Imaging of Trauma Patients

I. Introduction

The condition of the patient and the specific type of injury that is suspected determine the imaging modality that is most appropriate (e.g., plain-film radiography vs. computed tomography [CT] scan). In addition, the availability and location of imaging equipment as well as the clinical capabilities to support, monitor, and treat the patient during imaging are crucial in deciding how to proceed with imaging. Regardless of the type of imaging selected, the trauma patient requires constant monitoring and trauma team presence. The trauma team should plan the sequence of the resuscitation to minimize time loss and avoid radiographs that are likely to be technically impossible or have minimal diagnostic yield.

A.

Plain radiography remains an essential component of the immediate evaluation of the injured patient, especially those with injuries to the chest or obvious fractures. The seriously injured patient should undergo lateral cervical spine, AP chest, and AP pelvis radiographs as a part of the primary survey. This set of films is commonly referred to as the trauma series. These films should be accomplished without moving the patient from the trauma resuscitation room. The need for further films or studies will be based on the mechanism of injury and findings during the primary and secondary assessments. Some authors advocate skipping the lateral C-spine series in patients without neurological deficit and routine use of CT of the neck.

Initial chest x-ray studies are usually performed in the supine position. After the initial stabilization of the patient, an upright film may be obtained to better assess for aortic injury, pneumothorax, or pleural effusion. In order to determine trajectory of missiles in the case of penetrating wounds, radiopaque markers should be placed over each skin penetration site and radiographs obtained.

B.

Computed tomography has greatly advanced the diagnosis and management of the injured patient. The CT scan, which has become the standard modality used in the early diagnosis of head injury and pelvic fracture, provides a more comprehensive evaluation of chest injuries and maxillofacial fractures and allows for specific diagnosis of injury to the organs of the abdomen and retroperitoneum. The accuracy and speed of CT imaging has increased with development of spiral and multislice units. The increasing availability of multislice helical CT in or near the emergency department has expanded the role of CT in the trauma setting, allowing for a fast and comprehensive evaluation of the head, spine, thorax, abdomen, and pelvis, often in a single study. Newer multidetector-row computed tomography (MDCT) scanners allow for a thorough evaluation of the seriously injured patient in a single scan lasting only a few minutes.

C.

Magnetic resonance imaging (MRI) has several advantages over CT scan, particularly in the evaluation of soft tissues. MRI offers the ability to obtain images in sagittal, coronal, and oblique planes without any contrast administration, and can be used to define shear injuries to the brain, injuries to the spinal column and cord, or vascular abnormalities that are not apparent on other films. However, MRI is time-consuming, allows minimal access to the patient during the procedure, and has limited application in the initial evaluation of the trauma patient. Although the duration of studies has decreased with the introduction of newer scanners, MRI has a limited role in the acute trauma setting.

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D.

Ultrasonography is being used more frequently in the management of trauma patients. The focused abdominal sonography for trauma (FAST) is routinely used in most trauma centers and has largely replaced the diagnostic peritoneal lavage (DPL) in unstable patients. A rapid diagnosis of hemoperitoneum can be made noninvasively in the trauma patient with a sensitivity of approximately 85%. Ultrasound (US) can also be used to assess the hemithoraces and, in experienced hands, peripheral vascular injury.

E.

Angiography has been largely replaced by newer CT modalities in the diagnosis of vascular traumatic injury. It does, however, still play an important role in the definitive diagnosis of vascular injury, particularly when scans are equivocal or negative in the face of a high index of suspicion. In addition, its therapeutic role in such injuries has expanded. Angiography with embolization is the procedure of choice for difficult-to-access injuries (e.g., those to the vertebral artery, pelvic vessels, retroperitoneum) and selected vessels of the chest, abdomen, and large muscle masses.

II. Skull and Brain Trauma

A.

Plain-film radiography (i.e., skull x-ray studies) has limited indications in patients with blunt head injury. Plain films are sometimes indicated for penetrating injuries of the skull to determine the course, location, or number of gunshots or foreign-body fragments, as well as possible depressed skull fragments.

B.

Patients with a significant head injury, history of loss of consciousness (LOC), or postconcussive sequelae require immediate evaluation by CT scan. CT scan of the brain should be the initial screening tool for patients with symptoms indicating moderate to high risk of closed head injury. Technically, the CT scan images should be displayed with three windows: brain (shows edema, gray-white interface, ventricles, and cisterns), bone (outlines fractures, bony fragments), and blood (mass lesions, hemorrhage). Contrast enhancement is not used in the initial study.

• Common CT findings of brain injury
  • Basilar skull fractures can occur in 20% of craniofacial injuries, and CT is essential for complete evaluation. However, a negative CT scan does not exclude basilar skull fracture, especially with positive physical findings. Basilar skull fractures have significant associated morbidity, including cere-brospinal fluid (CSF) leak, damage to the internal carotid artery, and facial nerve injury. Multislice CT with multi-planar reconstruction of thin sections greatly improves the ease and accuracy of diagnosing basilar skull fractures.
  • Epidural hematomas result from the rupture of arteries and large venous sinuses resulting in an accumulation of blood that strips the dura off the inner table of the skull. The temporal region of the skull is most commonly injured, resulting in a tear of the middle meningeal artery. The characteristic appearance of an epidural hematoma is a biconvex (lentiform) fluid collection that does not cross the skull suture lines but can cross the midline if venous sinuses are ruptured.
  • Subdural hematomas result from the dissection of blood from ruptured veins that bridge through the subdural space. These hematomas are generally located between the dura and the arachnoid membrane. The typical subdural hematoma is a crescent-shaped fluid collection that conforms to the calvarium and underlying cerebral cortex. Recognition of atypical subdural hematomas is sometimes aided by coronal CT scan or repeat CT scan with enhancement.
  • Subarachnoid hemorrhage is seen commonly in the basilar cisterns of patients following head trauma. Non-contrast-enhanced CT detects about 90% of subarachnoid bleeding within the first 24 hours, regardless of cause, as the higher density of blood replaces the water density of CSF in the cistern and sulci.
  • Shear injury or diffuse axonal injury (DAI). Most brain parenchymal injuries are caused by shear-strain lesions; multiple and bilateral injuries are common. Linear and rotational acceleration-deceleration mechanisms

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    cause shearing along interfaces of tissue of different densities, such as CSF and brain as well as gray-white junctions with the brain and meninges. Unenhanced CT scan may show multiple small focal hemorrhagic lesions with minimal mass effect, but it is an insensitive test. In a patient who is severely depressed neurologically with a relatively normal CT study, the possibility of diffuse brain injury (or cerebrovascular injury) should be considered. MRI is more accurate in diagnosing diffuse axonal brain injury.
  • Cerebral contusions and intraparenchymal hematomas are relatively common findings seen on brain CT after injury. Such injuries can coalesce or enlarge. Routine follow-up CT is recommended in these patients within 24 to 48 hours.

III. Facial Trauma

Facial injuries are seldom life threatening, but often are associated with more acute problems, such as airway obstruction, head or cervical spine injury, or globe injury. Occasionally, hemorrhage into the nose, nasopharynx, or mouth requires immediate attention.

A.

Plain radiographs can be helpful for triage and initial management of facial injuries but are less comprehensive and confirmatory than other imaging modalities. Because of this, CT is preferred to evaluate facial fractures.

B.

CT scans of the face can be obtained at the time of CT scan of the brain, but only as patient condition permits. Axial and coronal CT sections are obtained routinely in the stable patient. Computer-aided, three-dimensional (3D) reconstructions from thin axial sections provide optimal delineation of midfacial fractures and the spatial relationship of the fragments. These reconstructions have become much more available and valuable with access to multislice CT technology.

IV. Spine Injuries

Every patient with an appropriate mechanism of injury (MOI) must be considered to have a spine injury until such is proved otherwise, either radi-ographically or clinically.

A.

Cervical spine. An alert, communicative adult trauma victim without distracting injury who denies symptoms, such as neck pain, without drugs or alcohol on board, and has no signs, such as neck tenderness, may be “cleared” on the basis of clinical examination. Patients with head injury often have accompanying cervical spine (C-spine) injuries, and radiographic evaluation of the C-spine is essential. The unconscious, intoxicated, noncommunicative, or multi-injured patient needs radiographic clearance. The cervical collar must not be removed until the C-spine has been evaluated and cleared. 1. Techniques for obtaining adequate plain-film radiographs for C-spine clearance

• The plain-film lateral view of the C-spine is not adequate unless C1 through T1 are visualized. If the shoulders obscure the lower cervical and upper thoracic spine, caudal traction of the arms must be applied during filming, unless contraindicated on clinical grounds. Useful techniques to further define the C-spine include the “swimmer's view” or left and right oblique views. Failure to adequately visualize the cervicothoracic junction or the craniocervical junction will necessitate CT scan.
• Technically adequate lateral, anteroposterior (AP), and open-mouth odontoid C-spine films are the minimal views necessary to evaluate the C-spine radiographically. A small percentage of patients with C-spine injury have only ligamentous injury and grossly normal static plain radiographs. Other studies, such as flexion-extension views, left and right oblique views, CT scan, or MRI, may be required to delineate these injuries or investigate areas that are not well visualized on plain films.
  • Active flexion-extension views are done voluntarily by the alert and cooperative patient only to the limit of pain tolerance. In the unconscious

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    patient, fluoroscopic examination of passive flexion and extension of the C-spine can be performed. This examination requires a physician familiar with fluoroscopic technique and recognition of the ligamen-tous instability of the spine. Recent practice tends to use flexion-extension views less often and rely on CT with reformatting and MRI when needed.
  • The purpose of the radiographic evaluation often is to identify possible C-spine bony injury that has not caused a neurologic deficit. In the hemo-dynamically unstable patient, protect and immobilize the spine, treat the condition causing instability, and clear the spine when the patient's condition permits. Do not spend time attempting to clear the C-spine in a hemodynamically unstable patient.
  • The availability of a CT scan within or near the emergency department facilitates emergent evaluation of C-spine trauma. In particular, MDCT offers the opportunity to obtain definitive and easily interpretable imaging of the C-spine quickly. These scanners also offer greater flexibility in three-dimensional image reconstructing. Reliable coronal and sagittal reformations are easily obtained from the initial scan without the need for reimaging. CT scan is the imaging modality of choice for suspected fractures and fracture-dislocations of the spine in which plain films are not diagnostic. These scans are usually performed on an axial plane with thin (1 mm) cuts.
  • MRI is the imaging procedure of choice for evaluation of injuries to the spinal column and cord but is a poor imaging technique for bone. In patients with myelopathy, MRI can establish the location, extent, and nature of the cord injury, as well as demonstrate the location and nature of nerve root injury in patients with radiculopathy. An MRI should be obtained to evaluate the spinal cord or suspected ligamentous injury, such as disruption of the posterior ligament complex due to anterior subluxa-tion (whiplash).

B. Thoracic and lumbar spine

Plain films of the thoracic and lumbar spine should be obtained whenever signs or symptoms suggest a spine injury or when mechanism of injury indicates a high probability of spine injury. In the patient with distracting injuries (e.g., chest or pelvic fractures) or a concomitant C-spine injury, a complete thoracic and lumbar (T&L) spine series is necessary. Certain mechanisms of injury warrant radiographic evaluation of the T&L spine: automobile-pedestrian collisions, rollovers, ejections from a vehicle, collisions involving unrestrained automobile passengers, motorcycle crashes, or falls from a height.

• Radiographs must include two views of the area of concern: usually AP and lateral. Oblique views can be helpful, but CT scan directed to the suspected area of injury is preferred. At times, portable studies are not possible because of the patient's large size. In this circumstance, the patient should have these films done in the radiology department, with proper monitoring and trauma team presence. MDCT also offers the ability to reliably review areas of concern by reformatting images obtained from scans of the chest, abdomen, and pelvis. We routinely generate 3-D reconstruction of the CT thoracolumbar spine images as part of our chest/abdomen/pelvis CT.

V. Chest Trauma

A.

The chest x-ray is the fundamental and primary examination in chest trauma. A frontal AP chest radiograph should be obtained in all major trauma cases. Ideally, an erect chest film is obtained because the anatomic alterations caused by the supine position can simulate disease (e.g., a widened mediastinum or interstitial lung disease) and mask pleural effusions or pneumotho-rax. However, the upright position is often not possible. To decrease magnification artifacts, the distance from the x-ray tube (camera) to the film should be

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maximized to approximately 60 to 72 inches (5–6 ft) in either the supine or reverse Trendelenberg position.

• Acute aortic injury should be suspected in any patient who suffers a significant deceleration injury. Among those patients who survive, the most common type and site of aortic injury is an incomplete tear through the intima and media of the descending thoracic aorta, just distal to the left subclavian artery. Mediastinal hemorrhage is present in most patients with aortic injury. However, 7% to 10% of patients with thoracic aortic injury have a normal admission chest x-ray study. In addition, only 10% to 20% of patients with plain chest film findings of mediastinal widening prove to have an aortic laceration.
  • A patient who has radiographic evidence of mediastinal bleeding may be clinically stable enough to allow definitive imaging evaluation of the aorta. There are common radiographic findings on plain chest film that are associated with blunt thoracic aortic injury, including a widened mediastinum (>8 cm), obliteration of the aortic knob, aortopulmonary window opacification, left apical pleural cap, deviation of the trachea to the right, depression of the left mainstem bronchus, widened paraspinous stripe, and a left pleural effusion. Any of these findings alert the physician to the possibility of aortic injury. Due to limitations of plain-film radiography in the trauma setting, any adult patient with significant blunt mechanism of injury should undergo CT evaluation of the thorax.
• CT scan is now the imaging modality of choice for the definitive diagnosis of aortic injury. Scanners using spiral and multislice technology are more accurate than earlier generation CT in the evaluation of the thoracic aorta and have been shown to accurately detect aortic injury. A complete scan of the chest plus the abdomen and pelvis can now be obtained without any increase in contrast exposure or time. CT findings of suspected aortic injury should be considered as representing:
  • Normal (no mediastinal blood, normal aortic contour)
  • Positive (mediastinal hemorrhage plus abnormal aortic contour)
  • Equivocal (mediastinal hemorrhage without an apparent aortic or arterial abnormality)
  Depending on other factors, including local experience and expertise and the degree of clinical concern, patients with unequivocally negative or positive studies can often be managed without aortography. Any uncertainty regarding aortic or major vascular injury requires catheter angiography, assuming adequate hemodynamic stability. CT may not be adequate in detecting injuries to the branches of the aortic arch. Therefore, a high level of clinical suspicion of an injury to the great vessels should lead to angiographic evaluation. Angiography remains an important diagnostic and therapeutic option for major vascular injury in trauma.
• The diagnosis of diaphragmatic rupture is difficult to make on plain film. Apparent elevation and distortion of the hemidiaphragm (usually the left) can be evident along with ancillary findings such as pleural effusion or rib fractures. Disruption of the diaphragm, the presence of abdominal contents outside the contour of the diaphragm (i.e., abdominal organs lying in a dependent position near the ribs), nasogastric tube in the chest, and the “pinched” appearance of a herniated bowel are reliable signs. CT scan using sagittal and coronal reformations can be useful in appreciating the altered contour of the diaphragm, but even with CT scan, this diagnosis can be difficult. The optimal imaging procedure for diagnosis of equivocal diaphragmatic rupture is MRI in the sagittal and coronal planes. However, MRI should be employed in the trauma setting only after the patient has been stabilized. In the acute setting, with an unstable or marginal trauma patient, newer helical CT is the diagnostic procedure of choice.
• Most lung parenchymal and pleural space abnormalities are adequately evaluated by plain radiograph examinations. CT scan can reveal unsuspected

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  pneumothorax or hemothorax, commonly seen on the upper cuts of an abdominal CT scan.

VI. Abdominal Trauma

A.

Penetrating trauma from gunshot wounds (GSWs) to the abdomen constitutes a special problem in preoperative evaluation. Chest and abdominal plain films are necessary to determine trajectory and localization of opaque foreign bodies and to identify injury in the stable patient. Large radiographs are used with radi-ographic markers placed over each skin penetration site. Two films are usually necessary, one under the chest and the second overlapping the chest slightly but covering the abdomen and pelvis.

• Some authors advocate a “one-shot intravenous pyelogram (IVP),” which can assist in evaluating the GSW if the kidney or ureter has been injured. Specifically, it can prove both the presence and the function of the contralat-eral kidney. The yield however, is very low in the patient without hematuria. A more accurate study for the evaluation of renal injury is the excretory phase CT, which involves repeating the pertinent cuts after contrast has reached the collecting system. This accurate evaluation of the renal collecting system adds only a few minutes to the standard abdominal CT, and may also be valuable in evaluating blunt renal injury. The technique for an IVP is:
  • Large-bore intravenous (IV) catheters are used to inject contrast material.
  • 100 mL of 60% contrast is infused rapidly.
  • A 2-minute postinjection film is obtained to show a bilateral nephrogram.
  • Contrast material should be visualized in the renal collecting system and ureters on a 10-minute film.
  • This study is contraindicated in patients with a severe intravenous allergy.
• Findings include:
  • Delayed function and visualization can be seen in renal contusion and minor parenchymal fractures.
  • Nonvisualization of a portion of the kidney usually indicates injury to that specific area and may require additional studies (i.e., CT scan or angiography).
  • Nonvisualization on one side is typical of major vascular injury such as renal artery injury, thrombosis, or renal pedicle avulsion. Unilateral non-visualization prompts immediate arteriography or surgery to establish diagnosis.
    Many centers prefer plain-film evaluation and surgical exploration with on-table IVP. This is more expedient if the abdomen requires exploration and avoids unnecessary use of dye or delays in definite surgical evaluation and repair.
• Stable patients with stab wounds to the back or flank can often be evaluated by triple-contrast-enhanced CT scan. Gunshot wounds that are thought to be tangential or extraperitoneal also can be evaluated with this study. Contrast material is administered orally, intravenously, and rectally prior to imaging.

B. Blunt trauma

In selecting the various diagnostic methods to evaluate blunt abdominal trauma, many factors are considered: clinical status of the patient, accuracy of the results, experience and expertise of those performing and interpreting the examination, cost, safety, and availability of the procedure.

• Plain radiography is not helpful for identification of significant abdominal injuries following blunt abdominal trauma.
• CT scan has replaced diagnostic peritoneal lavage (DPL) as the method for screening blunt abdominal trauma in stable patients. (Focused abdominal sonography for trauma [FAST] has replaced DPL as the screening tool for abdominal injury in unstable patients.) The major time factor in CT evaluation lies in the transport and positioning of the patient. Actual scanning and reconstruction of the images are done quickly. CT is accurate in identifying and quantifying hemoperitoneum, as well as identifying the site and extent of solid-organ injury; CT diagnosis of bowel injury is more challenging. A patient

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  who remains hemodynamically unstable following resuscitation is not a candidate for CT scan or other potentially time-consuming diagnostic imaging studies. In these patients, ultrasonography or DPL is recommended.
  • CT provides valuable information regarding the depth and extent of abdominal visceral injuries, the extent of hemorrhage, and other criteria that correlate well with the American Association for the Surgery of Trauma (AAST) grade of injury and prognosis. A properly performed and interpreted CT scan reliably demonstrates active bleeding (extravasation), which usually indicates a need for surgery or transcatheter angiographic embolization.
  • The technique for abdominal CT scan is
    • Intravenous contrast with or without oral contrast media. No IV contrast material should be given until the head scan is completed. The IV contrast (100–150 mL of 60% contrast) must be administered at a rate of 2.5 to 3.0 mL/second.
    • The oral contrast material is a dilute solution (2%) of aqueous iodi-nated contrast medium (e.g., Gastrografin or Gastroview). Alert patients can drink the solution, whereas patients with an altered sensorium have the solution administered through a nasogastric or orogastric tube after evacuation of stomach contents. Although the safety of oral contrast has been demonstrated, there is still much debate about its utility in the trauma setting.
    • If used, initial administration of “oral” contrast medium should be given as early as possible prior to the scan in order to facilitate bowel opacification and to minimize delays within the CT scan suite. Any delays in obtaining the scan in order to allow gastrointestinal passage of contrast material are not recommended.
  • Routine scans are done with slices taken at 5-mm intervals from the nipple line (upper heart) to the upper thigh (lesser trochanter). Helical CT scanners allow faster acquisition of higher resolution scans. MDCT scanners may acquire contiguous 1.0- to 2.5-mm-thick sections. These are usually viewed as 5-mm-thick sections, while the thinner sections are utilized to construct high-resolution, sagittal, coronal, and 3-D images.
• Ultrasonography (FAST) is useful in the diagnosis of hemoperitoneum. US is an alternative to DPL in the unstable patient, particularly if personnel with expertise in performance and interpretation are readily available. US is less accurate than CT in the diagnosis of injuries to solid abdominal viscera and does not depict bowel injuries nor the source of hemorrhage. FAST examination is used concomitantly with early resuscitation to rapidly determine hemoperitoneum, hemopericardium, or hemothorax. Due to the high false negative rate of this study, all stable patients with appropriate mechanism of injury should undergo abdominal CT.
• The diagnosis of hollow viscous injury is probably the most challenging aspect of the radiographic evaluation of the trauma patient. CT has been proven to be highly accurate when there is a positive finding or in the setting of a completely negative scan. If the CT is equivocal or there is a high clinical suspicion of bowel injury, close clinical monitoring with serial exams is mandatory.

VII. Pelvic Trauma

A.

The plain AP pelvic film is the key to the early diagnosis of pelvic fracture.

If the alert and communicative patient is asymptomatic without distracting injuries, this x-ray study is not essential. This radiographic examination requires a frontal pelvic view that includes the iliac crests, both hip joints, and the proximal portion of both femurs. This can be supplemented by angled projections of the pelvis of the caudal (“inlet”) and cephalad (“outlet”) because these provide a more accurate delineation of the extent and relationship of pelvic fractures and joint disruptions.

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B.

Traditionally, CT scan has had a minimal role in the immediate evaluation of the acutely injured pelvis. However, helical CT is now an easy and fast way to accurately identify active hemorrhage associated with pelvic fractures. Therefore, it plays a valuable role in the identification of bleeding that will require intervention via angiography. CT scan is also the most accurate method for assessing the need for operation. Computer-generated 3-D images from the axial CT sections of the pelvis assist in preoperative display and reconstruction of complex pelvic fractures. No second scan is necessary; therefore using 3-D reconstructions will not delay any operative intervention. Pelvic CT scan is essential in determining:

• Pelvic ring disruptions
• The spatial orientation and relationship of complex or displaced pelvic ring fragments
• The presence of joint instability
• Intra-articular fragments
• Fractures of the articular surface of the acetabulum or femoral head

C.

Immediate pelvic angiography should be considered for patients with hemodynamic instability from pelvic fracture. Pelvic angiography assists in the identification of pelvic arterial bleeding sites secondary to fracture that are amenable to percutaneous transcatheter embolization. Between 6% and 18% of patients with unstable pelvic ring disruption have pelvic arterial injuries that warrant embolization. When pelvic arterial bleeding is found at angiography, embolization successfully occludes the bleeding artery in 80% to 90% of cases. Completion arteriography is required to ensure control of hemorrhage after therapeutic embolization. If the patient has a torn venous plexus or cancellous bone fragments are bleeding, angiographic embolization will not be of benefit, and immediate operative intervention may be required.

D.

Retrograde urethrography (RUG) is essential in the evaluation of urethral injuries. Rupture of the bladder or urethral laceration occurs in approximately 20% of patients with significant pelvic ring disruptions. Therefore, RUG is the initial diagnostic procedure in patients with pelvic ring disruption and a clinical picture concerning for genitourinary injury. It is indicated for any male patient who has blood at the urethral meatus or a scrotal or perineal hematoma. When any of these findings are present, a RUG must be performed prior to insertion of a Foley catheter.

• Technique for RUG
  • An irrigating syringe filled with 10 mL of sterile 30% contrast material is inserted into the urethral meatus.
  • The penis is stretched slightly to the side.
  • The urethra is filled with the 10-mL bolus of contrast material.
  • A film is shot just at the completion of the injection at a 30-degree oblique angle to demonstrate the prostatic and membranous urethra.
• Alternate technique
  • Pass an 8 F Foley catheter into the urethral meatus (approximately 3–4 cm).
  • Position the balloon of the Foley catheter in the distal urethra with sufficient fluid to maintain a tight fit (usually 2–4 mL).
  • Inject the sterile undiluted contrast material (10 mL) in a retrograde fashion, allowing for easy and complete filling of the urethra.
• Findings
  • The most common site of urethral disruption is the prostatomembranous urethral junction.
  • Extravasation of contrast will be seen at the apex of the prostatic urethra, from the membranous urethra at the triangular ligament.
  • Partial visualization indicates incomplete disruption.
  • Complete disruption is indicated by an absence of contrast material in the bladder or prostatic urethra.
• If the urethrogram is negative, a cystogram is performed.
  • Technique for a cystogram
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    • Pass a 16 F Foley catheter into the bladder.
    • Gravity fill the bladder with 300 to 400 mL of sterile undiluted contrast material (i.e., Cystografin).
    • Frontal and oblique radiographs of the bladder are obtained when the bladder is full.
    • An AP post-void film is obtained to determine if an extraperitoneal bladder rupture is present.
  • Findings
    • Severe pelvic and lower abdominal pain, caused by extravasation of the contrast material, is a clinical indication of bladder rupture.
    • In the unconscious patient, free flow of the diluted contrast fluid can indicate bladder rupture and intraperitoneal extravasation.
    • These films detect bladder rupture with 98% accuracy.

VIII. Imaging in the Intensive Care Unit (ICU)

The imaging techniques discussed in this chapter are applicable to the trauma patient in the ICU. Any trauma patients who are better cared for (monitoring, pharmacologic therapy, etc.) in the ICU may have many of their imaging studies performed in the ICU or as their condition permits.

A. Chest x-rays

• A daily chest x-ray may be indicated in any patient who has one or more of the following (can vary with hospital protocol):
  • Acute respiratory failure
  • Endotracheal intubation
  • Positive end-expiratory pressure (PEEP) >5 cm H₂O
  • FiO₂ >0.5
  • Chest tube in place
  • Under treatment for active disease (e.g., pneumonia, atelectasis, etc.)
• Selective daily chest x-rays in the ICU for the following patients:
  • Weaning mode without change in cardiopulmonary status
• Chest x-ray is indicated after the following:
  • Any acute cardiac or pulmonary deterioration
  • Any invasive chest procedure (e.g., placement of a chest tube, central venous catheter, feeding tube, or endoscopy)
• Chest x-rays are not necessary when
  • A central line was changed over a guidewire without difficulty

B. Computed tomography

• CT scan of the head may be indicated when an unexplained change occurs in neurologic status or as a follow-up for a previous CT scan of head injury. CT scan for encephalopathy or multiple-system organ failure has a low yield.
• CT scan of the chest can be helpful in delineating the pathology involved in acute pulmonary failure (e.g., consolidated lung, loculated collections, empyema).
• CT scan of the abdomen without history or physical examination suggesting intraperitoneal pathology is of little benefit. CT scan of the abdomen can be helpful if
  • The patient has had previous surgery
  • It is performed to confirm a presumptive clinical diagnosis
  • It is necessary to direct a percutaneous study or procedure (i.e., abscess drainage)
  • Missed intraperitoneal injury is suspected
  • There is a suspicion of pancreatitis

C. Ultrasound

• Bedside US in the ICU is helpful to localize fluid collections and to diagnose acalculous cholecystitis.
• Duplex ultrasound can be useful in detecting venous thrombosis or arterial injury.
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• US is indicated if pericardial tamponade is suspected.

D. Fluoroscopy

• Fluoroscopy is being used in the ICU to guide the placement of invasive devices such as pulmonary artery catheters, central lines, inferior vena cava (IVC) filters, or enteral feeding tubes.

Axioms

• The more severely compromised the patient, the less time available for initial radiographic evaluation.
• Specific images should be obtained to answer the most vital and highest priority questions.
• Do not spend time attempting to clear the C-spine in an unstable patient.
• Axial skeletal and pelvic films may not be indicated in an alert patient without signs or symptoms of these injuries.
• Regional variations exist with regard to the availability of CT technology in emergency departments. However, MDCT has revolutionized the radiographic evaluation of the trauma patient, and there is a trend toward the institution of this technology in the ED.