Signs of kidney transplant rejection may include decreased urine output, increase in blood pressure, weight gain or swelling of the ankles. Other signs include elevated creatinine levels, pain, or swelling of the kidney, according to Vanderbilt Transplant.
There are three types of rejection that kidney transplant patients may experience, according to MedlinePlus: hyperacute, acute and chronic. All transplant patients, regardless of the type of transplant, experience a degree of acute rejection from one week to three months after surgery. This type of rejection rarely leads to complete organ failure. Hyperacute rejection occurs immediately after the transplant when the antigens do not match. This is life threatening and must be treated right away to prevent death. Chronic rejection occurs over years as the body's own immune system attacks the foreign organ and damages the tissue.
Chronic rejection is the No. 1 cause of transplant failure, as stated by MedlinePlus. This type of slow rejection cannot be treated with medication, and in many cases, a new organ is needed to sustain life. The reason that chronic rejection occurs is that the kidney recipient's immune system does not recognize the cells of the transplanted kidney. This is why transplant recipients receive immune-suppressing medication.