Sex: female
Age: 68 years
History
1995 resection of breast carcinoma with no evidence of recurrence.
Known gallbladder stone.
Laboratory data
Bilirubin 1,29 mg/dl, GOT 33 U/l, GPT 56 U/l, gGT 430 U/l.
Physical findings
Marked abdominal tenderness of right upper quadrant. No visible jaundice.
Case text
Sudden onset of upper right quadrant abdominal pain with nausea. No fever.
The patient was admitted to the hospital and emergency ultrasound was performed to rule out acute gallbladder inflammation or pancreatitis.
Ultrasound showed the known solitary gallbladder stone but no evidence for acute swelling of the gallbladder wall. The intrahepatic bile ducts appeared normal, and no enlargement of the common bile duct was seen. The pancreatic tissue was visible and showed pronounced fatty degeneration. The pancreatic duct was normal, no peripancreatic fluid collection was seen.
The patient still suffered from intermittent pain attacks.
8 days later cholangiography was performed and showed a marked dilatation of the common bile duct (2cm), with constant filling defect and stop in the distal portion. The gallbladder could not be visualized.
Endoscopic retrograde choledocho-pancreaticography (ERCP) was carried out with the attempt to do a papillotomy for stone removal, but was unsuccessful due to the presence of a duodenal diverticulum.
Due to persistent pain the patient was referred to the Department of Magnetic Resonance Imaging to perform a magnetic resonance choledocho-pancreaticography (MRCP) one week later.
Image 1-4
Magnetic resonance choledocho-pancreaticography (MRCP).
Axial breathhold strong T2-weighted images through the liver and the pancreatic region (TRUE FISP, slice thickness 5 mm, acquisition time: 19 sec).
Image 5-7
MRCP.
Ultrafast single shot fat suppressed image in an oblique orientation. 'RARE Sequence': TSE T2-weighted sequence, TR = 2800, TE =1100, echo train length: 240, slice thickness 70mm, fat saturation, acquisition time 7,12 sec.
Image 8-12
MRCP
Next a series of breathhold single shot fat suppressed T2-weighted images with slightly overlapping thin slices is acquired in the optimal plane that can be reconstructed by a maximum intensity projection (MIP) program.
'HASTE' Sequence: TR = 11.9, TE = 95, half fourier, 13 slices, 4 mm slice thickness, fat saturation, acquisition time 20 sec.
Image 13-16
MRCP, more images.
Image 1-4
1. What structures are best visible on these scans?
These heavily T2-weighted scans show all fluid filled spaces with bright signal. The bile ducts can easily be visualized. The stomach and duodenum are filled with oral negative contrast agent and thus do not show any signal from its contents.
2. What alternative sequences could be used to achieve a similar picture?
Turbo spin echo (fast spin echo) with fat saturation.
3. What is the diagnostic value of these images?
Although these images serve primarily as a road map for the subsequent cholangio sequences, several important information on the bile ducts (diameter, displacement, larger filling defects), as well as some information on the parenchymatous organs of the upper abdomen can be achieved (e.g. liver, pancreatic or renal cysts; larger focal liver lesions, lymph node enlargement).
Image 5-7
4. What is the diagnostic value of these images?
These images show a nice overview of the bile ducts, mimicking the radiographic projection technique. They are somewhat comparable to ERCP or cholangiography images without tomography. Subtle changes of the bile duct walls and small filling defects can be obscured by a overlying or overprojected bright signal from bile as well as the fluid contents of other organs (e.g. fluid filled stomach, spinal canal, renal pelvis) or cysts.
5. What is the importance of the short acquisition time of 7 sec?
This sequence allows for adequate depiction of the biliary tree even in patients that are unable to hold their breath. Due to the short measurement time there is little blurring from respiratory motion, however the image resolution is rather poor (voxel size 1,25x1,17x70 mm)
The shortness of this sequence allows for multiple repetitions in different view angles, if needed.
6. What are the findings in this case?
Marked dilatation of the common bile duct with filling defect in the distal part. Dilatation of the intrahepatic bile ducts. Solitary gallbladder stone.
Image 8-12
7. What is the diagnostic benefit of these images?
Due to the small slice thickness these images show resemblance to conventional tomographic images: The risk of obscuring pathology due to overlying structures is minimized. The spatial resolution is superior to the RARE sequence, and allows for depiction of more subtle pathologic changes (voxel size 1,46x1,37x4 mm).
These images can be postprocessed by a MIP program.
8. Why is the offline reconstruction with the MIP program useful?
The reconstruction of these slices with a MIP algorithm eliminates all non bright signals and allows for a better overview of the biliary tree from arbitrary chosen view angles. Displacement of bile ducts becomes best visible on rotating 3D reconstructions.
9. What is the drawback of MIP reconstructions?
An MIP reconstruction image is a collapsed image of a series of thin slices, thus small details could again be obscured by overlying structures. Therefore the individual slices should be examined before establishing a diagnosis.
10. What additional findings are shown in this case?
The individual stones in the common bile duct can be easier visualized, and their number can be evaluated. The normal course and diameter of the pancreatic duct is also seen.
Final diagnosis
Choledocho- and cholecystolithiasis.
Differential diagnosis
Suspected tumorous obstruction of the biliary tree could be ruled out.
Discussion
MRCP is a non invasive method to visualize the bile ducts. The short acquisition time of the measurement sequences also allows for the investigation of less cooperative patients that are unable to perform breath hold imaging. In these patients however, offline postprocessing and 3D reconstructions of the biliary tree is sometimes not feasible. The basic principle of this method is to use sequence parameters that highlight all fluid filled spaces while suppressing the signal from surrounding tissue. To avoid artifacts from bright signal intensities in fluid filled bowel loops, or the stomach, we routinely use a negative oral contrast agent to fill the upper gastrointestinal tract (Abdoscan® / Ferristene -Nycomed Amersham).
No differentiation can be made in MRCP between biliary stones and air bubbles in the biliary tree. Therefore this method is not usable in patients with aerobilia or immediately after ERCP. Tumorous obstructions usually can be differentiated by their shape, their soft tissue component in the first axial images or by the displacement of the bile duct.
In this case the presence of remaining common bile duct stones could be easily demonstrated by their typical shape, outlined by the bright bile fluid. After MRI, the patient underwent laparatomy with cholecystectomy and open removal of the choledochus stones. Unfortunately, a tumorous growth on the colon was discovered at operation which proved to be metastatic disease from breast cancer. A right sided hemicolectomy had to be performed.
Since the diagnostic value of MRCP is meanwhile well established, and the procedure bears almost no risk for side effects for the patient, it should be the preferred diagnostic method right after ultrasound. ERCP is usually well tolerated but more dramatic for the patient. The induction of an acute pancreatitis cannot totally be excluded. Because of the rapid examination, the cost of the MR procedure compares favorable to ERCP. ERCP should thus only be considered in patients where a therapeutic endoscopic intervention or the need for a histologic examination can be anticipated.