Technique
All CT examinations were performed with a 40 and 64-detector row CT scanner and all images were obtained in a craniocaudal direction.
The following parameters were used: reconstruction thickness,
1.25 mm; 120 kVp; pitch factor 0.98 ; and gantry rotation time,
0.4 second.
The use of oral contrast medium is controversial widely in the literature.
The risk of aspiration and delayed diagnosis with subsequent complications,
and especially the fact that the oral contrast does not provide additional information,
has led in at present,
in most trauma centers (including ours),
do not use oral contrast medium in patients with closed abdominal trauma.
Iodinated contrast agent was injected through an 18-gauge catheter placed in an antecubital vein.
We administered between 100 to 120 mL Intravenous contrast [ 300 mg of iodine per milliliter]; at a rate of 4 mL/sec by using a power injector
Intravenous contrast (100–120 mL) is administered to all patients,
and a 70-second delay is used for the portal venous phase acquisition.
In addition,
5- to 7-minute delayed images of the abdomen and pelvis are obtained selectively in patients with injuries identified or suspected on the portal venous phase images
In all cases,
multiplanar reformations in coronal and sagittal planes were provided.
Additional three-dimensional (3D) reconstructions with volume renderings and maximum intensity projection (MIP) reformats were performed by attending radiologists at independent workstations.
Special considerations by Bowel Segment
The Stomach
Gastric injuries are rare following blunt trauma with an incidence of 0.06%.
Gastric injuries are commonly seen in younger populations and Its most frequent location is the anterior wall,
followed by the major curvature,
the minor curvature and the posterior wall [15].
CT may show nonspecific signs such as free intraabdominal fluid,
or more specific signs such as a distended stomach,
extraluminal gas or oral contrast,
intramural hematoma.
The stomach often collapses around the site of injury,
so that a defect is not visible at imaging,
if large enough,
the defect may be visible by CT (Figure 7).
When injuries of the spleen,
diaphragm,
or left hemiliver are present,
gastric injury should also be considered [16].
The Duodenum
The duodenum demonstrates complex anatomic relationships.
The first portion is the only intraperitoneal segment,
others segments are retroperitoneal.
The intimate anatomic relationships between the duodenum and adjacent structures are critical for accurate description of duodenal injuries ,
for that reason it should be closely examine the second portion of the duodenum as well as the pancreas and biliary tree,
as injuries to these structures may require more complex surgical repairs.
CT is the primary means of diagnosing traumatic lesions of the duodenum.
The findings of duodenal injury are similar to those of the rest of the small bowel described above.
Free fluid and gas within the retroperitoneum are additional potential findings of duodenal injury due to its retroperitoneal location.
Duodenal trauma can manifest as duodenal contusion,
duodenal wall hematoma,
perforation and wall disruption,
the latter two indications of surgical treatment.
Duodenal contusion is the most frequent finding in duodenal trauma and is manifested by wall edema and hematoma,
intramural gas,
and focal thickening (figure 8).
The descending duodenum and the horizontal segment are the most involved portions of duodenal perforation,
which must be suspected when retroperitoneal collections of contrast medium or fluid,
extraluminal gas or lack of continuity of the duodenal wall exist.
The Colon
Blunt colonic injury is rare and occurs in less than 5% of patients with abdominal injuries [17].
Similar to those of the small bowel,
the direct CT findings of blunt traumatic colonic perforation are free abdominal air,
focal wall discontinuity,
and extravasation of oral contrast (figure 9).
There is no specific predilection by location.
Injury to the colon is usually a result of increased intraluminal pressure with blowout of the wall or avulsion injury to the mesocolon.
As both the ascending and descending colon are retroperitoneal structures,
injuries in these locations do not cause intraperitoneal free fluid.
Instead,
pneumoretroperitoneum or free retroperitoneal fluid may be present ; however,
as mentioned previously,
a duodenal source should also be considered [18].
Anorectal
anorectal trauma is associated with high morbidity and mortality given the propensity for concomitant injury of pelvic structures,
such as the urinary bladder,
urethra,
and pelvic vasculature[19] .The mortality in these patients with blunt anorectal trauma has been shown to be nearly three times as high as in those with blunt colonic injury,
with one series reporting mortality from blunt rectal trauma to be up to 50%[6,7].
Distinction between injuries to the intraperitoneal and extraperitoneal segments of the rectum is an important consideration in patients with rectal injury given differences in their subsequent management.
The anterior and lateral sidewalls of the upper two-thirds of the rectum are covered with peritoneum,
and injuries to these segments are considered intraperitoneal.
The distal one-third of the rectum circumferentially and the upper two-thirds of the rectum posteriorly are not covered with peritoneum and are considered extraperitoneal.
Patients with blunt trauma involving the intraperitoneal rectum are typically managed with primary repair,
often with fecal diversion.
Low,
extraperitoneal injuries from blunt trauma are repaired when accessible or when the injury is severely destructive.
Alternatively,
presacral drainage can be used to manage low,
blunt rectal injury[7]
Direct signs of anorectal injury that have the highest specificity include direct evidence of a transmural injury,
extraluminal air,
active hemorrhage related to a mural injury,
and active extravasation of intravenously administered contrast into the bowel lumen in absence of oral contrast (figure 10) The indirect signs of blunt anorectal injury are similar to those previously described for the small bowel and colon,
and include wall thickening,
mesenteric stranding/infiltration,
and free intraperitoneal or retroperitoneal air.
Injuries to the mesentery and mesenteric vessels
Mesenteric vascular injuries are uncommon but are significant because they are associated with the risk of subsequent bowel ischemia (figure).
The highest specificity findings related to vascular mesenteric injury at CT is active contrast material extravasation (100%) but is the less sensitive (17%) [20].
At imaging,
an extravascular hyperattenuating focus or “blush” is seen,
and this focus expands in subsequent more delayed phases of acquisition.
Other sign is presence of mesenteric hematoma may indicate the presence of a bowel injury or mesenteric vessel laceration.
Small isolated mesenteric hematomas are not always an indication for immediate surgery and can be treated with observation alone.
Larger hematomas occur in injuries to major mesenteric vessels,
and therapeutic laparotomy is usually required to avoid the risk of delayed bowel ischemia.
Enlargement or increased attenuation of the hematoma on delayed-phase is a sign of associated active bleeding that requires immediate action
Brofman et al retrospectively reviewed CT studies of patients with surgically proven bowel injury,
mesenteric injury,
or both.
Their study demonstrated that active mesenteric extravasation (17%),
mesenteric vascular beading (35%),
and abrupt termination of the mesenteric vessels (39%) are vascular injury imaging findings highly suggestive as direct signs of potential mesenteric and/or bowel [18].