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CHAPTER 264:  Trauma to the Flank and Butt ocks      1755 operative and nonoperative options. In patients in whom vascular injury is diagnosed, percutaneous transcatheter embolization with either stainless steel coils or Gelfoam pledgets can reliably arrest hemorrhage and is advancing as a nonoperative modality within trauma centers. Also using intravascular techniques, resuscitative endovascular balloon occlusion of the aorta may be employed at level 1 trauma centers and represents an intravascular “clamping” of the aorta with unresponsive shock due to intra-abdominal hemorrhage. Medication-induced coagulopathy is a management challenge in abdominal trauma patients. Patients on warfarin or on non–vitamin K oral anticoagulants are at higher risk for hemorrhage. For patients on warfarin or factor Xa inhibitors (rivaroxaban, apixaban, and edoxaban), reverse anticoagulation with prothrombin complex concentrate is available for all situations of life-threatening hemorrhage or hemodynamic instability. 22 For dabigatran, infusing the antidote idarucizumab is recommended. Consider tranexamic acid in all patients with traumatic abdominal hemorrhage.23 Based on the CRASH-2 trial, the risk of death was most reduced with tranexamic acid administration within 1 hour and in those with the most severe hemorrhagic shock, whereas treatment beyond 3 hours implicated an increased risk of death. 24 Physicians managing abdominal trauma should have tranexamic acid available within the ED. DISPOSITION AND FOLLOW-UP Patients with significant intra-abdominal injury need admission to the surgical or trauma service for definitive surgical intervention or observation. Given the high rate of concomitant injuries, even patients who suffer minor abdominal injury may need hospitalization to man age other injuries. In patients in whom ED discharge is considered, discuss appropriate follow-up and careful instructions for return to the ED. Patients who develop fever, vomiting, increased pain, or symptoms suggestive of blood loss (e.g., dizziness, weakness, fatigue) should return promptly for reevaluation. Admission for observation may be the best option in some patients. REFERENCES The complete reference list is available online at www.TintinalliEM.com. Trauma to the Flank and Buttocks Amy M. Stubbs INTRODUCTION Penetrating trauma to the flank or buttocks may result in a number of serious retroperitoneal, intraperitoneal, or vascular injuries, many of which require operative repair. Further complicating the evaluation, the signs and symptoms may be subtle or delayed in retroperitoneal, dia phragmatic, bowel, or rectal injuries. The decision to pursue an opera tive versus conservative course is informed by the emergency evaluation and imaging.  PENETRATING FLANK TRAUMA ANATOMY AND PATHOPHYSIOLOGY The flank is defined as the region between the anterior and posterior axillary lines, bordered superiorly by the sixth ribs and inferiorly by the iliac crests, containing retroperitoneal organs, soft tissue, ribs, and CHAPTER spine.1 Although a penetrating wound to the flank can produce intra peritoneal injury with the associated findings of peritonitis or hemoperitoneum, it is possible that a penetrating flank injury could injure only the retroperitoneal organs or musculoskeletal tissue, which can be difficult to ascertain from exam alone.

spine.1 Although a penetrating wound to the flank can produce intra peritoneal injury with the associated findings of peritonitis or hemoperitoneum, it is possible that a penetrating flank injury could injure only the retroperitoneal organs or musculoskeletal tissue, which can be difficult to ascertain from exam alone. The thoracic cavity, spine, intraabdominal, and retroperitoneal organs are all at risk for injury from a penetrating flank wound depending on the depth, trajectory, velocity, and construct of the projectile. Bullet or missile wounds, especially highvelocity wounds, may cause damage from direct trauma, kinetic energy, or cavitation. 2 Stab injuries are low velocity and cause injury through direct tissue damage.3 CLINICAL APPROACH Perform a primary survey using the Advanced Trauma Life Support protocol. Obtain information about the mechanism of injury, how much time has passed since the event, and the nature of the weapon. For gunshot wounds, attempt to ascertain the type of gun, number of wounds, and patient distance from the weapon. Examining the location of wounds may assist in estimating the bullet path and structures at risk for injury; however, trajectory estimates can be unreliable as bullets can fragment or ricochet. 4,5 For stab wounds, attempt to determine the size and trajectory of the weapon as well as the depth of penetration. Examine for abdominal tenderness and peritoneal signs that may indi cate intraperitoneal injury along with signs of injury to the GI or GU tracts, such as gross blood on rectal exam, at the urethral meatus, or in the urine. Spinal tenderness or neurologic deficits mandate further evaluation of the spine (Figure 264-1). Wounds near the costal margin or superior flank should raise concern for possible thoracic or diaphragmatic injury. DIAGNOSIS Patients with penetrating flank trauma who do not require emergent laparotomy need further evaluation to establish the extent of injury and to determine if the projectile has violated the peritoneum. Evaluation of flank trauma represents challenges related to its anatomic position and potential for retroperitoneal injury with late manifestations. Sparse data exist on isolated penetrating flank trauma; most of the recommenda tions for management come from studies of both flank and back trauma or flank and abdominal trauma. 6 Several diagnostic modalities exist to further evaluate penetrating flank trauma, each with some degree of limitation in its ability to exclude injury. Table 264-1 lists the diagnostic FIGURE 264-1. Bone  windows  of  abdominopelvic  CT  after  a  gunshot  wound  to  the flank. Comminuted  fracture  of  L3  with  retained  bullet  fragments  and  hematoma  in  spinal canal are visible (arrows). The patient was paraplegic and also had a perinephric hematoma. [Photo contributed by Truman Medical Center-Hospital Hill, Kansas City, MO.] Tintinalli_Sec21_p1669-1766.indd 1755 8/1/19 12:22 PM

flank. Comminuted  fracture  of  L3  with  retained  bullet  fragments  and  hematoma  in  spinal canal are visible (arrows). The patient was paraplegic and also had a perinephric hematoma. [Photo contributed by Truman Medical Center-Hospital Hill, Kansas City, MO.] Tintinalli_Sec21_p1669-1766.indd 1755 8/1/19 12:22 PM 1756 SECTION 21: Trauma TABLE 264-1 Diagnostic Modalities for Evaluation of Flank Trauma Modality Advantages Disadvantages CT Sensitive and specific for injury of peritoneal and retroperitoneal organs Useful for ascertaining injury path Can miss diaphragmatic injury or colon injuries Oral/rectal contrast, time consuming Ultrasound Rapid, portable, noninvasive Sensitive and specific for hemopericardium and intraperitoneal fluid Not sensitive for retroperitoneal or hollow viscous injuries Insufficient to rule out specific organ injury Diagnostic peritoneal lavage Sensitive for intraperitoneal injury Invasive, high false-positive rate Unable to detect diaphragmatic or retroperitoneal injuries Local wound exploration Sensitive for peritoneal violation in abdominal trauma when technically adequate Limited utility in flank/ back due to no discernable fascial planes3 Can lead to nontherapeutic laparotomy Laparoscopy Highly sensitive and specific for peritoneal and diaphragmatic injury6 Can avoid unnecessary laparotomy Invasive Not as sensitive for retroperitoneal injury FIGURE 264-3. Abdominal CT with IV contrast demonstrating a renal laceration from a stab wound. [Reproduced with permission from Block J, Jordanov MI, Stack LB, Thurman RJ (eds): The Atlas of Emergency Radiology. New York: McGraw-Hill, Inc.; 2013, Fig. 6-21.] FIGURE 264-2. Abdominopelvic  CT  with  IV  contrast  after  stab  wound  to  left  flank. Contrast extravasation is seen in the left paraspinous muscles with an adjacent retroperitoneal hematoma. [Photo contributed by Truman Medical Center-Hospital Hill, Kansas City, MO.] modalities available as well as their advantages and disadvantages (see also Chapter 263, “ Abdominal Trauma”). No single method is currently considered sufficient to rule out significant injuries and a combination of modalities, along with observation, is recommended. 6-9 Blind probing of the wound(s) with swabs or digits is not recommended.  LABORATORY TESTING AND IMAGING Initial laboratory testing and imaging often follow institutional proto cols. At minimum, obtain a hemoglobin/hematocrit, type and screen, urinalysis, urine pregnancy test (if applicable), and chest radiograph. Radiographs of the abdomen or pelvis are of minimal use unless attempting to determine trajectory. CT is the imaging modality of choice in hemodynamically stable patients with penetrating flank trauma. 3,6,10 Historically, double contrast (PO and IV) or triple contrast (PO, IV , and PR) has been recom mended. However, some evidence demonstrates that single contrast (IV) with modern multirow detector CT is sufficient to detect significant injuries (Figures 264-2 and 264-3). 11,12 The choice of imaging is depen dent on trauma and radiology protocols at the specific facility, as well as consideration of the drawbacks of PO/PR contrast administration. CT angiography is used in many medical centers now for suspected vascular injury. Free intraperitoneal fluid or air suggests peritoneal perforation. Bowel wall thickening with adjacent hematoma or contrast extravasation from the bowel suggests bowel injury. Delayed images of the GU tract are useful to detect urinary extravasation. The presence of a wound track near either the diaphragm or bowel mandates inspection for injury to either of those organs. TREATMENT AND DISPOSITION Evaluate and resuscitate patients with penetrating trauma to the flank according to standard protocols (see Chapter 254, “Trauma in Adults”).

detect urinary extravasation. The presence of a wound track near either the diaphragm or bowel mandates inspection for injury to either of those organs. TREATMENT AND DISPOSITION Evaluate and resuscitate patients with penetrating trauma to the flank according to standard protocols (see Chapter 254, “Trauma in Adults”). Obtain emergent surgical consultation. Administer broad-spectrum IV antibiotics, such as a carbapenem, to cover for gram-negative aerobic and anaerobic organisms for suspected intraperitoneal injury. 13 Exploratory laparotomy is indicated for patients who are hemodynamically unstable or who exhibit peritoneal signs after sustaining a penetrat ing wound to the flank. Resuscitative endovascular balloon occlusion of the aorta, if available, may also be considered as an option for signs of shock or hemorrhage. Selective nonoperative management, which combines serial exams and other diagnostic modalities, is appropriate for patients with stab wounds to the flank who are hemodynamically stable and have no abdominal tenderness. Traditionally, all patients with a gunshot wound to the flank underwent exploratory laparotomy; however, studies have demonstrated that selective nonoperative management is safe for specific patients with tangential injuries and no signs of instability or peritonitis. Benefits of this approach are decreased length of stay and lower rates of nontherapeutic laparotomies. 14-16 Appropriate patient selection, trauma center experience, and surgical staff availability are all key aspects to successful outcomes with selective nonoperative management. 6,8,9,14,15,17 Patients with penetrating trauma to the flank who are managed nonoperatively typically require admission to the hospital for observa tion and serial abdominal exams, which have been shown to be highly Tintinalli_Sec21_p1669-1766.indd 1756 8/1/19 12:22 PM