Abdominal and Renal Trauma

Published on 27/02/2015 by admin

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Abdominal and Renal Trauma

While head injuries are responsible for the majority of pediatric trauma deaths, intra-abdominal and retroperitoneal injuries can still result in significant morbidity and mortality. Diagnostic uncertainty and delays in diagnosis can lead to long-term complications and adversely impact quality of life. Injuries to intra-abdominal organs occur in 10–15% of injured children.1 The spleen is the most frequently injured organ, and low velocity mechanisms, such as falls, is the most frequent mechanism of injury. The combination of the unique anatomic and physiologic features of children and differences in mechanism result in patterns of injury unique to the pediatric population.

As just mentioned, falls are the most frequent mechanism of injury in children. However, motor vehicle crashes (MVC) are the most deadly, and are the leading cause of death for all children after the age of 1 year.2 From the perspective of abdominal trauma, and using the spleen as a marker for intra-abdominal injury, pediatric injuries tend to be the result of lower-velocity mechanisms when compared to adults. In a study that compared splenic injuries at an adult level one trauma center and a pediatric level one trauma center, MVC accounted for 66.9% of adult injuries but only 23.7% of pediatric injuries.3 On the other hand, ‘sports mishaps’ resulted in only 2.3% of the adult injuries, but 17% of injuries involving children. Even in the MVC population, pediatric injuries tend to differ from those suffered by adults. Children are less likely to be in the driver’s seat (and hence less likely to suffer injuries to the thorax from the steering wheel), and are more likely to be victims of poorly fitted restraint systems. It is an important part of the initial history to ascertain whether the pediatric victims in an MVC were restrained, and the type and appropriateness of that restraint for the child’s age.

Anatomically, the smaller size of children, as compared to adults, results in a closer proximity of organs. The abdominal wall, rib cage, and pelvic girdle are underdeveloped and provide less protection to the abdominal contents. In addition, children have less body fat, and hence, less ‘padding’ to absorb and diffuse external force.4 From the physiologic perspective, children are generally healthy and have fewer underlying medical problems than adults. It is uncommon for children to be on medications, particularly those that potentially affect hemodynamics or hemostasis. Therefore, injured pediatric patients are better able to effectively compensate for physiologic insults such as acute blood loss. It is generally accepted that children can lose up to 45% of their circulating blood volume, and exhibit tachycardia as the only abnormal vital sign.4 Persistent hypotension is an ominous finding, suggesting the failure of compensatory mechanisms and the potential development of irreversible shock. Complicating the evaluation of injured children is the normal variability of vital signs depending on age.

Initial Evaluation and Diagnosis of Abdominal Injuries

As the number of children with significant abdominal injuries is relatively low, but the consequences of a missed injury are high, accurate diagnosis is important. Initial assessment begins before the child arrives at the hospital. Important information from the first responders includes mechanism of injury, use of protective or restraint devices, condition of the child in the field, and, in the case of MVC, damage to vehicle. Once in the emergency department (ED), a thorough history and physical examination is essential. In most statistical models regarding the diagnosis of intra-abdominal injury, an abnormal physical examination is the highest variable.5–8 While the examination can be challenging given the developmental level of the child, use of comfort strategies and distraction can calm an initially distraught child to a degree that he/she can reliably participate in the evaluation. Important physical findings include vital signs (particularly the presence of persistent tachycardia), abdominal contusions or abrasions, tenderness, or distention. Particular physical findings, such as the ‘seat belt sign’ and ‘handle bar mark,’ are suspicious for the presence of intra-abdominal injury (and potential spine fracture in the case of the seat belt mark) (Fig. 16-1).9

Laboratory Testing

Laboratory testing for the purpose of diagnosing intra-abdominal injuries has generated considerable interest and conflicting results. One study reported that the combination of an abnormal physical examination and >50 red blood cells per high power field on urinalysis was a highly sensitive screen for the presence of intra-abdominal injury.5 The study, limited by the low number of children who actually had a documented injury (14 out of the total study population of 285), also concluded that laboratory abnormalities in this trauma population were relatively uncommon. The conclusion that routine laboratory studies add little to the evaluation has also been replicated in more recent studies.6,7 Conversely, studies using sophisticated regression analyses have demonstrated that elevations of aspartate aminotransferase (AST) and/or alamine aminotransferase (ALT), in combination with an abnormal physical examination, correlate with the presence of an intra-abdominal injury, although the tests are not diagnostic for a particular injured organ.8,10–12 A clinical prediction model using a combination of physical examination findings (hypotension and abnormal examination findings) and laboratory studies (AST, amylase, hematocrit, heme-positive urinalysis) successfully predicted the presence of intra-abdominal injury in a small, single center study.13 Interestingly, routine amylase and lipase determinations do not appear to be very reliable or cost effective screening tools.14 In the special population of children suspected of abuse, elevations in AST or ALT, or abnormal physical examination findings (such as bruising, distention, or tenderness), may indicate the need for further abdominal imaging looking for occult injury.15

In summary, it appears that laboratory panels in the evaluation of children at risk for intra-abdominal injuries are best utilized in conjunction with physical examination findings and as a screen to determine those children who might require further diagnostic testing, particularly imaging.

Computed Tomography

Computed tomography (CT) with intravenous contrast (IV) is the preferred modality for the diagnosis of intra-abdominal injuries in hemodynamically stable children.4 Newer generation scanners have excellent sensitivity and specificity, especially for the evaluation of solid organ injuries. Upwards of 95% of liver, spleen, and renal injuries can be diagnosed and staged by CT (Fig. 16-2). Injuries to the intestine and pancreas are more difficult to definitively diagnose by CT. However, with the addition of coronal reconstructions, CT provides significant information to guide the clinician regarding these injuries. Similarly, the risk of a ‘missed’ intra-abdominal injury in a child with a completely negative CT is very low, leading some to advocate using CT as a means to decrease the need for in-patient observation after blunt abdominal trauma.16

It has been suggested that in young children who lack visceral fat, the addition of oral contrast to the standard IV contrast may be helpful, especially in evaluating the duodenum and pancreatic head.17 The use of oral contrast, however, remains controversial due to concerns regarding aspiration, and may not provide significant additional information with current, multi-detector CT imaging. Intravenous contrast, however, is essential for the evaluation of traumatic injuries. If IV contrast is contraindicated, alternative methods of abdominal evaluation should be considered.

The radiation exposure during CT imaging has become an area of major concern in children. The use of CT has been rapidly increasing over the past decade, with over seven million scans performed on children, mostly for the evaluation of trauma and appendicitis.18 Using models extrapolated from radiation exposure from the atomic bomb explosions, a risk of one fatal cancer per 1000 CT scans performed in young children (above the baseline cancer risk of approximately one in four adults in the USA) has been estimated.19 A recently published longitudinal, population-based study in Great Britain demonstrated an increased incidence of leukemia and brain cancer after repeated CT scans in children.20 Infants and children are more sensitive than adults to the effects of radiation given their small size (larger absorbed dose per unit area) and growing organs.21 In response, the pediatric radiology community has developed an Image Gently® campaign to address the public’s concerns.21 In addition, two recent position papers, authored by the APSA Education Committee and the American Academy of Pediatrics (AAP) Radiology Committee, have addressed the issue of CT scans in children.22,23 Both endorse the ALARA principle (as low as reasonably achievable) and advocate for the use of scanners with pediatric dose reduction software, employing alternative imaging modalities (if available), limiting the number or phases of scans (for example with and without contrast or arterial and venous phases), and the use of limited scans. Other concepts include limiting the number of repeat scans and developing relationships with referring adult institutions to limit the number of scans performed on children prior to transfer.

Ultrasound

As concerns regarding CT have increased, there has been a renewed interest in the use of ultrasound (US) in the evaluation of pediatric abdominal trauma. The original descriptions about ultrasound in trauma centered on the rapid evaluation of the unstable adult trauma patient to determine the presence and source of life-threatening hemorrhage. The FAST (focused assessment with sonography in trauma) examination was developed to assess the presence of intra-abdominal free fluid (with examination of Morrison’s pouch, the pouch of Douglas, and the left flank) or fluid within the pericardial sac (subxiphoid view), and thus indicate the need for operative exploration. In multiple studies, the traditional FAST examination has been found to have a low sensitivity and specificity for the diagnosis of injury in children.24–27 A recently published large series directly comparing FAST examination in children to CT or laparotomy for the presence of free fluid concluded that a positive FAST suggested hemoperitoneum and associated abdominal injury, but a negative FAST adds little in decision making.28 In addition, since the majority of pediatric solid organ injuries, even those with significant free fluid (hemoperitoneum), can be managed nonoperatively, a positive FAST examination may not be very helpful in directing clinical care. On the other hand, the use of provider-performed ultrasound has increased dramatically over the past several years in the pediatric ED, and there is significant interest in developing algorithms that incorporate ultrasound into the evaluation of abdominal trauma.29,30 The ultimate goal is to limit the number of CT scans. In the less common scenario of the hemodynamically unstable child, a positive FAST examination supports the decision to rapidly proceed to the operating room.

Laparoscopy

Minimally invasive approaches are now well incorporated in pediatric surgical practice so it is not surprising that laparoscopy for the evaluation of abdominal trauma is being utilized. Despite the excellent anatomic definition provided by multi-detector CT, there remain areas of diagnostic uncertainty. The child with free fluid without evidence of solid organ injury, particularly with physical examination findings of a seat belt or handlebar mark, is one example. Another scenario is the child with significant abdominal tenderness with a nondiagnostic CT scan. If the findings at laparoscopy indicate the need for a formal laparotomy, an open approach can be targeted to the specific injury. In two relatively large reviews, laparoscopy was found to be safe and beneficial by avoiding laparotomy in a significant number of patients.31,32 Also, a number of injuries were amenable to laparoscopic repair. CT and laparoscopy now provide complementary information, with CT defining areas, such as the retroperitoneum, kidneys, and pancreas, which are difficult to assess using laparoscopy. On the other hand, laparoscopy allows for direct visualization of the bowel, mesentery, and diaphragmatic surfaces, regions that CT has traditionally not been as accurate (Fig. 16-3).

Management

Liver and Spleen

Close to 90–95% of injuries to the liver and spleen in children can be managed nonoperatively. It is rare for isolated low grade injuries to these organs to require blood transfusion.33 Nonoperative management (NOM) is dependent upon the accurate diagnosis and staging of the injured organ, usually by CT imaging at present. Injuries are graded according to the American Association for the Surgery of Trauma (AAST) organ injury scale, with grade I injuries representing small lacerations or hematomas and grade V injuries indicating complete vascular disruption or massive parenchymal injury (Table 16-1).34 In order to be a candidate for NOM, the child should have normal hemodynamics, and be monitored closely for signs of ongoing hemorrhage. Most children who fail NOM do so within four hours of injury as a result of shock, peritonitis, or persistent bleeding.35 Late failures are often the result of peritonitis due to an evolving intestinal injury. There are published, evidence-based guidelines for NOM in a child with a liver or spleen injury.36,37 Essentially, these guidelines recommend hospitalization for ‘grade of injury plus one’ days, and note that children with higher grade injuries may benefit from intensive care unit observation. Routine follow-up imaging is not indicated, and children can return to regular activity after grade of injury plus two weeks from the time of injury. More recent work challenges these recommendations, finding that more abbreviated periods of bed rest and hospitalization does not result in delayed bleeding or return to the hospital.38 Fortunately, most splenic and hepatic injuries in children will resolve without the need for operative intervention with excellent long-term outcomes.

TABLE 16-1

Liver/Spleen Injury Grading Scale from the AAST

image

From Tinkoff G, Esposito TJ, Reed J, et al. American Association for the Surgery of Trauma Organ Injury Scale I: spleen, liver, and kidney, validation based on the National Trauma Data Bank. J Am Coll Surg 2008;207:646–55.

While bleeding from most solid organ injuries in children will stop, there are a small number in which the bleeding is significant. Tachycardia, not responsive to fluid resuscitation, is the initial sign of shock in these children. Hypotension is often a late finding and suggests significant hemorrhage. Evidence of ongoing bleeding with an abnormal abdominal examination or a positive abdominal FAST examination necessitates urgent operative exploration. Rapid transfusion protocols, while not formally validated in children, are utilized with the goal of 1 : 1 : 1 transfusion of packed red blood cells (PRBC), fresh frozen plasma (FFP), and platelets. In infants and children, this translates to 20 mL/kg of PRBC, FFP and platelets.39 In the operating room, a rapid transfusion device and cell saver should be available in the event of rapid blood loss. The patient is prepped from neck to knees to allow for entrance into either the chest or abdomen, and to have access to the femoral vessels. Upon entrance to the abdomen, the four quadrants are packed to tamponade the bleeding and allow the anesthesiologists to ‘catch-up.’ The peritoneal contents are then explored in a systematic fashion. The goal of initial operative exploration is to stop bleeding and control the fecal stream (damage control).

Splenectomy easily controls bleeding in the hemodynamically unstable patient with active exsanguination from a massively damaged spleen, although at the theoretical cost of a long-term risk of postsplenectomy sepsis. Children with splenic injuries who have ongoing bleeding, but are not in shock, are potential candidates for splenic sparing operations. Partial splenectomy and mesh splenorrhaphy are techniques that can successfully save splenic parenchyma, although they may be time consuming, and are therefore not appropriate in the unstable patient.40

Postsplenectomy sepsis is a rare, but potentially fatal consequence of splenectomy due to overwhelming infection by encapsulated organisms. The reported incidence is around 0.23% a year, with an increased incidence in children less than 2 years of age, and those that underwent splenectomy for hematologic reasons.41 Vaccination with the 23-valent pneumococcal vaccine, as well as vaccinations against Haemophilus influenzae type B and meningococcus, should be administered after splenectomy. With high grade splenic injuries managed nonoperatively, assessment of splenic function may also be indicated.

A major hepatic injury is considerably more difficult to control in the operating room. The segmental anatomy of the liver and the location of important arterial, venous, and portal structures is very important. Peitzman and Marsh recently reviewed operative techniques for the management of complex liver injury.42 Key components of operative control of hepatic parenchymal injury include adequate exposure, an experienced co-surgeon, good anesthesia support, and supradiaphragmatic intravenous access. They recommend initial management of deep parenchymal fractures with compression, followed by suture ligation of bleeding vessels, and the avoidance of deep liver sutures. The Pringle maneuver can help differentiate between hepatic arterial bleeding (decreases when the clamp is engaged) and hepatic venous bleeding. Ideally, intermittent clamping of the porta hepatis should be performed to decrease the degree of hepatic ischemia.

Large fractures are best treated with anatomic or nonanatomic resection, assuming enough residual liver remains. Resection can be efficiently performed using mechanical staplers. While the definitive operation must control bleeding and bile leak, debride nonviable tissue, and adequately drain the resected margin, control of hemorrhage is the primary concern in an emergency operation. Temporizing maneuvers, such as packing with control of bleeding, are performed and a temporary abdominal closure is created to allow for ongoing resuscitation and to prevent abdominal compartment syndrome. Vacuum dressings have been developed specifically for this purpose, but techniques such as the ‘Bogota bag’ are still viable alternatives. Multiple trips to the operating room for wash-out, packing removal, and treatment of other injuries may be required before the patient is ready for formal abdominal closure.

Abdominal Compartment Syndrome

Abdominal compartment syndrome (ACS) is defined as sustained intra-abdominal hypertension (IAH) that is associated with new onset organ dysfunction or failure.43,44 It is an uncommon, but potentially lethal condition that occurs when abdominal distension associated with IAH causes reduced perfusion to the intra-abdominal organs. The result is ischemia and refractory metabolic acidosis along with interference with cardiopulmonary function secondary to reduced preload from decreased central venous return to the heart, decreased respiratory compliance, and decreased functional residual capacity.45 ACS is associated with a 40–60% mortality in children.4648

As IAH in children is different from adults, the current proposed working definition for ACS in children is an elevated intra-abdominal pressure (IAP) of 10 mmHg or greater with the development of new or worsening multiorgan failure.44 There are three different types of ACS: (1) primary ACS refers to ACS that occurs due to a primary intra-abdominal cause such as abdominal trauma; (2) secondary ACS or extra-abdominal compartment syndrome occurs as a result of massive bowel edema secondary to sepsis, capillary leak, and other conditions requiring massive fluid resuscitation; and (3) tertiary ACS or recurrent ACS in which ACS recurs after resolution of an earlier episode of either primary or secondary ACS.49 IAP can be measured by using the bladder pressure. If IAH is detected, serial IAP measurements are needed. It is important to note that clinical examination is an inaccurate predictor of IAP and should not be substituted for IAP measurement.50

Initial management strategies in the trauma patient include improving abdominal wall compliance via adequate sedation and paralysis, evacuation of intralumenal intestinal contents, evacuation of large abdominal fluid collections, optimization of fluid administration by goal-directed therapies and correcting positive fluid balance, and optimization of abdominal perfusion pressure.51 Over the last ten years, three major changes have led to significant reductions in the incidence and mortality from ACS in adult trauma patients. These are adoption of massive transfusion protocols and 1 : 1 blood to plasma transfusion strategies in trauma, the widespread use of damage control and open abdomen approaches to the polytraumatized abdominal cavity, and an increased use of plasma and colloids in the resuscitation of burn patients.51 Similar strategies and an increased awareness of ACS in pediatric trauma patients may also result in improved outcomes.

In the unstable trauma patient who requires an emergent laparotomy and massive fluid resuscitation, maintaining an open abdomen with planned staged closure may prevent the development of ACS but often needs to be performed prophylactically (Fig. 16-4A). In patients who develop ACS, early intervention via emergent decompressive laparotomy and some form of temporary abdominal wall closure, while awaiting resolution of IAH, can be lifesaving (Fig. 16-4B).46,48,52 The goals of operation are to decrease the elevated IAP to stop organ dysfunction, allow room for continued expansion of the viscera during ongoing resuscitation, provide temporary abdominal closure, prevent excessive fascial retraction, and allow a means for continued evacuation of fluid from the abdominal cavity.51 Application of a negative pressure wound dressing to the open abdomen is a useful temporary dressing as well as a modality to remove edema from the abdominal cavity and intestinal wall.53 Temporary patch abdominoplasty with a variety of materials and the placement of a silo have also been utilized in the setting of an open abdomen. However, these methods lack the capability to actively evacuate excess fluid. Subsequent staged abdominal closure with sutures or patch abdominoplasty is performed when IAH is corrected.

Role of Interventional Radiology

Angioembolization is a technique that is frequently utilized in adults with splenic or hepatic vascular injuries. The role of interventional radiology in children is less well defined. For example, embolization in adults is frequently employed for the management of a contrast blush demonstrated on CT scan. Multiple studies in children, however, demonstrate that a contrast blush is associated with the need for operative intervention in less than 20% of splenic injuries.54–56 Long-term follow-up of large cohorts of children with splenic and hepatic injuries also reveal a very low rate of late bleeding, suggesting that the rate of bleeding from an initially unrecognized arterial pseudoaneurysm is also very low.36,37 On the other hand, small single-center studies and case reports demonstrate that interventional radiological techniques are safe in children, and have been effective when utilized.5760 The population that seems most amenable to this technique are children with evidence of ongoing bleeding but are hemodynamically stable, or those that develop bleeding later in their hospital course. In our institution, we have effectively utilized angioembolization in a few cases of hepatic arterial bleeding (Fig. 16-5).

Special Considerations with Liver Injuries

The initial concern with hepatic injury is control of bleeding, but injury to the biliary system can also occur. High grade liver injuries are associated with a small (4%) risk of a significant bile leak.61 If the patient has required operative management for the injury, it is prudent to place closed suction drains around the liver, particularly if a nonanatomic resection was performed. With nonoperative management, the development of a significant bile leak is often heralded by feeding intolerance, abdominal pain, elevations in hepatic enzymes, and fever.62 Abdominal imaging (either ultrasound or CT) reveals the presence of a fluid collection. Initial management involves the insertion of drains, usually performed percutaneously with image guidance.

Endoscopic retrograde cholangiopancreatography (ERCP) has been used to identify the location of the leak, and more importantly, with the addition of sphincterotomy, to decrease biliary pressure and promote internal drainage.63,64 Placement of biliary stents can also be performed, both to improve drainage and to treat the ductal injury. Therapeutic ERCP requires operator expertise, and heavy sedation or general anesthesia for the procedure to be safely performed in children. In the case of stent placement, a second endoscopic procedure to remove the stent is usually necessary. Complications of ERCP include bleeding, sepsis, and stent migration or clogging.

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