To describe normal anatomy and common variants in biliary tree anatomy including the prevalence of these.

Transcription

1 Up for debate: Should 3.0T magnetic resonance pancreatography (MRCP) become a routine part of preoperative planning for patients undergoing laparoscopic cholecystectomy? Poster No.: C-0196 Congress: ECR 2010 Type: Topic: Educational Exhibit Abdominal Viscera (Solid Organs) Authors: D. Deeab, M. Khoo, M. Pelling, L. Sundblom, A. Anstee, W. Gedroyc, E. A. Dick; London/UK Keywords: DOI: 3 TESLA, MRI, pre laproscopic cholecystectomy /ecr2010/C-0196 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 17

2 Learning objectives To compare the spatial resolution of MRCP at 1.5T and 3.0T. To highlight how the improvements in spatial and temporal resolution of MRCP in 3 Tesla MRI have led to greater recognition of diseases and variants of the biliary tree. To describe normal anatomy and common variants in biliary tree anatomy including the prevalence of these. To outline the potential complications of laparoscopic cholecystectomy (LC). To debate whether 3.0T MRCP should be incorporated into routine pre-operative planning. Background Laparoscopic Cholecystectomy &its complications. The annual rate of laparoscopic cholecystectomy (LC) is 2/1000 population in US. Although LC has the advantage of being minimally invasive, it has a higher complication rate than conventional surgery and the rate of bile duct injury is %. Early complications: Common bile duct injury Bile leak Injury to viscera Hemorrhage Retained stones and abscess formation Biliary strictures Cystic duct clip stones Hemorrhage Misinterpretation of anatomy 70% Technical Errors Page 2 of 17

3 Given the potential complications of laparoscopic cholecystectomy, a noninvasive pre-operative "road map" of the biliary tree may be of value. Late complications: Common causes of CBD injury: Biliary strictures Cystic duct clip stones Hemorrhage Misinterpretation of anatomy 70% Technical Errors Given the potential complications of laparoscopic cholecystectomy, a noninvasive pre-operative "road map" of the biliary tree may be of value. Common causes of CBD injury: Misinterpretation of anatomy 70% Technical Errors Given the potential complications of laparoscopic cholecystectomy, a noninvasive pre-operative "road map" of the biliary tree may be of value. Anatomy of the biliary tree: According to the Couinaud classification, the liver consists of eight distinct hepatic segments, which have their own portal venous supply, hepatic venous and biliary drainage. (4). The classical orientation of the biliary tree found in % of population. (1, 4) The main hepatic duct (MHD) composed of union of right (RHD) and left hepatic ducts (LHD). The RHD drains segments V to VIII, usually formed by anterior and posterior segmental ducts. The right anterior duct drains segments V and VIII and has vertical course. The right posterior duct drains segments VI and VII and has almost horizontal course. The right posterior duct normally passes posterior to the right anterior duct and joins it from the left to form the right hepatic duct. There is a variable number of segmental left hepatic ducts joining to form the main LHD. The LHD drains segments, II to IV. After the confluence of the hepatic ducts, the common hepatic duct (CHD) is formed by convergence the of the main right and left hepatic ducts about 1 cm from the liver margin. The CHD transforms into the common bile duct (CBD) at the site of site of cystic duct insertion. The average diameter of the CBD is 5 mm in patients aged 50 years or younger and increases by 1 mm per decade of life after age 50. (1).The major and minor pancreatic ducts drain into the major and minor duodenal papillae, respectively. The papillae, in turn, open into the medial wall of the descending part of the duodenum. The maximum Page 3 of 17

4 diameter of the pancreatic duct is less than 3 mm on average but increases with age. The terminal portion of the CBD and pancreatic duct is encircled by smooth muscle formed by a common channel called the sphincter of Oddi. The sphincter complex consists of this muscle, the distal (intramural) part of CBD and pancreatic duct, and the papilla. The slightly dilated distal segment of the common channel also is known as the ampulla. Common variants of the biliary tree: Union of the RHD and the LHD 1) Drainage of the right posterior duct into the left hepatic duct before its confluence with the right anterior duct is the most common anatomic variant of the biliary system and reported to occur in 13-19% of the population.(4) 2) Triple confluence anomaly in which there is failure of formation of the right hepatic duct. The confluence is found in 11% of population and formed by the right posterior duct, right anterior duct, and left hepatic duct. 3) The right posterior duct will join into the right instead of the posterior aspect of the right anterior duct. This is found in 12 % of population. Cystic duct variants. 1. Low cystic duct insertion, characterized by a fusion of the cystic duct with the distal third of the extra hepatic bile duct (9%). As shown in figure 4 (C) 2. Medial cystic duct insertion, in which the cystic duct drains into the left side of the common hepatic duct. (D) 3. Parallel course of the cystic duct and CHD over at least a 2-cm segment. (E) Images for this section: Page 4 of 17

5 Fig. 1: Figure1 Pie chart shows percentages of Laparoscopic Cholecystectomy complications. Page 5 of 17

6 Fig. 2: Figure 1. Picture demonstrating the cystic duct/ common bile duct junction Page 6 of 17

7 Fig. 3: Figure 3. Drawing shows the normal anatomy of the non-dilated biliary tree. Page 7 of 17

8 Fig. 4: Figure 3. Variation of the anatomy of the cystic duct. Normal (60%), (A): accessory duct (of Luschka) draining into the cystic duct distal to the common bile duct junction (B); low insertion of the cystic duct onto the common hepatic duct, just proximal to its entry into the duodenum (C); spiral cystic duct joining the common hepatic duct posteromedially (D); parallel course of the cystic duct and common hepatic duct (E); right hepatic duct insertion (F); absent cystic duct (G). Page 8 of 17

9 Imaging findings OR Procedure details Magnetic Resonance pancreatography (MRCP) Recent developments in MRI, including higher fields, phased array coils and parallel imaging have further improved the diagnostic capability of MRCP (1). MRCP combines both cross sectional and projectional images. It can be used for presurgical planning and post-operative follow up where necessary. MRCP is also useful in failed or incomplete ERCP. (1) The advantages of 3T over 1.5 T MRCP as Patel et al (1) showed: 1. The signal to noise ratio at 3T is twice that at 1.5 T, and has been shown to produce significant better spatial resolution. (1). The contrast to noise ratio between periductal tissue and the bile duct is greater at 3T than 1.5 T, (Merkle,3) 2. Better identification of the intrahepatic biliary tree. This is important in identification of the disease of the non-dilated biliary tree and the normal variants.(2)(3) 3. 3T MRCP has an important role in pancreatic diseases, as there is better delineation of the pancreatic duct, especially the side branches. 4. Thin slices can acquired which lead to less motion artefact. MRCP has the following advantages over ERCP (5) 1. Non invasive with no complications such as sepsis, bile leak or pancreatitis which occur in 3% of ERCPs. 2. Does not require sedation. 3. Enables assessment of the ductal wall, periductal tissue and pancreatic parenchyma. 4. Lack of ionizing radiation, high soft tissue contrast, multiplaner reformatting capabilities 5. The quality of the images is improved with the introduction of 3T MRI. 6. Cost However, biopsy and interventional procedures cannot be performed by MRCP. MRCP should be performed with phased-array multicoils, to ensure high signal to noise ratio. After performing 3 plane localiser and calibre scan we perform the protocol shown in table 1. Page 9 of 17

10 Axial FIESTA Coronal FIESTA 2D radial thin SLAB 2D radial thick 3D MRCP Respiration SLAB FOV 40 cm 40 cm (MIP) Phase FOV Slice 5 thickness(mm) 1mmspace TE Minimum possible 5 1mmspace Minimum possible Minimum possible Minimum possible TR Flip angle Minimum possible 2D MRCP coronal thin slices frequency 200x x x X224 NEX BW ETL Imaging option 2D FIESTA 2D FIESTA 2D SE, FAT SAT. 2D SE, FAT SAT. 3D FRFSE 900 2D FRFSE fast imaging employing steady state acquisition fast imaging employing steady state acquisition Spin echo fat saturation Spin echo fat saturation Fast recovery fast spin echo Fast recovery fast spin echo Images for this section: Page 10 of 17

11 Fig. 1: showing the normal anatomy of the non-dilated biliary tree (40mm) thick Slices on 3T MRI 2D thin SLAB. Page 11 of 17

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13 Fig. 2: magnified view of the non-dilated biliary tree (40mm) on 3T MRI 2D thick slab Page 13 of 17

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15 Fig. 3: 3D MIP MRCP 1.6mm (thin slices) showing the normal non-dilated biliary tree for the same patient in the same patient. Fig. 4: 3 Tesla MRCP oblique thick slices 70mm, showing dilated CBD & normal pancreatic duct in another patient.. Page 15 of 17

16 Conclusion MRCP is the investigation of choice in the evaluation of the biliary tree and the pancreatic duct and is comparable to diagnostic ERCP. It is non-invasive and more economical procedure which usually does not require sedation.(5) 3.0 TESLA MRI offers better spatial resolution for both source and Maximum Intensity Projection images which can be reviewed by the surgeon and radiologist together to reduce the risk of duct damage. Personal Information D. Deeab, M. Khoo, M. Pelling, L. Sundblom, A. Anstee, W. Gedroyc; D. A. Dick Department of Radiology, St Mary's Campus, Imperial College NHS Trust, London, UK For infomration please contact Dr. Dhafer Deeab References 1. MR Cholangiopancreatography at 3.0 T, RadioGraphics 2009; 29: , Hemant T. Patel, MD, DNB, DMRE Ankur J. Shah, MD Shikha R.Khandelwal, DMRD Hiren F. Patel, MBBS Megha D. Patel, MBBS Versus 1.5-T MRCholangiography: A Pilot Study AJR 2006; 186: E M. Merkle1P. A. HauganJ. ThomasT. A. JaffeC. Gullotto 3. The potential of 3.0 Tesla MRI - focus on abdominopelvic imaging,rad Magazine, 35, 410, 31-32July 2009,Dr Elizabeth Dick, Consultant Radiologist and Honorary Senior Lecturer Imperial College NHS Trust, London 4. Anatomic Variants of the Biliary Tree: MRCholangiographic Findings and Clinical Applications, AJR 2001;177: X/01/ American Roentgen Ray Society Koenraad J. Mortelé1,2 and Pablo R. Ros3 5. MR cholangiopancreatography, APPLIED RADIOLOGY, March Aliya Qayyum, MD and Fergus V. Coakley Page 16 of 17

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