eMedicine Specialties > Emergency Medicine > Trauma & Orthopedics

Abdominal Trauma, Penetrating: Differential Diagnoses & Workup

Author: Paul A Testa, MD, Resident, Department of Emergency Medicine, New York University Medical Center, Bellevue Hospital
Coauthor(s): Eric Legome, MD, Chair, Department of Emergency Medicine, St Vincent's Hospital, Manhattan; Lewis J Kaplan, MD, FACS, FCCM, FCCP, Director, SICU and Surgical Critical Care Fellowship, Associate Professor, Department of Surgery, Section of Trauma, Surgical Critical Care, and Surgical Emergencies, Yale University School of Medicine
Contributor Information and Disclosures

Updated: Jul 28, 2008

Differential Diagnoses

Other Problems to Be Considered

Coagulopathy
Comorbid medical conditions
Concomitant closed head injury
Concomitant penetrating chest injury

Workup

Laboratory Studies

• Patients with penetrating abdominal trauma generally require complete laboratory profiles in case of need for emergent operation.
  • Blood type and crossmatch
  • Complete blood count (CBC)
  • Electrolyte levels
  • BUN level
  • Creatinine level
  • Glucose level
  • Prothrombin time (PT)/activated partial thromboplastin time (aPTT)
  • Venous or arterial lactate level
  • Calcium, magnesium, and phosphate levels
  • Urinalysis
  • Serum and urine toxicology screen
• Calculate the anion gap (reference range, 8-12 mmol/L) and base deficit (reference range, ±4 mmol/L) as guides to hypoperfusion.

Imaging Studies

• The imaging needs of each patient differ, depending on hemodynamic stability and associated injuries.
• Plain radiography
  • Plain abdominal radiography should be obtained with a history of projectiles or retained foreign body. The radiograph allows one to account for bullets, shrapnel, and foreign bodies. If all foreign bodies are not accounted for, consider the possibility that it is intraluminal or intravascular and a potential source of emboli distant from the site of entrance.
  • Chest radiography allows for evaluation of pneumothorax or hemothorax and is relatively specific, although insensitive, for diagnosing diaphragmatic injury.
• FAST examination: The focused assessment with sonography for trauma (FAST) examination has gained acceptance in the evaluation of penetrating abdominal trauma. Speed, noninvasiveness, and reproducibility make it a good diagnostic study to aid in rapidly diagnosing intraperitoneal injury that requires laparotomy. That is, a positive FAST result in the setting of penetrating trauma is usually an indication for laparotomy due to the high positive predictive value for a therapeutic laparotomy. Unfortunately, a negative FAST result cannot rule out the need for laparotomy and cannot be relied on to exclude important intraperitoneal injury.
• Ultrasonography: Sonographic evaluation of penetrating wounds also has been evaluated in the detection of fascial defects resulting from anterior abdominal stab injuries, reducing the need for local wound exploration. In one prospective trial, a positive fascial sonogram result obviated the need for invasive wound exploration because such patients were then taken to the operating room (OR). However, a negative fascial sonogram result did not rule out a penetration of the peritoneum.
• Computed tomography
  • Triple contrast computed tomography (CT), using intravenous, oral, and rectal contrast, enables evaluation of the intraperitoneal and retroperitoneal structures. It is useful for evaluation of penetrating flank and back wounds and is found to be 97% accurate. Exploration of these wounds is more difficult, less reliable, and therefore not indicated.
  • Abdominal CT is the most sensitive and specific study in identifying and assessing the injury severity to the liver or spleen. The presence of a contrast blush on CT or ongoing hemorrhage is indication for laparotomy or angiography and embolization.
  • The primary limitation is lack of sensitivity in diagnosing mesenteric, hollow visceral, and diaphragmatic injuries, all of which are common in penetrating trauma. Therefore, unless the wound is clearly superficial on CT scan, admission and serial observation is indicated, even with a negative CT result for injury.
  • No absolute indications exist for CT in anterior penetrating trauma. Some centers use CT as a screening tool to complement physical examination, while others perform serial examination or DPL.
  • Increasingly, CT scan is being used for penetrating, nontangential gunshot wounds with a decrease in the negative laparotomy rate. It should be used only with patients who are stable and do not have evidence of generalized peritonitis. While it has been studied in several forms, the latest study looked at intravenous contrast alone with good results.¹

Other Tests

• Almost all other tests relate to (1) a skeletal survey for associated fractures, (2) a CT scan of the brain for coincident head injuries, or (3) a retrograde urethrogram or cystogram in a stable patient who has blood at the urethral meatus or evidence of urethral or bladder injury from penetration.
• Nuclear medicine studies have no role in the acutely injured abdominal trauma patient.

Procedures

• Local wound exploration
  • In the trauma patient with an anterior stab wound, local wound exploration may be a valuable diagnostic aid. Its utility is dependent on the wound's mechanism and location. Stab wounds to the anterior abdomen are well suited for local wound exploration because many do not penetrate the fascia. Exploration requires aseptic technique, good overhead lighting, and local anesthesia. The wound is enlarged as necessary so that the posterior fascia may be evaluated. If penetration occurs or is inconclusive, the wound is considered intraperitoneal and must be evaluated further by DPL or more invasive procedures.
  • Gunshot wounds and those produced by thin instruments, such as an ice pick, are more difficult to explore, and accordingly, are generally considered intraperitoneal injuries.
  • Once the area is surgically prepared, draped, and anesthetized, the wound may be widened with gentle retraction and gently probed with a hemostat to determine if a tract exists. If the wound is small, extending it to aid visualization is accomplished with a No 10 blade scalpel. The rectus fibers may be separated by spreading in their direction using a hemostat or Kelly clamp. The posterior rectus sheath is easily identifiable as a white layer directly underlying the rectus musculature. If yellow fat or omentum is identified, a fascial violation is established.
• Diagnostic peritoneal lavage
  • The utility of DPL in the hemodynamically stable patient with penetrating abdominal injury is to identify hollow viscus or diaphragmatic injury. A DPL may be performed infraumbilically or supraumbilically. The bladder and stomach must be decompressed. An open mini-laparotomy or closed Seldinger technique may be used. Once the catheter is in place, the initial aspiration of gross blood or food particles mandates surgical exploration, and the procedure is terminated. If the aspiration is negative for blood, 1000 mL of warm Ringer lactate solution (20 mL/kg for pediatric patients) is infused rapidly and allowed to return by placing the intravenous bag on the floor.
  • Fluid is sent for analysis (eg, cell count, differential, Gram stain, bilirubin, amylase, vegetable matter, fecal matter). A positive test result varies with the mechanism of injury. A 100,000 RBC count or 100-500 WBC count may be considered positive in a stab wound. However, if a diaphragmatic injury is possible, some physicians lower the value of a positive test to 5000 RBC. Because of the more serious nature of gunshot wounds, clinicians often use a similarly lower value for a positive test when there is concern a projectile has entered the peritoneal cavity.
  • The lower the threshold for positivity, the more sensitive the test, but the higher the nontherapeutic laparotomy rate (ie, higher rate of false-positive result).
  • The primary disadvantages are invasiveness, inability to evaluate the retroperitoneum, moderate specificity for therapeutic laparotomy, and a significant false-positive rate.
• Proctosigmoidoscopy
  • This procedure is indicated for evaluation of suspected rectal or sigmoid injury. While mainly performed by surgeons, it is occasionally performed by emergency physicians.
  • The patient is placed in the left lateral decubitus position in a knee-chest manner (provided the spine is clear). The sigmoidoscope is introduced into the anal canal and directed toward the patient's umbilicus. Identification of rectal or low sigmoid colon full-thickness rents, intramural hematoma, or luminal arterial blood loss requires prompt surgical exploration.
• Laparoscopy
  • Laparoscopy is a reasonably safe, effective procedure for the evaluation and treatment of hemodynamically stable patients with abdominal trauma, and it can reduce the number of nontherapeutic laparotomies performed. In thoracoabdominal stab wounds, laparoscopy aids in the diagnosis of diaphragmatic and other intra-abdominal injuries.
  • Patients with stab wounds to the anterior abdomen or with uncertain peritoneal penetration are also candidates for diagnostic laparoscopy. Gunshot wounds to the anterior abdomen with questionable penetration may be assessed this way.
• Emergency department thoracotomy
  • Victims of penetrating abdominal trauma with loss of vital signs or in whom present with exsanguination hemorrhage that is not controllable with direct external pressure are candidates for an ED left anterolateral-left thoracotomy. The purpose of this procedure is to relieve cardiac tamponade, control cardiac bleeding, obtain proximal aortic control, and provide open cardiac massage to improve cardiopulmonary cerebral resuscitation efforts.
  • This procedure is performed only in extremely selected circumstances since survival from abdominal injury requiring a resuscitative ED thoracotomy is rare. It is much more effective if the arrest is due to cardiac injury with thoracoabdominal trauma. Patients who may be considered for thoracotomy are those who had vital signs on arrival or en route, with or without pulseless electrical activity (PEA) on the monitor. Thoracotomy is rarely successful in blunt trauma.
  • After rapidly preparing and draping the entire chest, a curvilinear incision is made from the left sternal border of the fifth intercostal space to the table, paralleling the course of the underlying rib. All tissues above the rib are divided with the scalpel, respirations are halted, and the intercostal muscle bundle above the rib is pierced with a finger or a Kelly clamp and then divided with a curved Mayo scissor for the length of the incision. The lungs are reinflated, and a rib spreader is inserted with a ratchet mechanism placed laterally. The pericardium is opened longitudinally to avoid injury to the pericardiacophrenic vessels and the phrenic nerve. Subluxing the heart into the left chest allows for open massage. The left lung is retracted superiorly using a moist laparotomy pad, and the inferior pulmonary ligament is divided using Metzenbaum scissors.
  • The tissues overlying and just lateral to the vertebral bodies contain the aorta, esophagus, thoracic duct, and countless nerves. Usually, blunt dissection frees the aorta enough to place a Satinsky or long, curved DeBakey clamp. In certain circumstances, the aorta is not identified easily, and the aorta and esophagus must be clamped en masse in a patient who is in extremis. Warm saline is essential to prevent cooling of the heart, and presser support usually is needed as well.

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