Corneal patients may be offered full thickness grafting (penetrating keratoplasty) or, less commonly, a newer technique in which only a partial thickness of the cornea is replaced. Full thickness grafting is carried out under a general anaesthetic and takes about an hour. The patient's own corneal button is removed and a disc cut from the donor cornea is stitched in its place. Some patients see the next day; other may have to wait for a while for the operated eye to reach its optimal effect.
This is an operation which does not rely solely on multi organ donors; graft material can come from any source, including donors dying at home, so long as removal is carried out within 24 hours of death. Also, cornea donors can be of any age. Donated corneas can be kept for up to 30 days, stored by one of two national eye banks or individual hospitals.
Kidneys tend to dominate the transplant scene, not least because chronic kidney failure has been treatable much longer than failure of other organs. The first successful kidney transplant -between identical twins - in Boston in 1954- took place long before dialysis equipment came into regular use.
Kidney transplants were started in Britain in 1961. Since then, kidney grafting has progressed to the point where it is overwhelmingly the treatment of choice for end-stage renal failure- cheaper and better in every way than dialysis. But, with an estimated 2,500 people going into chronic kidney failure in the UK each year, the queue for transplants continues to grow and many patients are still denied treatment. It is for this reason the need for kidneys is so urgent, for each gift of healthy kidneys frees two patients from the tiresome (and often debilitating) business of dialysis.
Kidney transplant
The operation itself is straightforward. Since there is rarely any need to remove the recipient's own kidneys, the donor organ is cradled within the pelvis.
About half the kidneys grafted start to work immediately; others begin to function within a week or two. Survival rates for kidney transplant are quoted as 85 per cent at one year and 70 per cent at five years.
Kidneys can be taken from donors ranging from two years to 75 years of age and above. They normally come from ventilated patients, but may also be recovered from other cadaver donors within one hour of death. Or, in rare cases, a kidney may be grafted from a living related donor more than 18 years of age. Kidneys can be stored for up to 36 hours.
Heart and lung transplants
Heart transplantation has come a long way since Christian Barnard shook the world by giving 45 year-old Louis Washkansky someone else's heart in Cape Town in 1967. Washkansky died - and so did others in the flurry of operations which followed the South African initiative. In fact the outcome was so dismal that many surgeons abandoned heart transplantation.
The operation was revived in Britain in 1979 - first at Papworth Hospital, near Cambridge, then a year later at Harefield Hospital in Middlesex. Today there are nine UK hospitals doing heart transplants. With improved surgical techniques, better post-operative care, and more selective anti-rejection drugs, the one-year survival rate for this operation is now around 80 per cent.
Approaching the same survival figures are the newer procedures of lung and heart - lung transplantation, now being offered to a growing range of patients (including cystic fibrosis sufferers) with severe lung disease. The combined operation was pioneered at Stanford University in California in 1982 and the first successful such operation in the UK was carried out at Papworth in 1984.
Hearts and lungs are taken form young multi organ donors who remain on ventilators until the retrieval operation. The organs are used ideally within four to six hours.
Liver transplant
The liver weighing around 3lbs in the adult male is the largest and most versatile of the human organs. It is often referred to as the body's metabolic centre because of its vital role in the conversion and distribution of energy. Liver transplant surgeons work without the fall-back which dialysis offers to kidney transplanters. Fortunately, liver failure is far less common than end stage renal disease.
Liver transplantation was developed in the United States by Dr Thomas Starzl and pioneered in Britain in 1968. The operation which lasts about five or six hours, is one of the most complex and challenging in the entire surgical repertoire. Liver patients are nursed in intensive care for two to three days post operatively and may remain in hospital for many weeks. The one-year survival rate stands at about 75 per cent.
Livers are taken from so-called beating heart donors - those, usually under 60 years of age, who have been declared brainstem dead. Donated organs can be kept for up to 20 hours in a special preserving fluid developed at the University of Wisconsin, USA.
Children tolerate liver transplant well. However, with 100 children entering terminal liver failure in Britain each year, some centres are trying to overcome the shortage of donor organs by fashioning appropriately sized grafts from adult livers. Until 1993, this was always done with cadaver livers in the UK, but now surgeons are attempting the same strategy with segments of liver acquired from living donors. Since the liver has massive powers of regrowth, the donor's liver regenerates within weeks.
Bone marrow transplantation
Bone marrow is the body's diffuse blood-forming tissue, contained in the cavities of certain bones - in the adult, principally in the pelvis, breastbone, ribs and skull. The stem cells found in bone marrow continually give rise to immature daughter cells, which differentiate into several types of blood cells. The failure of this blood forming process, as in leukaemia and certain other diseases, is lethal without treatment.
The transplantation procedure is deceptively simple. Donor marrow cells, taken from a living donor, are administered to the recipient intravenously, like a blood transfusion. Within 10 to 30 days, the cells migrate to the host's bone cavities and begin to function.
But the preparation, known as the conditioning, and post transplantation care are extremely complex, and both stages carry certain grave risks to the recipient. Space is created for the graft by destroying the recipient's own marrow, using chemotherapy and total body irradiation (TBI), over a period of several days. Immunosuppressive therapy is also begun pre-transplantation to reduce the likelihood of rejection. After transplant, the recipient, lacking any natural immunity to infection, is nursed in strict isolation. Transfusions of blood products, antibiotics, intravenous nutrition and immunosuppressive drugs must continue until normal marrow function resumes.
Grafted tissue may come from any one of a number of sources; from an identical twin or a close relative with identical antigen types; from an unrelated donor with closely matched types; or even from the recipient himself. Usually it is transfused immediately, but it may also be frozen at -196C and stored in a bone marrow bank. Blood groups of bone marrow donor and recipient may differ. In this case, any blood transfusions given after the graft are of the donor blood group; the recipient gradually assumes the same group as the donor.
However, marrow cells are also capable of rejecting the host. The anti-rejection drug cyclosporin is administered to control graft versus host disease (GVHD) until the recipient's body learns to tolerate the transplant, but both acute GVHD (occurring within 10 - 20 days) and chronic GVHD (after three months) remain life-threatening complications. Current research in bone marrow transplantation includes isolating and grafting stem cells only; and development of techniques to remove the immunological component (T-cells) form marrow before transplantation.
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