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1
Department of Diagnostic Radiology, University of Maryland Medical Center, 22
S. Greene St., Baltimore, MD 21201
2
Maryland Shock-Trauma Center, University of Maryland Medical Center,
Baltimore, MD 21201.
3
Present address: Forsyth Radiological Associates
Received March 23, 2001;
accepted after revision June 21, 2001.
Presented at the annual meeting of the American Roentgen Ray Society,
Seattle, April 2001.
Abstract
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SUBJECTS AND METHODS. Triple-contrast helical CT scans were obtained in 104 hemodynamically stable patients with penetrating injuries to the torso (thoracoabdominal region including tangential wounds to the anterior abdomen, flank, back, and pelvis) over a 17-month period. The study group included 54 patients with gunshot wounds and 50 with stab wounds. No patient had a radiographic or clinical indication for immediate laparotomy. A positive finding on CT was defined as evidence of peritoneal violation or injury to the retroperitoneal colon, major vessel, or urinary tract. Patients with a positive CT, except patients with isolated liver injury or free fluid, underwent laparotomy. Patients with a negative finding on CT were initially observed.
RESULTS. CT studies were positive in 35 (34%) of 104 patients and negative in 69 (66%) of 104 of patients. Laparotomy was performed in 21 (60%) of 35 patients with positive CT; 19 (86%) of 22 were therapeutic, two (9%) were nontherapeutic, and one (5%) was negative (no injury was found). Nine patients with isolated hepatic injuries were successfully treated without laparotomy. Among patients with a negative CT, 67 (97%) of 69 were treated nonoperatively with success. CT had 100% (19/19) sensitivity, 96% (69/72) specificity, 100% (69/69) negative predictive value, and 97% (101/104) accuracy in predicting the need for laparotomy.
CONCLUSION. Triple-contrast helical CT can accurately predict the need for laparotomy and exclude peritoneal violation in penetrating torso trauma including tangential abdominal wounds.
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Several treatment protocols have been used in the recent past to help improve the selection of hemodynamically stable patients who are asymptomatic or mildly symptomatic but who require laparotomy [4, 5, 10, 12,13,14,15,16,17,18]. These protocols include repeated physical examinations performed by the same surgeon, local wound exploration followed by diagnostic peritoneal lavage, laparoscopy followed by laparotomy, and use of CT for patients with penetrating injuries to the flank and back to determine the extent of retroperitoneal or intraperitoneal injury [8, 10, 14,15,16,17,18].
CT with administration of rectal, oral, and IV contrast material (triple-contrast) has been used to evaluate hemodynamically stable patients with penetrating injury to the flank and back for the past decade [18,19,20,21]. Two studies using this approach used either diagnostic peritoneal lavage or local wound exploration as the initial study to diagnose peritoneal violation [18, 21]. However, both studies reported that CT had a high negative predictive value in determining substantial retroperitoneal organ injury and that patients with a negative CT could be safely treated nonoperatively. Recent retrospective studies have also reported the high accuracy of CT for determining trajectory and peritoneal violation in selected patients with gunshot wounds to the torso [22, 23]. The authors undertook a prospective study to evaluate the effectiveness of triple-contrast helical CT in diagnosing peritoneal violation and the need for laparotomy in cases of penetrating torso trauma.
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Triple-contrast helical CT was performed in all 156 hemodynamically stable patients. These patients had a systolic blood pressure higher than 90 mm Hg, pulse higher than 50 but lower than 110 beats per minute, and base deficit less than -5; normal or equivocal physical examinations for signs of peritoneal irritation; and no evidence of peritoneal violation on conventional radiographs.
The institutional review board approved the study, and informed consent for study participation was obtained in 104 hemodynamically stable patients. These patients formed our study group. Fifty-four patients had gunshot wounds (16 with multiple wounds), 48 patients had been stabbed (seven had multiple wounds), and two patients fell on a sharp object. There were 95 males and nine females with an age range of 16-85 years (mean age, 31 years). Any patient with a known major allergy to IV contrast material and patients for whom CT would introduce an unacceptable delay in the treatment of other injuries, as judged by the attending surgeon, were excluded from the study.
To localize the site of entry of the stab or gunshot wound for this study, we further divided the torso into the anatomic regions illustrated in Figure 1A,1B,1C. The thoracoabdominal area was defined by the internipple line superiorly; the costal margins extended posteriorly to the inferior tip of the scapula inferiorly. The anterior abdomen was defined by the costal margins superiorly, the anterior axillary lines laterally, and the inguinal ligaments and symphysis pubis inferiorly. The flank was defined by the anterior and posterior axillary line (tip of the scapula superiorly and iliac crests inferiorly) and from the costal margin to the iliac crest. The back was defined by the tips of the scapula superiorly and the iliac crests inferiorly. The pelvis was defined by the iliac crests and inguinal ligaments superiorly and the upper thirds of the thighs inferiorly.
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Technique
Triple-contrast helical CT scans (Plus 4; Siemens, Iselin Medical Systems,
NJ) were obtained from the internipple line to the symphysis pubis, with a
collimation of 8 mm and table speed of 8 mm (pitch = 1) following
administration of 150 mL of IV contrast material (240 mg I2/mL) at
3 mL/sec using a power injector (Medrad 4; Medrad, Pittsburgh, PA). A total
volume of 600 mL of 2% sodium diatrizoate (Hypaque Sodium; Nycomed, Princeton,
NJ) oral contrast material was administered 30 min and immediately before
initiation of the scan. An enema with 1-1.5 L of 2% sodium diatrizoate was
also administered with the patient on the CT table to opacify the colon before
scanning. Delayed images were obtained routinely about 3 min following
injection of IV contrast material to evaluate the renal collecting system for
injuries.
Definitions
The CT scans were interpreted prospectively by the trauma radiologist for
peritoneal violation; injury to solid organs, bowel, and mesentery; renal
collecting system; bladder; diaphragm; or vascular structures. CT was
considered positive for peritoneal violation in the presence of a wound tract
outlined by air, hemorrhage, or bullet fragments caused by the missile or
knife entering the peritoneal cavity (trajectory of missile or knife).
Findings of intraperitoneal free air or fluid; bullet fragments; or
intraperitoneal organ, mesenteric, or vascular injury were also considered
positive for peritoneal violation. Vascular injuries were diagnosed in the
presence of active bleeding or pseudoaneurysm. Active bleeding was diagnosed
when an irregular area of contrast material was seen within a hematoma with
attenuation similar to or higher than that seen in the aorta or an adjacent
major vessel [24].
Posttraumatic pseudoaneurysms were defined as well-circumscribed, typically
rounded, foci with a density similar to or higher than that of the aorta or an
adjacent major vessel.
All patients with a penetrating injury tract adjacent to the diaphragm were considered potentially to have diaphragm injury. Diagnostic CT signs of diaphragm injury included the CT collar sign (constriction of a herniating viscus at the diaphragmatic rent), herniation of abdominal content into the thoracic cavity through the diaphragm [25], or the presence of contiguous organ injury on either side of the diaphragm in patients with a single gunshot or stab wound. CT findings suggestive of a diaphragm injury included a wound track outlined by air, hemorrhage, or bullet fragments caused by the missile or knife extending adjacent to the diaphragm; thickening of the diaphragm; and a defect in the continuity of the normal diaphragm or crus with no clear evidence of hematoma or blood.
CT findings of bowel or mesenteric injury included extravasation of oral or colonic contrast material, discontinuity or defect in the bowel wall, subjective impression of bowel-wall thickening, mesenteric bleeding, or focal mesenteric hematoma or infiltration [26, 27]. A wound tract extending up to the wall of a hollow viscus was also considered a CT sign of bowel injury. Free intraperitoneal air can be introduced into the peritoneal cavity by a bullet or knife wound. Isolated free intraperitoneal fluid (blood) may result from injury to the body wall with peritoneal penetration, or fluid may enter the peritoneal cavity from an extraperitoneal injury through the bullet or knife tract. For these reasons, the presence of isolated free intraperitoneal air or fluid was not considered a diagnostic CT sign of bowel injury in the setting of penetrating trauma.
For analysis of data, CT studies were considered negative if no evidence was seen of peritoneal violation with or without minor extraperitoneal injuries (small retroperitoneal or pelvic hematoma, minor renal injury) that did not require intervention. A positive CT scan was defined as showing evidence of peritoneal penetration; intraperitoneal visceral injury; or injury to the retroperitoneal colon, major vessel, or urinary tract. A therapeutic laparotomy required surgical repair of a visceral injury. A nontherapeutic laparotomy was defined as surgical exploration revealing injuries that did not require repair (minor mesenteric contusions, splenic or liver injury without bleeding). A negative laparotomy meant that no injuries were found.
Medical Records
Medical records were reviewed to determine patient demographics,
complications of surgical or nonsurgical treatment, and outcome. Operative
reports were reviewed to determine precise surgical findings.
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Organ and Vascular Injury
CT showed visceral injury in 25 (71%) of 35 patients with peritoneal
violation. The mechanism of injury was gunshot in 64% (16/25) of these
patients and stabbing in 36% (9/25). Table
1 illustrates the anatomic location of penetrating injury,
intraperitoneal and retroperitoneal visceral injuries diagnosed by CT, and the
mechanism of injury. The liver was the solid organ most commonly injured.
Isolated liver injuries were seen in 10 of 14 patients. Three patients with
liver injury needed angiographic embolization on the basis of CT finding in
one patient and clinical evidence of ongoing hemorrhage in two others.
Intraperitoneal vascular injuries were seen as active hemorrhage in 4% (4/104)
of patients, including the liver (n = 1) and spleen (n = 1)
(Fig.
5A,5B),
and the mesentery adjacent to the inferior mesenteric artery (n = 2).
A nonbleeding liver injury was confirmed at surgery in a patient who underwent
laparotomy to repair a right hemidiaphragm injury.
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Among the 66% (69/104) of patients whose CT findings were negative for peritoneal violation but who had extraperitoneal injuries seen on CT, we found 15 hematomas (retroperitoneal, n = 6; pelvic, n = 6; paraspinal, n = 2; perinephric, n = 1) and 14 fractures (pelvis, n = 10; spine, n = 3; femur, n = 1). In five patients, bullets were seen adjacent to major vascular structures, including the iliac vessels (n = 3), inferior vena cava (n = 1), and the femoral artery (n = 1). Active bleeding was seen within the gluteal muscle in one patient. Angiography was performed in two patients for clinical evidence of hemorrhage or proximity of the bullet to major vessels and was negative in both cases. CT did not identify any colonic, rectal, or urinary tract injuries in this group of patients.
Bowel and Mesenteric Injury
Among the 35 patients with peritoneal violation, 37% (13/35) showed bowel
or mesenteric injury on CT. The wound tract extending adjacent to the injured
bowel was the most common CT finding, seen in 69% (9/13) of the patients with
bowel injury. Other CT findings of bowel injury included subjective bowel-wall
thickening in 54% (7/13) and oral or rectal contrast extravasation in 15%
(2/13) of patients (Fig.
6A,6B).
All seven patients with bowel-wall thickening had bowel injury that required
intervention.
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CT did not prospectively specifically diagnose bowel injury in four patients. However, CT showed peritoneal violation in all four, and in three of these patients, CT showed a mesenteric injury adjacent to the bowel injury at the stomach (n = 2) (Fig. 7A,7B) or at the small bowel (n = 1). Indication for laparotomy in these four patients included a large amount of free intraperitoneal air and blood seen on CT on two patients, development of hematemesis on observation of one patient, and development of peritonitis in the other. On retrospective review of the CT scans of these four patients, a wound tract could be identified extending from the site of injury in the epigastrium to the stomach in two patients; bowel-wall thickening was identified in the proximal jejunum corresponding to the operative findings in another patient. The fourth patient had no CT findings to suggest a bowel or mesenteric injury.
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CT was false-positive in two patients for an injury to the stomach. In both patients, CT revealed blood within the lesser sac, caused by a pancreatic injury in one patient and a splenic injury in the other. At surgery, blood in the lesser sac and splenic and pancreatic injury were confirmed and required intervention, but no gastric injury was specifically identified in either patient.
Mesenteric injuries were identified in 29% (10/35) of patients with peritoneal violation, including active bleeding (n = 2), mesenteric contusion with adjacent bowel wall thickening (n = 5), and isolated mesenteric contusion or infiltration of the mesenteric fat (n = 3). All five patients with active bleeding in the mesentery or mesenteric contusion adjacent to thickened bowel wall had bowel or mesenteric injuries requiring surgical repair.
Diaphragm Injury
CT findings suggestive of a diaphragm injury were seen in 18% (19/104) of
patients and included a wound tract extending adjacent to the diaphragm in all
19 patients (100%), focal thickening of the diaphragm in 37% (7/19), and
discontinuity of the diaphragm in 5% (1/19) of patients. The mechanism of
injury included gunshot in 63% (12/19) and stabbing in 37% (7/19). Entrance
wounds were thoracoabdominal in 79% (15/19) of patients, abdominal in 10.5%
(2/19), and in the back in 10.5% (2/19).
CT signs diagnostic of diaphragm injury were seen in 47% (9/19) of patients, including contiguous organ injury on either side of the diaphragm in eight (Fig. 8A,8B) and herniation of abdominal fat through a diaphragm defect in one. The injury involved the right hemidiaphragm in six patients and left hemidiaphragm in three. In this group, three patients with CT findings of right-sided diaphragm injury were treated conservatively and six patients underwent either laparotomy (n = 3) or thoracoscopy (n = 3). In five of the six patients, operative reports confirmed a diaphragm injury; one patient had a large loculated right hemothorax evacuated at thoracoscopy, but no diaphragm injury was seen. Two patients with CT signs suggestive for diaphragm injury also had laparotomy. Although a colon injury was identified in one patient, neither patient had a diaphragm injury directly diagnosed.
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Outcome
Laparotomies were performed in 60% (21/35) of patients with positive CT and
one patient with a negative CT. Laparotomy was considered therapeutic in 86%
(18/21) of patients, nontherapeutic in 9% (2/21), and negative in 5% (1/21).
Both of the patients who underwent nontherapeutic laparotomies had sustained a
single stab wound and showed CT evidence of peritoneal violation and focal
infiltration of the mesentery. One patient with a negative laparotomy was
stabbed. CT showed pneumoperitoneum with intraperitoneal free fluid, but no
abdominal injuries or peritoneal violation was found at surgery. The second
patient with negative laparotomy findings had a gunshot wound to the pelvis
and negative CT findings. Laparotomy was performed because a hematoma was seen
on sigmoidoscopy. No injury was identified at laparotomy.
Overall in this study, triple-contrast CT had a sensitivity of 100% (18/18), specificity of 96% (69/72), negative predictive value of 100% (69/69), positive predictive value of 86% (18/21), and accuracy of 97% (101/104) in predicting the need for laparotomy.
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CT is the imaging modality of choice to evaluate patients who are hemodynamically stable following blunt trauma, and it has been shown to be highly accurate in diagnosing solid organ and hollow viscus injuries in this setting [24,25,26,27, 30,31,32]. Retrospective studies have shown that triple-contrast CT, alone or combined with diagnostic peritoneal lavage, can be used to screen asymptomatic or minimally symptomatic patients with penetrating injuries to the flank and back for intraperitoneal injury [18, 20, 21, 33]. To our knowledge, a prospective study has not been performed using helical CT to determine peritoneal violation or the extent of intraperitoneal and retroperitoneal visceral injury, or to predict the need for laparotomy in hemodynamically stable patients with penetrating injury to the torso.
In our study, CT revealed peritoneal violation in 34% (35/104) of patients. Laparotomy was performed in 21 patients with a positive CT, and peritoneal violation was surgically confirmed in 20 (95%). The most common CT finding seen in patients with peritoneal violation was intraperitoneal free fluid in 94% (33/35) of patients; this was the only finding of peritoneal violation in 11% (4/35) of patients. Other CT signs useful to diagnose peritoneal violation included intraperitoneal visceral injury, seen in 60% (21/35) of patients, and free intraperitoneal air, seen in 43% (15/35). These two signs were more often associated with gunshot wounds than with stab wounds. CT was negative for peritoneal violation in 66% (69/104) of study patients on initial evaluation and 97% (67/69) of these patients were treated nonoperatively with no late complications resulting from missed injuries. Our study shows that triple-contrast helical CT is highly accurate in excluding peritoneal violation and can be reliably used to select patients for nonoperative treatment.
The liver was the solid intraperitoneal organ most commonly injured by penetrating trauma, with such injury seen in 40% (14/35) of patients with peritoneal violation. Nonoperative treatment was attempted in nine patients with isolated liver injury caused by right thoracoabdominal gunshot wounds. Triple-contrast helical CT provided information necessary to attempt nonoperative treatment, including determination of bullet trajectory, extent of liver injury, and exclusion of other injuries that would mandate celiotomy. CT also provided additional information of concurrent abnormality in the thorax, including the size of any hemothorax, pleural effusion, or pneumothorax, or the evidence of pulmonary contusion, lung lacerations, and diaphragm injury. Angiography and embolization were required in three patients to arrest hepatic hemorrhage, and three patients had thoracoscopic repair of right diaphragm injury. Celiotomy was not needed in any of these nine patients. Our study agrees with results reported by Renz and Feliciano [15] in a prospective study of seven stable patients with right thoracoabdominal gunshot wounds, in which CT helped select patients with isolated liver injury for successful nonoperative treatment.
Hollow viscus injuries from penetrating injury to the abdomen are common [5, 8, 34,35,36]. Concern about the accuracy of CT in detecting gastrointestinal tract injuries has diminished the enthusiasm of some surgeons for using CT in an algorithm to evaluate hemodynamically stable patients with penetrating torso injuries [21, 34]. A wide variation in sensitivity and accuracy of CT in diagnosing blunt bowel injury has been reported [26, 27, 30, 34]. A recent study by Butela et al. [37] attributed these variations to CT technique and equipment, level of radiologist expertise, and the particular CT signs used to diagnose bowel and mesenteric injury.
We routinely use both oral and rectal contrast material to opacify the bowel and to identify extravasation of gastrointestinal contrast material, the only specific CT sign of full-thickness bowel injury mandating surgery in penetrating trauma. Although gastrointestinal contrast extravasation was seen in only 15% (2/13) of patients with bowel or mesenteric injury in our study, opacification of the bowel was subjectively helpful in diagnosing bowel-wall thickening and small mesenteric hematomas adjacent to bowel. In this study, irrespective of the mechanism of penetrating trauma, other CT signs of bowel or mesenteric injuries that required direct surgical inspection were active bleeding in the mesentery and bowel-wall thickening with adjacent mesenteric contusion or hematoma. Our study also emphasizes the importance of identifying the wound tract and its extension directly toward the bowel. Prior knowledge of the site of wound entry and use of optimum CT windows settings (window width, 550 H; level, 75 H) helped us identify wound tracts extending to the stomach in two patients and localize the injury sites.
The presence of pneumoperitoneum without evidence of a pneumothorax, pneumomediastinum, or retroperitoneal air decompressing into the peritoneal cavity is a specific CT finding of bowel injury and mandates surgery in blunt trauma. Because free air may be introduced into the intraperitoneal cavity by a bullet or knife during violation of the peritoneum, we did not include pneumoperitoneum as a sign of peritoneal violation that could be used as a specific CT finding of bowel injury. In penetrating trauma, free intraperitoneal blood may result from bleeding from an injury to the abdominal wall-peritoneal lining itself or from extraperitoneal blood leaking through a defect caused by a wound tract into the peritoneal cavity. Free intraperitoneal fluid in the absence of solid organ injury was considered a CT finding of peritoneal violation but not a nonspecific finding for bowel injury. The inability to use either of these two CT findings makes it far more challenging for the radiologist to diagnose bowel injury in patients with penetrating trauma than in patients with blunt trauma. A prospective study with a larger number of patients with penetrating trauma who have bowel injury would help validate our observations and determine the sensitivity, specificity, and accuracy of triple-contrast helical CT in specifically diagnosing bowel injury from penetrating trauma.
Additional studies are required to establish the role of helical CT to evaluate patients with penetrating injury to the diaphragm. Patients with entry wounds in the thoracoabdominal region or with wound tracts extending adjacent to the diaphragm are most likely to have diaphragm injury. Unlike the typically large diaphragmatic rents seen following blunt trauma, the most penetrating injuries to the diaphragm are less than 2 cm in length and are usually diagnosed at laparotomy [38]. The CT collar sign and herniation of abdominal viscera into the thoracic cavity are less likely to occur through such small defects. In this study, 18% (19/104) of patients had CT findings suggestive of diaphragm injury and 47% (9/19) of these patients had diagnostic CT signs of diaphragm injury. The most frequently observed CT sign diagnostic for diaphragm injury was contiguous organ injury seen on either side of the diaphragm arising from a single penetrating wound. Six patients with this CT sign had surgery or thoracoscopy, and the injury was confirmed in five. The need for surgical repair of all rightsided diaphragm injuries remains controversial among surgeons and may depend on the anatomic location of the injury. The sensitivity, specificity, and accuracy of CT signs to diagnose diaphragm injury in penetrating trauma cannot be determined because most patients with CT signs suggestive of a diaphragm injury did not undergo an optimal workup (such as thoracoscopy or surgery) to definitively diagnose or exclude the injury.
Multiple diagnostic tests, including diagnostic peritoneal lavage, local wound exploration, laparoscopy, and sonography, have been used to reduce the high nontherapeutic laparotomy rate among civilian patients who are hemodynamically stable after penetrating injuries [3,4,5, 8, 13, 14, 39]. A significant morbidity rate between 11% and 61% and a longer hospital stay in these patients with complications have been reported compared with uncomplicated nontherapeutic laparotomies performed in patients with penetrating torso injury [3, 9, 40, 41]. To our knowledge, no previous prospective study has been reported that used helical CT without other ancillary tests to diagnose peritoneal violation and thus indicate the need for laparotomy. In this study, peritoneal violation was surgically confirmed in 95% (20/21) of patients with positive CT findings. CT was able to accurately exclude bowel and mesenteric injuries in nine patients with isolated liver injury, thus assisting in successful nonoperative treatment. Regardless of the anatomic location of the entry wound, triple-contrast helical CT had a high sensitivity and negative predictive values of 100%, specificity of 96% and accuracy of 96% to predict the need for laparotomy in hemodynamically stable patients with penetrating torso injury. As shown in Table 2, our results are comparable with other studies using diagnostic peritoneal lavage, local wound exploration, laparoscopy, or serial clinical examination to enhance successful outcome of selective treatment in patients with stable penetrating trauma [4, 10, 12, 14, 35].
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None of our patients with negative CT findings had a missed injury that needed later surgical intervention or readmission to the hospital. The majority of patients with negative CT findings and minor injuries were discharged after observation and serial clinical examinations within 12 hr of admission.
In conclusion, triple-contrast helical CT was highly accurate in excluding peritoneal violation in hemodynamically stable patients with penetrating trauma to the torso. Among patients with peritoneal violation, helical CT was accurate in predicting the need for laparotomy and verifying isolated liver injury, thereby permitting nonoperative treatment for patients with penetration limited to the right upper quadrant. Further prospective studies are needed to determine the accuracy of triple-contrast helical CT in identifying specific injury sites, such as the diaphragm or bowel, in patients with penetrating trauma.
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