The human body has a great physiological reserve. One kidney may be lost without a detectable deterioration in renal function. One lung may be lost without a lethal outcome. Very little of the gastrointestinal tract is actually required to maintain life. The short bowel syndrome occurs in patients who have lost large amounts of their intestine and consequently have defective intestinal absorbtion. Definitions of the short bowel syndrome vary. Some authors describe it as the syndrome that occurs when there has been loss of 50% or more of the small bowel. Others as the syndrome that occurs when there is less than 200 cm of jejeunum-ileum remaining. However, these definitions do not take account of the health of the remaining bowel, the exact length does not exactly correlate with the altered physiology observed. The best definition therefore would be one that reflects a pathophysiological state consequent to loss of the absorbtive function of the intestine.
The concepts of this chapter are important for understanding short bowel syndrome, nutritional consequences of bowel resection, Crohn's disease and jejeuno-ileal bypass (operations for morbid obesity, bariatric surgery).
Management of the short bowel syndrome demands a detailed understanding of the absorbtive functions of the gut, the consequences of major resection, fluid and electrolyte balance and replacement of nutrients, vitamins and minerals. The natural history of the short bowel syndrome is divided into three parts; the initial illness, the adaptive phase and long term management. The main problems associated with the initial illness are the underlying pathology, the systemic inflammatory response syndrome and sepsis. The adaptive phase is oncerned with managing initial nutriion and fluid and electrolyte balance and the final chronic phase is concerned with management of malabsorbtion, diarrhoea, parenteral nutrition and nutritional deficiencies.
The liver has the ability to `regenerate' up to 75% of its mass and recover normal function. The adaption of the jejeuno-ileum is nearly as good. Recent advances include therapies to increase jejeuno-ileal adaptation and bowel transplantation which is becoming better understood and more widely practiced. The focus of this chapter is to outline the functions of the bowel, the causes and consequences of massive resection and to use these starting points to gain an insight into the management of the short bowel syndrome.