Gavin Low

Multimodality Imaging of Neoplastic and Nonneoplastic Solid Lesions of the Pancreas

Solid lesions of the pancreas represent a heterogeneous group of entities that can be broadly classified as either neoplastic or nonneoplastic. Neoplastic lesions include pancreatic adenocarcinoma, pancreatic neuroendocrine tumor, solid pseudopapillary tumor, pancreatoblastoma, pancreatic lymphoma, metastases to the pancreas, and rare miscellaneous neoplasms. Nonneoplastic lesions include focal pancreatitis, fatty infiltration-replacement, intrapancreatic accessory spleen, congenital anomalies such as prominent pancreatic lobulation and bifid pancreatic tail (pancreatic bifidum), and rare miscellaneous lesions (eg, pancreatic sarcoidosis, Castleman disease of the pancreas). A variety of imaging modalities are available for assessing these solid lesions, including ultrasonography (US), computed tomography (CT), magnetic resonance imaging, endoscopic US, and hybrid nuclear imaging techniques such as single photon emission computed tomography-CT and positron emission tomography-CT, each of which has its own strengths and limitations. Accurate diagnosis can be challenging, and use of a multimodality imaging approach is often helpful in equivocal or complex cases. Knowledge of relevant clinical information and key radiologic features is essential for confident lesion characterization and differentiation.

Pheochromocytoma: The Range of Appearances on Ultrasound, CT, MRI, and Functional Imaging

OBJECTIVE Pheochromocytomas are relatively rare neuroendocrine tumors of the adrenal medulla. Their variable clinical presentation and biologic behavior often make accurate diagnosis challenging. A variable spectrum of imaging appearances--some of which may also mimic other diseases--has been recognized. This article reviews the epidemiology; associations; and clinical, biochemical, pathologic, and multimodality imaging features of pheochromocytomas including diagnostic pearls and pitfalls. CONCLUSION Pheochromocytomas are often considered the great mimicker of other adrenal tumors. Because of their varied clinical, imaging, and pathologic appearances, accurate diagnosis can be challenging. The various imaging appearances on ultrasound, CT, MRI, and functional imaging can be complementary and have features that are useful for differentiating pheochromocytoma from other lesions of the adrenal.

Role of Imaging in Clinical Islet Transplantation

Islet transplantation is an innovative and effective clinical strategy for patients with type 1 diabetes whose clinical condition is inadequately managed even with the most aggressive medical treatment regimens. In islet transplantation, purified islets extracted from the pancreas of deceased donors are infused into the portal vein of the recipient liver. Engrafted islets produce insulin and thus restore euglycemia in many patients. After islet transplantation performed with the original Edmonton protocol, 80% of patients were insulin independent at 1 year and approximately 20% were insulin independent at 5 years. With more recent technical advances, 50% of patients or more maintain insulin independence 5 years after islet transplantation. The success rate with single-donor islet infusions has markedly improved over time. Even in patients who lose insulin independence, islet transplantation is considered successful because it provides improved glycemic control and a higher quality of life. Imaging plays an important role in islet transplantation and is routinely used to evaluate potential recipients, guide the transplantation process, and monitor patients for posttransplantation complications. Because of the success of islet transplantation and its increasing availability worldwide, familiarity with the role of imaging is important.

Imaging of Vascular Complications and Their Consequences Following Transplantation in the Abdomen

Transplantation is the surgical treatment of choice for end-stage organ failure. Transplantation procedures performed in the abdomen include liver, renal, pancreas, islet, intestinal, and multivisceral transplantations. Imaging plays a pivotal role in the posttransplantation setting for monitoring the transplant allograft and screening for complications. Knowledge of the surgical techniques employed in abdominal transplantation is essential because it facilitates radiologic understanding and interpretation of the posttransplantation anatomy. This article includes a basic description of the standard surgical techniques performed in the abdomen, with emphasis on the relevant vascular anastomotic reconstructions used. Posttransplantation complications can be broadly classified as vascular or nonvascular in origin. Many of these complications can be accurately depicted and characterized at imaging and dealt with definitively by using interventional radiology techniques, which can be graft- and life-saving and can obviate further complex surgical intervention. The article discusses imaging appearances of vascular complications and their consequences after transplantation in the abdomen. These vascular complications include arterial thrombosis, arterial stenosis, venous thrombosis and stenosis, arteriovenous fistula formation, and pseudoaneurysm formation. The relevant predisposing factors, clinical features, imaging appearances, and potential treatment options for vascular complications of various types of transplantation are presented in a logical and integrated fashion. Knowledge and imaging recognition of the posttransplantation vascular complications discussed in this article will aid radiologists in accurate imaging characterization and thereby facilitate appropriate clinical management and therapy.

Imaging evaluation of potential donors in living-donor liver transplantation.

Liver transplants, originally obtained from deceased donors, can now be harvested from living donors as well. This technique, called living-donor liver transplantation (LDLT), provides an effective alternative means of liver transplantation and is a method of expanding the donor pool in light of the demand and supply imbalance for organ transplants. Imaging plays an important role in LDLT programmes by providing robust evaluation of potential donors to ensure that only anatomically suitable donors with no significant co-existing pathology are selected and that crucial information that allows detailed preoperative planning is available. Imaging evaluation helps to improve the outcome of LDLT for both donors and recipients, by improving the chances of graft survival and reducing the postoperative complication rate. In this review, we describe the history of LDLT and discuss in detail the application of imaging in donor assessment with emphasis on use of modern computed tomography (CT) and magnetic resonance imaging (MRI) techniques.

Review of renal cell carcinoma and its common subtypes in radiology

Representing 2%-3% of adult cancers, renal cell carcinoma (RCC) accounts for 90% of renal malignancies and is the most lethal neoplasm of the urologic system. Over the last 65 years, the incidence of RCC has increased at a rate of 2% per year. The increased incidence is at least partly due to improved tumor detection secondary to greater availability of high-resolution cross-sectional imaging modalities over the last few decades. Most RCCs are asymptomatic at discovery and are detected as unexpected findings on imaging performed for unrelated clinical indications. The 2004 World Health Organization Classification of adult renal tumors stratifies RCC into several distinct histologic subtypes of which clear cell, papillary and chromophobe tumors account for 70%, 10%-15%, and 5%, respectively. Knowledge of the RCC subtype is important because the various subtypes are associated with different biologic behavior, prognosis and treatment options. Furthermore, the common RCC subtypes can often be discriminated non-invasively based on gross morphologic imaging appearances, signal intensity on T2-weighted magnetic resonance images, and the degree of tumor enhancement on dynamic contrast-enhanced computed tomography or magnetic resonance imaging examinations. In this article, we review the incidence and survival data, risk factors, clinical and biochemical findings, imaging findings, staging, differential diagnosis, management options and post-treatment follow-up of RCC, with attention focused on the common subtypes.

Clinical and imaging overview of functional adrenal neoplasms.

Adrenal adenoma, adrenocortical carcinoma, pheochromocytoma and neuroblastoma are four discrete adrenal neoplasms that have the potential for functional activity. Functional adrenal neoplasms can secrete cortisol, aldosterone, sex hormones or catecholamines. These heterogeneous groups of tumors show varied biological behavior and clinical outcomes. These neoplasms are encountered with increasing clinical frequency as a result of an expansion in the volume of medical imaging carried out. The clinical presentation, including prognosis and treatment options, and the imaging features of these neoplasms are discussed. The key radiological observations of each of these neoplasms are shown using multimodality images. Familiarity with the clinical and imaging features of these neoplasms improves diagnosis, and facilitates appropriate clinical decision‐making and patient management.

Multimodality imaging findings of pheochromocytoma with associated clinical and biochemical features in 53 patients with histologically confirmed tumors.

OBJECTIVE The purpose of this study was to determine the spectrum of imaging appearances of pheochromocytoma and the associated clinical and biochemical features. MATERIALS AND METHODS In this retrospective study, a citywide pathology database (2000-2011) was searched to identify the records of patients with pheochromocytoma. The search yielded the cases of 53 patients (28 men, 25 women; mean age, 50 years). The institutional PACS and radiology information system records, hospital charts, and the provincial electronic health records of these patients were reviewed. Imaging appearances and clinical and biochemical features related to pheochromocytomas were recorded. RESULTS One chart was not available for review. In the 52 cases analyzed, 40 of the patients had symptoms: 31 patients had hypertension; 10 had the triad of palpitations, diaphoresis, and headaches; and all had elevated urinary metanephrine concentrations. Seven patients had a familial syndrome, and five had bilateral pheochromocytomas. One patient had an extraadrenal pheochromocytoma, and five had malignant tumors. The mean size of pheochromocytomas was 4.0 cm. Most pheochromocytomas were heterogeneous (CT, 56%; MRI, 65%; ultrasound, 45%) and were MIBG positive (90%). Eleven of 34 (32%) pheochromocytomas had T2 signal intensity greater than that of the spleen. Most pheochromocytomas were less enhancing than the spleen (CT, 85%; MRI, 71%). Contrast-enhanced CT was performed on 33 tumors, of which 20 enhanced less than the spleen and 8 showed similar enhancement to the spleen; contrast-enhanced MRI was performed on 24 tumors, of which 12 enhanced less than the spleen and 5 showed similar enhancement to the spleen. Predominant cystic change was found in 4 of 20 (20%) ultrasound, 9 of 41 (22%) CT, and 11 of 34 (32%) MRI examinations. Eight of 34 (24%) pheochromocytomas were hemorrhagic, two (5%) had calcifications, and three of six were PET positive. Two cystic pheochromocytomas and one lipid-containing pheochromocytoma were misdiagnosed as adrenal adenomas. CONCLUSION Most pheochromocytomas were heterogeneous at imaging, were MIBG positive, accompanied elevated urinary metanephrine concentrations, and were symptomatic. High T2 signal intensity was found in approximately one third of solid tumors. Atypical imaging features included homogeneity, cystic change, hemorrhage, intense enhancement, calcifications, intracellular lipid, bilaterality, and malignancy.

Doppler Ultrasound Velocities and Resistive Indexes Immediately After Pediatric Liver Transplantation: Normal Ranges and Predictors of Failure

OBJECTIVE We sought to determine the ranges of Doppler ultrasound findings immediately after pediatric liver transplantation that are associated with successful outcomes or postoperative complications. MATERIALS AND METHODS This study included consecutive children who underwent Doppler ultrasound less than 48 hours after liver transplantation from 2001 to 2011. Operative reports and clinical outcome data were recorded. We had 110 patients (54% girls) with mean age at transplantation of 2.9 years (median, 1.3 years; range, 0-14 years) and a median follow-up interval of 3.5 years. Two pediatric radiologists reviewed ultrasound images in consensus. We computed descriptive statistics, interindex correlations, and analysis of variance. RESULTS Twenty-four of 110 patients had a vascular complication, most commonly hepatic arterial thrombosis (seven patients). Compared with published adult normal values, normal pediatric Doppler parameters at postoperative day 1 trended toward higher normal velocities and resistive indexes (up to 0.95). Absent or low-velocity common hepatic artery flow less than 50 cm/s or a common hepatic artery resistive index less than 0.50 were significantly associated with hepatic artery thrombosis, whereas absent or low-velocity portal venous flow less than 30 cm/s or low-velocity hepatic venous flow less than 25 cm/s were significantly associated with vascular complications and a monotonic hepatic venous waveform was significantly associated with venous complications. CONCLUSION Flow in a pediatric liver on the first day after transplantation is normally hyperdynamic, especially in the youngest transplant recipients, and, as a result, low velocities or resistive indexes are particularly concerning for complications. The pediatric-specific ranges of expected posttransplantation Doppler ultrasound findings presented in this article should assist in identifying normal variation and potentially life-threatening complications.

Appropriateness of CT of the Chest, Abdomen, and Pelvis in Motorized Blunt Force Trauma Patients Without Signs of Significant Injury

OBJECTIVE The purpose of this article is to determine the frequency of clinically significant injuries detected on CT of the chest, abdomen, and pelvis in adult patients involved in motorized blunt force trauma with normal clinical examinations. MATERIALS AND METHODS A retrospective review of the medical records of patients presenting with a triage history of motorized blunt force trauma who underwent CT of the chest, abdomen, and pelvis at the time of presentation was performed. Hemodynamically stable adult patients without abnormal physical examination findings to suggest injury of the trunk (e.g., tenderness, deformity, or bruising over the chest, abdomen, or pelvis) were included in the study. The formal report of the CT scan was reviewed and all acute injuries were recorded. Admission and discharge dates and surgical interventions were also recorded. RESULTS Records for 542 patients were reviewed; 108 patients (74 men and 34 women; median age, 36 years) fulfilled the inclusion criteria. Eleven of the 108 patients (10%; 95% CI, 4.4-15.6%) had acute injuries detected on CT of the chest, abdomen, and pelvis. None of the injuries required direct medical intervention. Alcohol intoxication or distracting injuries were present in eight of these patients. The median time in hospital, from emergency department presentation to discharge, was 4.4 days (interquartile range, 2.5-8.5 days) for patients who were admitted and 6.7 hours (interquartile range, 4.8-10.3 hours) for those who were discharged. CONCLUSION The clinical yield of performing CT of the chest, abdomen, and pelvis in motorized blunt trauma patients with normal clinical examinations in our study was minimal.