Renal Mass Imaging with MRI Clear Cell Likelihood Score: A User's Guide.

Small solid renal masses (SRMs) are frequently detected at imaging. Nearly 20% are benign, making careful evaluation with MRI an important consideration before deciding on management. Clear cell renal cell carcinoma (ccRCC) is the most common renal cell carcinoma subtype with potentially aggressive behavior. Thus, confident identification of ccRCC imaging features is a critical task for the radiologist. Imaging features distinguishing ccRCC from other benign and malignant renal masses are based on major features (T2 signal intensity, corticomedullary phase enhancement, and the presence of microscopic fat) and ancillary features (segmental enhancement inversion, arterial-to-delayed enhancement ratio, and diffusion restriction). The clear cell likelihood score (ccLS) system was recently devised to provide a standardized framework for categorizing SRMs, offering a Likert score of the likelihood of ccRCC ranging from 1 (very unlikely) to 5 (very likely). Alternative diagnoses based on imaging appearance are also suggested by the algorithm. Furthermore, the ccLS system aims to stratify which patients may or may not benefit from biopsy. The authors use case examples to guide the reader through the evaluation of major and ancillary MRI features of the ccLS algorithm for assigning a likelihood score to an SRM. The authors also discuss patient selection, imaging parameters, pitfalls, and areas for future development. The goal is for radiologists to be better equipped to guide management and improve shared decision making between the patient and treating physician. © RSNA, 2023 Quiz questions for this article are available in the supplemental material. See the invited commentary by Pedrosa in this issue.

The Use of Enteric Contrast in the Emergency Setting.

Historically, computed tomography of the abdomen and pelvis had been performed routinely with enteric contrast to help improve diagnostic accuracy. However, the utility of enteric contrast has been called into question recently, particularly in the high-patient-volume setting of the emergency department. This article reviews the role of enteric contrast in the emergency setting. Particular emphasis is given to specific clinical scenarios in which enteric contrast provides value. These include the identification of abdominal postsurgical complications such as anastomotic leaks and fistulas, detection of penetrating bowel injuries, evaluation of acute appendicitis, and assessment of small-bowel obstructions.

Body MRI: Imaging Protocols, Techniques, and Lessons Learned.

Body MRI has evolved from a niche subspecialty to a standard modality in the practice of abdominal radiology. However, the practicing radiologist may feel uncomfortable interpreting body MRI studies owing to a lack of case volume and inconsistent exposure. The authors highlight teaching points and subtleties central to better acquisition and interpretation of body MRI studies. Appropriate contrast agent selection and arterial phase acquisition timing provide greater diagnostic certainty in answering common clinical questions at liver MRI, such as assessing cirrhosis and evaluating focal liver lesions. Clinically relevant artifacts and physiologic phenomena, such as magnetic susceptibility and transient hepatic intensity difference, must be recognized and appropriately used when reading a study. Fat within organs and lesions is commonly encountered at body MRI. The authors discuss the nuances of common and uncommon entities, how to address fat suppression failure, assessment of bone marrow at body MRI, and an organized approach to fat-containing renal and adrenal masses. Motion artifacts are more commonly encountered at body MRI than at MRI of other anatomic regions, and understanding the various techniques, their benefits, and trade-offs will aid the body imager in protocol design and moving beyond "nondiagnostic" examinations. Challenging anatomic sites to evaluate at body MRI are reviewed. Finally, the authors offer tips for accurate interpretation of diffusion-weighted imaging, hepatobiliary phase imaging, and posttreatment imaging studies. By reviewing this article, the abdominal imager will be better prepared to perform and interpret body MRI studies confidently and accurately. An invited commentary by Kalb is available online. Online supplemental material is available for this article. ©RSNA, 2022.

The Role of Magnetic Resonance in Evaluating Abdominopelvic Trauma - Part 1: Pancreatic and Hepatobiliary Injuries.

Trauma is an important cause of mortality, particularly in the young. While computed tomography (CT) is the mainstay of body imaging in the setting of trauma, magnetic resonance (MR) imaging can be useful in stable patients. Although more commonly used in spinal and musculoskeletal trauma, MR also has a role in abdominopelvic trauma. Broadly, its uses include clarification of equivocal cases, monitoring complications of trauma, particularly with solid organ injury, or as a primary imaging modality for patients with low suspicion for injury for whom avoiding ionizing radiation is a priority-namely, in pediatric and pregnant patients. In this two-part review article, we will review clinical scenarios where this may be encountered, utilizing case examples. This first installment will focus on pancreatic and hepatobiliary injuries. Pancreatic trauma may be difficult to diagnose on CT, and MR may aid in demonstrating pancreatic duct disruption, allowing for accurate grading according to American Association for the Surgery of Trauma (AAST) criteria. It may also be a useful modality for monitoring evolution of pancreatic injuries and/or pseudocyst development, guiding potential stenting, and/or drainage. Biliary injuries are also optimally evaluated with MR, particularly when aided by the use of hepatobiliary contrast material. This can allow for accurate delineation of biliary ductal anatomy and aid in planning percutaneous or endoscopic treatment of bile leaks.

The Role of Magnetic Resonance in Evaluating Abdominopelvic Trauma - Part 2: Trauma in Pregnancy, Vascular, and Genitourinary Injuries.

Trauma is an important cause of mortality, particularly in the young. While computed tomography (CT) is the mainstay of body imaging in the setting of trauma, magnetic resonance (MR) imaging can be useful in stable patients. Although more commonly used in spinal and musculoskeletal trauma, MR also has a role in abdominopelvic trauma. Broadly, its uses include clarification of equivocal cases, monitoring complications of trauma, particularly with solid organ injury, or as a primary imaging modality for patients with low suspicion for injury for whom avoiding ionizing radiation is a priority-namely, in pediatric and pregnant patients. In this two-part review article, we will review clinical scenarios where this may be encountered, utilizing case examples. Our second installment will focus on the use of MR in pregnant patients and in the characterization of vascular and genitourinary trauma. Body MR can be useful in pregnant patients in characterizing injuries both specific for and not specific for pregnancy. Placental injuries and hematomas in particular may be better seen on MR relative to CT, owing to its superior contrast resolution. MR angiography can be performed either without or with contrast and can be useful to monitor low-grade traumatic aortic injuries. Renal and ureteral injuries can be followed with MR to help identify urine leaks, either in a delayed presentation or in patients who have an iodinated contrast allergy. Lastly, penile injuries are often imaged with ultrasound, but may benefit from additional imaging with MR when the tunica albuginea cannot be completely seen due to overlying hematoma.

Concurrent metastases of papillary thyroid carcinoma to the scalp and Meckel's cave.

We present the case of a 65-year-old man with severe headaches and unilateral facial weakness, seen in consultation by the dermatology service to rule out primary cutaneous melanoma after brain imaging identified an enlarging mass within the right trigeminal (Meckel's) cave. Examination revealed only a pair of erythematous papules on the scalp, for which biopsy demonstrated metastatic papillary thyroid carcinoma. Further evaluation and subsequent thyroidectomy confirmed the origin of widespread internal disease, followed by definitive excision of scalp lesions and multimodal management of systemic involvement. Whereas presentation of metastasis to the skin is highly variable, a low threshold for biopsy may allow for histological identification of internal disease not otherwise considered in the clinical differential.