Dietary fibre: consensus and controversy.

Technological advances have reduced and refined man's plant food intake and consequently brought about an unprecedented decline in his consumption of dietary fibre (DF). The emergence of certain diseases selectively in regions which have been affected the most by this dietary change has led to an enhanced awareness of the functions of DF. DF is a heterogeneous group of substances which resist digestion by the endogenous enzymes of the human gut, although they are fermented to a substantial extent by the bacterial flora of the large intestine. Chemically, DF essentially consists of nonstarch polysaccharides and lignin, and its major constituents are cellulose, hemicelluose, lignin and pectin. The physiological effects of DF are attributable largely to its physicochemical properties. DF primarily affects gastrointestinal (GI) function; its effects are observable at all stages from ingestion through defaecation. It restricts caloric intake, shows gastric and small intestinal transit, and affects the activity of digestive enzymes and release of GI hormones. Its overall impact is to reduce apparent digestibility of nutrients marginally but consistently. In the large intestine, DF accelerates transit, supports bacterial growth and serves to hold water. As a result, the faecal weight and water content increase, and the transit time generally becomes shorter. Secondary to its GI effects, DF attenuates postprandial glycaemia and has long term effects on glucose tolerance and lipoprotein metabolism. These effects have important implications in the aetiopathogenesis of constipation and its sequelae including diverticulosis, cholesterol gallstones, colorectal cancer, obesity, diabetes mellitus and atherosclerosis. DF has traditionally been used therapeutically for constipation; now its use in diabetes is also well established. Our appreciation of the role of DF in human nutrition has undergone a major change in the last two decades. From a redundant constituent of plant foods, it has now moved to the position of an essential nutrient, the deficiency of which seems to have serious consequences.

The left transverse colostomy.

The right transverse colostomy is the one traditionally performed for distal colonic obstructive tumors, perforated sigmoid diverticulitis, distal colonic injuries, or for the protection of precarious low colonic anastomoses. However, the right transverse colostomy has a tendency to prolapse; its effluent is frequently liquid; it cannot be performed without producing adhesions in the right upper quadrant; and it obligates the surgeon generally to three operations when done as the first part of a staged colonic resection. The left transverse colostomy has the advantages of a reduced incidence of prolapse, an increased length of absorptive surface, absence of adhesions in the right upper quadrant, and the possibility of a two-stage resection. Fifteen instances in which left transverse colostomies were performed with diverse indications formed the basis for this report.