Rejection of the kidney transplant is caused by the immune response of the body to destroy the graft. The immune system consists of a network of cells, tissues and organs whose only job is to protect the body against “foreign invaders”. These invaders are usually bacteria, parasites, viruses and fungi. In case of a person who has received a transplant, it is that new organ that is considered “foreign” that the immune system wants to protect against.
This process of this “rejection” of the “foreign” organ starts the minute the kidney receives its blood supply in the patient. A protective system in the body known as “innate immunity” is the first to react against the transplant by introducing a group of cells known as lymphocytes and other complex chemicals to the new kidney. This kind of rejection is called “cellular rejection” which is different from another form called “humoral rejection” where the recipient has pre-existing antibodies that attack the new kidney. Antibodies are proteins that the body’s immune system produces against a specific antigen on the transplanted kidney.
Hyperacute rejection is an uncommon phenomenon today but describes the earliest form of rejection due to pre-existing antibodies in the blood of the recipient to the donor kidney. Right after the blood starts to flow into the new kidney, the kidney swells up, turns pale or blue and essentially becomes non-functional. The only treatment at this point is to remove and discard the kidney. This type of rejection is seen within minutes to hours after the transplant.
Hyperacute rejection is prevented by testing the recipient’s blood for the pre-existing antibodies to the donor by a process called as a crossmatch, which is done just prior to the transplant between the recipient’s blood and the lymph tissue procured from the donor.
Acute rejection is usually seen in the first few months after the transplant and can be caused by cells known as lymphocytes or by antibodies to the new kidney. The crossmatch process helps to identify pre-existing specific antibodies against the kidney and will help in starting appropriate anti-rejection medications to prevent rejection episodes.
Chronic rejection is observed months to years after the transplant and represents a slow decline in the function of the kidney. It can be delayed by ensuring adequate doses of medications that will prevent acute rejection and by protecting the graft from high blood pressure, diabetes, high cholesterol and certain viral infections, such as CMV.
How is acute rejection diagnosed?
Patients with a kidney transplant who suffer an acute rejection episode will usually have the following clinical features:
- Flu like symptoms with chills, mild fever, body aches or nausea
- Decrease in the amount of urine made by the kidney
- Pain over the transplant
- General feeling of unease
With these symptoms, blood work is ordered and may show a rise in the serum creatinine with a definitive diagnosis reached after a biopsy. This is usually done with the help of an ultrasound in the radiology department. In addition to the biopsy, the ultrasound looks for any anatomical issues like hydronephrosis (swelling in the kidney due to backed up urine) or any blood vessel abnormalities within the kidney as well.
How is acute rejection treated?
Most patients, especially with biopsy confirmed rejection episodes early after transplantation are admitted to the hospital for a short stay in order to adequately treat and closely monitor the response to the treatment.
If the biopsy shows acute cellular rejection, the first line of treatment is steroids through the intravenous route. Each day, the blood work is checked to look for a decrease in the creatinine and to monitor the white blood count, blood glucose levels and a change in the urine output. Usually 3 to 5 doses via the intravenous route are given. Once the parameters improve, the steroids are converted to oral form and the patient is then discharged with a change in the doses of the immunosuppression medications in order to adequately quell the rejection. Frequent follow up visit are set up to ensure adequate treatment.
If the biopsy shows antibody mediated rejection, treatment with special medications such as thymoglobulin are given to treat this more severe form of rejection. During this treatment, admission is definitely warranted and close monitoring of the kidney function and the development of new infections is closely monitored as well. Once the kidney function improves, the patient is discharged with frequent follow up visits planned.