Intestine transplantation (intestinal transplantation, or small bowel transplantation) is the surgical replacement of the small intestine for chronic and acute cases of intestinal failure. While intestinal failure can oftentimes be treated with alternative therapies such as parenteral nutrition (PN), complications such as PN-associated liver disease and short bowel syndrome may make transplantation the only viable option. One of the rarest type of organ transplantation performed, intestine transplantation is becoming increasingly prevalent as a therapeutic option due to improvements in immunosuppressive regimens, surgical technique, PN, and the clinical management of pre and post-transplant patients.
History Intestine transplantation dates back to 1959, when a team of surgeons at the University of Minnesota led by Richard C. Lillehei reported successful transplantation of the small intestine in dogs. Five years later in 1964, Ralph Deterling in Boston attempted the first human intestinal transplant, albeit unsuccessfully. For the next two decades, attempts at transplanting the small intestine in humans were met with universal failure, and patients died of technical complications, sepsis, or graft rejection. However, the discovery of the immunosuppressant ciclosporin in 1972 triggered a revolution in the field of transplant medicine. Due to this discovery, in 1988, the first successful intestinal transplant was performed in Germany by E. Deltz, followed shortly by teams in France and Canada. Intestinal transplantation was no longer an experimental procedure, but rather a life-saving therapy. In 1990, a newer immunosuppressant drug, tacrolimus, appeared on the market as a superior alternative to ciclosporin. In the two decades since, intestine transplant efforts have improved tremendously in both number and outcomes.
Pre-transplant diagnoses and short bowel syndrome Failure of the small intestine is life-threatening due to the inability to absorb nutrients, fluids, and electrolytes from food. Without these essential substances and the ability to maintain energy balances, homeostasis cannot be maintained and one's prognosis will be dismal. Causes of intestinal failure may be clinically complex, and may result from a combination of nutritional, infectious, traumatic, and metabolic complications that affect ordinary anatomy and physiology. Many underlying conditions that serve as precursors to failure are genetic or congenital in nature. For example, severe inflammation, ulceration, bowel obstruction, fistulation, perforation, or other pathologies of Crohn's disease may severely compromise intestinal function. Despite the danger these conditions may pose in themselves, they may lead to even further, more serious complications that necessitate replacement of the diseased intestine. The single leading cause for an intestinal transplant is affliction with short bowel syndrome, oftentimes a secondary condition of some other form of intestinal disease. Short-bowel syndrome was the cause for 73% of American intestinal transplantations in 2008, followed by functional bowel problems for 15% and other causes representing 12% of cases. Natural SBS is mercifully rare, estimated to be 3 per 100,000 births. Surgical removal is the most common cause, performed as a treatment for various gastroenterological and congenital conditions such as Crohn's disease, necrotizing enterocolitis, mesenteric ischemia, motility disorder, omphalocele/gastroschisis, tumors, and volvulus.
Alternative treatments
Regardless of the underlying condition, the loss of intestinal function does not necessarily necessitate a transplant. Several conditions, such as necrotizing enterocolitis or volvulus, may be adequately resolved by other surgical and nonsurgical treatments, especially if SBS never develops. An individual can obtain nutrients intravenously through PN, bypassing food consumption entirely and its subsequent digestion. Long-term survival with SBS and without PN is possible with enteral nutrition, but this is inadequate for many patients as it depends on the remaining intestine's ability to adapt and increase its absorptive capacity. Although more complicated and expensive to perform, any person may receive PN. Although PN can meet all energy, fluid, and nutrient needs and can be performed at home, quality of life can be significantly decreased. On average, PN takes 10 to 16 hours to administer but can take up to 24. Over this time frame, daily life can be significantly hindered as a consequence of attachment to the IV pump. Over long periods of time, PN can lead to numerous health conditions, including severe dehydration, catheter-related infections, and liver disease. PN-associated liver disease strikes up to 50% of patients within 5–7 years, correlated with a mortality rate of 2–50%. Another alternative treatment to transplant for patients with SBS is surgical bowel lengthening via either serial transverse enteroplasty (STEP) or the older longitudinal intestinal lengthening and tailoring (LILT) technique. Although both procedures contribute to an approximate 70% increase in length, STEP appears somewhat more favorable in terms of lower mortality and progression to transplant. Nevertheless, a positive reception to either procedure may reduce the level of PN required, if not negate its required use altogether.
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