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1
Department of Radiology (R-109), University of Miami School of Medicine,
Jackson Memorial Medical Center, 1611 N. W. 12th Ave., West Wing 279, Miami,
FL 33136.
2
Department of Radiology, Jackson Memorial Hospital—MRI, Diagnostic
Treatment Center, 1080 N. W. 19th St., Miami, FL 33136.
3
Department of Surgery (M-875), University of Miami School of Medicine, P. O.
Box 016310, Miami, FL 33101.
Received October 2, 2000;
accepted after revision July 3, 2001.
Address correspondence to V. J. Casillas.
Abstract
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SUBJECTS AND METHODS. In this prospective study, MRCP was performed in 10 postoperative patients (nine female and one male, ranging in age from 17 to 79 years) suspected of having bile duct injury as a result of surgery. Presence or absence of biliary dilatation, excision injury, stricture, fluid collection, and free fluid was noted. Excision injury was diagnosed if a segment of bile duct was not visible on any of the MRCP sequences. Positive cases were classified according to anatomic location and extent of injury. Results were compared with endoscopic retrograde cholangiopancreatography in five patients, percutaneous transhepatic cholangiography in one, surgery in four, and clinical follow-up in three.
RESULTS. Three patients had normal findings on MRCP and remained asymptomatic on clinical follow-up. Four patients had bile duct excision injury on MRCP that was surgically proven, and one had stricture, confirmed by percutaneous transhepatic cholangiography. Of these five patients, one had Bismuth type I injury, two had type II, one had type III, and one had type IV. Two patients had findings suggestive of cystic duct leak on MRCP that were confirmed on cholangiography.
CONCLUSION. MRCP can accurately diagnose postoperative biliary strictures and excision injuries and can characterize and anatomically classify these injuries for planning reparative surgery. It can also suggest the presence of cystic duct leaks in patients who have undergone cholecystectomy.
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Nine patients were female and one was male; their ages ranged from 17 to 79 years. Nine of the 10 patients had undergone cholecystectomy (seven laparoscopic and two open surgeries) and one had undergone extensive and difficult gallbladder fossa dissection during abdominal aortic aneurysm repair. The latter was an unusual case of severe kyphoscoliotic deformity and aortic aneurysm lying intrahepatically. Surgical resection was difficult because adhesions due to diverticulitis were present in the right upper quadrant. Postoperative biliary injury was suspected because this patient had persistent right upper quadrant pain.
Final diagnosis was made on the basis of findings at surgery in four patients, at ERCP in one, on transhepatic cholangiography in one, and on the cholangiogram obtained at catheter injection in one. In three patients with clinical findings suggestive of bile duct injury, MRCP showed negative findings. Contrast cholangiography was not performed in these three patients; they were treated conservatively and followed up to clinical recovery.
Technique
MRCP was performed on a 1.5-T scanner (Picker Eclipse; Marconi, Cleveland,
OH) using VIA 2.0 software (Marconi), an image quality—enhancing
program. A body coil was used on all patients. Breath-hold T2-weighted
half-Fourier acquisition single-shot turbo spin-echo (HASTE) fat-suppressed
imaging was performed using the following parameters: TR/effective TE,
18,000/80; matrix, 256 x 256; acquisitions, 1; scanning time, 18 sec.
HASTE is a rapid spin-echo sequence and a single-shot acquisition technique
that collects all the data in one TR period in a single 18-sec breath-hold and
uses half-Fourier acquisition. Axial images were acquired first with 8-mm
slice thickness, no gap. Four 30- to 50-mm-thick sections were then acquired
in oblique coronal planes in the course of the bile duct (as seen in the axial
images) using a field of view of 35 cm. The scanning time for each thick
section was less than 8 sec. Next, 5-mm-thick no-gap coronal images were
obtained. Three-dimensional images were generated from the coronal source
images using maximum-intensity-projection algorithms and multiplanar
reformatting techniques. The total scanning time in all patients was between
10 and 15 min.
MRCP was performed from 1 to 30 days after the initial surgery; eight of 10 patients were imaged within 2 weeks of surgery. The images were considered to be of diagnostic quality in all patients and no examination had to be canceled because of lack of patient compliance.
Interpretation
All examinations were interpreted clinically at the time of patient
presentation by two experienced abdominal imaging radiologists without
knowledge of any other radiologic investigations whose final decisions were
reached by consensus. MR imaging was evaluated in all patients for bile duct
discontinuity, stricture, biliary dilatation and proximal anatomy filling
defects, free fluid, collections, and other associated findings. Biliary
excision injury was defined as complete lack of visualization of a bile duct
segment on MR cholangiopancreatographic images as well as on the source
images.
When biliary excision or stricture was seen, an attempt was made to classify the finding according to the Bismuth classification [7, 8] (Fig. 1). Bismuth type I injury is a traumatic injury of the main bile duct occurring more than 2 cm distal from the biliary confluence. A type II injury is located less than 2 cm from the biliary bifurcation. A type III injury completely destroys the common hepatic duct stump but leaves the confluence intact. A type IV injury completely or partially involves the biliary confluence. A type V injury (not shown at Fig. 1) involves the right variant segmental branch, with or without involvement of the main duct.
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ERCP was performed in five patients and PTC in one. ERCP cannulation failed in one patient. Cholangiography in this patient was incidentally performed on fistulography at fluoroscopy of a subhepatic fluid collection. The radiologists interpreting contrast-enhanced cholangiograms were unaware of the results of MRCP. The MR imaging findings were then compared with either ERCP or transhepatic cholangiography.
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Of the seven patients with abnormal findings, four had excision injuries, including two biliary excisions with leak (one with ductal ligation), one partial excision with obstruction, and one ligation with obstruction. One patient had short stricture, and two patients had leaks from patent cystic duct remnants. All seven patients with findings positive for biliary injury underwent cholangiography, surgery, or both within 3 days of MRCP.
Bismuth Classification
One patient had Bismuth type I injury, two had type II, one had type III,
and one had type IV on MRCP. Final diagnosis in all these patients was based
on either surgery (n = 4) or PTC (n = 1). Two patients were
not classified because they showed leak from cystic duct remnant.
Stricture
One patient had Bismuth type I injury with tight stricture (<1 cm in
length) at the mid common bile duct. MRCP revealed biliary dilatation and no
free fluid (Fig.
2A,2B).
PTC was performed but added no further information. The stricture was treated
by balloon dilatation.
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Excision Injury
Four patients showed evidence of bile duct excision seen on MRCP as a
persistent discontinuity in the visualization of a bile duct segment on thick
sections and coronal source images. One patient had Bismuth type II injury
with a 1.8-cm-long discontinuity and intrahepatic biliary dilatation on MRCP.
ERCP showed only the distal common bile duct stump and a complete cutoff at
that point (Fig.
3A,3B).
The proximal common hepatic duct had been partially excised and clipped at
surgery, leading to obstruction. Hepaticojejunostomy was performed using the
Hutson-Russell procedure
[9].
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In one patient, MRCP showed a Bismuth type III injury with a 2-cm-long discontinuity and intrahepatic biliary dilatation. ERCP showed only the distal stump of the common bile duct. Evidence was found at surgery of extensive fibrosis as the cause of obstruction at the porta hepatis, and clipping of the common bile duct was noted. Hepaticojejunostomy was performed.
One patient had a Bismuth type IV injury with a 4-cm-long discontinuity involving the bifurcation, absence of biliary confluence, presence of free fluid, and no biliary dilatation on MRCP (Fig. 4). ERCP was not performed. At surgery, four transected ducts were seen in the hilar region with evidence of bile leak in the peritoneal cavity. Hepaticojejunostomy and the Hutson-Russell procedure were performed for reconstruction of the ductal anastomosis.
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MRCP revealed a Bismuth type II injury in one patient with a 2-cm-long discontinuity just distal to bifurcation, a fluid collection 3 mm in diameter, and free fluid. ERCP showed the distal common bile duct stump and a complete cutoff. At surgery, evidence was seen of ligation of the common hepatic duct near the bifurcation with cautery injury at the bifurcation leading to bile leak. Evidence of right hepatic artery ligation was also noted. Hepaticojejunostomy was performed.
We found that MRCP allowed differentiation between bile duct excision (n = 4) and stricture (n = 1). All three patients who presented with jaundice had biliary ductal dilatation on MRCP and were found to be obstructed at surgery or PTC.
Bile Leak
In two patients, MRCP revealed an intact biliary tree with small
collections adjacent to the cystic duct remnant and evidence of free fluid.
Cystic duct leak was suggested as the diagnosis on the basis of these
findings. One patient had ERCP that confirmed bile leak (Fig.
5A,5B).
This patient was treated by endoscopic sphincterotomy. In the second patient,
the collection was drained by percutaneous catheter and follow-up
fistulography via the catheter showed communication with the bile duct, thus
confirming the leak. This patient had an unusually long cystic duct
remnant.
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Another two patients with excision injury were found to have free fluid on MRCP, as already described. Both of these patients had proven bile leaks at surgery. ERCP on one of these patients failed to reveal the leak because the injury was proximal to the site of obstruction. MRCP showed no free fluid in six patients. All six patients had negative findings for bile leak on PTC (n = 1), surgery (n = 2), or followup (n = 3), but three of the six had limited subhepatic collections away from the surgical bed.
Four patients underwent sonography or CT; all showed loculated fluid collections in the right upper quadrant. In addition, two patients showed free fluid in the right upper quadrant or elsewhere in peritoneal cavity. None of the seven patients with findings positive for biliary injury on MRCP showed biliary dilatation on sonography or CT.
Most of the patients had multiple metallic clips in the gallbladder area and around the common bile duct. No image-degrading susceptibility artifact was noted in our study, perhaps because we used the half-Fourier technique as described [4]. None of the patients with metallic clips had complications after MRCP.
Comparison of MRCP with ERCP and PTC
ERCP was performed in five patients; in four of these patients, MRCP was
superior for the purposes of surgical planning. In three patients with
excision injury of the bile duct, MRCP accurately revealed the proximal
biliary anatomy and the site of the injury, whereas ERCP showed only the
distal stump of the remaining bile duct. ERCP cannulation failed in one
patient with cystic duct leak, whereas MRCP showed findings that suggested the
diagnosis. In another patient whose findings on MRCP suggested cystic duct
leak, the diagnosis was confirmed on ERCP. One patient had PTC followed by the
initial MRCP. No additional information was revealed on PTC.
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Postoperative bile duct injury may be classified as a leak, stricture, or complete transection and excision of a segment of duct, with or without obstruction of the proximal biliary tree by surgical clips. Percutaneous stenting and balloon dilatation are variably used by different institutions; however, the procedures are generally more useful for recurrent strictures or for patients who are not candidates for surgery [1,10]. Bismuth classification, which requires display of the entire biliary anatomy, is a useful method for surgical planning in these patients. When stricture or excision is present, the length of the intact common duct distal to the bifurcation determines whether choledochojejunostomy or hepaticojejunostomy is performed, whereas disruption of the confluence requires its reconstruction in addition to hepaticojejunostomy [1].
To our knowledge, only one article, based on a study of five patients by Yeh et al. [5], has described MR cholangiopancreatographic findings in such patients. However, these researchers included two patients who had undergone biliary reconstruction surgery. One patient did not have bile duct injury but presented with similar clinical findings caused by retained calculi in the common bile duct. In that study, only two patients had MRCP before surgical reconstruction. Both were classified as Bismuth type II injury. One of these patients appears to have an injury that is comparable to a patient in our study with Bismuth type II injury (Fig. 3A,3B). Our study gives a more elaborate account of ductal injuries on MRCP than does the research presented by Yeh et al., and we focus on the recognition of such injuries before surgical reconstruction.
In our study, MRCP accurately diagnosed stricture (n = 1) and excision injuries (n = 4). The location of injury was accurately predicted in all cases by applying the Bismuth classification to findings on MRCP. Because MRCP can display the entire biliary tree, it is useful in predicting biliary obstruction (n = 2) and in depicting the length of the injury, making MRCP an ideal tool for preoperative planning.
It has been stated that it is difficult to distinguish between biliary stricture and transection on MRCP [10]. In our experience, if a segment of common bile duct showed complete lack of visualization on MR cholangiopancreatographic images as well as on the source images, transection and probably excision might be present (Fig. 3A,3B). This finding was seen clearly in four patients in our study. Three of these patients also underwent ERCP that did not add further information; therefore, ERCP was not performed in the fourth patient (Fig. 4). This patient had a proximal injury suggested by the lack of visualization of biliary confluence on thick-section MR images as well as on axial and coronal T2-weighted images. (The entire anatomic display of the abnormality on a contrast-enhanced cholangiogram in this situation would require separate injection of the left hepatic duct and multiple right hepatic ducts.)
Small leaks are treated by sphincterotomy and placement of a stent to temporarily divert the bile flow from the injured segment and permit healing [1, 11, 12]. Bile leak or fistula may require surgery, endoscopic papillotomy, or endobiliary stent placement [1, 10]. Large bilomas may be drained under sonographic or CT guidance. Excision injuries and strictures generally require surgery [1, 10].
Bile leak was suggested by findings on MRCP in four patients with free intraperitoneal fluid. Of particular interest were two patients with small collections adjacent to the cystic duct remnant and intact biliary trees (Fig. 5A,5B). All four of these patients had proven leaks. However, ERCP failed to show the leak in one patient because the injury was proximal to the site of obstruction. In a second patient, ERCP failed because the gastroenterologist was unable to cannulate the duct. MRCP correctly predicted the three patients with intact biliary trees as was correlated by clinical follow-up.
Limitations of our study include a small sample size and lack of definitive proof of diagnosis in three patients with negative findings on MRCP. These patients improved on clinical follow-up without intervention (ERCP or surgery); final diagnosis of "no bile duct injury" was therefore based on clinical improvement. The theoretical possibility of a small self-limiting leak (e.g., cystic duct remnant) could not be ruled out in these patients.
Safety of MR imaging with respect to the presence of metallic surgical clips during the immediate postoperative period is a minor concern. Most surgical clips are made from nonferrous material (titanium) and have been proven safe for MR imaging [13]. One group of researchers has reported that magnetic susceptibility artifacts projected over the bile duct can interfere with image interpretation [14]. These artifacts may produce false filling defects or strictures. False filling defects have become less of a concern with the current use of the half-Fourier technique [4].
Separation of postoperative collection from choledochal cyst may be difficult on MRCP, whereas this distinction may be made easily on contrast cholangiography (ERCP or PTC) if the involved duct is opacified. MRCP is not a functional study, and it does not directly show leaks. In our experience, two of four patients with biliary leak had obvious structural changes in the duct on MRCP that required surgical intervention. Presence of free fluid on the right side of the abdomen, with or without fluid collection adjacent to the injured bile duct, should suggest the diagnosis of bile leak. Free or loculated abdominal fluid revealed by CT and sonography has been documented in association with bile leak [11, 12, 15]. Heavily T2-weighted MR imaging, such as MRCP, is extremely sensitive to the detection of unbound fluid.
Accurate diagnosis is a prerequisite for the management of ductal injury caused by cholecystectomy. Abdominal sonography is usually the initial investigation because it is readily available and noninvasive. MRCP is generally considered superior to abdominal sonography of choledocholithiasis because it results in better ductal visualization [16]. To our knowledge, no direct comparison has been made between sonography and MRCP for the evaluation of bile duct injury. However, multiple reports on sonographic findings in patients with bile duct injury have appeared in the literature [12, 17,18,19]. Although sonography may accurately show biliary ductal dilatation and fluid collections, it is difficult on sonography to differentiate among postoperative seroma, hematoma, lymphocele, and bile leak due to bile duct disruption [18,19]. Indeed, nonspecific sonographic and CT findings were seen in three patients in our study who proved to be negative for bile duct injury on MRCP and clinical follow-up. Rayter et al. [17] and Brugge et al. [12] found no notable relationship between sonographic findings and bile leak on radionuclide imaging. Other researchers have found equivocal findings on sonography, CT, or both in frank disruption of the bile duct [18, 19].
A cholangiogram is required for classification of the type of injury and accurate anatomic depiction of a disrupted biliary system before planning surgical reconstruction. Scintigraphy is good for the detection of leakage; however, it lacks the anatomic detail needed for preoperative planning. Direct imaging of the anatomic abnormality often requires cholangiography. In the classic injury involving bile duct transection, ERCP shows only the cutoff sign of the common bile duct. It therefore becomes necessary to perform PTC in order to determine the nature of injury as well as to define the anatomy of the proximal biliary tree. This information is essential in planning the strategy for biliary reconstruction because the type of injury affects the prognosis. Nevertheless, PTC is associated with potentially serious complications, particularly in those who have cirrhosis, ascites, perihepatic bilious collections, and coagulopathy.
Our preliminary research suggests that MRCP has a diagnostic value similar to that of PTC and ERCP in patients with bile duct injuries. MRCP has additional advantages: It is rapid, safe, and noninvasive and therefore can be performed emergently, facilitating the workup in this group of patients whose treatment requires quick decision making. It can "see" above and below the level of obstruction, a capability provided by neither ERCP nor PTC that is essential for surgical planning. It has few contraindications. Finally, it can detect on T2-weighted sectional images other conditions, such as liver abscess, that mimic the bile duct injury pattern of clinical presentation.
In conclusion, our preliminary results support and further elaborate on the findings of Yeh et al. [5] that MRCP is a useful diagnostic test in patients suspected to have bile duct injury after surgery. MRCP depicts the signs of stricture and excision injury accurately and displays the anatomy completely and accurately. The information derived from MRCP enables the radiologist to classify the type of injury and helps to determine treatment, whether endoscopic, percutaneous, or surgical. In our small sample, MRCP accurately predicted an intact biliary tree, visualized transection injuries as different from focal stricture, and predicted the presence of bile leaks. Validation from studies with larger sample sizes is needed to establish the accuracy of this imaging procedure.
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