Small
bowel transplantation
Progress in small bowel transplantation has lagged well behind that of
other types of solid organ transplantation. Intestinal transplants stimulate a
particularly strong graft rejection response, probably because the small
intestine contains very large amounts of lymphoid tissue. Moreover, ischaemia
and rejection increase intestinal permeability and allow translocaton of
bacteria from the lumen of the bowel. Added to this, the operation is often
complex and made technically difficult because of repeated previous abdominal
surgery. Consequently, graft rejection and infection remain a major problem
after small bowel transplantation and the results obtained are inferior to those
seen after other types of
• intestinal atresia;
• necrotising enterocolitis;
• volvulus;
• disorders of motility;
• mesenteric infarction;
• Crohn’s disease;
• trauma;
• desmoid tumours.
Because
of the substantial risks associated with small bowel transplantation, the
procedure should be considered only for those patients where long-term total
parenteral nutrition (TPN) has failed, usually because venous access has become
impracticable or because of frequent life-threatening line sepsis. The need for
small bowel transplantation is estimated at around 0.5—1.0 patients per
million population and around 50 per cent of cases are children.
Small
bowel transplantation may be carried out as an isolated procedure, performed
together with a liver transplant or undertaken as a component of a multivisceral
transplant. Around half of all small bowel transplants are performed in
children. Where possible, isolated small bowel transplantation is undertaken
because patient survival is higher.
A
small bowel transplant from a cadaveric donor comprises the entire small bowel
but it is no longer considered advisable to include the ascending colon in the
graft. The superior mesenteric artery of the graft (with an aortic patch is
anastomosed to the recipient aorta and the superior mesenteric vein is
anastomosed to the inferior vena cava or to the side of the portal vein. The
proximal end of the small bowel graft is anastomosed to the recipient jejunum or
duodenum. The distal end of the graft is anastomosed to the side
of the colon (with a loop ileostomy) or is fashioned as an end ileostomy.
A gastrostomy tube (to overcome delayed gastric emptying) and a feeding
jejunostomy tube are inserted.
About
half of all patients who require small bowel transplantation have cholestatic
liver disease secondary to TPN and require combined liver and small bowel
transplantation. Cholestatic liver disease due to TPN is especially common in
children. When combined liver and small bowel transplantation is carried out
the two grafts are transplanted en bloc. The donor aorta is fashioned
into a conduit including the superior mesenteric and coeliac arteries, and
anastomosed to the recipient aorta. The portal vein anastomosis is as for
isolated liver transplantation.
Multivisceral
or ‘cluster’ transplants may be necessary in the case of large desmoid
tumours where excision of both the small bowel and adjacent organs is required,
when there has been extensive thrombosis of the splanchnic vessels and for
generalised disorders of gastrointestinal motility.
The
1-year graft survival rate after small bowel transplantation is about 60 per
cent for both isolated small bowel transplantation and combined liver and small
bowel transplantation. After 3 years the graft survival rate is around 40 per
cent. As already noted, however, patient survival is better after isolated small
bowel transplantation than after combined liver and small bowel
transplantation, where loss of the graft usually equates with death of the
recipient. Most of the mortality after small bowel transplantation is due to
sepsis and multiorgan failure. The risk of infection after small bowel
transplantation is heightened by the additional requirements for
immunosuppression in order to control graft rejection. This accounts for the
relatively high incidence of lymphoproliferative disease (around 10 per cent)
observed in patients who have undergone small bowel transplantation. Because of
the large amount of donor lymphoid tissue transplanted graft-versus-host disease
(GVHD) may occasionally be an added complication. Despite the hazards, small
bowel transplantation offers patients with intestinal failure a chance to lead
an active life free from the constraints of long-term nutritional support.