MR imaging of the gallbladder: a pictorial essay

A meta-analysis of the performance of ultrasound, hepatobiliary scintigraphy, CT and MRI in the diagnosis of acute cholecystitis

PURPOSE

To evaluate the recently reported relative diagnostic accuracy of US, CT, MRI, and cholescintigraphy for diagnosing acute cholecystitis.

METHODS

2 radiologists independently performed systematic electronic searches for articles published between 2000 and 2021 and applied inclusion/exclusion criteria. 2 different radiologists extracted data from the articles and scored each with a methodological quality tool. Pooled estimates of sensitivity and specificity were calculated with a bivariate linear mixed model. A second analysis made head-to-head comparisons (US vs. CT, US vs. cholescintigraphy). Factors were also analyzed for potential confounding effects on diagnostic accuracy.

RESULTS

Of 6121 initial titles, 22 were included. The prevalence of cholecystitis varied widely across studies (9.4-98%). Pooled sensitivity and specificity estimates were 69% (confidence limit [CL] 62-76%) and 79% (CL 71-86%) for US, 91% (CL 86-94%) and 63% (CL 51-74%) for cholescintigraphy, 78% (CL 69-84%) and 81% (CL 71-88%) for CT, and 91% (CL 78-97%) and 93% (CL 70-99%) for MRI. Regarding head-to-head comparisons, the sensitivity of CT (87.6%, CL 70-96%) was significantly higher than US (66.8%, CL 43-84%), while specificities (81.7% with CL 54-95% for US, 91.9% with CL 67-99% for CT) were similar. The sensitivity of cholescintigraphy (87.4%, CL 76-94%) was significantly greater than US (61.6%, CL 44-77%), while the specificity of US (82%, CL 65-92%) was significantly higher than cholescintigraphy (68%, CL 47-84%).

CONCLUSION

Recent data suggests that CT may have a higher sensitivity than US for diagnosing acute cholecystitis, with similar specificity. Cholescintigraphy remains a highly sensitive modality with lower specificity than previously reported. MRI remains under studied, but with promising results.

Gallbladder polyps and adenomyomatosis

Incidental findings are commonly detected during examination of the gallbladder. Differentiating benign from malignant lesions is critical because of the poor prognosis associated with gallbladder malignancy. Therefore, it is important that radiologists and sonographers are aware of common incidental gallbladder findings, which undoubtedly will continue to increase with growing medical imaging use. Ultrasound is the primary imaging modality used to examine the gallbladder and biliary tree, but contrast-enhanced ultrasound and MRI are increasingly used. This review article focuses on two common incidental findings in the gallbladder; adenomyomatosis and gallbladder polyps. The imaging features of these conditions will be reviewed and compared between radiological modalities, and the pathology, epidemiology, natural history, and management will be discussed.

RadFormer: Transformers with global-local attention for interpretable and accurate Gallbladder Cancer detection

We propose a novel deep neural network architecture to learn interpretable representation for medical image analysis. Our architecture generates a global attention for region of interest, and then learns bag of words style deep feature embeddings with local attention. The global, and local feature maps are combined using a contemporary transformer architecture for highly accurate Gallbladder Cancer (GBC) detection from Ultrasound (USG) images. Our experiments indicate that the detection accuracy of our model beats even human radiologists, and advocates its use as the second reader for GBC diagnosis. Bag of words embeddings allow our model to be probed for generating interpretable explanations for GBC detection consistent with the ones reported in medical literature. We show that the proposed model not only helps understand decisions of neural network models but also aids in discovery of new visual features relevant to the diagnosis of GBC. Source-code is available at https://github.com/sbasu276/RadFormer.

Differentiating benign from malignant gallbladder wall thickening in non-contrast MRI imaging: Preliminary study of a combined diagnostic indicator

To synthetically evaluate the diagnostic accuracy of image features for differentiating benign from malignant gallbladder wall thickening disease with non-contrast MRI and establish the optimal diagnostic indicator. A total of 23 patients with wall thickening type gallbladder carcinoma and 61 patients with benign wall thickening disease were included. The diagnostic performance of six image features including the layered pattern on T2-weighted imaging (T2WI) and diffusion-weighted imaging (DWI) images, T2WI signal intensity, papillary growth, the apparent diffusion coefficient (ADC) value, and the lesion to liver parenchyma ratio (LLR) of gallbladder were evaluated and compared. The receiver operating characteristic (ROC) curve and binary logistic regression analysis were used to construct the optimally combined indicator. All six indicators showed high diagnostic accuracy. The layered pattern on DWI and LLR had the highest area under the curve (AUC) value (0.904), followed by the layered pattern on T2WI (0.883), T2WI signal intensity (0.859), ADC value (0.836), and papillary growth (0.796). There was no statistically significant difference in the AUC among indicators for pairwise comparisons. A combination of layered patterns on DWI and papillary growth was shown to be the optimal indicator by binary logistic regression analysis. The AUC value of the combination (0.972) was higher than the layered pattern on DWI (0.904) and papillary growth (0.796) (P < .001). Non-contrast MRI provides several reliable indicators for differentiating benign from malignant gallbladder thickening disease. The combination of layered patterns on DWI and papillary growth is the optimal indicator.

Preoperative Assessment and Perioperative Management of Resectable Gallbladder Cancer in the Era of Precision Medicine and Novel Technologies: State of the Art and Future Perspectives

Gallbladder carcinoma (GBC) is a rare malignancy, with an estimated 5-year survival rate of less than 5% in the case of advanced disease. Surgery is the only radical treatment for early stages, but its application and effectiveness depend on the depth of tumoral invasion. The extent of resection is usually determined according to the T-stage. Therefore, an early and correct preoperative assessment is important for the prognosis, as well as for the selection of the most appropriate surgical procedure, to avoid unnecessary morbid surgeries and to reach the best outcomes. Several modalities can be used to investigate the depth of invasion, from ultrasounds to CT scans and MRI, but an ideal method still does not exist. Thus, different protocols are proposed according to different recommendations and institutions. In this scenario, the indications for laparoscopic and robotic surgery are still debated, as well as the role of new technologies such as next-generation sequencing and liquid biopsies. The aim of this article is to summarize the state of the art current modalities and future perspectives for assessing the depth of invasion in GBC and to clarify their role in perioperative management accordingly.

Manifestations of Sickle Cell Disorder at Abdominal and Pelvic Imaging

Sickle cell disorder (SCD) refers to a spectrum of hematologic disorders that cause a characteristic clinical syndrome affecting the entire body. It is the most prevalent monogenetic hemoglobinopathy worldwide, with a wide range of focal and systemic expressions. Hemoglobin gene mutation leads to the formation of abnormal sickle-shaped red blood cells, which cause vascular occlusion and result in tissue and organ ischemia and infarction. Recurrent episodes of acute illness lead to progressive multisystem organ damage and dysfunction. Vaso-occlusion, hemolysis, and infection as a result of functional asplenia are at the core of the disease manifestations. Imaging plays an essential role in the diagnosis and management of SCD-related complications in the abdomen and pelvis. A thorough understanding of the key imaging findings of SCD complications involving hepatobiliary, gastrointestinal, genitourinary, and musculoskeletal systems is crucial to timely recognition and accurate diagnosis. The authors aim to familiarize the radiologist with the SCD spectrum, focusing on the detection and evaluation of manifestations that may appear at imaging of the abdomen and pelvis. The topics the authors address include (a) the pathophysiology of the disease, (b) the placement of SCD among hemoglobinopathies, (c) the clinical presentation of SCD, (d) the role of imaging in the evaluation and diagnosis of patients with SCD who present with abdominal and pelvic manifestations in addition to extraperitoneal manifestations detectable at abdominal or pelvic imaging, (e) imaging features associated with common and uncommon sequelae of SCD in abdominal and pelvic imaging studies, and (f) a brief overview of management and treatment of patients with SCD. Online supplemental material is available for this article. ^©RSNA, 2022.

Bile Flow Dynamics in Patients with Cholelithiasis: An Evaluation with Cine-Dynamic Magnetic Resonance Cholangiopancreatography Using a Spatially Selective Inversion-Recovery Pulse

Background: A variety of pathophysiological changes in the biliary system occur in patients with cholelithiasis, but the changes in the bile flow dynamics in those patients remain unclear. The purpose of this study was to elucidate the changes in the bile flow dynamics in patients with cholelithiasis using cine-dynamic magnetic resonance cholangiopancreatography (MRCP) with a spatially selective inversion-recovery (IR) pulse. Methods: We retrospectively examined 25 patients with gallstones (gallstone group) and 69 patients without gallstones (non-gallstone group) who underwent abdominal MRI, including in- and opposed-phase T1-weighted images and cine-dynamic MRCP with a spatially selective IR pulse. The frequency and secretion grade of the antegrade and reverse flow of the bile on the cine dynamic MRCP images and the signal intensity ratio (SIR) of the gallbladder in the in- and opposed-phase T1-weighted images were evaluated. Results: The frequency and mean secretion grade of the antegrade bile flow were significantly higher in the gallstone group than in the non-gallstone group (p = 0.011 and p = 0.003), while no significant differences in those values of the reverse bile flow were found between the two groups. The SIR of the gallbladder in the T1-weighted gradient-echo in-phase images was significantly lower in the gallstone group than in the non-gallstone group (p = 0.004). Conclusions: Cine-dynamic MRCP with a spatially selective IR pulse can noninvasively visualize changes in the bile flow dynamics of patients with gallstones.

Spectrum of MRI Features of Mucin-producing Neoplasms in the Abdomen and Pelvis

Mucin-producing neoplasms in the abdomen and pelvis are a distinct entity, separate from simple fluid-containing neoplasms and loculated fluid collections. Mucin is a thick gelatinous substance and-owing to its high water content-has imaging features that can be mistaken for those of simple fluid-containing neoplasms with multiple imaging modalities. However, mucin-producing neoplasms arise from specific organs in the abdomen and pelvis, with unique imaging appearances, knowledge of which is important to guide accurate diagnosis and management. With its large field of view and high soft-tissue resolution, MRI has advantages over other imaging modalities in characterizing these neoplasms. The authors focus on the spectrum of MRI features of such mucin-producing neoplasms and illustrate how-despite a varied organ origin-some of these neoplasms share similar MRI and histopathologic features, thereby helping narrow the differential diagnosis. One common finding in these tumors is that the presence of internal complexity and solid enhancing components increases as the degree of malignant transformation increases. Lack of internal complexity generally indicates benignity. These tumors have a varied range of prognosis; for example, a low-grade appendiceal mucinous neoplasm is indicative of a good prognosis, while a mucinous tumor of the rectum is known to manifest at an early age with aggressive behavior and poorer prognosis compared with its nonmucinous counterpart. Online supplemental material is available for this article. ^©RSNA, 2022.

Manganese(II) EOB-Pyclen Diacetate for Liver-Specific MRI

MRI is increasingly utilized for the diagnosis of liver disease and focal liver lesions. Although liver-targeted gadolinium-based contrast agents (GBCAs) have high efficacy, there continue to be safety concerns regarding release of toxic Gd(III) ions. Herein, Mn(EOB-PC2A) is synthesized as a nongadolinium alternative for liver-specific MRI. Mn(EOB-PC2A) has an r₁ relaxivity of 2.8 mM^-1 s^-1 in Dulbecco's phosphate-buffered saline (DPBS) and 5.9 mM^-1 s^-1 in saline containing human serum albumin at 1.5 T. It has a strong uptake in hepatocytes with minimal toxicity and demonstrated robust liver-specific enhancement at a dose of 60 μmol/kg. Mn(EOB-PC2A) is a promising liver-specific contrast agent for liver MRI.

IL4Rα and IL13Rα1 Are Involved in the Development of Human Gallbladder Cancer

Background: Gallbladder cancer is commonly associated with inflammation, which indicates that inflammation-related cytokines and cytokine receptors are related to the progression of gallbladder cancers. Interleukin 4 (IL4) is a well-known cytokine that promotes the differentiation of naive helper T cells (Th0) to T helper type 2 cells (Th2). IL13 is a cytokine that is secreted by Th2 cells. IL4 and IL13 are closely related in immune responses. However, the role of IL4Rα and IL13Rα1 signaling pathway has not been fully understood in the development of gallbladder cancer. Methods: In human gallbladder carcinomas, the expression of IL4Rα and IL13Rα1 were evaluated with immunohistochemical staining in tissue microarray tissue sections. After knockdown of IL4Rα or IL13Rα1, cell assays to measure the proliferation and apoptosis and Western blotting analysis were conducted in SNU308 human gallbladder cancer cells. Since Janus kinases2 (JAK2) was considered as one of the down-stream kinases under IL4Rα and IL13Rα1 complex, the same kinds of experiments were performed in SNU308 cells treated with AZD1480, Janus-associated kinases2 (JAK2) inhibitor, to demonstrate the cytotoxic effect of AZD1480 in SNU308 cells. Results: Immunohistochemical expression of IL4Rα was significantly associated with the expression of IL13Rα1 in human carcinoma tissue. In univariate analysis, nuclear expression of IL4Rα, cytoplasmic expression of IL4Rα, nuclear expression of IL13Rα1, and cytoplasmic expression of IL13Rα1 were significantly associated with shorter overall survival and shorter relapse-free survival. Multivariate analysis revealed nuclear expression of IL4Rα as an independent poor prognostic indicator of overall survival and relapse-free survival. Then, we found that knockdown of IL4Rα or IL13Rα1 decreased viability and induced apoptosis in SNU308 cells via activation of FOXO3 and similarly, AZD1480 decreased viability and induced apoptosis in SNU308 cells with dose dependent manner. Conclusions: Taken together, our results suggest that IL4Rα and IL13Rα1 might be involved in the development of human gallbladder cancer cells and IL4Rα and IL13Rα1 complex/JAK2 signaling pathway could be efficient therapeutic targets for gallbladder cancer treatment.

Gallbladder reporting and data system (GB-RADS) for risk stratification of gallbladder wall thickening on ultrasonography: an international expert consensus

The Gallbladder Reporting and Data System (GB-RADS) ultrasound (US) risk stratification is proposed to improve consistency in US interpretations, reporting, and assessment of risk of malignancy in gallbladder wall thickening in non-acute setting. It was developed based on a systematic review of the literature and the consensus of an international multidisciplinary committee comprising expert radiologists, gastroenterologists, gastrointestinal surgeons, surgical oncologists, medical oncologists, and pathologists using modified Delphi method. For risk stratification, the GB-RADS system recommends six categories (GB-RADS 0-5) of gallbladder wall thickening with gradually increasing risk of malignancy. GB-RADS is based on gallbladder wall features on US including symmetry and extent (focal vs. circumferential) of involvement, layered appearance, intramural features (including intramural cysts and echogenic foci), and interface with the liver. GB-RADS represents the first collaborative effort at risk stratifying the gallbladder wall thickening. This concept is in line with the other US-based risk stratification systems which have been shown to increase the accuracy of detection of malignant lesions and improve management.

Imaging of gallbladder metastasis

Gallbladder metastasis (GM) is a rare condition, often with a late diagnosis or detected upon autopsy. There is no extensive literature on the imaging diagnosis of GM. Here we present a comprehensive review of the literature with the aim of helping to interpret the clinical findings and imaging features of such patients. Few studies on GM are reported in literature. GM by melanoma accounts for about 55.6% of cases. The remaining cases origin from breast cancer (13.6%), hepatocellular carcinoma (13.6%), renal cell carcinoma (6.8%), lung cancer (4.5%), lymphoma (3.5%) and gastric cancer (2.4%). The most common clinical presentation of GM is abdominal pain from cholecystitis due to obstruction of the cystic duct. The main ultrasound (US), computed tomography (CT) and magnetic resonance imaging (MRI) findings that clinicians and radiologists should consider in their everyday medical activity were discussed. The diagnosis of GM was often achieved through a combination of more than one imaging modality. In more than 90% of cases, the diagnosis of GM is often late and combined with other organs involvement in the terminal stage of the malignancy. The knowledge of the clinical features and different imaging techniques through careful evaluation of the gallbladder can help to achieve early diagnosis and avoid misdiagnosis or false negative results.

Problem-solving with MRI in acute abdominopelvic conditions, part 1: gastrointestinal, hepatobiliary, and pancreatic diseases

The purpose of this article is to review the benefit and added value and advantages of magnetic resonance imaging (MRI) compared with other cross-sectional imaging in patients presenting with abdominopelvic emergencies. During the past decade, there has been increased utilization of MRI in the emergency department with widespread availability of MR scanners, improvement in rapid imaging techniques, and methods to overcome motion-related artifacts. This has benefited patients at higher risk of radiation, particularly children and pregnant women, and patients with contraindications to iodinated contrast including allergy and renal dysfunction. Still the challenges are: on site MR scanner in the emergency department, after-hour services, as well as availability of time slot to rapidly scan emergency patient. MRI has additional advantages over other imaging modalities due to its high contrast resolution, which allows it to better characterize tissue and fluid collections, and may avoid the need for intravenous contrast. Radiologists must be familiar with the role and added value of MRI, spectrum of imaging findings, and problem-oriented modified MR protocols in abdominal and pelvic emergencies. In part 1, we will discuss the utility of MRI in gastrointestinal, hepatobiliary, and pancreatic diseases. In part 2, the authors will focus on the key MR imaging features of female pelvic gynecological diseases, pregnancy related complications, abdominal vascular complications, and renal diseases.

Concentration of Gallbladder Phosphatidylcholine in Cholangiopathies: A Phosphorus-31 Magnetic Resonance Spectroscopy Pilot Study

BACKGROUND

Biliary phosphatidylcholine (PtdC) concentration plays a role in the pathogenesis of bile duct diseases. In vivo phosphorus-31 magnetic resonance spectroscopy (³¹ P-MRS) at 7 T offers the possibility to assess this concentration noninvasively with high spectral resolution and signal intensity.

PURPOSE

Comparison of PtdC levels of cholangiopathic patient groups to a control group using a measured T₁ relaxation time of PtdC in healthy subjects.

STUDY TYPE

Case control.

SUBJECTS

Two patient groups with primary sclerosing cholangitis (PSC, 2f/3 m; age: 43 ± 7 years) and primary biliary cholangitis (PBC, 4f/2 m; age: 57 ± 6 years), and a healthy control group (CON, 2f/3 m; age: 38 ± 7 years). Ten healthy subjects for the assessment of the T₁ relaxation time of PtdC.

FIELD STRENGTH/SEQUENCE

A 3D phase-encoded pulse-acquire ³¹ P-MRSI sequence for PtdC quantification and a 1D image-selected in vivo ³¹ P spectroscopy for T₁ estimation at 7 T, and a T2-weighted half-Fourier single-shot turbo spin echo MRI sequence for volumetry at 3 T.

ASSESSMENT

Calculation of gallbladder volumes and PtdC concentration in groups using hepatic gamma-adenosine triphosphate signal as an internal reference and correction for insufficient relaxation of PtdC with a T₁ value assessed in healthy subjects.

STATISTICAL TESTS

Group comparison of PtdC content and gallbladder volumes of the PSC/PBC and CON group using Student's t-tests with a significance level of 5%.

RESULTS

PtdC T₁ value of 357 ± 85 msec in the gallbladder. Significant lower PtdC content for the PSC group, and for the female subgroup of the PBC group compared to the CON group (PSC/CON: 5.74 ± 0.73 mM vs. 9.64 ± 0.97 mM, PBC(f)/CON: 5.77 ± 1.44 mM vs. 9.64 ± 0.97 mM). Significant higher gallbladder volumes of the patient groups compared to the CON group (PSC/CON: 66.3 ± 15.8 mL vs. 20.9 ± 2.2 mL, PBC/CON: 49.8 ± 18.2 mL vs. 20.9 ± 2.2 mL).

DATA CONCLUSION

This study demonstrated the application of a ³¹ P-MRSI protocol for the quantification of PtdC in the human gallbladder at 7 T. Observed differences in PtdC concentration suggest that this metabolite could serve as a biomarker for specific hepatobiliary disorders.

LEVEL OF EVIDENCE

2 TECHNICAL EFFICACY STAGE: 3.

Complications of cholecystitis: a comprehensive contemporary imaging review

Acute cholecystitis is a common cause of right upper quadrant pain in patients presenting to the emergency department. Ultrasound, computed tomography, HIDA scans, and magnetic resonance imaging are increasingly utilized to evaluate suspected cases. The prognosis of acute cholecystitis is usually excellent with timely diagnosis and management. However, complications associated with cholecystitis pose a considerable challenge to the clinician and radiologist. Complications of acute cholecystitis may result from secondary bacterial infection or mural ischemia secondary to increased intramural pressure. The recognized subtypes of complicated cholecystitis are hemorrhagic, gangrenous, and emphysematous cholecystitis, as well as gallbladder perforation. Acute acalculous cholecystitis is a form of cholecystitis that occurs as a complication of severe illness in the absence of gallstones or without gallstone-related inflammation. Complicated cholecystitis may cause significant morbidity and mortality, and early diagnosis and recognition play a pivotal role in the management and early surgical planning. As appropriate utilization of imaging resources plays an essential role in diagnosis and management, the emergency radiologist should be aware of the spectrum of complications related to cholecystitis and the characteristic imaging features. This article aims to offer a comprehensive contemporary review of clinical and cross-sectional imaging findings of complications associated with cholecystitis. In conclusion, cross-sectional imaging is pivotal in identifying the complications related to cholecystitis. Preoperative detection of this complicated cholecystitis can help the care providers and operating surgeon to be prepared for a potentially more complicated procedure and course of recovery.

Current update on gallbladder carcinoma

Gallbladder (GB) carcinoma is a relatively rare malignancy and is associated with poor prognosis. Numerous risk factors have been associated with the development of GB carcinoma. GB carcinomas may present as mass lesions replacing the GB, focal or diffuse thickening of the GB wall, and intraluminal mass in the GB. Various benign conditions can mimic GB carcinoma. This article reviews the epidemiology, pathology, clinical findings, imaging features, and management of GB carcinomas.

Role of magnetic resonance imaging in Bouveret's syndrome: A case report with review of the literature

Bouveret's syndrome is a rare form of gallstone ileus occurring due to obstructing gallstone into the proximal duodenum through a cholecystoduodenal fistula. We report the case of a 72-year-old female presenting with abdominal pain secondary to a large gallstone in the region of the duodenal bulb, causing the upstream gastric obstruction. Here we discuss the clinical features, imaging technologies, and surgical management of Bouveret's syndrome.

Gallbladder Carcinoma and Its Differential Diagnosis at MRI: What Radiologists Should Know

Gallbladder carcinoma is the most common cancer of the biliary system. It is challenging to diagnose because patients are often asymptomatic or present with nonspecific symptoms that mimic common benign diseases. Surgical excision is the only curative therapy and is best accomplished at early non-locally advanced stages. Unfortunately, gallbladder cancer often manifests at late locally advanced stages, precluding cure. Early tumors are often incidentally detected at imaging or at cholecystectomy performed for another indication. Typical imaging features of localized disease include asymmetric gallbladder wall thickening, polyps larger than 1.0 cm, and a solid mass replacing the gallbladder lumen. Advanced tumors are often infiltrative and can be confusing at CT and MRI owing to their large size. Determination of the origin of the lesion is paramount to narrow the differential diagnosis but is often challenging. It is important to identify gallbladder cancer and distinguish it from other benign and malignant hepatobiliary processes. Since surgical resection is the only curative treatment option, radiologist understanding and interpretation of pathways of nodal and infiltrative tumor spread can direct surgery or preclude patients who may not benefit from surgery. While both CT and MRI are effective, MRI provides superior soft-tissue characterization of the gallbladder and biliary tree and is a useful imaging tool for diagnosis, staging, and evaluation of treatment response. ^©RSNA, 2020.

Gallbladder Cancer Presenting as Mirizzi Syndrome Complicated by Rapidly Evolving 23 rRNA Gene-Linezolid Resistance with Vancomycin-Resistant Enterococcus Infection Resulting in Fatal Cholangial Sepsis

We describe the case of a 71-year-old woman who presented with obstructive jaundice and subhilar bile duct stenosis. MRI showed extensive cholecystolithiasis with an impacted bile stone in the cystic duct suggesting Mirizzi syndrome. Delayed enhancement of the thickened gallbladder wall suggested inflammation instead of carcinoma. After drainage of the obstructed bile duct via ERCP, the patient developed liver abscesses with a nosocomial vancomycin-resistant enterococcus infection treated by linezolid. After 4 weeks, the VRE infection was complicated by a new-onset 23 rRNA gene-mediated linezolid resistance in the same bacterial strain, which was proven via core genome multilocus sequencing. Meropenem and tigecycline were administered according to a resistogram. Furthermore, percutaneous transhepatic biliary drainage of both sides of the liver was necessary. After demission, the patient had to be admitted again due to septic shock. An emergency operation revealed extended, inoperable gallbladder cancer. The patient died a few days later in the intensive care unit. An earlier diagnosis of bile duct infiltrating gallbladder cancer by cholangioscopy or laparoscopy and treatment of vancomycin-resistant enterococcus infection with daptomycin may have changed the clinical course of the disease.

Benign gallbladder diseases: Imaging techniques and tips for differentiating with malignant gallbladder diseases

Benign gallbladder diseases usually present with intraluminal lesions and localized or diffuse wall thickening. Intraluminal lesions of the gallbladder include gallstones, cholesterol polyps, adenomas, or sludge and polypoid type of gallbladder cancer must subsequently be excluded. Polyp size, stalk width, and enhancement intensity on contrast-enhanced ultrasound and degree of diffusion restriction may help differentiate cholesterol polyps and adenomas from gallbladder cancer. Localized gallbladder wall thickening is largely due to segmental or focal gallbladder adenomyomatosis, although infiltrative cancer may present similarly. Identification of Rokitansky-Aschoff sinuses is pivotal in diagnosing adenomyomatosis. The layered pattern, degree of enhancement, and integrity of the wall are imaging clues that help discriminate innocuous thickening from gallbladder cancer. High-resolution ultrasound is especially useful for analyzing the layering of gallbladder wall. A diffusely thickened wall is frequently seen in inflammatory processes of the gallbladder. Nevertheless, it is important to check for coexistent cancer in instances of acute cholecystitis. Ultrasound used alone is limited in evaluating complicated cholecystitis and often requires complementary computed tomography. In chronic cholecystitis, preservation of a two-layered wall and weak wall enhancement are diagnostic clues for excluding malignancy. Magnetic resonance imaging in conjunction with diffusion-weighted imaging helps to differentiate xathogranulomatous cholecystitis from gallbladder cancer by identifying the presence of fat and degree of diffusion restriction. Such distinctions require a familiarity with typical imaging features of various gallbladder diseases and an understanding of the roles that assorted imaging modalities play in gallbladder evaluations.

In Vivo 1 H MR Spectroscopy of Biliary Components of Human Gallbladder at 7T

BACKGROUND

Previous in vivo proton MR spectroscopy (MRS) studies have demonstrated the possibility of quantifying amide groups of conjugated bile acids (NHCBA), olefinic lipids and cholesterol (OLC), choline-containing phospholipids (CCPLs), taurine and glycine conjugated bile acids (TCBA, GCBA), methylene group of lipids (ML), and methyl groups of bile acids, lipids, and cholesterol (BALC1.0, BALC0.9, and TBAC) in the gallbladder, which may be useful for the study of cholestatic diseases and cholangiopathies. However, these studies were performed at 1.5T and 3T, and higher magnetic fields may offer improved spectral resolution and signal intensity.

PURPOSE

To develop a method for gallbladder MRS at 7T.

STUDY TYPE

Retrospective, technical development.

POPULATION

Ten healthy subjects (five males and five females), two patients with primary biliary cholangitis (PBC) (one male and one female), and one patient with primary sclerosing cholangitis (PSC) (female).

FIELD STRENGTH/SEQUENCE

Free-breathing single-voxel MRS with a modified stimulated echo acquisition mode (STEAM) sequence at 7T.

ASSESSMENT

Postprocessing was based on the T₂ relaxation of water in the gallbladder and in the liver. Concentrations of biliary components were calculated using water signal. All data were corrected for T₂ relaxation times measured in healthy subjects.

STATISTICAL TESTS

The range of T₂ relaxation time and concentration per bile component, and the resulting mean and standard deviation, were calculated.

RESULTS

The concentrations of gallbladder components in healthy subjects were: NHCBA: 93 ± 66 mM, OLC: 154 ± 124 mM, CCPL: 42 ± 17 mM, TCBA: 48 ± 35 mM, GCBA: 67 ± 32 mM, ML: 740 ± 391 mM, BALC1.0: 175 ± 92 mM, BALC0.9: 260 ± 138 mM, and TBAC: 153 ± 90 mM. Mean concentrations of all bile components were found to be lower in patients.

DATA CONCLUSION

This work provides a protocol for designing future MRS investigations of the bile system in vivo.

EVIDENCE LEVEL

2 TECHNICAL EFFICACY STAGE: 1.

Chronic inflammation-related radiological findings of gallbladder adenomyomatosis

PURPOSE

This study aimed to assess radiological findings of adenomyomatosis advancing to chronic inflammation to differentiate between adenomyomatosis with and without chronic inflammation.

MATERIALS AND METHODS

We retrospectively identified 79 patients with pathologically proven adenomyomatosis without (n = 10) or with chronic inflammation (n = 69), who underwent computed tomography (CT) and magnetic resonance imaging (MRI) followed by surgery. MRI analysis included evaluation of GB wall-thickening type, presence and location of intramural cysts, and presence of stones. CT analysis included GB wall-thickening type only. Multivariate logistic regression analysis was used to identify the image-based findings of adenomyomatosis associated with chronic inflammation.

RESULTS

On univariate analysis, MRI-based GB wall-thickening type and presence of stones, and CT-based GB wall-thickening type were significantly different between adenomyomatosis with and without chronic inflammation. On multivariate analysis, only the absence of stones was identified as a significant predictor of adenomyomatosis without chronic inflammation (odds ratio 5.58; 95% confidence interval 1.20-26.01; p = 0.029). There was no significant difference in other MRI- and CT-based findings between adenomyomatosis with and without chronic inflammation.

CONCLUSION

In patients with adenomyomatosis, the presence of stones was independently associated with chronic inflammation.

Rapidly growing neuroendocrine carcinoma of the gallbladder: A case report

Gallbladder neuroendocrine carcinomas are rare tumors with a prognosis poorer than that of other gallbladder carcinomas. These tumors are often detected late and are difficult to treat. We present the case of a 68-year-old woman with small-cell gallbladder neuroendocrine carcinoma. Abdominal sonography and dynamic contrast-enhanced MRI performed at different points in time showed rapid growth. Treatment with surgical resection and adjuvant chemotherapy was instituted. In view of the rapid growth of these tumors, suspicious cases should at least be considered for close follow-up with appropriate imaging studies.

Emergent MRI for acute abdominal pain in pregnancy-review of common pathology and imaging appearance

Acute abdominal pain in pregnancy remains a clinically challenging presentation, often requiring imaging. The threat of morbidity and mortality to both mother and fetus necessitates quick and accurate imaging diagnosis, often via ultrasound. However, many of the common causes of acute abdominal pain are not readily diagnosed with sonography, and magnetic resonance imaging (MRI) is increasingly favored in this setting. The purpose of this review is to familiarize the reader with common pathologies which may be encountered in pregnant females presenting with acute abdominal pain requiring emergent MRI.

[Differential diagnosis of gallbladder abnormalities : Ultrasound, computed tomography, and magnetic resonance imaging]

CLINICAL ISSUE

Due to the high prevalence of clinically suspected cholecystitis or cholecystolithiasis the gallbladder is one of the organs examined the most by imaging.

STANDARD RADIOLOGICAL METHODS

In most clinical settings ultrasound is the primary imaging method because of its wide availability, speed and superior spatial resolution. In cases of ambiguous findings or potential complications computed tomography (CT) and magnetic resonance imaging (MRI) are used.

METHODICAL INNOVATIONS

When specific problems arise these imaging modalities may be enhanced by special techniques, e. g. contrast-enhanced ultrasound or dual-energy CT, and specific MRI sequences.

PERFORMANCE

Special variants of cholecystitis, such as xanthogranulomatous cholecystitis and adenomyomatosis, may pose a particularly difficult diagnostic problem as they may resemble other diseases. Sequelae of cholecystolithiasis, such as the Mirizzi syndrome and acute bowel obstruction, may complicate the imaging algorithm as the location and the symptoms shift. Cases of neoplastic diseases of gallbladder cancer and other malignancies require a broad spectrum of imaging modalities.

ACHIEVEMENTS

Although the gallbladder can easily be examined with ultrasound, some cases require a more thorough ultrasound examination. In some cases only a combination of multiple imaging modalities yield the diagnosis. Further developments regarding technical issues and the diagnostic algorithm can be expected.

PRACTICAL RECOMMENDATIONS

Ultrasound is the best first imaging modality. In cases of ambiguous findings or clinical complications CT or MRI are recommended.

Uncommon Intraluminal Tumors of the Gallbladder and Biliary Tract: Spectrum of Imaging Appearances

Intraluminal pathologic conditions of the bile ducts and gallbladder are common, most frequently consisting of calculi and adenocarcinoma. In recent years, intraductal papillary neoplasm of the bile ducts (IPN-B), which is analogous to intraductal papillary mucinous neoplasm of the pancreas, has been recognized as a distinct pathologic entity and a precursor lesion to adenocarcinoma of the bile ducts. Intraductal tubulopapillary neoplasm (ITPN) of the bile duct was subsequently described as a distinct pathologic entity. With increased awareness and advances in imaging techniques, these lesions are diagnosed with increased frequency at preoperative imaging. A similar neoplasm in the gallbladder is referred to as intracholecystic papillary neoplasm. These lesions are often diagnosed at a preinvasive stage and have a better prognosis than invasive cholangiocarcinoma when treated with curative resection, underscoring the importance of an accurate imaging diagnosis. The most common causes of polypoid lesions of the gallbladder are cholesterol polyps and adenomyomatosis. These lesions need to be differentiated from the less common but clinically important adenocarcinoma of the gallbladder. Imaging is crucial to identify polyps that are at high risk for malignancy so that the appropriate management choice between imaging follow-up and cholecystectomy can be made by the treating physicians. Other less common gallbladder tumors, such as gallbladder adenomas, lymphoma, and metastases to the gallbladder, can manifest as intraluminal tumors; and awareness of these lesions is also important. In this article, the recent literature is reviewed; and the imaging appearances, histopathologic findings, and management of uncommon intraluminal tumors of the bile ducts and gallbladder and their mimics are discussed. ^©RSNA, 2019.

Usefulness of noncontrast MRI in differentiation between gallbladder carcinoma and benign conditions manifesting as focal mild wall thickening

BACKGROUND

Magnetic resonance imaging (MRI) is a reliable imaging tool for evaluating gallbladder carcinoma, but it is costly and time-consuming.

PURPOSE

To compare noncontrast MRI with multidetector row CT (MDCT) and gadoxetic acid-enhanced whole MRI in distinguishing gallbladder carcinoma from benign disease.

MATERIALS AND METHODS

101 patients (36 with gallbladder carcinoma and 65 with benign disease) with mild focal gallbladder wall thickening were included. Two radiologists reviewed the MDCT and MRI to determine the differential features between malignancy and benignity. Then, the diagnostic performance of MDCT and MRI (T1-, T2- and diffusion-weighted images) with and without gadoxetic acid enhancement in the diagnosis of gallbladder carcinoma was evaluated.

RESULTS

The benign group more often showed T2 necklace sign or T2 hyperintensity within the thickened wall (P < 0.0001) and T1 hyperintensity within the wall or gallbladder lumen (P = 0.0002). Meanwhile, malignancy more frequently showed T2 moderate hyperintensity of the thickened wall, papillary appearance, and diffusion restriction (all P < 0.0001). There were significant differences in sensitivity (79.2% vs 98.6% for observer 1; 84.7% vs 100% for observer 2) and specificity (80.7% vs 96.9%; 79.2% vs 95.4%) between the MDCT and noncontrast MRI (P < 0.05). We found similar diagnostic values between the noncontrast MRI and whole MRI (P = 0.479-1.000) for both observers.

CONCLUSION

Noncontrast MRI could be a useful alternative to gadoxetic acid-enhanced MRI in the diagnosis of gallbladder carcinoma that presents as mild gallbladder wall thickening on MDCT.

MRI of the Nontraumatic Acute Abdomen: Description of Findings and Multimodality Correlation

Obtaining a specific diagnosis in the nontraumatic acute abdomen can be clinically challenging, because a wide range of disease processes affecting a number of different organ systems may have very similar presentations. Although computed tomography and ultrasound examination are the imaging tests most commonly used to evaluate the acute abdomen, MRI can often offer comparable diagnostic performance, and may be considered when other modalities are equivocal, suboptimal, or contraindicated. In some circumstances, MRI is emerging as an appropriate first-line imaging test.

Pope's hat sign: another valuable CT finding of early acute cholecystitis

PURPOSE

To determine the diagnostic performance of minor computed tomography (CT) findings for acute cholecystitis and demonstrate the incremental benefit of pope's hat sign as an additional minor CT finding in patients suspected to have early acute cholecystitis.

MATERIALS AND METHODS

Two radiologists reviewed CT scans of 116 patients with early acute cholecystitis and 116 control patients. All cases in the patient group were surgically proven to have acute cholecystitis and preoperative dynamic CT scans. Evaluated CT parameters included major criteria (gallstone, distension of gallbladder (GB) lumen, GB wall edema, pericholecystic fat infiltration, and pericholecystic fluid collection) and minor criteria (GB bed hyperemia, tensile GB fundus sign, hyperdense GB wall sign, increased bile attenuation within GB, and pope's hat sign).

RESULTS

In a univariate analysis, among the minor criteria, GB bed hyperemia, tensile GB fundus sign, increased bile attenuation within GB, and pope's hat sign were more frequently observed (P < 0.05) in the early acute cholecystitis group. The optimal cut-off value of GB distension for discriminating between the two groups was 3.05 cm. In a multivariable analysis, GB bed hyperemia, pope's hat sign, and GB lumen > 3.05 cm were significant findings for differentiating the two groups (P < 0.001). Among all combinations of these findings, the combination of GB bed hyperemia and pope's hat sign exhibited the highest specificity (96.5%) and the combination of all three findings showed the highest sensitivity (94.0%).

CONCLUSION

Pope's hat sign is a new finding that could improve CT diagnostic performance for early acute cholecystitis in patients with RUQ pain in the emergency department. The combination of pope's hat sign with GB bed hyperemia or GB lumen distension > 3.05 cm may be even more helpful in the early stage or in mild forms of acute cholecystitis.

Clinical and Imaging Features of Noncutaneous Melanoma

OBJECTIVE

The purpose of this article is to summarize the epidemiologic characteristics, clinical aspects, and radiologic appearance of as well as the management considerations and differential diagnoses for noncutaneous primary melanomas occurring at specific anatomic sites. Primary ocular, sinonasal, meningeal, biliary, adrenal, alimentary tract, and genitourinary melanomas are highlighted.

CONCLUSION

Noncutaneous primary melanomas are a complex group of malignancies with biologic findings that are unique when compared with findings for cutaneous melanomas. Each noncutaneous primary melanoma has its own specific diagnostic and management challenges, depending on the anatomic location where they arise.

Gallbladder adenomyomatosis: imaging findings, tricks and pitfalls

Abstract

Gallbladder adenomyomatosis (GA) is a benign alteration of the gallbladder wall that can be found in up to 9% of patients. GA is characterized by a gallbladder wall thickening containing small bile-filled cystic spaces (i.e., the Rokitansky–Aschoff sinuses, RAS). The bile contained in RAS may undergo a progressive concentration process leading to crystal precipitation and calcification development. A correct characterization of GA is fundamental in order to avoid unnecessary cholecystectomies. Ultrasound (US) is the imaging modality of choice for diagnosing GA; the use of high-frequency probes and a precise focal depth adjustment enable correct identification and characterization of GA in the majority of cases. Contrast-enhanced ultrasound (CEUS) can be performed if RAS cannot be clearly identified at baseline US: RAS appear avascular at CEUS, independently from their content. Magnetic resonance imaging (MRI) should be reserved for cases that are unclear on US and CEUS. At MRI, RAS can be identified with extremely high sensitivity, but their signal intensity varies widely according to their content. Positron emission tomography (PET) may be helpful for excluding malignancy in selected cases. Computed tomography (CT) and cholangiography are not routinely indicated in the suspicion of GA.

Teaching points

1. Gallbladder adenomyomatosis is a common benign lesion (1–9% of the patients).

2. Identification of Rokitansky–Aschoff sinuses is crucial for diagnosing gallbladder adenomyomatosis.

3. Sonography is the imaging modality of choice for diagnosing gallbladder adenomyomatosis.

4. Intravenous contrast material administration increases ultrasound accuracy in diagnosing gallbladder adenomyomatosis.

5. Magnetic resonance is a problem-solving technique for unclear cases.

Tumefactive Gallbladder Sludge at US: Prevalence and Clinical Importance

Purpose To evaluate the prevalence of tumefactive sludge of the gallbladder detected at ultrasonography (US) and to assess whether any clinical and imaging differences exist between benign and malignant tumefactive sludge. Materials and Methods The institutional review board approved this retrospective study. The requirement for informed consent was waived. The study included a cohort (n = 6898) of patients with gallbladder sludge drawn from all adults (n = 115 178) who underwent abdominal US between March 2001 and March 2015. Tumefactive sludge was identified according to the following US findings: (a) nonmovable mass-like lesion and (b) absence of posterior acoustic shadowing at B-mode US and vascularity at color Doppler US. Follow-up examinations were arranged to ascertain whether the results showed true sludge or gallbladder cancer. Risk factors for malignant tumefactive sludge based on clinical and US characteristics were identified with multivariate logistic regression analysis. Results The prevalence of gallbladder and tumefactive sludge at abdominal US during the observation period was 6.0% (6898 of 115 178) and 0.1% (135 of 115 178), respectively. Twenty-eight (20.7%) patients were lost to follow-up. Of the 107 with tumefactive sludge, 15 (14%) were confirmed to have malignant tumefactive sludge. The risk factors for malignant tumefactive sludge were old age (odds ratio [OR], 1.06; P = .035), female sex (OR, 5.48; P = .014), and absence of hyperechoic spots within the sludge (OR, 6.78; P = .008). Conclusion Although the prevalence of tumefactive sludge at US was rare, a considerable proportion of patients had a malignancy. Careful follow-up is essential, especially for older patients, women, and those with an absence of hyperechoic spots at US. ^© RSNA, 2016 Online supplemental material is available for this article.

Tumefactive gallbladder sludge: the MRI findings

AIM

To evaluate the conventional and diffusion-weighted magnetic resonance imaging (MRI) images of tumefactive gallbladder sludge.

MATERIALS AND METHODS

The institutional review board approved this retrospective study. Between January 2006 and January 2015, 3478 patients were diagnosed with gallbladder sludge by ultrasonography (US). Of them, 12 patients (eight male, four female; mean age, 63.6 years) with 12 tumefactive gallbladder sludge lesions, who underwent subsequent MRI for further evaluation within 1 month, were included in this study. Data regarding the clinical features, presence of enhancement, and signal intensities of the T2-, T1-, and diffusion-weighted images were collected.

RESULTS

All cases of tumefactive sludge were detected incidentally. None of the patients had any predisposing factors for biliary sludge. The tumefactive gallbladder sludge was predominantly seen as a well-defined mass-like lesion. It showed hyperintensity on T1-weighted images (91.7%, 11/12), and variable signal intensities on T2-weighted images. Most of the tumefactive sludge lesions showed no enhancement on the dynamic phases (90%, 9/10). There were no cases with diffusion restriction. Among the patients with follow-up US data (n=7), all the lesions were found to have either disappeared or decreased in size.

CONCLUSION

Although tumefactive gallbladder sludge on US can mimic gallbladder cancer, its hyperintensity on a T1-weighted image, and the absence of enhancement and diffusion restriction on MRI images can be helpful for differentiating it from a tumorous condition.

Diffusion-weighted magnetic resonance imaging to differentiate malignant from benign gallbladder disorders

PURPOSE

To retrospectively evaluate the utility of apparent diffusion coefficient (ADC) and lesion to spinal cord ratio (LSR) in diffusion-weighted magnetic resonance (MR) imaging (DWI) as compared with morphological assessment alone, for differentiating malignant from benign gallbladder disorders.

METHODS

This study was approved by the ethics committee, and written informed consent was waived. Ninety-one patients (13 malignancy and 78 benignancy) were reviewed. ADC was calculated using two DW images with different motion-probing gradient strengths (b=0, 1000s/mm(2)). LSR was measured by dividing the signal intensity of a thickened gallbladder wall by the maximum signal intensity of the lumbar enlargement of the spinal cord. In addition, the morphology of the gallbladders was assessed with conventional MR imaging.

RESULTS

In receiver operating characteristic curve analysis, the areas under the curves for ADC and LSR were 0.861 and 0.906, respectively. Three morphological findings were considered: a massive formation, a disrupted mucosal line, and the absence of a two-layered pattern. When a combination of two or more of these morphological findings was positive for malignancy, the sensitivity, specificity, and accuracy were 76.9%, 84.0%, and 83.0%, respectively. When a combination of three or more of the above morphological findings together with ADC of less than 1.2 × 10(-3)mm(2)/s or LSR of more than 0.48 were positive for malignancy, these values were 73.0%, 96.2%, and 92.9%, respectively. There were significant differences in specificity and accuracy.

CONCLUSION

Use of ADC and LSR in DWI can improve diagnostic performance for differentiating malignant from benign gallbladder disorders.

A literature review of radiological findings to guide the diagnosis of gallbladder adenomyomatosis

BACKGROUND

Gallbladder adenomyomatosis (GA) is a benign gallbladder entity discovered as an asymptomatic gallbladder mass. Since gallbladder cancer is in the differential diagnosis for gallbladder masses, the ability to differentiate benign disease avoids a more extensive oncologic resection. This study sought to review imaging modalities used to diagnose GA.

METHODS

PubMed and SciVerse Scopus were systematically searched using the terms: "gallbladder adenomyomatosis" and "gallbladder imaging" for articles published between January 2000 and January 2015.

RESULTS

A total of 14 articles were reviewed in this analysis. Contemporary series report the use of ultrasound (US), computed tomography (CT) or magnetic resonance imaging (MRI) in GA imaging. Ultrasound detection of Rokitansky-Aschoff sinuses, visualized as small cystic spaces with associated "comet-tail" or "twinkling" artifact, is pathognomonic for GA. A "Pearl-Necklace" sign of small connected sinuses on MRI or "Rosary" sign on CT are additional characteristics that may assist in establishing a diagnosis.

CONCLUSION

Ultrasound is the most commonly used tool to investigate GA. If not diagnostic, CT or MRI are effective in attempting to differentiate a benign or malignant cholecystic mass. Characteristic signs should lead the surgeon to perform a laparoscopic cholecystectomy in symptomatic patients or manage non-operatively in asymptomatic patients.

Utility of diffusion-weighted MRI for differentiating acute from chronic cholecystitis

PURPOSE

To assess the use of diffusion-weighted imaging (DWI) for differentiating acute from chronic cholecystitis, in comparison with conventional magnetic resonance imaging (MRI) features.

MATERIALS AND METHODS

Liver MRI including DWI (b-values 0/500/1000s/mm(2) ) was performed at 1.5T ≤30 days before cholecystectomy in 83 patients with abdominal pain. Two radiologists assessed cases for conventional (gallstones, wall thickening, pericholecystic fluid, pericholecystic fat changes, gallbladder distension, pericholecystic liver enhancement, mural T2 -hyperintensity, mural hyperenhancement, mural striations, abscess, intraluminal membranes, and mural defect) and DWI (increased mural signal on high b-value images, visually low apparent diffusion coefficient [ADC], and ADC values) features.

RESULTS

Acute cholecystitis was present in 43%; chronic cholecystitis was present in 57%. Nine of 12 conventional features were more frequent in acute cholecystitis for both readers (P ≤ 0.003). Increased mural signal on high b-value images was more frequent (P < 0.001) in acute than chronic cholecystitis for R1 (92% vs. 32%) and R2 (83% vs. 30%). Sensitivity and specificity of increased signal on high b-value images were: R1, 92%/68%; R2, 83%/70%. Visually low ADC was more frequent in acute cholecystitis for R2 (P < 0.001) but not R1 (P = 0.406); ADC values were not different between groups for either reader (P = 0.104-0.139). Among conventional and DWI features, only increased signal on high b-value DWI was independently associated with acute cholecystitis for both readers (P = 0.006-0.012).

CONCLUSION

Visually increased mural signal on high b-value DWI was highly sensitive and moderately specific for acute cholecystitis, being an independent predictor relative to conventional features for both readers. Although requiring larger studies, DWI (particularly the high b-value images) may have additive value relative to conventional MRI-suspected acute cholecystitis. J. Magn. Reson. Imaging 2016;44:89-97.

Diffusion-weighted magnetic resonance imaging for non-neoplastic conditions in the hepatobiliary and pancreatic regions: pearls and potential pitfalls in imaging interpretation

Potentially, diffusion-weighted magnetic resonance imaging (DWI) can assess the functional information on concerning the status of tissue cellularity, because increased cellularity is associated with impeded diffusion. DWI in the hepatobiliary and pancreatic regions has demonstrated the usefulness to detect malignant lesions and differentiate them from benign lesions. However, it has been shown more recently that there is some overlap in ADC values for benign and malignant neoplasms. Moreover, some non-neoplastic lesions in the hepatobiliary and pancreatic regions exhibit restricted diffusion on DWI, because of pus, inflammation, or high cellularity. Focal eosinophilic liver disease, hepatic inflammatory myofibroblastic tumor, granulomatous liver disease, acute cholecystitis, xanthogranulomatous cholecystitis, focal pancreatitis, or autoimmune pancreatitis frequently exhibit restricted diffusion on DWI, which may be confused with malignancy in the hepatobiliary and pancreatic regions. Thus, DWI should not be interpreted in isolation, but in conjunction with other conventional images, to avoid the diagnostic pitfalls of DWI. Nevertheless, the presence of diffusion restriction in the non-neoplastic lesions sometimes provides additional information regarding the diagnosis, in problematic patients where conventional images have yielded equivocal findings. DWI may help differentiate hepatic abscess from malignant necrotic tumors, gallbladder empyema from dense bile or sludge in the gallbladder, and pylephlebitis from bland thrombosis in the portal vein. Therefore, knowledge of DWI findings to conventional imaging findings of diffusion-restricted non-neoplastic conditions in the hepatobiliary and pancreatic regions helps establishing a correct diagnosis.

Accumulation of Bile in the Gallbladder: Evaluation by means of Serial Dynamic Contrast-Enhanced Magnetic Resonance Cholangiography with Gadolinium Ethoxybenzyl Diethylenetriaminepentaacetic Acid

The aim of this study was to evaluate the process of biliary excretion of gadolinium ethoxybenzyl diethylenetriaminepentaacetic acid (Gd-EOB-DTPA) into the biliary tract and to assess the accumulation patterns in the gallbladder using MR cholangiography obtained with Gd-EOB-DTPA which is a liver-specific hepatobiliary contrast agent. Seventy-five patients underwent Gd-EOB-DTPA enhanced MR imaging. Serial multiphasic hepatobiliary phase imaging was qualitatively reviewed to evaluate the process of the biliary excretion of contrast agent into the bile duct and the gallbladder. The accumulation pattern of contrast agent into gallbladder was classified into two groups (group 1 = orthodromic type and group 2 = delayed type). Furthermore, the results in differences of the presence of T1 hyperintense bile or sludge of gallbladder, gall stones, wall thickening of gallbladder, chronic liver disease, and liver cirrhosis between two groups were compared. Forty-eight of 75 patients (64%) were included in group 1, and remaining 27 (36%) were in group 2. The frequency of the presence of T1 hyperintense bile or sludge of gallbladder was significantly higher in patients with group 2 than that in patients with group 1 (P = 0.041). MR cholangiography obtained with Gd-EOB-DTPA showed that there may be an association between the biliary accumulation pattern in the gallbladder and the pathological condition.

MR cholangiopancreatography of the pancreas and biliary system: a review of the current applications

MR cholangiopancreatography (MRCP) is still a rapidly evolving technique, but it has been already accepted as clinically useful and is widely used to evaluate biliary or pancreatic diseases. The advantages of this technique are that it does not use contrast media or ionizing radiation, it is noninvasive and complication free, and the examination is relatively short. MRCP has high sensitivity and specificity for diagnosing biliary dilatation and for determining the site and cause of stenosis. With further improvements of hardware and technique, MRCP is expected to replace diagnostic endoscopic retrograde cholangiopancreatography to examine the biliary and pancreatic ducts in the near future. The other applications include evaluation of primary sclerosing cholangitis, stenosis after liver transplantation, and bilioenteric anastomoses. This article reviews the current applications of MRCP in the evaluation of the pancreas and the biliary system.