ABSTRACT
The small bowel is about 250 cm long in the full-term newborn infant. Subsequent growth is highly variable, as small bowel length increases to approximately 400-750 cm by adulthood.1,2 Because solid foods must be liquefied for digestion and assimilation, the upper digestive tract secretes approximately 8,000 mL of fluid into the gut lumen daily under the stimulus of food, accompanied by a variable quantity of dietary water.3 Contributions to lumen fluid are as noted in Table 3.1. Although most regions of the gut secrete and absorb fluid simultaneously, the balance favors absorption in most of the jejunum and ileum (6,500 mL) and colon (1,000-1,500 mL), resulting in only about 200 mL of fecal water loss daily.3 It is axiomatic that the magnitude of diarrhea following intestinal resection is determined by the location as well amount of gut loss, or, more accurately, the type and quantity of remnant bowel, given the considerable variation in normal small bowel length.4 Resection of 400 cm of jejunoileum may result in profound increases in stool volume and nutrient malabsorption when original small bowel length is only 450 cm. Conversely, the same amount of resection may have little or no effect in persons with native small bowel length of 500 cm or more.
