waitlist, 94% of whom were u.s. citizens. regardless of transplant type, over half of new registrants are 5 years of age or younger. adults compromise the next largest cohort, followed by pediatric patients aged 6 and older. in 2008, the ethnic composition of the intestinal transplant waitlist was 65% white, 18% black, 16% hispanic, 1% asian, and 0.5% other or mixed race, resembling the demographics of the american general population at the time aside from a below-average asian cohort. abo blood types also matched the general population, with 31% a, 14% b, 5% ab, and 50% o. in 2004, the average waiting period to receive a transplant was 220 days, with a median of 142 days in 2008. the rate of waitlist additions has shifted from year to year; gains increased until 2006 (with 317 added), but then decreased in 2012 (to 124 added). in 2007, only 9% of patients on the u.s. waitlist died while waiting for a transplant. waitlist mortality peaked around 2002 and was highest for liver-intestine (pediatric) patients. deaths among all pediatric groups awaiting intestine-liver transplants have decreased in the years leading up to 2014 whereas adult intestine-liver deaths have dropped less dramatically. the decrease in recent years is likely due to improved care of infants with intestinal failure and subsequently a decrease in referrals for transplant. although many improvements have been made in the states, outcomes everywhere still demonstrate much room for improvement. worldwide, 25% of pediatric patients on the waitlist for an intestinal transplant die before they can receive one. procurement protocol following matching of the organ, the complicated procurement of the small bowel can be performed by a team of abdominal transplant surgeons. once a donor has been selected and approved for donation, several pretreatments may be initiated to destroy microorganisms and immune cells. the donor intestine must be decontaminated with several antibiotics, including neomycin, erythromycin, amphotericin b, and cephalosporin. they may also be treated with anti-lymphocyte antibodies (anti-thymocyte globulin, alemtuzumab), irradiation directed against excessive mesenteric lymphatic tissue, and have their bowel irrigated. once donor preparation is accomplished, procurement can begin by utilizing the same standard techniques for all abdominal organ procurements. the team exposes the abdominal cavity and inserts two cannulae for the infusion of university of wisconsin organ preservation solution into the aorta and inferior mesenteric vein. as the abdominal organs are cooled in situ, the surrounding tissue is dissected so that they may be quickly extracted. in the next step, the aorta is cross-clamped, cutting off blood supply to the organs. once blood and oxygen supply to an organ is cut off, organ death will approach swiftly unless steps are taken to preserve them until transplant. organs are therefore fully drained of blood, flushed with cool preservation solution, and removed from the body. in an isolated intestinal transplant, the colon will be detached from the small intestine. the cecum and ascending colon are devascularized, while care is taken to preserve major vasculature in the ileum. the jejunum will be separated from the duodenum while preserving the vasculature of the jejunum, ileum, mesentery, and the pancreas. if healthy, the pancreas can oftentimes be retrieved as an additional isolated procurement. the intestinal allograft, when ready to be extracted, is attached by the mesenteric pedicle, where the vessels converge out of the intestinal system. this pedicle will be stapled closed, and can be separated from the body via a transverse cut to create a vascular cuff. the complete intestinal allograft can then be removed and wrapped in a surgical towel. the protocols for combined liver and multivisceral procurements are far more complicated and meticulous than isolated intestine alone. transplantation protocol isolated intestine transplant diagram. first, any abdominal scar tissue from previous surgeries must be removed. the aorta and vena cava are dissected in preparation for vascular anastomosis, followed by dissection of the proximal and distal ends of the digestive tract. anastomosis is then performed to revascularize the graft. arterial vessels are connected to the abdominal aorta, below the kidneys. however, venous drainage, or the reattachment of the transplanted organ to the venous system, may be performed differently depending on the unique intra-abdominal vasculature of the recipient. the graft is usually drained systemically into the infrarenal vena cava, but may also be drained portally into the hepatic portal or superior mesenteric vein. the graft is then reperfused with blood and any bleeding is stopped before the proximal and distal ends of the transplant bowel are connected to the original digestive tract. a loop ileostomy is then created as to provide easy access for future endoscopic observation and biopsies. a gastronomy or jejunostomy feeding tube may be placed before the abdominal wall is closed. when a liver is being transplanted in conjunction with the intestine, the recipient must first have their own liver removed. following this, the aorta, cava, and portal veins of the donor and recipient are anastomosed. the graft is then flushed before the caval clamps are removed. the intestine is then reconstructed as in an isolated intestinal transplant, before being connected to the bile duct servicing the new liver. multivisceral transplants are especially difficult and susceptible to complications because all organs must survive a conjoined procurement, transport, and transplantation. all three of these measures are tailored to the individual needs of the recipient. preservation of the native spleen, pancreas, and duodenum during a multivisceral transplant can reduce the risk of additional complications related to these structures. post-operative period following the procedure, the patient is actively monitored in an intensive care unit (icu). broad-spectrum antibiotics are administered, bleeding monitored, and serum ph and lactate levels measured for evidence of intestinal ischemia. the patient's immune system is strongly modulated immediately post-operation. the initial phase of treatment consists of the administration of tacrolimus with corticosteroids to suppress t-lymphocyte activation. next, various assortments of interleukin-2 (il-2) receptor antagonists (daclizumab, basiliximab), anti-proliferation agents (azathioprine, mycophenolate mofetil), and the drugs cyclophosphamide and sirolimus are administered on an individual patient basis to further suppress the immune system. the bioavailability of these drugs is dependent on intestinal surface area and transit time, and therefore the length of the allograft determines the immunosuppression regimen. intravenous administration of prostaglandin e1 is occasionally performed for the first 5 to 10 days following transplant to improve intestinal circulation and a potential dispensing of immunosuppressive effects. the gut is selectively decontaminated against high-risk flora and preventative care is taken against cmv and fungal infections. it is ideal to commence enteral nutrition as early as possible following transplantation. therefore, a feeding tube connecting to the stomach or jejunum is quickly placed to facilitate rehabilitation. if gastrointestinal function is restored, a diet can be reestablished and cautiously advanced as tolerated. most patients are weaned from pn within 4 weeks of transplantation, and nearly all are free from additional enteral supplementation by one year. evidence for the restoration of function includes decreasing gastrostomy tube returns and increasing gas and enteric contents in the ileostomy. routine surveillance endoscopy and biopsies via the ileostomy should be performed with decreasing frequency over several months to observe signs of rejection, ideally before clinical symptoms present themselves. should the patient continue to perform well through the first post-transplant year, the ileostomy would generally be closed. should rejection be suspected in the future, endoscopies would be performed and an appropriate antirejection therapy will be tailored. the median time for hospital discharge varies between procedures. the median times for isolated intestine, intestine-liver, and multivisceral transplants are 30, 60, and 40 days post-operation respectively. within the first several months, carbohydrate and amino acid absorptive capacity should normalize, followed by the absorptive capacity for fats. once enteral nutrition is capable of providing all nutritional needs, pn can be discontinued. nearly all patients with a successful transplant are free of pn within one year. biological complications intestinal transplantation is the least performed type of transplant due to a number of unique obstacles. the most major of these is the profound immunosuppression required due to the ability of the intestine to elicit strong immune responses. because of exposure to a wide range of gut flora and material consumed by the body, the intestinal epithelium possesses a highly developed innate immune system and antigen-presenting abilities. immunosuppression is the primary determinant of outcome in small bowel transplantation; the risk for graft rejection is increased by under-immunosuppression and for local and systemic infection with over-immunosuppression. ensuring an appropriate dose of immunosuppressant can therefore be difficult, especially as both ciclosporin (14–36%) and tacrolimus (8.5–22%) have generally low bioavailabilities. a major problem due to immunosuppression in intestinal transplant patients is post-transplant lymphoproliferative disorder, in which b-lymphocytes excessively proliferate due to infection by ebv and result in infectious mononucleosis-like lesions. intestinal transplant recipients are also at risk for chronic renal failure because calcineurin inhibitors are toxic to the kidneys. a transplant recipient must remain on immunosuppressants for the rest of his or her life. intestinal transplants are highly susceptible to infection even more so than the standard immunocompromised recipient of other organs due to the great composition and variety of the gut flora. a complex assortment of microorganisms inhabits the human digestive tract, with concentrations of up to 104–107 cfu/ml in the jejunoileum and 1011–1012 cfu/ml in the colon. while suppression of the immune system may prevent immune attack on the new allograft, it may also prevent the immune system's ability to keep certain gut microbial populations in line. despite pre and post-decontamination of the transplant, recipients are at risk of local and systemic infection by both natural and external flora. the common symptom of graft dysfunction, whether due to infection, rejection, or some other condition, is diarrhea. transplant outcomes and impact intestinal transplant outcomes have improved significantly in recent years. despite mild incongruities in survival rate percentages between centers in north america, europe, australia, and elsewhere, intestinal transplantations mostly approach survivorship rates of lung transplantation. at one-year, graft survival rates for isolated intestine currently waver around 80%, and 70% for intestine-liver and multivisceral. over the same time period, patient survival for isolated intestine patients may even exceed 90%, while the more complicated multiorgan transplants do not show any increase in patient survival when compared to patients surviving with the intestinal graft alone. the five-year survival rate for patients and transplants ranges from 50 to 80% (overall mean 60%), depending on underlying disease and presurgical morbidity. very young (<1 year) and very old (>60 years) patients receiving a transplant have pronounced rates of mortality. after 4 years, pediatric survival significantly worsens compared to adults. several factors relating to superior patient and graft prognosis have proven to be statistically significant. patients who have been admitted for transplant directly from home rather than the hospital, younger patients over one year of age, those receiving their first transplant, those receiving transplants at experienced transplant centers, and who receive antibody or sirolimus-based induction therapies have increased rates of survival. furthermore, underlying etiology, the presence of comorbidity, the frequency of previous surgery, nutritional status, and the level of liver function have been found to affect patient-graft survival . patients with a pre-transplant diagnosis of volvulus were found to possess a lower risk of mortality. as of 2008, the longest recorded surviving transplant survived for 18 years. between 1999 and 2008, 131 retransplant procedures were performed in the united states. the improvement to quality of life following an intestinal transplantation is significant. of living patients 6 months after transplant, 70% are considered to have regained full intestinal function, 15% are at partial function, and 15% have had their grafts removed. for those with full function, enteral nutritional autonomy is high. the ability to resume regular activities such as the ability to consume food and exert control over digestive function is certainly a welcome return for patients. the low quality of life induced by intestinal failure is oftentimes further supplemented by significant psychosocial disability and narcotic dependence. following transplantation, these have been found to generally decrease. according to surveys comparing patients who have undergone transplants and those that have not, there seems to be a remarkable improvement for transplant recipients in such areas as anxiety, depression, appearance, stress, parenting, impulsiveness, optimism, medical compliance, and the quality of relationships. financial considerations receiving an organ transplant of any kind is a highly significant investment financially, but a successful, well-functioning transplant can be