Objectives

Describe and illustrate the use of abdominal ultrasonography (US) and contrast enhanced computed tomography (CT) imaging in the detection and characterization of focal benign tumors of the liver.

List the differentiating clinical, radiologic and histopathologic findings in most frequent liver lesions.

Background

Incidental focal lesions in the liver are frequently detected at routine US and many may present with atypical imaging features. Other imaging modalities such as contrast-enhanced ultrasound (CEUS) and CT are helpful for characterization of these lesions. The development of CEUS has considerably improved the diagnostic accuracy and allows real-time evaluation of the microcirculation and macrocirculation of the hepatic lesions. The knowledge of the CEUS enhancement is crucial in the appropriate management of these patients.

Imaging findings OR Procedure findings

Benign hepatic lesions such as cyst, hemangioma, focal nodular hyperplasia, adenoma, biliary microhamartomas or focal fatty infiltration are classified according to their cell of origin into tumors of hepatocellular, cholangiocellular or mesenchymal origin and have characteristic imaging findings.

Often the sonographic findings are nonspecific and other imaging modalities such as CEUS and CT are helpful for characterization of these lesions.

Conclusion

The vast majority of the benign hepatic tumors can be diagnosed with ultrasound and CT imaging. Even when a specific diagnosis cannot be provided, the benign nature of the tumor can be confidently suggested, avoiding more aggressive diagnostic approaches such as biopsy or surgical excision. Radiologists should be familiarized the classic US, CEUS and CT imaging appearances of focal liver lesions to help to ensure a presumptive diagnosis and shorten the diagnostic workup.

Objectives

- Describe and highlight the most important features of liver vascular anatomy;

- Review and classify the different disorders that may affect hepatic vascularization, focusing on the imaging features that allow their diagnosis;

Background

The liver is a unique organ with a dual blood supply (the portal vein and the hepatic artery) and a single outflow via the hepatic veins. There are several anastomoses between the hepatic artery and the portal vein, allowing a delicate autoregulation of the blood inflow.

Imaging findings OR Procedure findings

In this review we were able to demonstrate different causes of liver vascular disorders, focusing on the mechanisms and imaging findings that allow the correct diagnosis.

Hepatic vascular abnormalities were divided according to the affected vessel: portal vein – leading to decreased portal flow such as in thrombosis, compression or arterio-portal shunts; hepatic artery – decreased flow (due to stenosis, thrombosis or infarction), increased flow or in aneurysms of this vessels; hepatic vein – as in Budd-Chiari syndrome, Veno-occlusive syndrome, right sided heart failure, among other diseases; intrahepatic vascular communications.

Conclusion

Knowledge of the liver vascularization and the compensatory mechanisms that develop after each hepatic vascular disorder are important in order to understand and diagnose very frequent pathologies that the radiologist may face in the clinical practice.

Objectives

The purpose of this education exhibit is to review typical and atypical imaging features of pancreatic neuroendocrine tumors (PNETs) on contrast enhanced computed tomography (CT) and magnetic resonance imaging (MRI) and to discuss new updates in the grading and staging systems.

Background

PNETs are rare and represent a heterogeneous group of tumors in their pathologic, clinic and imaging features. These have different prognoses depending on WHO and pTNM classifications.

The role of imaging includes localization of small functioning tumors, identification of signs of malignancy, assessment of disease extent and differentiation from other lesions such as adenocarcinoma or metastasis.

Imaging findings OR Procedure findings

Morphological imaging, such as CT and MRI, are the most widely used techniques to initially detect and stage these lesions.

PNETs have a broad spectrum of appearance. At CT and MRI, most functioning PNETs typically present as small, well-defined lesions, with intense and homogeneous enhancement in the arterial and portal phases. However, some PNETs with more fibrous content may have a later enhancement, which is better illustrated on the delayed phases. Other findings also found are cystic changes and calcifications. Non-functioning PNETs are generally larger with less intense and more heterogeneous enhancement.

Conclusion

PNETs are rare neoplasms and they can present a diagnostic challenge, both clinically and radiologically.

Imaging contributes greatly to patient care and is crucial in the detection and characterization of primary lesions, staging and subsequent follow-up.