Pancreaticoduodenal Groove: Spectrum of Disease and Imaging Features.

The pancreaticoduodenal groove (PDG) is a small space between the pancreatic head and duodenum where vital interactions between multiple organs and physiologic processes take place. Muscles, nerves, and hormones perform a coordinated dance, allowing bile and pancreatic enzymes to aid in digestion and absorption of critical nutrition. Given the multitude of organs and cells working together, a variety of benign and malignant entities can arise in or adjacent to this space. Management of lesions in this region is also complex and can involve observation, endoscopic resection, or challenging surgeries such as the Whipple procedure. The radiologist plays an important role in evaluation of abnormalities involving the PDG. While CT is usually the first-line examination for evaluation of this complex region, MRI offers complementary information. Although features of abnormalities involving the PDG can often overlap, understanding the characteristic imaging and pathologic features generally allows categorization of disease entities based on the suspected organ of origin and the presence of ancillary features. The goal of the authors is to provide radiologists with a conceptual approach to entities implicating the PDG to increase the accuracy of diagnosis and assist in appropriate management or presurgical planning. They briefly discuss the anatomy of the PDG, followed by a more in-depth presentation of the features of disease categories. A table summarizing the entities that occur in this region by underlying cause and anatomic location is provided. ©RSNA, 2022.

Hepatocellular Carcinoma With Atypical Imaging Features: Review of the Morphologic Hepatocellular Carcinoma Subtypes With Radiology-Pathology Correlation.

Hepatocellular carcinoma (HCC) is the fastest growing cause of cancer death in the United States with the incidence rate more than doubling in 20 years. HCC is unique since a noninvasive diagnosis can be achieved with imaging alone when specific clinical criteria and imaging characteristics are met, obviating the need for tissue sampling. However, HCC is a highly heterogeneous neoplasm. Atypical HCC subtypes vary significantly in their morphology, which can be attributed to specific histologic and molecular features, and can cause deviations from the classic imaging characteristics. The different morphologic subtypes of HCC frequently present a diagnostic challenge for radiologists and pathologists since their imaging and pathologic features can overlap with those of non-HCC malignancies. Identifying an atypical subtype can have important clinical implications. Liver transplant, albeit a scarce and limited resource, is the optimal treatment for conventional HCC, potentially curing both the tumor and the underlying pre-malignant condition. Some HCC subtypes as well as mimickers are associated with unacceptably high recurrence and poor outcome after transplant, and there remains limited data on the role and prognosis of liver transplantation for treatment of rare HCC subtypes. Other subtypes tend to recur later than classic HCC, potentially requiring a different follow-up scheme. This review will discuss the appearance of different HCC subtypes in relation to their histopathologic features. LEVEL OF EVIDENCE: 5 TECHNICAL EFFICACY: Stage 3.

Ultrasound Evaluation for Extremity Deep Vein Thrombus in COVID-19-Positive Patients: Exam Positivity Rate and Association With D-Dimer Level.

OBJECTIVES: Determine the rate of positive extremity ultrasound exams for DVT in patients with COVID-19 and assess for differences in laboratory values in patients with and without DVT, which could be used as a surrogate to decide the need for further evaluation with ultrasound. METHODS: Retrospective case control study with 1:2 matching of cases (COVID-19+ patients) to controls (COVID-19- patients) based on age, gender, and race. Laboratory values assessed were serum D-dimer, fibrinogen, prothrombin time, international normalized ratio, and C-reactive protein. Demographic variables, comorbidities, and clinical variables including final disposition were also evaluated. P-values for categorical variables were calculated with the chi-square test or Fisher's exact test. P-values for continuous variables were compared with the use of a two-tailed unpaired t-test. RESULTS: The rate of extremity ultrasound exams positive for DVT were similar in patients with (14.7%) and without (19.3%) COVID-19 (P = .423). No significant difference was observed in laboratory values including the D-dimer level in COVID-19 patients without (mean 9523.9 ng/mL (range 339 to >60,000)) or with DVT (mean 13,663.7 ng/mL (range 1193->60,000)) (P = .475). No differences were found in demographic variabilities or co-morbidities among COVID-19 patients with and without extremity DVT. CONCLUSIONS: We found no statistically significant difference in rate of positive DVT studies between COVID-19+ and COVID-19- patients. D-dimer levels are elevated, in some cases markedly, in COVID-19 patients with and without DVTs and therefore these data do not support their use as a surrogate when assessing the need for ultrasound evaluation.

Skull Base-related Lesions at Routine Head CT from the Emergency Department: Pearls, Pitfalls, and Lessons Learned.

Routine non-contrast material-enhanced head CT is one of the most frequently ordered studies in the emergency department. Skull base-related pathologic entities, often depicted on the first or last images of a routine head CT study, can be easily overlooked in the emergency setting if not incorporated in the interpreting radiologist's search pattern, as the findings can be incompletely imaged. Delayed diagnosis, misdiagnosis, or lack of recognition of skull base pathologic entities can negatively impact patient care. This article reviews and illustrates the essential skull base anatomy and common blind spots that are important to radiologists who interpret nonenhanced head CT images in the acute setting. The imaging characteristics of important "do not miss" lesions are emphasized and categorized by their cause and location within the skull base, and the potential differential diagnoses are discussed. An interpretation checklist to improve diagnostic accuracy is provided. ©RSNA, 2019.