The short bowel syndrome: underdiagnosis or undertreatment?

Abstract

While retention of up to 70% of small bowel can be well tolerated with preservation of the ileocaecal valve, the "short bowel syndrome" may occur after resection of more than 50% of the small intestine and is characterised by weight loss, malnutrition and steatorrhoea. It is not the physical length that matters so much as how the remaining intestine functions i.e. physiological length and the concept of "intestinal failure". In general, long-term parenteral nutrition will be required if less than 1 metre remains. If up to 2 metres remain there will be a significant alteration in lifestyle and supplemental nutrition will be required for those with between 2 and 3 metres remaining 1. The causes of the short bowel syndrome have changed over the years. In 1935, volvulus, strangulated herniae and mesenteric thrombosis were the major causes z. More recently Crohn's disease is the predominant cause 3,4,J while mesenteric thrombosis and volvulus are still significant causes. Crohn's disease was not described until 1932, and radical surgery for this has resulted in many cases of short bowel syndrome. Conservative surgery is now the rule and with more limited resections and stricturoplasties 6, there should be less Crohn's patients with short bowel in the future. With the availability of parenteral nutrition and even Home Parenteral Nutrition (HPN), extensive enterectomy is now possible in patients with intestinal infarction who would previously not have survived. The body responds to intestinal resection by adaptation 7, resulting in dilatation but not elongation, hyperplasia of the mucosa and an increase in the number of microvilli per mucosal cell. There is no increased number of villi but simply in their size s , due to increased cell migration. There is increased absorption per unit length, but this is nonspecific 7. In.rats this occurs within two weeks 9, but in humans it may take up to two years. Adaptation is maximal in younger patients and is not clinically significant after the age of 65'. The major factors affecting adaptation are the site and extent of the resection, a luminal nutrient stream and gastro-intestinal secretions l~ Minor factors include enteric hormones, the mucosal blood flow and the autonomic nervous system. With resection of small intestine ranging from l0 to 80% the adaptive response is directly proportional to th e length resected. The adaptive response of the