Imaging of Biliary Tree Abnormalities.

Pathologic conditions of the biliary system, although common, can be difficult to diagnose clinically. Challenges in biliary imaging include anatomic variants and the dynamic nature of the biliary tract, which can change with age and intervention, blurring the boundaries of normal and abnormal. Choledochal cysts can have numerous appearances and are important to diagnose given the risk of cholangiocarcinoma potentially requiring surgical resection. Choledocholithiasis, the most common cause of biliary dilatation, can be difficult to detect at US and CT, with MRI having the highest sensitivity. However, knowledge of the imaging pitfalls of MRI and MR cholangiopancreatography is crucial to avoid misinterpretation. Newer concepts in biliary tract malignancy include intraductal papillary biliary neoplasms that may develop into cholangiocarcinoma. New paradigms in the classification of cholangiocarcinoma correspond to the wide range of imaging appearances of the disease and have implications for prognosis. Accurately staging cholangiocarcinoma is imperative, given expanding curative options including transplant and more aggressive surgical options. Infections of the biliary tree include acute cholangitis or recurrent pyogenic cholangitis, characterized by obstruction, strictures, and central biliary dilatation. Inflammatory conditions include primary sclerosing cholangitis, which features strictures and fibrosis but can be difficult to differentiate from secondary causes of sclerosing cholangitis, including more recently described entities such as immunoglobulin G4-related sclerosing cholangitis and COVID-19 secondary sclerosing cholangitis. The authors describe a wide variety of benign and malignant biliary tract abnormalities, highlight differentiating features of the cholangitides, provide an approach to interpretation based on the pattern of imaging findings, and discuss pearls and pitfalls of imaging to facilitate accurate diagnosis. ©RSNA, 2024 Supplemental material is available for this article.

Pancreatic Cystic Lesions and Malignancy: Assessment, Guidelines, and the Field Defect.

The widespread use of high-spatial-resolution cross-sectional imaging has led to an increase in detection of incidental pancreatic cystic lesions. These lesions are a diverse group, ranging from indolent and premalignant lesions to invasive cancers. The diagnosis of several of these lesions can be suggested on the basis of their imaging appearance, while many other lesions require follow-up imaging and/or aspiration. The smaller cystic lesions, often branch-duct intraductal papillary mucinous neoplasms, have overlapping imaging characteristics that make diagnostic assessment of the natural history and malignancy risk confusing. Expert panels have developed societal guidelines, based on a consensus, for surveillance of these lesions. However, these guidelines are often inconsistent and are constantly evolving as additional scientific data are accumulated. Identification of features associated with increased risk of malignancy is important for proper management. The concept of field defect, whereby pancreatic adenocarcinoma develops at a site different from the site of the pancreatic cyst, adds to the complexity of screening guidelines. As a result of the differences in guidelines, key stakeholders (eg, radiologists, gastroenterologists, and surgeons) must review and come to a consensus regarding which guideline, or combination of guidelines, to follow at their individual institutions. Standardized reporting and macros are helpful for ensuring the uniformity of interpretations. Radiologists play a critical role in the detection and characterization of pancreatic cystic lesions, in the follow-up recommendations for these lesions, and in the detection of associated cancer. An invited commentary by Zaheer is available online. Online supplemental material is available for this article. ©RSNA, 2021.

Reactions to Both Nonionic Iodinated and Gadolinium-Based Contrast Media: Incidence and Clinical Characteristics.

OBJECTIVE: The objective or our study was to assess the incidence rate and clinical characteristics of allergiclike reactions in patients who received both nonionic iodinated contrast medium (ICM) and gadolinium-based contrast medium (GBCM). MATERIALS AND METHODS: Acute allergiclike reactions in patients who received both ICM and GBCM to nonionic ICM or GBCM injections during a 5-year period were analyzed. Allergy preparation was not administered when patients received a different type of contrast material. Acute allergiclike reactions to both ICM and GBCM were evaluated. RESULTS: Of 302,858 contrast injections (155,234 ICM and 147,624 GBCM) during a 5-year period, 1006 (752 ICM and 254 GBCM) acute allergiclike contrast reactions were reported. The overall rate of reaction to ICM was 0.48% (95% CI, 0.45-0.52%), and the overall rate of reaction to GBCM was 0.17% (95% CI, 0.15-0.19%). A total of 19,237 patients received at least one ICM injection and one GBCM injection, with a total of 56,310 injections (19,237 initial injections and 37,073 subsequent injections). Nine patients had reactions to both ICM and GBCM with the primary reaction rate of 9/19,237 (incidence rate, 0.047%; 95% CI, 0.044-0.050%), and the secondary reaction rate of 9/37,073 (incidence rate, 0.024%; 95% CI, 0.023-0.026%). All secondary reactions in patients who had a reaction to both ICM and GBCM were mild. None of the patients required medication for the treatment of the secondary reaction. CONCLUSION: An allergiclike reaction to both nonionic ICM and GBCM was an extremely rare event that presented as a mild acute reaction without significant clinical consequences despite the fact that an allergy preparation was not administered.

CT and MR imaging for evaluation of cystic renal lesions and diseases.

Cystic renal lesions are commonly encountered in abdominal imaging. Although most cystic renal lesions are benign simple cysts, complex renal cysts, infectious cystic renal disease, and multifocal cystic renal disease are also common phenomena. The Bosniak classification system provides a useful means of categorizing cystic renal lesions but places less emphasis on their underlying pathophysiology. Cystic renal diseases can be categorized as focal, multifocal, or infectious lesions. Diseases that manifest with focal lesions, such as cystic renal cell carcinoma, mixed epithelial and stromal tumor, and cystic nephroma, are often difficult to differentiate but have differing implications for follow-up after resection. Multifocal cystic renal lesions can be categorized as acquired or heritable. Acquired entities, such as glomerulocystic kidney disease, lithium-induced nephrotoxicity, acquired cystic kidney disease, multicystic dysplastic kidney, and localized cystic renal disease, often have distinct imaging and clinical features that allow definitive diagnosis. Heritable diseases, such as autosomal dominant polycystic kidney disease, von Hippel-Lindau disease, and tuberous sclerosis, are usually easily identified and have various implications for patient management. Infectious diseases have varied imaging appearances, and the possibility of infection must not be overlooked when assessing a cystic renal lesion. A thorough understanding of the spectrum of cystic renal disease will allow the radiologist to make a more specific diagnosis and provide the clinician with optimal recommendations for further diagnostic testing and follow-up imaging.

Imaging features of benign and malignant ampullary and periampullary lesions.

The ampulla of Vater is an important anatomic landmark where the common bile duct and main pancreatic duct converge in the major duodenal papilla. Imaging evaluation of the ampulla and periampullary region poses a unique diagnostic challenge to radiologists because of the region's complex and variable anatomy and the variety of lesions that can occur. Lesions intrinsic to the ampulla and involved segment of the biliary tree can be neoplastic, inflammatory, or congenital. Neoplastic lesions include ampullary adenocarcinomas and adenomas, which often are difficult to differentiate, as well as pancreatic or duodenal adenocarcinomas, pancreatic neuroendocrine tumors, and cholangiocarcinomas. Ultrasonography (US), computed tomography, magnetic resonance (MR) imaging, and MR cholangiopancreatography are commonly used to evaluate this region. Endoscopic retrograde cholangiopancreatography or endoscopic US examination may be necessary for more definitive evaluation. Periampullary conditions in the duodenum that may secondarily involve the ampulla include neoplasms, duodenitis, duodenal diverticula, and Brunner's gland hyperplasia or hamartomas. Because these lesions can exhibit a wide overlap of imaging features and subtle or nonspecific imaging findings, diagnosis is made on the basis of patient age, clinical history, and imaging and laboratory findings. Given the complexity of imaging evaluation of the ampulla and periampullary region, it is essential for radiologists to understand the variety of lesions that can occur and recognize their imaging characteristics.

Feasibility of sub-second CT angiography of the abdomen and pelvis with very low volume of contrast media, low tube voltage, and high-pitch technique, on a third-generation dual-source CT scanner.

BACKGROUND: Concerns about potential risks of using contrast media in patients with chronic renal insufficiency limit the utilization of CT angiography in this population. PURPOSE: To evaluate the feasibility of abdominopelvic CTA with very low volumes of contrast media. MATERIAL AND METHODS: In this retrospective study, 20 patients with chronic renal insufficiency underwent high-pitch abdominopelvic (AP) CTA on a third-generation dual-source CT scanner with 30 mL of nonionic iodinated contrast. The homogeneity of intravascular attenuation at the suprarenal aorta, infrarenal aorta, and the right common iliac artery was measured. Image noise, contrast-to-noise ratio (CNR), and signal-to-noise ratio (SNR) were used to assess objective image quality. Subjective image quality was evaluated on a 5-point scale (1 = unacceptable; 5 = excellent). RESULTS: Twelve male and eight female patients underwent CTA of the abdomen and pelvis at 80 kVp. Five CTAs also included the chest (CAP). The mean scan duration was 0.78 ± 0.19 s for AP and 0.96 ± 0.06 s for CAP CTAs. The mean ± SD of attenuation at suprarenal aorta, infrarenal aorta, and right common iliac artery were 235.1 ± 68.0, 249.2 ± 61.3, and 254.4 ± 67.7 HU, respectively. The attenuation was homogeneous across vascular levels (P = 0.06). All scans had diagnostic subjective image quality with the median (IQR) of 3.5 (1.75). CNR and SNR were homogeneous across vascular levels (P = 0.08 and P = 0.14, respectively). CONCLUSION: Sub-second, high-pitch abdominopelvic CTA with a low volume of contrast in patients with chronic renal insufficiency is technically and clinically feasible with good diagnostic image quality and homogenous attenuation across vascular levels.

An Unusual Cause of Acute Pancreatitis in a Liver Transplant Recipient.

Posttransplant lymphoproliferative disorder (PTLD) in liver transplant recipients is relatively uncommon, with an estimated incidence of 1%-3%. Retrospective reviews of liver transplant recipients have mainly reported posttransplant lymphoproliferative disorder affecting the liver, gastrointestinal tract, or lymph nodes. In this case report, we describe a 45-y-old female with a history of deceased donor liver transplantation for autoimmune hepatitis who had recurrent hospital admissions for acute pancreatitis. Ultimately, imaging revealed numerous complex pancreatic and peripancreatic masses, appearing to originate from pancreatic lymphoid tissue. Tissue biopsy later confirmed monomorphic Epstein-Barr virus-negative large B-cell lymphoma. Overall, PTLD involving the pancreas after liver transplantation is incredibly rare. The patient's cumulative immunosuppression drug dose and time posttransplant were suspected to be her main risk factors, given that she had been exposed to several years of treatment with tacrolimus, azathioprine, mycophenolate mofetil, and prednisone. She was treated with rituximab monotherapy and later escalated to chemoimmunotherapy due to lack of response. PTLD involving the pancreas is an unusual cause of pancreatitis and should be considered in cases of recurrent pancreatitis in transplant recipients.

Gastric outlet obstruction in the setting of acute cholecystitis.

Acute cholecystitis is a rare cause of gastric outlet obstruction (GOO) and may manifest with nonspecific symptoms which may preclude or delay diagnosis. During the latter part of the 20th century, benign disease was responsible for most cases of GOO in adults with peptic ulcer disease accounting for up to 90% of these cases. Although precise estimates on GOO incidence and prevalence are lacking, as many as 2000 surgical operations were reportedly performed annually for GOO in the United States in the 1990s. We present clinical and imaging findings of a case of a 101-year-old woman with GOO resulting from extrinsic compression from a massively dilated gallbladder related to acute cholecystitis. In addition, we review other rare biliary causes of GOO.

Pancreatitis in the developmentally anomalous pancreas.

Developmental anomalies of the pancreas include more common entities such as pancreas divisum and annular pancreas, and unusual entities such as heterotopic pancreas. While these anomalies can present a diagnostic challenge to the radiologist, when the pancreatic tissue involved in these processes develops pancreatitis, the radiographic appearance can present a diagnostic dilemma. Awareness of these pancreatic anomalies and familiarity with their appearance when inflamed is necessary to distinguish pancreatitis in the developmentally anomalous pancreas from other inflammatory or neoplastic processes.

Renal Pretransplantation Work-up, Donor, Recipient, Surgical Techniques.

Renal transplant is the single best treatment of end-stage renal disease. Computed tomography (CT) is an excellent method for the evaluation of potential renal donors and recipients. Multiphase CT is particularly useful because of detailed evaluation of the kidneys, including the vascular anatomy and the collecting system. MR imaging has no ionizing radiation, but is limited for stone detection, making it a less preferred method of evaluating donors. Preoperative knowledge of the renal vascular anatomy is essential to minimize risks for donors. Imaging evaluation of recipients is also necessary for vascular assessment and detection of incidental findings.

Taking advantage of chemical shift imaging: using opposed-phase images to locate the normal appendix on MR.

Multiple sequences of 50 consecutive adult pelvic MRI exams were retrospectively reviewed by two radiologists to determine if opposed-phase T1 gradient echo imaging can assist in locating the normal appendix on pelvic MRI. If the appendix was visualized, it was always seen on the T2 sequence, except for one exam. The opposed-phase sequence had the second highest visualization rate, and the appendix was identified the least on the post-gadolinium sequence. The presence of a "button nose" sign was also assessed and was present in one third of cases.