Radiologic evaluation of nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease(NAFLD)is a frequent cause of chronic liver diseases,ranging from simple steatosis to nonalcoholic steatohepatitis(NASH)-related liver cirrhosis.Although liver biopsy is still the gold standard for the diagnosis of NAFLD,especially for the diagnosis of NASH,imaging methods have been increasingly accepted as noninvasive alternatives to liver biopsy.Ultrasonography is a well-established and costeffective imaging technique for the diagnosis of hepatic steatosis,especially for screening a large population at risk of NAFLD.Ultrasonography has a reasonable accuracy in detecting moderate-to-severe hepatic steatosis although it is less accurate for detecting mild hepatic steatosis,operator-dependent,and rather qualitative.Computed tomography is not appropriate for general population assessment of hepatic steatosis given its inaccuracy in detecting mild hepatic steatosis and potential radiation hazard.However,computed tomography may be effective in specific clinical situations,such as evaluation of donor candidates for hepatic transplantation.Magnetic resonance spectroscopy and magnetic resonance imaging are now regarded as the most accurate practical methods of measuring liver fat in clinical practice,especially for longitudinal followup of patients with NAFLD.Ultrasound elastography and magnetic resonance elastography are increasingly used to evaluate the degree of liver fibrosis in patients with NAFLD and to differentiate NASH from simple steatosis.This article will review current imaging methods used to evaluate hepatic steatosis,including the diagnostic accuracy,limitations,and practical applicability of each method.It will also briefly describe the potential role of elastography techniques in the evaluation of patients with NAFLD.

CT colonography in the diagnosis and management of colorectal cancer:Emphasis on pre-and post-surgical evaluation

This article addresses the use of computed tomographic colonography(CTC)for the diagnosis and management of colorectal cancer,focusing on presurgical evaluation of the colon proximal to an occlusive cancer and surveillance after cancer resection surgery.The key evidences accumulated in the literature and future work needed are summarized.CTC is a technically robust and the most practical method to evaluate the colon proximal to an occlusive cancer,which prevents colonoscopic examination past the occlusion,either before or after metallic stent placement.The high sensitivity of CTC for detecting cancers and advanced adenomas in the proximal colon can help prevent additional surgical procedures in patients showing negative results.However,the accuracy of CTC for distinguishing intramural cancers from adenomas is low,and the technique is limited in guiding management when a medium-sized lesion that do not show invasive features such as pericolic extension or nodal metastasis is found in the proximal colon.A maximal diameter≥15 mm has been proposed as a criterion for surgical removal of proximal lesions.However,this needs to be verified in a larger cohort.In addition,the influence of presurgical CTC results on the current post-cancer resection colonic surveillance timeline remains to be determined.CTC can be readily added to the routine abdominopelvic CT in the form of contrast-enhanced CTC,which can serve as an effective stand-alone tool for postcancer resection surveillance of both the colorectum and extracolonic organs.Although the accuracy of CTC has been demonstrated,its role in the current colonoscopy-based postoperative colonic surveillance protocols remains to be determined.Readers of CTC also need to be knowledgeable on the colonic lesions that are unique to the postoperative colon.