Review Articles

In 2002, the United Network for Organ Sharing introduced the model for end-stage liver disease (MELD)/pediatric end-stage liver disease (PELD) organ allocation system. This Review discusses the history of donor liver allocation in the US, the development of the MELD/PELD allocation system, its success so far and its shortcomings, and the need to optimize the donor organ pool.

Two new types of imaging technology—laser-scanning confocal endoscopy series and contact endoscopy series—could reduce the number of biopsies that need to be taken by enabling anin vivo'virtual' histological diagnosis. Although it is currently not clear which technology should be adopted, microscopic evaluation of living tissue is now a reality.

The histologic spectrum of nonalcoholic fatty liver disease extends from isolated hepatic steatosis to steatohepatitis. Its pathogenesis is linked to insulin resistance and underlying metabolic syndrome. This Review discusses the physiologic basis for hepatic lipid homeostasis, its disturbance in insulin resistance and the genesis of nonalcoholic fatty liver and nonalcoholic steatohepatitis.

Over the past 20 years the applications of endoscopic ultrasound (EUS) have expanded, with real-time EUS-guided fine-needle aspiration and fine-needle injection now possible. This Review describes the current clinical status of EUS in gastrointestinal oncology, possible future and novel indications and therapeutic strategies.

The past decade has witnessed substantial advances in the treatment of chronic hepatitis B, and the nucleoside and nucleotide analog inhibitors lamuvidine and adefovir dipivoxil have been a major part of this. This article discusses the benefits and limitations of treatment with lamuvidine and adefovir dipivoxil, and nucleoside and nucleotide analogs being evaluated in phase II/III clinical trials.

Basic research has led to rapid progress in understanding the mechanisms underlying hepatic fibrosis. Fibrogenic hepatic cell types have been characterized, as have general and disease-specific mechanisms. Studies also indicate that hepatic fibrosis is reversible. The impact of this work on clinical practice is that treating hepatic fibrosis is now emerging as a real possibility.

Our understanding of carcinogenesis in Barrett's esophagus has markedly increased in the past decade, thanks to the close interaction of clinicians, epidemiologists and basic scientists. This review discusses how reflux of gastroduodenal contents, dietary habits, obesity, upper gastrointestinal infections and exposure to carcinogens might contribute to the development of cancer in Barrett's esophagus.

During the past few years there has been renewed interest in the management of chronic anal fissure. Treatment with botulinum neurotoxin is less expensive and easier to perform than surgery and does not require anesthesia. It is also more efficacious than nitrate therapy and is not related to the patient's willingness to complete treatment.

Hepcidin is the iron-regulatory hormone that links innate immunity and iron metabolism. Normally, a regulatory feedback loop with circulatory iron controls hepatic hepcidin production. Inflammatory stimuli upregulate hepcidin production, which can lead to anemia. Anemia downregulates hepcidin production. Human disorders associated with inappropriate hepcidin levels include anemia of inflammation and hereditary hemochromatosis.

At present there is no cure for chronic pancreatitis—a progressive condition that culminates in the destruction of the pancreas. Recent advances in genetic and immunologic research have spawned new insights into the mechanisms underlying chronic pancreatitis, and new models are helping us understand associated risk factors and etiologies.

The etiology and pathogenesis of ulcerative colitis remain unclear, but evidence is accumulating that both genetics and the environment are important. Although diagnosis remains based on well-established clinical, endoscopic and histologic criteria, recent advances in the detection of fecal and serologic markers and the use of wireless capsule endoscopy promise to aid diagnosis.

At present, there is no uniformly effective treatment for recurrentClostridium difficile-associated disease. Tapering and pulsing antibiotics after a 10-day standard course can decrease the recurrence of disease, as can adjunct use of the probiotic Saccharomyces boulardii. Restoration of normal colonic flora might be another treatment option, and new treatment approaches being developed include a vaccine.