Clinical renal transplantation Flashcards
what are the key functions of the kidney?
- filtration
- maintain composition of extracellular fluid and electrolytes
- remove waste products: urine, creatinine and potassium ions - hormone production
- EPO = erythrocyte production
- renin = blood pressure control
- conversion of vitamin D
what are the symptoms of renal failure?
high blood pressure
tiredness or lethargy
persistent headaches
fluid retention
how is kidney disease measured?
chronic kidney disease has stages from 1 to 5:
- measured by glomerular filtration rate
- Stage 5 = <15 or on dialysis = kidney transplant
how can kidney disease be treated?
- dialysis
- haemodialysis
- peritoneal dialysis - transplant
what is haemodialysis?
take blood from patient system, clean it and return it to the patient via circuit
- tubes contain membrane to enable filtration of waste products and clean fluid to pass through
what is peritoneal dialysis?
- dialysis fluid is directed into the abdominal cavity via a catheter
- peritoneum (lining of abdomen) acts as a membrane for osmosis to draw out the waste products into the dialysis fluid
what renal transplants can be performed? what are their advantages/disadvantages?
- living donation - provides the best kidney as it reduces time outside donor into recipient
- can also be better planned an both are in the same hospital - cadaveric - someone who is passing away
- emergency, with transport time involved
donation after brain death (DBD):
- their organs are functional and are retrieved whilst still on support
- cold ischemia only - better graft outcomes in short and long term
donation after cardiac death (DCD):
- warm and cold ischemia - more damage
200 kidney transplants per year at QE
how are transplants allocated?
national waiting list, complex points-based system for cadaveric organs
- Geography important: DCD <12hrs, DBD <18hrs - Geography determines how long the graft kept in cold storage
- patients waiting longest are prioritised
- MHC match
- children prioritised
- those patients who are highly sensitised are prioritised
- age difference - wouldn’t transplant between 20 yr old and 80 yr old
- CRF score: calculation reaction frequency - look at last 10,000 donors and see how many of these the patient would match to - the less donors, the more prioritised these patients are
what determines how well a renal transplant does?
How well graft kidneys do are impacted by how long is spent outside of the donor until inside the recipient with blood re-establishment:
- Cold ischemia time duration impacts delayed graft function (DGF) – kidney is alive and viable with blood flow, but is functionally asleep
- Once transplanted, the main function is filtration, less so involved in hormones – but stress delays this function
Long term: patient survival, graft survival – second transplant maybe needed if in a younger person
- serum creatinine is an indirect measurement of kidney function
what happens physiologically during kidney failure?
Build up of waste in ECF, lack of hormones
- anaemia, high blood pressure, low vitamin D and electrolyte imbalance
- lethargy, fluid retention (not clearing excess body from fluid – swollen ankles and fluid in lungs), persistent headaches
what are the limitations of haemodialysis?
- patient in hospital 3x a week, 4 hours each time
- arteriovenous fistulas which are uncomfortable for patients
- fistulas in same place can became aneurysmal and large, which causes damage
- fistulas can cause high blood flow back to the heart, putting strain on the heart
what are fistulas?
- need robust entry with high flow to avoid clotting, where needles can go in and out of patient vein repetitively
- artery walls become damaged with needle, so fistulas arteriolise a vein, which are more amenable to needles
- but veins naturally have slow flow, so arteriovenous fistulas are used to connect artery and vein together to create a high flow vein, where blood flow is fast enough to avoid clotting
what are the limitations of peritoneal dialysis?
continuous: patient needs to be hooked up to a machine for a few hours to maintain the osmotic gradient for waste removal
discontinuous: put fluid in, disconnect and then empty after a certain number of hours
- slower as fresh fluid isn’t constantly going into the patient
higher mortality risk and lower quality of life when on dialysis
why is dialysis worse than transplantation?
transplantation enables 24/7 kidney function
fluid going in and out of the patient leads to seesaw dialysis:
- patient feels worse as toxins build up, then dialysis clears the waste, so electrolyte composition changes, but patient is now exhausted
- by the time they feel better, the waste products are already building back up
- maintenance of life, but no quality of life due to fatigue
- impact of these build-ups is also a health risk to patients
why is dialysis an important option?
Not all patients are amenable for transplant as they may not be fit enough, so dialysis is the only option, but higher mortality on dialysis
