CASE 14481 Published on 10.07.2017
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Diffusion-weighted MRI: findings and role in acute cholecystitis

Section

Abdominal imaging

Case Type

Clinical Cases

Authors

Tonolini Massimo, MD

"Luigi Sacco" University Hospital,
Radiology Department;
Via G.B. Grassi 74
20157 Milan, Italy;
Email:mtonolini@sirm.org
Connected authors
Patient

60 years, female

Categories
Area of Interest Biliary Tract / Gallbladder ; Imaging Technique MR, CT
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Clinical History
Woman with cholelithiasis and chronic obstructive lung disease, admitted to emergency department because of epigastric pain and vomiting. Physically found afebrile, with upper abdominal tenderness but no peritonism.
Laboratory assays revealed leukocytosis, marked increase of serum lipase (8000 U/l), lactate-dehydrogenase (548 U/l) and C-reactive protein (81 mg/l); 4mg/dl total bilirubin.
Imaging Findings
Requested to investigate clinical and biochemical diagnosis of acute pancreatitis (AP), CT (Fig.1) showed distended gallbladder with small calcific stones, moderately thickened wall and mucosal hyperenhancement suggesting acute cholecystitis; non-dilated intrahepatic and common bile ducts (CBD) without detectable calculi; normal size and enhancement of pancreatic gland without necrosis; absent pericholecystic and peripancreatic fluid.
After clinical and laboratory improvement on conservative treatment, MR-cholangiopancreatography (Fig. 2) was requested to choose between immediate and delayed cholecystectomy: compared to CT the gallbladder showed decreasing mural thickness and upper-normal degree of distension. Additionally, high b-value diffusion-weighted imaging (DWI) showed hyperintense signal in the gallbladder wall with corresponding low apparent diffusion-coefficient, indicating persistently acute inflammation. The normal-sized pancreas showed restricted diffusion progressively worsening from tail to head consistent with oedematous AP.
On the basis of DWI findings, the patient underwent early cholecystectomy including endoscopic rendezvous which yielded some biliary sludge from the CBD. Surgical pathology confirmed imaging diagnosis of acute cholecystitis.
Discussion
Secondary to gallstone disease in the vast majority (>90%) of cases, acute cholecystitis (AC) remains one of the commonest surgical causes of hospitalisation. Characteristic clinical manifestations (such as upper right quadrant pain and tenderness, positive Murphy’s sign, nausea or vomiting, fever) and consistent laboratory changes often suggest the diagnosis of AC, which requires imaging confirmation to differentiate AC from biliary colic, to identify possible complications and coexistent choledocholithiasis. Ultrasound represents the first-line investigation for suspected acute conditions involving the biliary tract and has variable sensitivity (37.5-91%) and specificity (60-100%) for AC; unfortunately sonography may be impaired by obesity, bowel gas and uncooperativeness, and does not consistently assess the common bile duct for stones. Some clinicians increasingly rely on multidetector CT to overcome limitations of ultrasound: however, CT involves use of ionising radiation, requires intravenous contrast medium and is unreliable for non-calcified gallstones [1-3].
Therefore, with the availability of state-of-the art scanners and faster acquisition protocol MRI is increasing used to investigate urgent abdominal conditions such as AC, particularly in patients with equivocal or inconclusive clinical, laboratory and ultrasound findings. With its excellent tissue contrast, MRI consistently shows gallstones and sludge, and signs of AC such as gallbladder overdistension, diffuse mural thickening and oedematous T2-hypersignal, pericholecystic and perihepatic fluid. Some series reported MRI to have 88%-95% sensitivity and 69%-89% specificity for AC. Furthermore, MR-cholangiopancreatography sequences provide crucial information for appropriate therapeutic choice regarding early or deferred, open or laparoscopic cholecystectomy with or without preoperative or intraoperative treatment of choledocholithiasis [4-8].
As this case exemplifies, the inclusion of diffusion-weighted (DW) sequences in standard and fast/urgent abdominal MRI acquisition protocols may further increase the diagnostic confidence for AC rapidly and noninvasively. The inflamed gallbladder wall is visually hyperintense on high b-value DW images with apparent diffusion coefficient (ADC) values significantly lower than those observed in normal conditions and reported to fall in the range 1.68-1.96x10-3 mm2/s. The key differential diagnosis of restricted gallbladder wall diffusion are chronic cholecystitis, which lacks diffusion restriction, and cancer, which generally shows ADC values below 1.2x10 x10-3 mm2/s. Albeit some authors believe that confident differentiation is possible between malignant versus benign mural thickening, some overlap may exist between ADC values: therefore DW findings should be always interpreted in conjunction with standard MRI sequences, in which AC mural thickening is generally smooth and diffuse with preserved mucosal contour, compared to the solid, non-layered, focal or asymmetric tumours [9-14].
Differential Diagnosis List
Acute cholecystitis, interstitial oedematous pancreatitis in cholelithiasis.
Chronic cholecystitis
Xanthogranulomatous cholecystitis
Gallbladder adenomyomatosis
Gallbladder carcinoma
Oedematous mural thickening from liver failure or hypoproteinemic state
Final Diagnosis
Acute cholecystitis, interstitial oedematous pancreatitis in cholelithiasis.
Case information
URL: https://www.eurorad.org/case/14481
DOI: 10.1594/EURORAD/CASE.14481
ISSN: 1563-4086
License

This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.

Figure 1

Urgent unenhanced and post-contrast multidetector CT at admission

Urgent unenhanced and post-contrast multidetector CT at admission
Preliminary unenhanced acquisition showed distended gallbladder with small calcific stones and moderately thickened wall (arrow), normal-sized pancreas (*), absent peripancreatic effusion. Note hypoattenuating liver from steatosis.
Urgent unenhanced and post-contrast multidetector CT at admission
Axial (b,c) and coronal (d,e) portal-venous phase enhanced images showed preserved homogeneous pancreatic enhancement (*), distended gallbladder with moderately thickened wall (arrows) and mucosal enhancement (thin arrows).
Urgent unenhanced and post-contrast multidetector CT at admission
Axial (b,c) and coronal (d,e) portal-venous phase enhanced images showed preserved homogeneous pancreatic enhancement (*), distended gallbladder with moderately thickened wall (arrows) and mucosal enhancement (thin arrows).
Urgent unenhanced and post-contrast multidetector CT at admission
Coronal (d,e) portal-venous phase enhanced images showed preserved homogeneous pancreatic enhancement (*), distended gallbladder with moderately thickened wall (arrows) and mucosal enhancement (thin arrows).
Urgent unenhanced and post-contrast multidetector CT at admission
Coronal (d,e) portal-venous phase enhanced images showed preserved homogeneous pancreatic enhancement (*), distended gallbladder with moderately thickened wall (arrows) and mucosal enhancement (thin arrows). Note normal-calibre choledochus (arrowhead).
Figure 2

Unenhanced MRI including diffusion-weighted and MR-cholangiopancreatography (MRCP)

Unenhanced MRI including diffusion-weighted and MR-cholangiopancreatography (MRCP)
Ten days after CT, fat-saturated T1-weighted image showed decreasing gallbladder mural thickness (arrow) compared to Fig.1, and persistently normal pancreatic (*) thickness.
Unenhanced MRI including diffusion-weighted and MR-cholangiopancreatography (MRCP)
T2-weighted images (b.c) showed decreasing gallbladder mural thickness (arrow) compared to Fig.1, small calculi and sludge in the lumen, absent pericholecystic fluid, persistently normal pancreatic (*) thickness.
Unenhanced MRI including diffusion-weighted and MR-cholangiopancreatography (MRCP)
T2-weighted images (b.c) showed decreasing gallbladder mural thickness (arrow) compared to Fig.1, small calculi and sludge in the lumen, absent pericholecystic fluid, persistently normal pancreatic (*) thickness.
Unenhanced MRI including diffusion-weighted and MR-cholangiopancreatography (MRCP)
High (800) b-value diffusion-weighted images (d,e) showed visually hyperintense signal in the gallbladder wall (arrows) indicating acute inflammation, and pancreatic gland (*) gradually progressive hypersignal consistent with oedematous acute pancreatitis from tail to head.
Unenhanced MRI including diffusion-weighted and MR-cholangiopancreatography (MRCP)
High (800) b-value diffusion-weighted images (d,e) showed visually hyperintense signal in the gallbladder wall (arrows) indicating acute inflammation, and pancreatic gland (*) gradually progressive hypersignal consistent with oedematous acute pancreatitis from tail to head.
Unenhanced MRI including diffusion-weighted and MR-cholangiopancreatography (MRCP)
Apparent diffusion coefficient map showed hypointensity indicating restricted diffusion in gallbladder wall (arrow, 1.45-1.6x10-3 mm2/s) and pancreas (*, progressively increasing from 0.8 at head to 1.1x10-3 mm2/s in tail).
Unenhanced MRI including diffusion-weighted and MR-cholangiopancreatography (MRCP)
MRCP showed upper normal caliber of main bile duct (arrowheads), without detectable intraluminal calculi. Note unremarkable appearance of Wirsung duct, absent pericholecystic and perihepatic fluid.