The efficacy of enteral nutrition as primary therapy of active Crohn's disease is controversial. The aim of the study was to compare by meta-analysis the likelihood of clinical response to liquid diet therapy vs. corticosteroids and to assess the importance of formula composition to efficacy.

The Inflammatory Bowel Disease Study Group at the Royal Free Hospital School of Medicine has tested the hypothesis that the primary pathological abnormality in Crohn's disease is in the mesenteric blood supply. Early morphological studies involved arterial perfusion-fixation and either resin casting and scanning electron microscopy or vascular immunostaining of resected intestine affected by Crohn's disease. Granulomatous and lymphocytic damage to intramural blood vessels, even in macroscopically normal areas, was observed. We put forward possible mechanisms by which a chronic ischemic process might account for many of the idiosyncracies of Crohn's disease. It was proposed that persistent viral infection of the mesenteric microvascular endothelium might underly this vasculitic process; based on certain behavioral characteristics of measles virus, including its tropism for the submucosal endothelium of the intestine, this agent was investigated further. This report reviews the preliminary evidence from both epidemiological and basic scientific data for persistent measles virus in the intestine of patients with Crohn's disease. Possible mechanisms for virus persistence and subsequent reactivation are discussed. In conclusion, we believe that Crohn's disease may be a chronic granulomatous vasculitis in reaction to a persistent infection with measles virus within the vascular endothelium. This granulomatous inflammation, perhaps aggravated by either a hypercoagulable state or mechanical stress, results in the clinical features of Crohn's disease.

The liver can be affected by a number of conditions that can involve the liver focally or diffusely. CT and MRI are reliable techniques for demonstrating these abnormalities, and both imaging tools play an important role in the clinical evaluation of the patients. However, each technique provides different information, and the most appropriate cross-sectional technique used should be tailored in each instance to the individual patient situation.

Patients are often referred for evaluation of a wide range of GI complaints including dysphagia, abdominal pain, bloating, nausea, constipation or diarrhoea. Many are diagnosed with 'functional' disease when endoscopy or conventional radiological studies fail to identify an anatomic cause for the patient's symptoms. In such cases nuclear medicine offers non-invasive methods for objectively demonstrating disease involving different areas of the gastrointestinal tract. Increasingly scintigraphy is playing a primary role in the evaluation of patients with suspected acute cholecystitis, active gastrointestinal bleeding, gastroparesis, and small and large bowel motility disorders. In addition, it supplements other studies when results are inconclusive in diagnosing oesophageal dysmotility, gastro-oesophageal reflux, acalculous cholecystitis, and postoperative complications of gastrointestinal surgery.

The role of angiography in acute upper GI tract bleeding is less a diagnostic than a therapeutic one because it provides a guide to selective embolization of either the left gastric artery, or the gastroduodenal artery and its two principal branches, the pancreaticoduodenal and the right gastroepiploic artery. Angiographic catheter techniques may also provide substantial diagnostic and therapeutic support for the management of acute lower GI bleeding from a variety of bleeding sources. The advantages are minimal invasion and relatively low risk. The intermittent nature of GI bleeding often interferes with the ability of angiography to demonstrate the source of bleeding. However, at times angiographic techniques provide the only reasonable means of localizing and controlling bleeding.

US using graded compression plays a central role in the diagnostic work-up of acute right lower quadrant disease, but its results should always be integrated with clinical data and results of other possible radiological examinations. Direct US visualization of an inflamed appendix is solid proof of appendicitis. Pitfalls are secondary enlargement in perforated peptic ulcer, caecal carcinoma or Crohn's disease. If a normal appendix is visualized in its full length, appendicitis can be excluded. However, this is rarely the case. In practice, the only means to exclude appendicitis is to demonstrate an alternative condition, which in most cases is possible by US alone. Concomitant adynamic ileus is a valuable US finding. Abscesses related to appendicitis, Crohn's disease and colonic carcinoma respond well to percutaneous drainage, which is technically possible in 95% of cases. Some of these abscesses evacuate spontaneously to neighbouring bowel. For abscesses due to caecal diverticulitis spontaneous evacuation to the caecal lumen is the rule. For indication and drainage strategy, integration of US, CT and clinical data are indispensable. The use of US in right lower quadrant disease will not only lead to a strong improvement of diagnostic accuracy, but also to better understanding of the incidence and natural course of various conditions such as abortive appendicitis, appendiceal abscess, caecal diverticulitis, bacterial ileocaecitis and right-sided segmental infarction of the omentum.

Because of the high diagnostic yield, its widespread availability and the possibility of bedside examinations, US has become the imaging modality of choice in patients with acute right upper quadrant pain caused by inflammatory disorders such as liver abscesses, acute cholangitis and acute cholecystitis. Computed tomography (CT) can be reserved for more complex cases. US, often in combination with fluoroscopy, is also widely used to control interventions. In patients with liver abscesses the therapeutic strategy is determined by the size of the abscess, its uni- or multifocal presentation and the causative micro-organisms cultured after diagnostic percutaneous aspiration. Small-sized pyogenic abscesses (< 3 cm), most fungal and amoebic abscesses can be treated medically. Large-sized pyogenic abscesses should be drained percutaneously and can be cured in 75-90%. Surgery should be restricted to patients with prolonged sepsis after percutaneous drainage and patients with infected pre-existing hepatic lesions. In patients with acute cholangitis drainage of the infected bile is essential. Invasive imaging such as percutaneous or endoscopic cholangiography procedures such as nasobiliary drainage, stent placement and sphincterotomy has decreased mortality rates dramatically. Percutaneous drainage should be considered in patients in whom endoscopic procedures fail. Surgery may have a place in the treatment of bile duct obstruction which causes cholangitis. In patients with suspected acute cholecystitis, imaging modalities such as cholescintigraphy and CT can be reserved for patients with inconclusive sonographic studies and more complex cases. The contribution of percutaneous gallbladder aspiration and culture to diagnose acute cholecystitis seems limited. Percutaneous cholecystostomy is an effective procedure with a low morbidity and mortality for high-risk patients. The drainage catheter in the gallbladder does not interfere with cholecystectomy at a later stage in patients with calculous cholecystitis. In most patients with acalculous cholecystitis, percutaneous cholecystectomy provides a definitive treatment.

In most patients with a pancreatic head carcinoma or a cholangiocarcinoma of the liver (Klatskin tumour) US is the first imaging modality. Tumour detection using US can exceed that of CT. For small tumours, endosonography or ERCP is recommended. Enlarged lymph nodes are not a major diagnostic parameter, because a reliable differentiation between reactive and malignant lymph nodes is generally not possible. Very tiny liver and peritoneal metastases are missed by the current imaging modalities including US and only detectable by laparoscopy and/or laparoscopic US. Tumour involvement of the portal venous system is an important determinant for irresectability which can often be assessed by duplex Doppler US obviating invasive or expensive imaging modalities. In pancreatic head carcinoma an abnormal pulsed Doppler signal is highly suspicious for involvement of the portal venous system. However, a normal pulsed Doppler signal does not exclude involvement at all. In Klatskin tumour, Doppler US had an accuracy of 91% compared with surgical findings in predicting portal venous involvement. In most cases of pancreatic head carcinoma or Klatskin tumour, US can assess irresectability. However, assessment of curative resectability in these tumours remains a problem.

CT is the primary modality for the evaluation of patients with pancreatic disease. A number of pitfalls can occur in interpretation of the scans, but most can be avoided by using state-of-the-art scanners and dynamic contrast enhancement techniques and by recognizing normal anatomic variants. However, in other cases, CT may show only nonspecific findings and a correct diagnosis can be reached only by utilization of additional imaging techniques or guided FNAB.

Three-dimensional display of intrahepatic vascular structures, tumour(s) and liver surface offers the possibility of perceiving the complex individual anatomy in a coherent fashion. Since this presentation of anatomical structures can be varied at will, the resulting interactive dynamic display of the 3-D data sets can be considered an example of Virtual Reality; the surgeon experiences the interactive 3-D display as a realistic presentation of the patient's surgical anatomy. Three-dimensional display offers the possibility of planning a specific resection in detail, tailored to the individual anatomy. The benefits and problems of various surgical approaches can be worked out in detail, and potential hazardous phases in the operation can be anticipated, thus minimizing unexpected complications. However, because the generation of detailed 3-D renderings takes considerable time investment by an experienced operator it is important to select patients, in whom such an effort is warranted. In our experience, 3-D display of the liver is most likely to be of benefit in the presence of central tumours, or if segmental resections are considered.

While plain abdominal radiographs retain an essential place in acute abdominal emergencies, the dramatic advances in ultrasound, computed tomography and magnetic resonance imaging witnessed over the past two decades have revolutionized the practice of emergency medicine. Cross-sectional imaging techniques now play a key role in evaluating patients with abdominal emergencies, and allow confident diagnoses to be made in an ever increasing proportion of these patients. Unnecessary laparotomies are now uncommon, and a wide array of interventional radiological techniques can be used to treat abdominal emergencies without surgery.

Endoscopic imaging capabilities have significantly improved over the past 10 years. Improvements in fibreoptic technology have made possible the development of very thin endoscopes that can directly visualize the biliary and pancreatic ducts. The application of the CCD to endoscopy has made electronic endoscopy possible, and holds promise for stereoendoscopy. The ability to digitize endoscopic images can be developed to store, transmit, magnify, enhance and otherwise manipulate data obtained during endoscopy, and will probably be utilized routinely in the future. Laser and ultrasound technology are likely to enhance significantly our ability to examine ultrastructural aspects of gastrointestinal organs and surrounding tissues, and may play an important role in cancer surveillance programs. Vital staining techniques are likely to find widespread use in early cancer detection programmes, and may be useful to follow prospectively lesions observed or treated during endoscopy. Finally, the new developments in 'virtual imaging' may find applications in the field of gastrointestinal endoscopy and other 'minimally invasive' surgical procedures.

The enteric nervous system contains neurons with well-defined functions. However, when neurons of the same function are examined in different regions or species, they are found to show subtle differences in their pharmacologies of transmission and different chemical coding. Individual enteric neurons use more than one transmitter, i.e., transmission is plurichemical. For example, enteric inhibitory neurons have three or more primary transmitters, including nitric oxide, vasoactive intestinal peptide, and possibly adenosine triphosphate and pituitary adenylyl cyclase activating peptide. Primary transmitters are highly conserved, although their relative roles vary considerably between gut regions. Multiple substances, including transmitters and their synthesizing enzymes and nontransmitters (such as neurofilament proteins), provide neurons with a chemical coding through which their functions and projections can be identified. Although equivalent neurons in different regions have the same primary transmitters, other chemical markers differ substantially. Caution must be taken in extrapolating pharmacological and neurochemical observations between species or even between regions in the one species. On the other hand, careful interregion and interspecies comparisons lead to an understanding of the features of enteric neurons that are highly conserved and can be used in valid extrapolation.

Endoscopic postoperative recurrence often occurs a few months after surgical therapy for Crohn's disease, even if the resection margins were macroscopically free of disease. Why the disease primarily recurs at the anastomotic site is not known. This study investigated resection margins in Crohn's disease in an attempt to clarify whether early lesions are relevant to the interpretation of postoperative recurrence.

Osteopenia in the form of osteoporosis is a common clinical problem associated with chronic cholestatic liver disease, and clinical morbidity from atraumatic fractures is increasing as more patients with PBC and PSC undergo successful liver transplantation. In the absence of symptomatic fractures, the clinical diagnosis may not be evident and must be sought by specific means to assess bone mineral density. The clinical problem has now been defined, but much remains unknown, from etiologic mechanisms to effective therapies. At present, it seems reasonable to provide aggressive supportive therapy in an attempt to maximize skeletal well-being until more effective therapies for osteopenia become available.