Why have successful transplants been difficult to achieve?

The intestine has been more difficult to transplant than other solid organs. Possible reasons include:

Patients must take anti-rejection drugs to suppress their immune system so their body will accept the transplanted bowel. They must take enough drugs to prevent rejection, but not too many or they may have problems with infection. Prograf® (FK506, tacrolimus) is the most common anti-rejection drug used.