma has resulted in decreased hospital stays, lower transfusion requirements, and diminished abdominal infection rates.