Bowel resection induced intestinal adaptation: progress from bench to bedside.

Intestinal adaptation after massive short bowel resection (SBR) is characterized structurally by an increase in intestinal wet weight, protein, DNA content, villus height, crypt depth, and absorptive surface area. These structural characteristics are driven by a proliferative stimulus that increases crypt cell division and augments cellular progression along the crypt-villus axis. Functional characteristics of adaptation include an upregulation of NA+/Glucose cotransporters, Na+/H+ exchangers, and other enzymes involved in digestion and absorption. The combination of structural and functional adaptation are physiologic live-saving events that compensate for the sudden loss of digestive and absorptive capacity in the remnant intestine. If intestinal adaptation does not occur or is inadequate, a lifelong dependence on parenteral nutrition will ensue, which ultimately results in devastating cholestatic liver dysfunction. Several mediators are thought to play an influential role in postresection small bowel adaptation, including intraluminal nutrients, gastrointestinal secretions, hormones, growth factors, and other genetic/biochemical factors. A thorough understanding of the mechanisms that drive intestinal adaptation will be essential in the development of novel and innovative therapies that result in saving lives.