Intestinal Transplantation
There are three main types of intestinal transplantation
performed. All involve transplanting a sufficient length of small intestine to
achieve independence from parenteral nutrition (PN). The large intestine is not
usually transplanted, although its inclusion has been proposed as a way to
reduce fluid losses. The terminal ileum is brought out as an ileostomy to
facilitate biopsy, although this may be reversed in the long term by
anastomosis to the native colon (if still present) to restore gut continuity.
Where there is pre-existing renal failure it is sensible to perform a kidney
transplant at the same time.
Other operative combinations are possible (such as liver
and small bowel alone), but the three below are the most common.
Multivisceral transplant
Where there is intestinal failure and severe associated
liver disease, it is customary to perform a transplant that includes liver and
small bowel; this is most easily accomplished by implanting a bloc of tissue (a
cluster) which also includes the stomach, duodenum and pancreas, and which
receives its arterial supply from the coeliac trunk and superior mesenteric
artery (SMA), with venous drainage via the hepatic veins with the liver
implanted either using the caval replacement or piggyback technique (see Chapter
35). The donor stomach is anastomosed to a cuff of recipient stomach just below
the diaphragmatic hiatus.
The transplanted stomach is denervated, so the vagus
nerve supply is absent, resulting in closure of the pylorus, which prevents
gastric emptying. A gastric drainage procedure is therefore necessary, either
a pyloroplasty or a gastroenterostomy.
Modified multivisceral transplant
Where the liver is minimally diseased with an
anticipation of recovery, a transplant excluding liver is appropriate. If there
has been previous gastric or pancreatic disease, such as PN-related
pancreatitis, the bloc of tissue should include the stomach and duodenum, with
the portal vein being anastomosed to the recipient portal vein at the hilum of
the liver.
Small bowel alone
Isolated small bowel transplantation is the simplest
procedure to undergo. The SMA is anastomosed to the aorta, the superior
mesenteric vein (SMV) to the inferior vena cava (IVC); if the liver function is
satisfactory there is no need for a portal venous anastomosis.
An isolated intestinal transplant has the additional advantage
that, should serious complications occur, it can be readily removed and the
patient returned to PN until fit for a retransplant.
Donor assessment
Since the majority of patients undergoing intestinal
transplantation have had multiple bowel resections there is very little perito-
neal cavity remaining (known as abdominal domain). Donor organs therefore need
to be smaller than the recipient wherever possible, to enable closure of the
abdomen.
Aside from the issues of size, the donor organs are generally
best obtained from slim individuals with little mesenteric fat in order to
facilitate rapid cooling on retrieval.
Operative issues
Anaesthetic concerns
1.
Volume replacement: requires at least one large-volume line.
2.
For veno-veno bypass where caval replacement or cross-clamping of the IVC is involved, a patient
central vein above the diaphragm is necessary.
3. Reperfusion of
multivisceral block can release a large
volume of cold potassium-rich preservation solution, which precipitates cardiac
arrest.
Surgical issues
1. Abdominal domain: is there sufficient space in the abdomen to fit the new intestine/bloc of
tissue? It is undesirable to leave the abdomen open, although sometimes
necessary in small children.
2. Arterial inflow to the
graft is via an SMA anastomosis on to the
infrarenal aorta in an isolated graft; for a multivisceral graft a conduit of
donor aorta is used to take blood from the infrarenal aorta to the SMA and
coeliac trunk. It is undesirable to clamp the aorta above the renal arteries
because of the renal ischaemia this causes.
3.
A gastric drainage
procedure, such as a pyloroplasty, is required when
the stomach is part of the multivisceral bloc.
4. Tolerance of the
intestine to cold ischaemia is much more critical
than that of the liver or kidney. It is desirable to reperfuse the intestinal
bloc within 4 hours where possible, although inevitably this is a compromise
between proximity of the donor and difficulties encountered during the
operation to prepare the recipient to take the bloc, an operation that may take
many hours.
Post-transplant complications
Peri-operative complications
1. Thrombosis of arterial
supply or venous drainage is a risk, because many
of the recipients have lost their original bowel due to a procoagulant
tendency. In some cases this will have been cured by replacement of the liver.
2. Delayed resumption of
normal bowel function is common. The stomach is
the last organ to start to work, often taking more than 3 weeks before
peristalsis starts and it empties. Nutrition during this time is achieved using
a jejunostomy into the new bowel.
Transplantation related complications
1. Rejection is more common than with other organs, hence enhanced immunosuppression is
required. Typical presentations are with increased or decreased bowel activity,
with sepsis a common feature. The latter is a consequence of rejection
impairing the mucosal barrier and permitting translocation of bacteria. The
result is a need to enhance immunosuppression in a septic patient.
2. Infection is common, and often associated with intestinal rejec- tion or
intra-abdominal collections.
3. Renal impairment. Intestinal transplant recipients have the highest incidence of kidney
failure of any non-renal transplant type. This is in part due to the
high-volume fluid losses from the gut, as well as the nephrotoxic
immunosuppression.
4.
Recurrent disease, such as Crohn’s disease, may occur.
5. Graft versus host disease
is more likely after a multivisceral transplant than
other forms of solid organ transplant and tends to occur within the first 3 or
4 months. This is because of the large amount of lymphoid tissue (mesenteric
lymph nodes and mucosaassociated lymphoid tissue) in the graft, particularly if
the donor spleen has been transplanted, as used to occur in some centres in the
US. Lymphocytes transplanted with the donor can ‘reject’ the recipient, rather
than the other way around. Features include perfect function of the donor
organs, but rash, impaired liver function (only if liver is not part of graft)
and fever. It is fatal in a significant proportion of those affected.
