24 PENETRATING ABDOMINAL TRAUMA
Clay Cothren M.D., Ernest E. Moore M.D.

1. Why is there a different approach to stab and gunshot wounds?

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Whereas one third of stab wounds to the anterior abdomen do not penetrate the peritoneum, 80% of gunshot wounds violate the peritoneum. Furthermore, penetration of the peritoneum by a bullet is associated with visceral or vascular injuries in > 95% of cases, whereas only one third of stab wounds violating the peritoneal cavity produce significant injury. (See Figure 24-1.)

Figure 24-1 Management of patients witih penetrating abdominal trauma.

2. What is the secondary survey for a penetrating abdominal wound?

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The ABCs (i.e., airway, breathing, and circulation) are the first priority in every trauma patient. Look everywhere-watch out; it is easy to overlook synchronous injuries. This includes looking for additional entry or exit sites; evaluation for blood in the gastrointestinal (GI), genitourinary (GU), and gynecologic systems; and blunt mechanism injuries (e.g., some unfortunate patients are both stabbed and beat up). The “mechanism” of injury includes the time of injury, type of weapon, length or caliber of the weapon, depth of penetration, and estimated blood loss at the scene.

3. What are the appropriate initial studies in patients with penetrating abdominal trauma?

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In stable patients, a chest radiograph excludes hemo- or pneumothorax and determines the position of intravenous catheters (e.g., endotracheal, nasogastric, and pleural tubes). Biplanar abdominal radiographs are helpful in locating retained foreign bodies, such as bullets, and may reveal pneumoperitoneum. Entrance and exit wounds should be identified with a radiopaque marker. This may be helpful in determining the trajectory of missiles. Injuries in proximity to the rectum obligate sigmoidoscopy (see Chapter 28), whereas injuries in proximity to the urinary tract should be evaluated with computed tomography (CT) scanning (see Chapter 31).

Figure 24-2 An example of how the path of a bullet through contorted body can produce confusion when the patient is examined in the emergency department. An entrance wound will be found at the left upper arm and an exit wound at the medial aspect of the right knee. The bullet could have damaged any structure that was in between these two wounds when the patient’s body was contorted.

4. What are the indications for prompt laparotomy in patients with stab wounds?

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Abdominal distention and hypotension, overt peritonitis, and obvious signs of abdominal visceral injury (hematuria, hematemesis, proctorrhagia, evisceration; palpation of diaphragmatic defect on chest tube insertion; radiologic evidence of injury to GI or GU tracts) mandate immediate exploration.

5. What are the indications for immediate laparotomy in patients with gunshot wounds?

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Because of the high incidence of visceral injury, early exploration is indicated for all gunshot wounds that violate the peritoneum.

6. When is emergency department (ED) thoracotomy indicated for a penetrating abdominal wound?

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Almost never. But it should be considered when a patient, after penetrating trauma, presents in cardiac arrest or profound hypotension (< 60 mmHg) refractory to initial resuscitation. Thoracotomy allows open cardiac massage and access to cross clamp the descending aorta to improve coronary and cerebral perfusion as well as decrease subdiaphragmatic hemorrhage. Closed cardiac massage is ineffective when the patient is hypovolemic. (See Figure 24-3.)

7. What is the general plan for abdominal exploration in patients with penetrating trauma?

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A midline abdominal incision provides rapid entry and wide exposure; it may be extended as a median sternotomy to access the chest or continued inferiorly into the pelvis. The aorta should be palpated to assess blood pressure (BP). All findings, including a low BP, should be communicated to the anesthetist. Evacuation of blood and placement of tamponade packs into areas of suspected blood loss should be followed by exploration of the wound tract. Actively bleeding areas are digitally controlled until the culprit vessel can be occluded. Hollow visceral injuries are temporarily isolated with noncrushing clamps. The entire abdomen is systematically explored before undertaking extensive repairs so that injuries can be prioritized.

Figure 24-3 Treatment of gunshot wounds.

8. How is an anterior abdominal stab wound evaluated in asymptomatic patients?

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The first step is local exploration of the wound to determine peritoneal penetration. If the tract clearly terminates superficially, above the fascia, no further evaluation or treatment is required. If the fascia is penetrated or the peritoneum violated, diagnostic peritoneal lavage (DPL) is performed. Double-contrast (oral and intravenous) CT scanning is not routinely used because of its relative insensitivity for detecting hollow visceral injuries. Ultrasonography is useful for detecting intraperitoneal fluid but is helpful only if the results are positive. (See Figure 24-4.)

Figure 24-4 Treatment of stab wounds.

9. What constitutes a positive DPL result after penetrating trauma?

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A grossly positive tap (aspiration of >10 mL of blood or aspiration of GI or biliary contents) mandates immediate exploration. A negative initial aspirate result is followed by the instillation of 1000 mL of saline (15 mL/kg in children) into the abdomen through a dialysis catheter, followed by gravity drainage of the fluid back into the saline bag. The finding of > 100,000/mm3 red blood cells (RBCs), the combined elevation of amylase > 20 IU/L and alkaline phosphatase > 3 IU/L, or elevated bilirubin level are also indications for exploration.

10. How are stab wounds to the flank and back evaluated?

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The incidence of significant injuries is 10% for stab wounds to the back and 25% for stab wounds to the flank. However, evaluation of such wounds is problematic because the retroperitoneum is not sampled by DPL and physical examination is even less sensitive. The major concern is missed colonic perforation. At present, triple-contrast (oral, intravenous, and rectal) CT scan and serial physical examination are the two primary modes of assessment. Operative exploration is advisable if CT scanning demonstrates wound trajectory in the vicinity of the colon.
KEY POINTS: CLINICAL APPROACH TO PENETRATING ABDOMINAL TRAUMA

1. Gunshot wounds to the abdomen generally require operative exploration (> 80% violate the peritoneum).
2. Stab wounds with evisceration or hypotension are operatively explored.
3. Stab wounds in stable patients are managed with local wound exploration (66% violate the peritoneum) plus DPL, ultrasound, or CT scan. If tests are positive, the patient goes to the operating room.
4. During celiotomy, pack the upper quadrants and pelvis; then address vascular, solid organ, and alimentary tract injuries in succession.
5. Prophylactic antibiotics for the first 24 hours decrease postoperative wound infection.

11. How is a lower chest stab wound evaluated?

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The lower chest is defined as the area between the nipple line (fourth intercostal space) anteriorly, the tip of the scapula (seventh intercostal space) posteriorly, and the costal margins inferiorly. Because the diaphragm reaches the fourth intercostal space during expiration, the abdominal organs are at risk (even after what appears to be a clear “chest” wound). Stab wounds to the lower chest are associated with abdominal visceral injury in 15% of cases, whereas gunshot wounds to the lower chest are associated with abdominal visceral injury in nearly 50% of cases. Thus, wounds to the lower chest should also be managed as abdominal wounds to rule out intraabdominal injury. In the case of lower chest stab wounds, an RBC count of > 10,000/mm3 warrants laparotomy to rule out a diaphragmatic injury; thoracoscopic exploration (not thoracotomy) may also be performed for counts of 1000-10,000/mm3.

12. Which patients with abdominal gunshot wounds are managed nonoperatively?

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Stable patients with tangential missile tracts or equivocal peritoneal penetration are candidates for DPL. The cutoff for RBC counts is reduced to 10,000/mm3, above which laparotomy is indicated. Patients with a negative DPL result are observed for 24 hours. For RBC counts of 100-10,000/mm3, laparoscopy may be used to exclude intraperitoneal injury. Selective management of gunshot wounds to the back and flank are generally based on triple contrast CT.

13. What is the role for presumptive antibiotics?

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Short courses (< 24 hours) of high-dose antibiotics are initiated only when the decision has been made to perform a laparotomy. Coverage of both anaerobic and aerobic flora is desirable. Tetanus prophylaxis should be given to all patients with penetrating injuries.