Acute rejection happens to almost all patients who receive organ transplants. The patient's immune system and white blood cells recognize the transplanted organ as being foreign and mount a defense against the organ. The new organ is then incapable of working at full efficiency, and symptoms of rejection become apparent to the transplant recipient. These symptoms of rejection are very similar to the symptoms of organ failure. Early detection is essential to successful reversal of acute rejection. For this reason, the transplant recipient carries a large responsibility for maintaining his or her health. Acute rejection is almost always reversible with special medication. Once successfully reversed, some patients never have trouble with acute rejection again, although some patients do have subsequent episodes. Most rejection episodes require admission to the hospital. Acute rejection is rare beyond the first year of transplant. In addition to the subjective symptoms of worsening organ function that the transplant recipient feels, there are indicators of organ rejection which the health care team can identify. Various blood tests are used to identify possible rejection, and biopsies (the removal of a small piece of organ tissue via a thin needle) are done to confirm rejection.

Chronic rejection is different from acute rejection in that it is usually not reversible, but it is also a response of the patient's immune system. A patient's white blood cells produce special proteins called antibodies that are created specifically to "latch onto" the transplanted organ. While attached to the organ, the antibodies alert the rest of the immune system to attack the organ slowly and continuously. Most people will have little or no chronic rejection. Some people have some chronic rejection, leaving their organ function less than perfect but still adequate. Some people will lose complete function of the organ. Because chronic rejection is usually not reversible, the best defense is to prevent it from happening in the first place by taking the anti-rejection medications exactly as prescribed.

Signs and symptoms of rejection for specific organs follow:

Signs and Symptoms of Kidney Rejection
Fever over 38°C or 100.4°F
Decreased urine output
Weight gain over 2 pounds per day
Increased blood pressure
Pain over kidney

Signs and Symptoms of Liver Rejection
Fever over 38°C or 100.4°F
Fatigue
Jaundice (yellowing of skin or eyes)
Darkening of urine
Clay-colored stools
Pain over liver

Signs and Symptoms of Pancreas Rejection
Fever over 38°C or 100.4°F
Increased blood sugars
Pain over pancreas