Radiological studies play a crucial role in the evaluation of patients with biliary duct obstruction, allowing for the guidance of clinical diagnosis towards a malignant or stone-induced etiology through the recognition of relevant imaging features, which must be continuously revisited given their prognostic significance. This article aims to emphasize the importance of recognizing crucial imaging aspects of malignant and stone-induced biliary obstruction.

The term IgG4-related autoimmune liver disease (AILD) refers to hepato-biliary manifestations of Immunoglobin G4-related disease (IgG4-RD) including IgG4-related sclerosing cholangitis and IgG4-related pseudotumor. The association of some forms of autoimmune hepatitis to IgG4-RD remains controversial. Although autoimmune phenomena have not been clearly observed in IgG4-AILD, perturbation of the adaptive immune system and activation of the humoral response represent established pathophysiological hallmarks and potential therapeutic targets. Clinical manifestations of IgG4-AILD are virtually indistinguishable from bile duct cancer or primary sclerosing cholangitis and are due to mass forming lesions and thickening of the biliary tract that progressively lead to biliary ducts obstruction. There are no current reliable biomarkers for IgG4-AILD and diagnosis should rely on the integration of clinical, serological, radiological, and histological findings. In analogy to most IgG4-RD manifestations, and in contrast to its major mimickers, IgG4-AILD promptly responds to glucocorticoids but frequently relapses, thus requiring long-term maintenance therapy to avoid progressive fibrosclerotic disease and liver cirrhosis. Accumulating evidence on the efficacy of B-cell depletion therapy in patients with systemic IgG4-RD is gradually changing the treatment paradigm of IgG4-AILD and biologics will be increasingly used also for gastroenterological manifestations of IgG4-RD to spare glucocorticoids and traditional immunosuppressive agents. Looking ahead, identification of reliable biomarkers and of mini-invasive strategies to obtain informative biopsies from the biliary tree represent unavoidable priorities to optimize diagnosis and management of IgG4-AILD.

To evaluate the visualization of gallbladder stones on susceptibility-weighted imaging (SWI).

Imaging data from 47 patients who underwent clinically indicated cholecystectomy was reviewed. Breath-hold SWI was added to the magnetic resonance imaging protocol and magnitude and phase data was reviewed for gall-stones visualization. Phase signature, that is, diamagnetic, paramagnetic, or mixed, was also noted in the stones. Magnetic susceptibility value of surgically extracted gallstones were imaged ex vivo (n = 37).

In 45 of 47 cases, gallstones were surgically confirmed. In 43 cases, gallstones were visualized in the SWI. In 1 case, although routine imaging failed, stones were visualized on SWI. In 29 diamagnetic, 7 paramagnetic and 9 cases mixed phase were seen. In an ex vivo study, magnetic susceptibility of stones was found ranging between -0.102 and -0.916 ppm for diamagnetic and 0.203 and 486 ppm for paramagnetic stones.

Gallbladder stones can be visualized with SWI and may be added to the routine magnetic resonance imaging protocol for its evaluation.

To report our cancer centre experience in the biliary tumours incidence other than cholangiocellular-carcinoma, emphasizing the radiological features.

197 patients with biliary disease undergoing Gd-EOB-DTPA-enhanced MRI were reviewed. Four radiologists evaluated retrospectively size, structure, anatomical site and signal intensity of lesions on MRI. Enhancement-pattern during the arterial-, portal- and late-phase on ultrasound, CT and MR study was assessed as well as the enhancement pattern during the hepatobiliary-phase on MRI.

23 patients were selected. The lesion was intraductal in 5 cases, periductal in 14 and intrahepatic in 4. 16 lesions were solid, 5 uniloculated cystic and 2 complex cystic. In five patients the lesion was simple cyst, with a signal intensity in T₁ weighted (T1W) and T₂ weighted (T2W) similar to the gallbladder. In two patients with complex cystic lesion, the solid component was heterogeneously hypointense in T₁ W, hyperintense in T₂ W with a restricted diffusion. The solid component showed heterogeneous contrast-enhancement on CT, MR and ultrasound. The tumour was intrahepatic in two patients, with signal hypointense in T₁ W and hyperintense in T₂ W. Diffusion was restricted. The lesions showed heterogeneous contrast-enhancement. The periductal lesions were hypointense in T₁ W, hyperintense in T₂ W with restricted diffusion. The lesion showed progressive contrast-enhancement. Peribiliary melanoma was hyperintense in T₁ W, hyperintense in T₂ W with restricted diffusion and progressively contrast-enhanced.

Biliary tumours can have a wide spectrum of radiologic appearances and consequently represent a diagnostic challenge for the radiologist. Advances in knowledge: MRI is the technique of choice in diagnosing biliary tumours, including rare (non-CCC) tumours.

Magnetic resonance imaging is useful for evaluating pancreaticobiliary diseases in children after initial sonography, obviating the use of ionizing radiation or invasive procedures such as endoscopic retrograde cholangiopancreatography (ERCP) or transhepatic biliary procedures. Advanced MRI applications have improved depiction of pediatric pancreaticobiliary anatomy and have greatly impacted management of biliary and pancreatic diseases in children. In this article, we review current MRI and magnetic resonance cholangiopancreatography (MRCP) techniques and discuss their role in the assessment of common pancreatic and biliary disorders in children.

On the basis of the similarities in the histopathologic findings and the clinical-biologic behaviors of select biliary and pancreatic conditions, a new disease concept, "biliary diseases with pancreatic counterparts," has been proposed. Both nonneoplastic and neoplastic pathologic conditions of the biliary tract have their counterparts in the pancreas. Immunoglobulin G4 (IgG4)-related sclerosing cholangitis is the biliary manifestation of IgG4-related sclerosing disease, and type 1 autoimmune pancreatitis is its pancreatic counterpart. People with chronic alcoholism can develop peribiliary cysts and fibrosis as well as pancreatic fibrosis and chronic pancreatitis simultaneously. Pancreatic ductal adenocarcinoma, intraductal papillary mucinous neoplasm, and mucinous cystic neoplasm are considered pancreatic counterparts for the biliary neoplasms of extrahepatic cholangiocarcinoma, intraductal papillary neoplasm of the biliary tract, and hepatic mucinous cystic neoplasm, respectively. The anatomic proximity of the biliary tract and the pancreas, the nearly simultaneous development of both organs from the endoderm of the foregut, and the presence of pancreatic exocrine acini within the peribiliary glands surrounding the extrahepatic bile ducts are suggested as causative factors for these similarities. Interestingly, these diseases show "nearly" identical findings at cross-sectional imaging, an observation that further supports this new disease concept. New information obtained with regard to biliary diseases can be used for evaluation of pancreatic abnormalities, and vice versa. In addition, combined genetic and molecular studies may be performed to develop novel therapeutic targets. For both biliary and pancreatic diseases, imaging plays a pivotal role in initial diagnosis, evaluation of treatment response, efficacy testing of novel drugs, and long-term surveillance.