Diego A. Aguirre

Fatty Liver: Imaging Patterns and Pitfalls

Fat accumulation is one of the most common abnormalities of the liver depicted on cross-sectional images. Common patterns include diffuse fat accumulation, diffuse fat accumulation with focal sparing, and focal fat accumulation in an otherwise normal liver. Unusual patterns that may cause diagnostic confusion by mimicking neoplastic, inflammatory, or vascular conditions include multinodular and perivascular accumulation. All of these patterns involve the heterogeneous or nonuniform distribution of fat. To help prevent diagnostic errors and guide appropriate work-up and management, radiologists should be aware of the different patterns of fat accumulation in the liver, especially as they are depicted at ultrasonography, computed tomography, and magnetic resonance imaging. In addition, knowledge of the risk factors and the pathophysiologic, histologic, and epidemiologic features of fat accumulation may be useful for avoiding diagnostic pitfalls and planning an appropriate work-up in difficult cases.

Cirrhosis-associated Hepatocellular Nodules: Correlation of Histopathologic and MR Imaging Features

Cirrhotic livers are characterized by advanced fibrosis and the formation of hepatocellular nodules, which are classified histologically as either (a) regenerative lesions (eg, regenerative nodules, lobar or segmental hyperplasia, focal nodular hyperplasia) or (b) dysplastic or neoplastic lesions (eg, dysplastic foci and nodules, hepatocellular carcinomas). The differentiation of these lesions is important because regenerative nodules are benign, whereas dysplastic and neoplastic nodules are premalignant and malignant, respectively. However, their accurate characterization may be difficult even at histopathologic analysis. Differential diagnosis may be facilitated by comparing the clinical and pathologic findings with radiologic imaging features; in particular, nodule size, vascularity, hepatocellular function, and Kupffer cell density assessed at magnetic resonance (MR) imaging are suggestive of the correct diagnosis. MR imaging is more useful than computed tomography for such assessments because it provides better soft-tissue contrast and a more nuanced depiction of different tissue properties. Moreover, a wider variety of contrast agents is available for use in MR imaging. Familiarity with the MR imaging characteristics of cirrhosis-associated hepatocellular nodules is therefore important for optimal diagnosis and management of cirrhotic disease.

Spinal CT-guided interventional procedures for management of chronic back pain.

PURPOSE Image-guided interventional procedures have arisen as an alternative for management of back pain, with controversial indications and efficacy. This study describes the technique, clinical impact, and complications of computed tomography (CT)-guided infiltrations for the management of chronic back pain. MATERIALS AND METHODS One hundred eleven patients with chronic back pain treated with CT-guided infiltrations were studied prospectively. Procedures performed included nerve root, facet joint, epidural, and sacroiliac joint blocks. Pain intensity was evaluated with use of a visual analog scale. RESULTS Two hundred twenty-two infiltrations were performed in 111 consecutive patients. After 18 months of follow-up, pain improvement lasted for a mean duration of 9 months and the complication rate was less than 1%. Moderate to good pain response was seen in 95% of followed patients and 4% of patients required surgery. CONCLUSION Spinal CT-guided infiltration constitutes an effective therapy for chronic back pain. This series confirms a low complication rate, good response, and high therapeutic value.

Advances in contrast media research1

The need for contrast media to highlight structures of interest and thereby improve imaging technologies has existed since the first use of radiography to diagnose disease and dysfunction. Regardless of improvements in tissue contrast resolution afforded by the latest new imaging modality, the need for contrast media to distinguish between two dissimilar regions with similar imaging appearances has stimulated and fueled the field of contrast media development. Multiple areas of contrast media research are pursued that include

Intrahepatic Bile Duct Dilatation Due to Liver Metastases From Colorectal Carcinoma

OBJECTIVE The objective of our study was to assess the association between colorectal liver metastases and intrahepatic bile duct dilatation and compare its frequency with the frequency of intrahepatic bile duct dilatation in other common noncolorectal metastases and hepatocellular carcinoma (HCC). MATERIALS AND METHODS A retrospective review of the radiology database was performed to obtain the records of patients who underwent CT for staging of histologically proven colorectal carcinoma (n = 1,000), noncolorectal carcinomas (n = 1,000), and HCC (n = 226). The CT scans of the 2,226 patients were reviewed for the presence of liver metastases and masses, the presence of intrahepatic bile duct dilatation directly related to the masses, the size of the largest lesion, and the associated caliber of the dilated intrahepatic bile duct. RESULTS Of the 297 patients with colorectal liver metastases, 49 (16.5%) had intrahepatic bile duct dilatation, whereas of the 263 patients with noncolorectal liver metastases, only eight (3%) had dilated ducts. Thirteen (5.7%) of the 226 patients with HCC had intrahepatic bile duct dilatation. Intrahepatic bile duct dilatation was present in significantly more patients with colorectal liver metastases (p < 0.05) than those with noncolorectal and HCC metastases. The mean sizes of the lesions and mean caliber of the dilated bile duct from colorectal metastases, noncolorectal metastases, and HCC were 5.3, 3.9, and 5.6 cm, respectively, and 5.1, 4.6, and 4.8 mm, respectively. Overall lesion size irrespective of diagnosis had no significant correlation with the probability of bile duct dilatation (p = 0.16; odds ratio = 1.08; 95% CI, 0.97-1.20). Lesion size also did not have a significantly different effect on the probability of dilatation for the three diagnoses (p = 0.71). The caliber of bile duct dilatation did not significantly differ among the three groups of patients by diagnosis (p = 0.70). CONCLUSION Colorectal liver metastases have a significantly higher tendency to cause intrahepatic bile duct dilatation than noncolorectal metastases and HCC due to the characteristic features, such as cholangiocarcinoma, of intrabiliary growth. This association has important diagnostic, surgical, and prognostic implications that make it necessary to highlight this finding while communicating with clinical colleagues.

Posttransplantation Lymphoproliferative Disease: Proposed Imaging Classification

Posttransplantation lymphoproliferative disease (PTLD) is the second most common tumor in adult transplant recipients. Most cases of PTLD are attributed to Epstein-Barr virus. Decreased levels of immunosurveillance against this tumor virus as a result of immunosuppressive regimens are thought to account for most cases of PTLD. Histologically, PTLD ranges from relatively benign lymphoid hyperplasia to poorly differentiated lymphoma, and tissue sampling is required to establish the subtype. The frequency of PTLD varies depending on the type of allograft and immunosuppressive regimen. PTLD has a bimodal manifestation, with most cases occurring within the first year after transplantation and a second peak occurring 4-5 years after transplantation. Patients are often asymptomatic or present with nonspecific symptoms, and a mass visible at imaging may be the first clue to the diagnosis. Imaging plays an important role in identifying the presence of disease, guiding tissue sampling, and evaluating response to treatment. The appearance of PTLD at imaging can vary. It may be nodal or extranodal. Extranodal disease may involve the gastrointestinal tract, solid organs, or central nervous system. Solid organ lesions may be solitary or multiple, infiltrate beyond the organ margins, and obstruct organ outflow. Suggestive imaging findings should prompt tissue sampling, because knowledge of the PTLD subtype is imperative for appropriate treatment. Treatment options include reducing immunosuppression, chemotherapy, radiation therapy, and surgical resection of isolated lesions.

Nonvascular post-liver transplantation complications: from US screening to cross-sectional and interventional imaging.

Orthotopic liver transplantation is becoming an increasingly routine procedure for a variety of benign and malignant diseases of the liver and biliary system. Continued improvements in surgical techniques and post-transplantation immunosuppression regimens have resulted in better graft and patient survival. A number of potentially treatable nonvascular complications of liver transplantation are visible at imaging, and accurate diagnosis of these complications allows patients to benefit from potential treatment options. Biliary complications include stricture (anastomotic and nonanastomotic), leak, biloma formation, and development of intraductal stones. Pathologic conditions, including hepatitis C infection, hepatocellular carcinoma, hepatic steatosis, and primary sclerosing cholangitis, may recur after liver transplantation. Transplant patients are at increased risk for developing de novo malignancy, including post-transplantation lymphoproliferative disorder, which results from immunosuppression. Patients are also at increased risk for systemic infection from immunosuppression, and patients with hepatic artery and biliary complications are at increased risk for liver abscess. Transplant recipients are typically followed with serial liver function testing; abnormal serum liver function test results may be the first indication that there is a problem with the transplanted liver. Ultrasonography is typically the first imaging test performed to try to identify the cause of abnormal liver function test results. Computed tomography, magnetic resonance imaging, angiography, and/or cholangiography may be necessary for further evaluation. Accurately diagnosing nonvascular complications of liver transplantation that are visible at imaging is critically important for patients to benefit from appropriate treatment.

Portal biliopathy: imaging manifestations on multidetector computed tomography and magnetic resonance imaging

Portal biliopathy refers to biliary abnormalities secondary to extrahepatic portal vein obstruction and cavernous transformation and is caused by vascular compression from peribiliary collateral vessels, producing segmental stenoses of the common bile duct and abnormal liver function test (LFT) results. A review of imaging studies yielded 18 patients with abnormal LFT results, biliary tract dilatation, and extrahepatic portal vein obstruction with cavernous transformation. Multidetector computed tomography and magnetic resonance imaging showed biliary stenotic segments in 11 patients secondary to extrinsic compression from enlarged peribiliary collaterals. Clinical and imaging follow-up demonstrated improvement in LFT results with minimal decrease in bile duct dilatation, eliminating percutaneous or endoscopic biliary intervention.

Multilocular Cystic Nephroma: A Systematic Literature Review of the Radiologic and Clinical Findings

OBJECTIVE The objective of our study was to systematically summarize the published evidence of demographic, clinical, diagnostic imaging, and therapeutic characteristics of patients with multilocular cystic nephroma (MLCN). CONCLUSION Cross-sectional imaging evaluation is important for suggesting the diagnosis of MLCN but has several limitations. The number of radical nephrectomies reported for MLCN encourages discussion concerning the utility of percutaneous presurgical biopsy and frozen-section intraoperative biopsy as a more conservative diagnostic approach.

DICOM Gray-Scale Standard Display Function: Clinical Diagnostic Accuracy of Chest Radiography in Medical-Grade Gray-Scale and Consumer-Grade Color Displays

OBJECTIVE The purpose of this study was to compare the diagnostic accuracy achieved with and without the calibration method established by the DICOM standard in both medical-grade gray-scale displays and consumer-grade color displays. MATERIALS AND METHODS This study involved 76 cases, six radiologists, three displays, and two display calibrations for a total of 2736 observations in a multireader-multicase factorial design. The evaluated conditions were interstitial opacities, pneumothorax, and nodules. CT was adopted as the reference standard. One medical-grade gray-scale display and two consumer-grade color displays were evaluated. Analyses of ROC curves, diagnostic accuracy (measured as AUC), accuracy of condition classification, and false-positive and false-negative rate comparisons were performed. The degree of agreement between readers was also evaluated. RESULTS No significant differences in image quality perception by the readers in the presence or absence of calibration were observed. Similar forms of the ROC curves were observed. No significant differences were detected in the observed variables (diagnostic accuracy, accuracy of condition classification, false-positive rates, false-negative rates, and image-quality perception). Strong agreement between readers was also determined for each display with and without calibration. CONCLUSION For the chest conditions and selected observers included in this study, no significant differences were observed between the three evaluated displays with respect to accuracy performance with and without calibration.