Bailliere's clinical gastroenterology最新文献

Nutrition is clearly disturbed by active intestinal inflammation. Appetite is reduced, yet energy substrates are diverted into the inflammatory process, and thus weight loss is characteristic. The nutritional disturbance represents part of a profound defect of somatic function. Linear growth and pubertal development in children are notably retarded, body composition is altered, and there may be significant psychosocial disturbance. Macrophage products such as tumour necrosis factor-α and interleukins-1 and 6 may be the central molecules that link the inflammatory process to this derangement of homeostasis. Intriguingly, there is also increasing evidence that an aggressive nutritional programme may in itself be sufficient to reduce the mucosal inflammatory response. Recent evidence suggests that enteral nutrition alone may reduce many pro-inflammatory cytokines to normal and allow mucosal healing. In addition, specific nutritional components, such as n-3 polyunsaturated fatty acids, may have an anti-inflammatory effect as they may alter the pattern of leukotrienes generated during the immune response. The recent discovery of the specific molecular mediators of appetite and body composition, such as leptin and myostatin, may allow increased therapeutic specificity and further improvement in the nutritional treatment of the inflammatory bowel diseases.

As most diseases can have nutritional consequences, the assessment of nutritional status may help to detect an underlying disease, to identify nutritional disorders related to a given disease, and to quantify the impact of nutritional therapy. The aims and methods used for nutritional assessment depend on the circumstances in which nutritional assessment is performed.

Whatever the context or aim, nutritional status is assessed through a simple, mainly clinical approach, based on the past history, dietary intake, auxological analysis, anthropometric measurements, body compartment and biological parameters. Accurate techniques for measuring body compartments are available in children such as dual-energy X-ray absorptiometry to assess fat body mass or bioelectrical impedance analysis for body water and lean body mass. Measuring energy expenditure allows for a more accurate monitoring of the patient's energy needs and decreases the risks associated with underfeeding or overfeeding.

In clinical practice, the analysis should be longitudinal and take into account situations carrying a risk of malnutrition. Preventive use of nutritional assessment allows nutritional support to be introduced in a timely fashion, thereby avoiding morbidity/mortality and limiting the long-term impact of malnutrition on growth and development.

The quantity and quality of dietary lipids and their metabolism are of major importance for the growth, body composition, development and long-term health of children, both in health and disease. Lipids are the major source of energy in early childhood and supply essential lipid-soluble vitamins and polyunsaturated fatty acids that are required in relatively high amounts during early growth. Lipids affect the composition of membrane structures, and modulate membrane functions as well as the functional development of the central nervous system. Some long-chain polyunsaturated fatty acids serve as precursors for bioactive lipid mediators, including prostaglandins, thromboxanes and leukotrienes, which are powerful regulators of numerous cell functions such as thrombocyte aggregation, inflammatory reactions and immune functions. Here we review some aspects of the biochemistry and physiology of lipids and their implications for lipoprotein metabolism, energy balance and the lipid supply during early childhood through the placenta, human milk, enteral diets and parenteral lipid emulsions.

A reappraisal of available data, together with new studies, suggests that normal infants' energy and protein requirements might be substantially lower than previously estimated. For example, the safe level of protein intake would amount to only 10 g per day during the first 2 years of life and to about 12 g per day during the third. This has direct consequences for the management of malnourished children, particularly for defining an optimal protein:energy ratio. A reduced food intake has long been accepted as the main cause of malnutrition. However, evidence has accumulated suggesting that metabolic dysregulation may also play a part. This is particularly true for proteins. Net protein deposition in the growing child results from protein synthesis rates being higher than protein breakdown. However, this setting can be disrupted by a significant increase in protein breakdown in response to cytokines. This mechanism, which is found in acute as well as in chronic inflammatory processes, may lead to severe protein malnutrition and is not always amenable to nutritional support.

Adequate nutritional intervention in diarrhoeal disease in children is crucial in obtaining optimal control of a disorder that may become life-threatening. During recent years, important advances have been made in our understanding of the pathophysiology of diarrhoeal states, in the formulation of oral rehydration solutions and in the role of micro- and macronutrients in diarrhoeal disorders. This chapter outlines some of the relevant concepts in the pathophysiology of diarrhoeal disease and provides a rationale for nutritional intervention. Guidelines for nutritional management in the settings of acute-onset diarrhoea, post-enteritis protracted diarrhoea and chronic non-specific diarrhoea are provided, mostly based on controlled clinical trials and meta-analyses of evidence-based medicine.

The prevalence of home enteral and parenteral nutrition programmes is rising rapidly all over the world, in children as in adults. Home artificial nutrition, especially parenteral nutrition, is an expensive technology but is life-saving for many patients. The only possible alternative to home treatment is keeping patients in hospital, and cost-benefit studies have demonstrated that home nutrition is about 70% more cost-effective than hospital-based therapy. Although home nutrition is usually considered by children and families to lead to an improvement in their quality of life, the complications of these techniques, including psychological consequences, have to be carefully assessed and prevented.

Malnutrition is an adverse prognostic factor in cystic fibrosis, influencing the course of pulmonary disease and correlating inversely with survival. A positive energy balance between energy intake and the combination of total energy expenditure, energy losses and growth-related energy cost is essential to maintain normal nutritional status. Before starting nutritional supplementation, it is important to rule out pathological conditions that may have a deleterious effect on nutritional status: persistent exocrine pancreatic insufficiency, chronic bacterial pulmonary colonization, impaired glucose tolerance, specific nutritional deficits and associated disorders leading to a decrease of energy intake. Several methods are available, ranging from boosted oral nutrition to behavioural intervention, oral supplementation, enteral nutrition and, rarely, parenteral nutrition. The use of elemental nutrients for either oral supplementation or enteral nutrition seems of no nutritional benefit and is more expensive than conventional polymeric nutrients. Provided that the goals of the nutritional supplementation are fulfilled, simpler is often better.