Renal transplantation and renal failure: staging, immunosuppression and graft dysfunction
What the exam tests
Staging of chronic kidney disease, indications for renal replacement therapy, transplant work-up and immunosuppression, and the diagnosis of post-transplant dysfunction.
Core rules
- Chronic kidney disease is staged on eGFR and albuminuria; acute kidney injury is staged on creatinine rise and urine output. Emergency dialysis indications are refractory hyperkalaemia, severe acidosis, fluid overload, uraemic complications and certain poisonings.
- Transplant work-up includes HLA typing, crossmatching and donor-specific antibody screening; a positive crossmatch predicts hyperacute rejection.
- Standard maintenance is a calcineurin inhibitor (tacrolimus), an antimetabolite (mycophenolate) and a corticosteroid, with induction therapy at the time of surgery.
- A rising creatinine after transplantation has four broad causes: rejection, drug toxicity, obstruction and infection. Ultrasound is the first test because it cheaply excludes obstruction and vascular thrombosis.
- BK virus nephropathy and cytomegalovirus are important infective causes of graft dysfunction; antibody-mediated rejection is diagnosed on biopsy with donor-specific antibodies.
Worked example
Three months after transplant, creatinine rises from 130 to 220 micromol/L, the tacrolimus trough is low and donor-specific antibodies are detected. Reasoning: subtherapeutic tacrolimus with new antibodies suggests antibody-mediated rejection. Ultrasound first to exclude obstruction, then biopsy, then plasma exchange and intravenous immunoglobulin alongside optimisation of immunosuppression.
Traps
Attributing every creatinine rise to rejection; forgetting BK nephropathy; ignoring the increased skin cancer and post-transplant lymphoproliferative risk; using nephrotoxic drugs at standard doses in a graft recipient.