Multidetector Computed Tomography of Pancreatic, Small Bowel, and

Multidetector Computed Tomography of Pancreatic, Small Bowel, and Mesenteric Traumas Mariano Scaglione, MD,* Luigia Romano,† Giorgio Bocchini, MD,* Giacomo Sica, MD,* Franco Guida, MD,* Antonio Pinto, MD,† and Roberto Grassi, MD‡

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ancreatic injuries after blunt trauma are rare, accounting for about 1% of all patients suffering from blunt abdominal trauma. The deep anatomic location and its relatively fixed position anterior to the spine make pancreatic trauma a relatively uncommon event.1 Concomitant injuries are common (50%-98%), with the liver most commonly affected (46.8% of cases) followed by stomach (42.3%), major vessels (41.3%), spleen (28.0%), kidney (23.4%), and duodenum (19.3%). In pancreatic trauma, the main influencing factors of patient outcome are the mechanism of trauma, identification/characterization of injuries, and presence or absence of major ductal injury.2 Because imaging findings are subtle, the correct diagnosis can be delayed. The resulting delayed diagnosis, missed findings, and incorrect classification of the injury can increase the morbidity and mortality considerably.3 A delay in diagnosis of ⬎24 hours is a risk factor for death in up to 40% of patients, as opposed to 11% of those patients who undergo surgery within 24 hours.4 In general, the morbidity and mortality after pancreatic trauma are remarkably high: mortality ranges between 9% and 34%. However, only 5% of the pancreatic injuries are directly the cause of the fatal outcome.2 The morbidity ranges between 11% and 62%, which covers all types of complications. Posttraumatic complications occur in 30%-60% of all cases.3-5 Diagnostic peritoneal lavage has not proved useful in the diagnosis of significant injuries to the pancreas; similarly, the elevation of serum amylase is time dependent and does not correlate with the degree of pancreatic injury.1 However, both elevated amylase in serum and abnormal results of a diagnostic peritoneal lavage (if performed) in the setting of blunt trauma mandate further investigation, such as ultrasonography, computed tomography (CT), endoscopic retrograde cholangiopancreatography (ERCP), magnetic resonance cholangiopancreatography, or surgical exploration. Small bowel and mesenteric traumas are relatively uncommon, occurring in approximately 3%-5% of patients undergoing laparotomy for blunt abdominal trauma.6 Small bowel injuries typically occur in the proximal jejunum near the ligament of Treitz or at the distal ileum near the ileocecal junction, where mobile and fixed segments of the intestine are joined and can move during a blunt deceleration trauma. The mechanisms of blunt trauma that can cause intestinal and mesenteric injuries include crushing injury of the bowel between the vertebral bodies or steering wheels/handlebars; deceleration shearing of the small bowel at fixed points, such as the ligament of Treitz, the ileocecal valve, and around the mesenteric artery and; closed loop rupture caused by sudden increase in intra-abdominal pressure. The presence of a “seat-belt sign” should raise the suspicion for enteric and mesenteric injuries.6

*Department of Radiology, Pineta Grande Medical Center, Caserta, Italy. †Department of Radiology, Cardarelli Hospital, Napoli, Italy. ‡Department of Radiology, Second Univeristy of Napoli, Napoli, Italy. Address reprint requests to Mariano Scaglione, MD, Department of Radiology, Pineta Grande Medical Center, Via Domitiana km 30, 81030, Castel Volturno, Caserta, Italy. E-mail: [email protected]

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0037-198X/12/$-see front matter © 2012 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1053/j.ro.2012.05.005

The clinical diagnosis of intestinal and mesenteric trauma and the differentiation between injuries requiring surgery from those that can be treated conservatively can be difficult. Signs and symptoms often take hours to manifest clinically. As a result, delays in the diagnosis and surgical repair of bowel and mesenteric injury increase the incidence of fatal complications, such as acute bleeding, peritonitis, and abdominal abscesses.7 The mortality varies between 5% and 65%. Mesenteric injuries are approximately 3 times more frequent than bowel injuries, and associated nongastrointestinal injuries occur in at least half of the cases.6,7

Multidetector Computed Tomography Protocol Considerations Multidetector computed tomography (MDCT) is the first-line imaging tool in patients with suspected pancreatic, small bowel, and mesenteric injuries after blunt trauma, as it is the fastest and most comprehensive means of diagnosis. A contrast-enhanced MDCT protocol after the injection of an intravenous contrast agent with a high concentration of iodine (370-400 mg/mL) and high injection rates (at least 4 mL/s) is recommended; also, this should be followed by a 30-50 mL saline chaser at a rate of 4 mL/s. The use of higher concentrations of iodine at high injection rates allows optimal depiction of vessels, vascular injuries, and anatomic maps in postprocessing evaluations, thus providing useful information for identification and characterization of injuries and surgical management options. A volume of 100120 mL of contrast medium is generally sufficient for the MDCT evaluation. Preliminary nonenhanced CT scan is not considered necessary. However, in some occasional cases, it is helpful for identifying preexisting hyperattenuating material in the peritoneal cavity or bowel lumen, such as clots, metallic clips used for endoscopic hemostasis, suture materials, foreign bodies, drugs, or contrast material retained in the intestinal lumen. The use of an arterial and venous acquisition protocol gives a comprehensive evaluation of pancreatic, mesenteric, intestinal, and associated injuries, providing useful information for the best management approach. The arterial phase (30-40 seconds postinjection) helps identify associated vessel injuries (Fig. 1), arterial mesenteric bleeding, and early extravasation of contrast medium within the bowel lumen. The portal phase acquisitions (65-80 seconds postinjection) result in optimal pancreatic and bowel wall enhancement and are useful to depict traumatic findings. The use of oral contrast material has been questioned by several authors based on literature reports about the lack of substantial added benefits for depicting bowel and mesenteric injuries.8,9 Moreover, intraluminal highdensity oral contrast material can obscure the wall of the injured intestinal loops, thereby delaying the diagnosis.9 At our institution, all initial CT scans for trauma patients are obtained without oral contrast material. The use of oral contrast material is reserved for follow-up CT studies or “second look”

MDCT of pancreatic, small bowel, and mesenteric trauma

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Figure 1 Pseudoaneurysm associated with a mesenteric hematoma after blunt trauma. Contrast-enhanced axial computed tomography (CT) acquired in the arterial phase shows a pseudoaneurysm of a jejunal branch of the superior mesenteric artery (arrowhead) surrounded by a large mesenteric hematoma (arrows).

evaluations, in the small number of patients in whom bowel injuries are specifically suspected (Fig. 2).

Pancreatic Injuries CT is the preferred imaging tool for the detection of pancreatic injury with a reported sensitivity of 65-75%, with presumably higher sensitivity with newer MDCT scanners.10 CT findings of pancreatic trauma include fluid in the pararenal space, lesser sac, between the splenic vein, and the posterior aspect of the pancreas, pancreatic edema, hematoma, laceration, and transection. These findings are best detected on portal venous phase CT images. The pancreatic “neck” and “body” are involved in two-thirds of cases, whereas the remainder is equally distributed between the “head” and “tail.” Isolated pancreatic injuries are rare (Fig. 3); the liver, spleen, stomach, (Fig. 4) and duodenum are frequently involved concomitantly. Finally, be-

Figure 2 Delayed jejunal perforation in a trauma patient presenting with symptoms of peritonitis 7 days after a motor vehicle collision. Noncontrast axial CT scan demonstrates extravasation of oral contrast material in the peritoneal cavity (arrows). During surgery, a large jejunal laceration was found.

Figure 3 Isolated pancreatic injuries after blunt trauma. Three distinct cases. (A) Contusion of the pancreatic tail (arrow) associated with haziness of the adjacent peripancreatic fat, (B) superficial laceration of the pancreatic tail (arrow) without periglandular changes, and (C) deep laceration at the pancreatic isthmus (arrow) associated with a large hematoma in the lesser sac (arrowheads); small amount of free fluid in the left pararenal space and peritoneal cavity is also visible.

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Figure 4 Pancreatic head disruption associated with gastric laceration. Contrast-enhanced axial CT scan shows pancreatic body transection (black line) associated with hemoretroperitoneum (star), free air (brackets), and low-density free fluid in the peritoneal spaces. Surgery revealed a deep pancreatic body transection with fragmentation of the pancreatic head and a large gastric laceration. (Image courtesy of Vittorio Miele, S. Camillo-Forlanini Hospital, Roma.)

M. Scaglione et al teric folds. Retroperitoneal gas bubbles indicate a rupture of the duodenum, ascending or descending colon.17 The use of an appropriately “wide window” to scrutinize small gas bubbles is recommended in the routine assessment of abdominal CT scans (Fig. 8). However, it should be emphasized that intraperitoneal free air is not a pathognomonic sign of bowel perforation, but may also be associated with traumatic bladder injury or be the result of pneumothorax, pneumomediastinum, mechanical ventilation, diagnostic peritoneal lavage, or penetrating injury without hollow viscus injury.18 Direct interruption of bowel wall or discontinuity of the wall profile is rare (Fig. 8C); nevertheless, the use of thin axial slices might increase its detection. Direct evidence of oral contrast extravasation into the peritoneal spaces is also a rare observation and is indicative of a full discontinuity of the injured bowel wall (Fig. 8D). The normal distended bowel wall is 1- to 2-mm thick, whereas the collapsed wall is 3-4-mm thick. A segmental bowel wall thickening on CT is generally because of an intramural hematoma or edema, especially if associated with a mesenteric hematoma. When the admission CT study demonstrates an isolated focal bowel wall thickening and a nonoperative management is accepted, a repeat CT should

cause of the deep central location of the pancreas, major vascular injuries may coexist and be fatal (Fig. 5). Pancreatic injuries after blunt trauma are often difficult to detect at the initial CT assessment. Identification of direct signs of pancreatic injury is one on the 2 critical issues in blunt trauma, the other being the determination of pancreatic duct integrity. The initial CT scan of 20%-40% patients with pancreatic injuries may show no pathological findings within the first 12 hours after the injury.3 A delay in making a correct diagnosis of 24 hours or more is potentially fatal.4 A close inspection of the thin-section axial images and the corresponding multiplanar reconstructions is mandatory.10 In general, the use of multiplanar reformations, thin-slice axial images, and image acquisition in the portal/ pancreatic parenchymal phase can improve the diagnostic confidence.10,11 However, initial findings may be subtle or even misleading (Fig. 6) because the pancreas may have a completely normal morphology and appearance. Nevertheless, in some cases, a high index of suspicion, suspicious mechanism of trauma, or suspected force vectors through the pancreas are the key for radiologists to suggest a follow-up CT evaluation at 24-48 hours postadmission (Fig. 7). The integrity of the pancreatic duct is the most crucial parameter in the decision whether surgery is required and in determining patient outcome. Ductal injuries can be detected by MDCT with a sensitivity of up to 91%;3-5 in particular, in cases of severe pancreatic laceration involving more than half of the organ’s diameter, ductal injury has to be strongly suspected (Fig. 8). Extravasation of contrast material from the pancreatic duct can be shown by ERCP. As a second-line diagnostic tool, magnetic resonance imaging can be used in combination with magnetic resonance cholangiopancreatography and ERCP to clarify the ductal integrity.10-12

Small Bowel Injuries The most important CT findings of small bowel injuries include extraluminal intra- or retroperitoneal air, free mesenteric or peritoneal fluid, thickened bowel wall and/or abnormal wall enhancement, bowel wall defect, fluid between loops, and extraluminal oral contrast material.13-15 Extraluminal intra- or retroperitoneal air or mesenteric air may indicate a bowel wall perforation.16 Free gas bubbles in the peritoneum can be distributed adjacent to the abdominal wall or surround the liver and spleen. Gas bubbles can also accumulate in the hepatic hilum or in the mesen-

Figure 5 Pancreatic laceration associated with left renal artery injury. (A) Contrast-enhanced CT scan shows complete laceration of the pancreatic tail. (B) A more distal CT scan acquired in the arterial phase shows a spot of active bleeding from the left main renal artery and hemoretroperitoneum; note, CT signs of hypovolemic shock. The renal artery was surgically clamped and reimplanted while the pancreatic tail was removed.


Figure 6 Pancreatic cleft mimicking laceration in a young patient involved in a motor vehicle accident. (A, B) Two contiguous axial CT scans show a hypodense line at the pancreatic tail (arrow) suggestive of a parenchymal laceration. A 5-day follow-up CT shows on both axial scan (C) and coronal reformatted image (D) identical morphology of this finding (arrows), which, in the absence of peripancreatic changes and enzyme movement, can be ascribed to a pancreatic cleft.

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Figure 8 Multidetector computed tomography (MDCT) findings of bowel injury after blunt trauma. Four distinct cases. (A) Multiple free gas bubbles (arrows) distributed along the jejunal loops and mesenteric folds, (B) gas bubble at the mesenteric boundary of an ileal loop (arrow), (C) discontinuity of small bowel wall contour (arrowheads), and (D) intraperitoneal extravasation of oral contrast (arrows) because of traumatic small bowel injuries.

be performed after 6-8 hours. If this new CT scan demonstrates imaging stability, conservative management can generally be adopted. Bowel enhancement is classified as abnormal if it is increased or decreased compared with the enhancement of adjacent bowel loops. An alteration in bowel wall enhancement can be related to intramural edema (hypodense) (Fig. 9A) or hemorrhage (hyperdense) (Fig. 9B). Sometimes, there is a nonhomogeneous patchy enhancement of the injured bowel loop that may be related to a slow blood perfusion. In this case, the damage of submucosal vascular plexus can lead both to ischemia and to an intramural leakage of contrast material. Bowel vascular damage can also depend on the interruption of the blood supply, with thrombosis or laceration of the arterial vessels.

In cases of arterial leak, MDCT can localize areas of active bleeding for angiographic embolization or surgery (Fig. 9C). Free fluid in the peritoneal spaces is a relatively frequent finding in abdominal trauma, whether it is associated to solid or hollow organ injuries or not. Careful evaluation of the quantity, density, and location of fluid is important for optimal management: large amounts of free (especially if high in attenuation) fluid in more than one space or focal mesenteric fluid may be suggestive of an underlying bowel/mesenteric injury and may warrant surgery, clinical observation, or CT follow-up, whereas small amount of lowattenuation fluid (especially in females) should be initially considered a benign finding, not necessarily associated to bowel or mesenteric injury.19,20

Figure 7 Pancreatic injury after motor vehicle accident. (A) Initial CT shows sternal and costal fractures (white arrows), adrenal contusion (red arrow), and descending colonic contusion with perivisceral haziness. The yellow line shows the imaginary direction of the force vector of trauma, which has necessarily passed through the pancreas. However, at this moment, the pancreatic morphology is absolutely normal. (B) Twenty-two hours later, nonenhanced CT scan shows a hyperdense fluid collection at the level of the pancreatic neck (arrows) and free fluid in the left pararenal space. (C) At the same level, contrast-enhanced CT scan shows a low attenuation line suggestive of pancreatic laceration (arrow). (D) Magnetic resonance cholangiopancreatography performed to evaluate the possible ductal involvement shows integrity of the main duct. Physical examination and laboratory findings were within the normal range. (Color version of figure is available online.)

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368 Thus, follow-up CT scans and close clinical/laboratory observations are critical measures in those situations.16,20

Mesenteric Injury Mesenteric injuries can appear at MDCT scans as hazy infiltrations, hematomas, or active extravasation of contrast material in the mesenteric folds.13-16 CT attenuation values of mesenteric-clotted blood range between 40 and 70 HU (Fig. 10), whereas those of active hemorrhage vary from 70 to 370 HU (Fig. 11). Hazy infiltration is generally associated with a mesenteric contusion without vascular leakage.21 Irregularity of the mesenteric vessels include a beaded appearance with irregular contour and abrupt termination (Fig. 10B) highlighted by the lack of continuity of

the artery or vein. Active bleeding frequently occurs within a large mesenteric hematoma irrespective of whether associated to a bowel injury (Fig. 11). Isolated mesenteric contusion or hematoma without active extravasation requires a follow-up CT evaluation after 6-8 hours.13-16 If this scan demonstrates imaging stability, conservative management is generally adopted, whereas if a mesenteric vascular injury or a bowel loop ischemia develops, the patient undergoes surgery and/or angiographic embolization.13-16 CT findings, such as active extravasation of intravenous contrast medium within the lumen of the injured bowel loop or in mesenterial folds/peritoneal spaces, disruption of the bowel wall or thickened bowel wall with free air in mesenteric folds and/or peritoneal cavity, require immediate surgery.18-21

Figure 9 MDCT findings of bowel wall injury after blunt trauma. Three distinct cases. (A) Segmental ileal loops wall thickening (arrows) with a stratified appearance because of intramural hypodense edema, (B) segmental jejunal loops wall thickening with a hyperdense appearance because of intramural hemorrhage (arrows), and (C) “Pooling” of active bleeding at mesenteric fold (white arrow) and a peritoneal recess (arrowhead) associated with a large amount of free hemoperitoneum at the paracolic gutters (black arrows).


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Figure 10 MDCT of mesenteric injuries after blunt trauma. Two distinct cases. (A) High-density fluid collection at a mesenteric fold (arrows) with typical “triangle” shape adjacent to a duodenal loop and (B) arterial mesenteric vessels (arrows) with a beaded appearance, irregular, contours and abrupt termination within a highdensity mesenteric hematoma; large amount of free hemoperitoneum is also evident.

Serosal tears, bowel wall contusion and hematomas without wall thickness tear, and mesenteric hematomas in the absence of active bleeding can initially be monitored and treated conservatively.21 The sensitivity and specificity of bowel and mesenteric injuries at CT compared with surgical findings are reported in the paper by Atri et al.22

Conclusions Timely identification of pancreatic, small bowel, and mesenteric injuries is important because morbidity and mortality of trauma patients may increase significantly in cases of delayed or missed diagnosis. Because clinical signs and symptoms are often subtle and misleading, CT imaging is the only tool available to reach a correct diagnosis and the most appropriate treatment. Although CT findings may be initially minimal, a rigorous contrast-enhanced CT protocol is essential for a comprehensive and definitive assessment. Finally, in doubtful cases, force vectors and trauma dynamics may be

Figure 11 MDCT of active bleeding in the mesenteric root and peritoneal spaces. (A) Nonenhanced axial CT scan shows a high-density fluid collection at the mesenteric root (arrow). (B-D) Contrast-enhanced MDCT scans acquired at the arterial (B), portal (C), and delayed (D) phases demonstrate an increasing “pooling” of ongoing hemorrhage spreading from the mesenteric root (B) to the peritoneal spaces (C, D).

370 the only basis to warrant a follow-up CT study to confirm or exclude the presence of a traumatic injury.

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M. Scaglione et al 12. Soto JA, Alvarez O, Múnera F, et al: Traumatic disruption of the pancreatic duct: Diagnosis with MR pancreatography. AJR Am J Roentgenol 176:175-178, 2001 13. Killeen KL, Shaunmuganathan K, Poletti PA: Helical computed tomography of bowel and mesenteric injury. J Trauma 1:26-36, 2001 14. Malhotra AK, Fabian TC, Katsis SB, et al: Blunt bowel and mesenteric injuries: The role of screening computed tomography. J Trauma 48:91100, 2000 15. Brody JM, Leighton DB, Murphy BL, et al: CT of blunt trauma bowel and mesenteric injury: Typical findings and pitfalls in diagnosis. Radiographics 20:1525-1537, 2000 16. Yu J, Fulcher AS, Turner MA, et al: Blunt bowel and mesenteric injury: MDCT diagnosis. Abdom Imaging 36:50-61, 2011 17. Bugis SP, Blair NP, Letwin ER: Management of blunt and penetration colon injuries. Am J Surg 163:567-550, 1992 18. Pinto A, Scaglione M, Giovine S, et al: Comparison between the site of multislice CT signs of gastrointestinal perforation and the site of perforation detected at surgery in forty perforated patients. Radiol Med 108: 208-217, 2004 19. Pinto A, Magliocca M, Scaglione M, et al: Role of computerized tomography in the diagnosis of peritoneo-intestinal lesions resulting from closed trauma. Experience at 2 emergency departments [in Italian]. Radiol Med 101:177-182, 2001 20. Scaglione M, Lassandro F, Romano L, et al: Value of contrast-enhanced CT for managing mesenteric injuries after blunt trauma: Review of five-year experience. Emerg Radiol 9:26-31, 2002 21. Hanks PW, Brody JM: Blunt injury to mesentery and small bowel: CT evaluation. Radiol Clin North Am 41:1171-1182, 2003 22. Atri M, Hanson JM, Grinblat L, et al: Surgically important bowel and/or mesenteric injury in blunt trauma: Accuracy of multidetector CT for evaluation. Radiology 249:524-533, 2008