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Traumatic Disruption of the Pancreatic Duct

Diagnosis with MR Pancreatography

¹ Department of Radiology, Universidad de Antioquia, Hospital Universitario San Vicente de Paúl, Calle 64 x Kra. 51D, Medellín, Colombia.
² Department of Gastroenterology, Universidad de Antioquia, Hospital Universitario San Vicente de Paúl, Medellín, Colombia.
³ Department of Pediatrics, Universidad de Antioquia, Hospital Universitario San Vicente de Paúl, Medellín, Colombia.

Received March 30, 2000; accepted after revision June 8, 2000.

 
Address correspondence to J. A. Soto.

Abstract

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OBJECTIVE. We evaluated the ability of MR pancreatography to reveal traumatic disruptions of the pancreatic duct compared with retrograde pancreatography.

CONCLUSION. MR pancreatography is an adequate noninvasive test for the detection of complete traumatic disruptions of the main pancreatic duct. MR pancreatography is especially useful for delineating the segments of the duct that cannot be evaluated with retrograde pancreatography.

Introduction

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Pancreatic injuries occur in 2-12% of patients with blunt abdominal trauma [1, 2]. These injuries are being recognized with increasing frequency, in part because of the widespread use of helical CT in trauma patients. Helical CT is a sensitive method for revealing injuries in the pancreatic parenchyma [3], but determination of duct integrity may require retrograde pancreatography [4, 5]. However, this procedure is invasive and may result in significant complications. Although a potential role for MR pancreatography in the examination of pancreatic trauma patients has been recently suggested [6], it is unclear if duct injuries are adequately revealed on MR imaging. We assess the ability of MR pancreatography to reveal traumatic duct disruptions compared with retrograde pancreatography; we also describe the characteristic MR imaging appearance of pancreatic fracture lines.

Materials and Methods

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From February 1999 through January 2000, 12 patients with pancreatic injuries were treated at our institution. Four patients underwent surgical resection (distal pancreatectomy) during the 24 hr that followed admission, before MR imaging could be performed. The clinical condition of one additional patient hindered transportation to the MR imaging suite. The remaining seven patients were examined with MR imaging, mainly to evaluate the status of the pancreatic duct. These seven patients constitute the population of this article. Before MR imaging, diagnosis of pancreatic trauma was established with helical CT in five patients and with surgical findings in two patients. Five patients were male and two were female. The mean age was 16 years (age range, 5-33 years). Mechanism of injury was blunt trauma in six patients and penetrating trauma in one patient. Mean delay between the traumatic event and MR imaging was 6 days (range, 1-15 days). Before MR imaging was performed, informed consent was obtained from the patient or a close relative. Retrograde pancreatography was performed 1-6 days (mean, 3 days) after MR imaging.

MR imaging was performed on a 1.5-T system (ACS-NT; Philips Medical Systems, Best, The Netherlands). We used a body coil for adult patients and a surface coil (E1; Philips Medical Systems) for children. The MR imaging protocol included a fat-suppressed T1-weighted spin-echo axial sequence (TR/TE, 400/12; acquisitions, 4; matrix, 172 x 256; scan time, 5 min 50 sec) and a fat-suppressed T2-weighted fast spin-echo axial sequence (3000/120; acquisitions, 4; matrix, 185 x 256; echo train length, 21; scan time, 4 min 40 sec). Non—fat-suppressed T1-weighted spin-echo axial images (400/12; acquisitions, 4; matrix, 172 x 256; scan time, 5 min 23 sec) were also acquired in four patients. For MR pancreatography, we used a non—breath-hold respiratory-triggered three-dimensional (3D) fast spin-echo sequence (TR range/TE, 2000-2300/240; partition thickness, 2 mm [40 partitions, 8 slabs]; acquisitions, 2; matrix, 128 x 256; echo train length, 39-43). This sequence was performed in the coronal and axial planes in all patients. In four patients, we also performed a breath-hold single-section half-Fourier rapid acquisition with relaxation enhancement sequence (TR/TE, infinite/300; section thickness, 35 mm; acquisitions, 1; matrix, 128 x 256; echo train length, 128; scan time, 2.5 sec; 65% partial K-space filling factor).

MR images were interpreted by two radiologists, and diagnosis was reached by consensus. No information regarding clinical status of the patient or results of other imaging studies was provided to the radiologists. Interpretation occurred at an independent workstation (Easy Vision; Philips Medical Systems). When required, the radiologists generated two-dimensional and 3D reformations of MR pancreatography raw data, using standard software available with the workstation (maximum-intensity pixel projection and multiplanar reformation). Postprocessing was performed only on images obtained with the 3D fast spin-echo sequence because the breath-hold sequence provides a "snap-shot" image of the biliary tree and pancreatic duct; therefore, no postprocessing is necessary.

The radiologists initially evaluated MR images for degradation by motion artifacts. Subsequently, they assessed the status of the pancreatic duct by determining the presence of the following abnormalities: dilatation (defined as duct diameter measuring 2 mm and classified as focal or diffuse), transection (focal interruption of duct continuity), and apparent communication with fluid collections (when present). Additional findings that were recorded included pancreatic fracture line, peripancreatic fluid collections, ascites, and associated organ injuries. MR imaging findings were compared with those of retrograde pancreatography.

Results

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In two patients, MR images were degraded by motion artifacts. However, all studies were deemed diagnostic by the radiologists. A complete pancreatic fracture line was identified in all patients and was seen as linear discontinuity of gland parenchyma extending from the anterior to the posterior surface (Figs. 1A,1B,1C,1D and 2A,2B,2C,2D). Fractured segments were separated in all patients, and the space between the fractured portions was occupied by fluid (Fig. 1A,1B,1C,1D). The fracture was located in the neck of the gland in two patients (Fig. 2A,2B,2C,2D), in the body in three patients (Fig. 1A,1B,1C,1D), and in the tail in two patients.

View larger version (143K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1A. —22-year-old man with pancreatic fracture resulting from motor vehicle collision. Axial fat-suppressed T1-weighted MR image shows normally hyperintense pancreatic parenchyma divided by fracture (curved arrow). Note peripancreatic fluid collection (straight arrow).

View larger version (129K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1B. —22-year-old man with pancreatic fracture resulting from motor vehicle collision. Axial fat-suppressed T2-weighted MR image shows peripancreatic fluid collection (straight arrow) and intrapancreatic collection (curved arrow) occupying space between gland fragments. Note apparent communication of duct in tail with fluid collection (open arrow).

View larger version (133K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1C. —22-year-old man with pancreatic fracture resulting from motor vehicle collision. MR cholangiopancreatogram obtained using three-dimensional fast spin-echo sequence (frontal maximum-intensity pixel projection reformation) shows slightly dilated duct in tail of gland (short arrow) and fluid collections (long arrows). Note normal common bile duct (open arrow).

View larger version (137K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1D. —22-year-old man with pancreatic fracture resulting from motor vehicle collision. Retrograde pancreatogram obtained on same day as A-C shows site of duct disruption (straight arrow) and contrast material accumulating in fluid collection (curved arrow). Duct segment located beyond fracture line is not visible.

View larger version (162K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 2A. —15-year-old boy with upper abdominal trauma from bicycle crash. Helical CT (not shown) revealed pancreatic fracture and fluid collections. Patient underwent surgical exploration and drainage of fluid collections before MR imaging. Fat-suppressed T1-weighted axial MR image shows fracture in neck of pancreas (straight arrow), small residual fluid collection (curved arrow), and dilated pancreatic duct (open arrow).

View larger version (160K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 2B. —15-year-old boy with upper abdominal trauma from bicycle crash. Helical CT (not shown) revealed pancreatic fracture and fluid collections. Patient underwent surgical exploration and drainage of fluid collections before MR imaging. Fat-suppressed T2-weighted axial MR image shows fracture site (straight arrow), fluid collection (curved arrow), and dilated pancreatic duct (open arrow).

View larger version (137K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 2C. —15-year-old boy with upper abdominal trauma from bicycle crash. Helical CT (not shown) revealed pancreatic fracture and fluid collections. Patient underwent surgical exploration and drainage of fluid collections before MR imaging. MR cholangiopancreatogram obtained with three-dimensional fast spin-echo sequence (frontal maximum-intensity pixel projection reformation) shows peripancreatic fluid collection (curved arrow) and dilated duct in body and tail of gland (open arrow). Note drainage catheter located adjacent to fluid collection (straight arrow).

View larger version (131K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 2D. —15-year-old boy with upper abdominal trauma from bicycle crash. Helical CT (not shown) revealed pancreatic fracture and fluid collections. Patient underwent surgical exploration and drainage of fluid collections before MR imaging. Retrograde pancreatogram obtained 1 day after A-C confirms site of duct disruption (arrowhead) and shows contrast material accumulating in small fluid collection (curved arrow) as well as in surgically placed drain (straight arrow). However, dilated segment of duct was not depicted on retrograde imaging.

In all patients, MR imaging findings indicated disruption of the pancreatic duct associated with the fracture. Disruptions were clearly seen as focal interruptions of duct continuity with proximal dilatation (Figs. 1A,1B,1C,1D and 2A,2B,2C,2D). The presence (as well as the location) of a complete duct disruption was confirmed with retrograde pancreatograms in all patients (Figs. 1A,1B,1C,1D and 2A,2B,2C,2D). The status of the duct in the gland beyond the transection site could not be assessed with retrograde pancreatography. In four patients, MR images showed peripancreatic fluid collections (Figs. 1A,1B,1C,1D and 2A,2B,2C,2D), and retrograde pancreatograms revealed filling of fluid collections from the duct at the site of the transection (Figs. 1A,1B,1C,1D and 2A,2B,2C,2D). In one patient, MR images suggested communication of the dilated duct in the tail of the gland with an intrapancreatic fluid collection (Fig. 1A,1B,1C,1D). Given the location of this apparent communication (beyond the transection site), it could not be confirmed with retrograde pancreatography. Other MR imaging findings included ascites (n = 2), liver laceration (n = 1), and renal contusion (n = 1).

Discussion

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The widespread use of helical CT for blunt abdominal trauma has allowed early recognition of pancreatic injuries, which occur in up to 12% of patients with significant trauma [1, 2]. The typical mechanism of trauma involves compression of the pancreas against the vertebral bodies [7]. This compression may result in a pancreatic contusion, hematoma, complete fracture, or partial laceration. Despite early diagnosis, treatment of pancreatic injuries remains problematic, with a mortality rate exceeding 30% [1, 2]. The presence of a main pancreatic duct disruption appears to be an important factor determining the prognosis of patients with parenchymal injuries [2]. Surgical exploration, with or without operative pancreatography, has traditionally been considered the treatment of choice for pancreatic transections and duct disruptions [1, 8]. However, nonoperative therapy with endoscopic intervention has recently been shown to be an effective alternative to surgery [4, 5].

On well-performed contrast-enhanced helical CT, pancreatic injuries may appear as diffuse gland enlargement with pancreatitis, as peripancreatic hematoma, or as large peripancreatic fluid collections. However, subtle findings such as focal enlargement, small accumulations of fluid in peripancreatic spaces, or contour irregularities may be the only signs suggesting a relatively minor injury [3, 9]. A pancreatic fracture line is shown on CT as a hypoattenuating line involving the neck, body, or tail of the gland. This fracture is easily detected when there is sufficient separation of the fractured pancreatic fragments. However, diagnosis is difficult when this separation is minimal or nonexistent. The fracture line is occupied with fluid; therefore, MR imaging depicts it as hyperintense on T2-weighted images and hypointense on T1-weighted images.

Because main duct disruption is a critical factor determining the prognosis of pancreatic trauma patients, the early assessment of duct integrity is crucial. Presence of a complete fracture is usually associated with a concomitant duct transection. Occasionally, the pancreas may have almost normal morphologic features on CT despite the presence of a duct disruption [10]. Therefore, retrograde pancreatography is the test usually performed when duct disruption is suspected [5].

MR pancreatography has emerged as a useful noninvasive tool for diagnosing various abnormalities affecting the pancreas and the pancreatic duct. Its value for revealing malignant and benign focal duct stenoses [11, 12], changes of chronic pancreatitis [11, 12], and congenital anatomic variants [11, 12] has been well established. A potential use of MR pancreatography in the setting of abdominal trauma has also been proposed [6, 12]. Nirula et al. [6] recently described their experience using MR pancreatography with four trauma patients and concluded that it is an attractive technique for the evaluation of pancreatic injuries. However, their patients did not undergo retrograde pancreatography to confirm MR pancreatography findings.

We describe our experience with MR pancreatography for the determination of main pancreatic duct integrity in seven trauma patients. MR pancreatography accurately depicted the status of the duct and the site of duct disruption in all patients. Moreover, segments of the duct located beyond (upstream of) the injury site were well depicted on MR pancreatography but not on retrograde pancreatography. This advantage of MR pancreatography over retrograde pancreatography could be of critical importance because fluid collections may communicate exclusively with the proximal duct.

Although our conclusions are limited by the small number of patients included in our study, our preliminary data suggest that MR pancreatography is an adequate noninvasive alternative for determining the duct integrity of trauma patients. Given the risks of significant procedure-induced pancreatitis and other complications that can occur with retrograde pancreatography, the noninvasive nature of MR pancreatography makes it an appealing diagnostic test. Although MR imaging is unlikely to replace CT as a method for the diagnosis of pancreatic injuries, MR pancreatography can be used to plan therapeutic surgical or retrograde interventions in this setting. However, confirmation of this use will require further testing in a larger patient population.

References

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