dialysis and transplant

Question 1

Goals of dialysis

Answer 1

remove toxins that are normally cleared by the kidney and to maintain euvolemia in the patient. Ideally, chronic dialysis will improve signs and symptoms of uremia

Question 2

Indications for starting dialysis

Answer 2

Life threatening conditions (severe hyperkalemia, volume overload, uremic pericarditis). If patient doesn’t have appropriate dialysis access, use vascular catheter. Less severe symptoms (mild cognitive changes with uremia, etc) warrant dialysis initiation if appropriate access. Otherwise, weight the risks vs benefits of catheter infection. GFR alone is not sufficient

Question 3

What is hemodialysis

Answer 3

Blood is rapidly moved through extracorporeal circuit, then removed by needle or catheter port into a tuble with semi-permeable membrane. A dialysate is outside the tube moving in counter current. Solutes in blood move into dialysate by diffusion (concentration gradient), then blood is returned to patient via separate needle/port. Fluids can also be removed by positive transmembrane pressure.

Question 4

Methods for hemodialysis access

Answer 4

AV fistula, AV graft, lumen catheters

Question 5

What is an AV fistula

Answer 5

Preferred access for dialysis: surgical anastomoses of artery to vein, usually in arm. Low infection rate but take 6weeks to 9 months to develop.

Question 6

AV graft

Answer 6

synthetic grafts that are connected to the artery and vein. AVGs can be used more quickly and have a higher primary success rate than AV fistula. However, AVGs fail quicker than AVFs due to neointimal hyperplasia, require frequent interventions to maintain patency, and have a higher infection risk

Question 7

Pros and cons to lumenal catheters

Answer 7

Catheters are most often placed in the internal jugular vein and can be used immediately for dialysis. Catheters have a much higher infection rate than AVFs or AVGs and also have a high rate of dysfunction.

Question 8

Pros to convential hemodialysis

Answer 8

Rapid removal of small molecular solutes (ie urea), precise control of ultrafiltration

Question 9

Cons to hemodialysis

Answer 9

Not continuous treatment, so large volume of fluid is removed in 4 hr period. Also, not effective at removing large solutes that are protein bound

Question 10

Complications of dialysis

Answer 10

Muscle cramps, Hypotension, Headache, Chest pain, Air embolism (very rare), infection
Muscle cramps, Hypotension, Headache, Chest pain, Air embolism (very rare), infection
Muscle cramps, Hypotension, Headache, Chest pain, Air embolism (very rare), infection

Question 11

What is peritoneal dialysis

Answer 11

continuous therapy done at home. Coiled catheter placed in peritoneal cavity, then high glucose fluid is instilled in peritoneal cavity. This fluid provides high oncotic pressure, so fluid moves from blood to peritoneal cavity, and solutes move with fluid by convection. The dialysate plus flitered fluid are then drained from cavity and new dialysate is added. 3-4 exchanges are done per day

Question 12

Types of peritoneal dialysis

Answer 12

Continuous ambulatory peritoneal dialysis (CAPD) is a manual therapy. The patient does three to four manual exchanges of dialysate daily. Continuous cycling peritoneal dialysis (CCPD) is an automated therapy. A cycler machine instills and drains dialysate many times throughout the night and leaves a dwell of dialysate in the peritoneum in the morning.

Question 13

Pros of peritoneal dialysis

Answer 13

lower cost, more freedom, fluid removal is gradual

Question 14

Peritoneal dialysis complications

Answer 14

Infections (peritonitis and exit site infections), catheter dysfunction or problems draining, hernias due to increased abd pressure, metabolic problems such as hyperglycemia, scarring of peritoneal membrane

Question 15

Prognosis on dialysis

Answer 15

bad

Question 16

Prognosis with kidney transplant

Answer 16

Transplant improves long term patient survival compared to dialysis. Immediately following the surgery, however, relative risk of death is higher for transplant patients compared to dialysis due to surgical complications

Question 17

Transplant procedure

Answer 17

Left kidney is preferred for donation due to longer length of the renal vein. • Renal vein and artery anastomosis to recipient external iliac vein and artery, commonly on the right due to accessibility of the right external iliac vein.Donor ureter anastomosed to recipient bladder.

Question 18

Problems with deceased donor kidneys

Answer 18

• Warm ischemia: time from cardiac death to cold perfusion (max ~60 min)• Cold ischemia: time from cold perfusion to recipient anastomosis (max 24-36 hours)
• Warm ischemia: time from cardiac death to cold perfusion (max ~60 min)• Cold ischemia: time from cold perfusion to recipient anastomosis (max 24-36 hours)

Question 19

Standard criteria donor

Answer 19

Donor brain death, organs remain perfused until cross-clamping (minimizing warm ischemia)

Question 20

Donation after cardiac death

Answer 20

Organ recovery occurs after cardiopulmonary death. Increases warm ischemia time and risk of delayed function once transplanted. This is “controlled” in the US (ventilator and/or pressor support is withdrawn in the OR) and often uncontrolled in Europe (asystolic in the field after attempts at resuscitation).

Question 21

Extended criteria donor

Answer 21

Donor > 60 years old, or Donor age 50-59 with at least two of either 1) history of hypertension, 2) death by stroke, or 3) elevated terminal creatinine. Associated with 70% increased risk of graft failure within 2 years vs. SCD. For this reason, ECD kidneys are generally reserved for patients with especially high mortality while on dialysis (older patients and patients with diabetes)
Donor > 60 years old, or Donor age 50-59 with at least two of either 1) history of hypertension, 2) death by stroke, or 3) elevated terminal creatinine. Associated with 70% increased risk of graft failure within 2 years vs. SCD. For this reason, ECD kidneys are generally reserved for patients with especially high mortality while on dialysis (older patients and patients with diabetes)

Question 22

How many HLA matches are taken into account with kidney transplant

Answer 22

6- Two copies each of HLA-A, HLA-B and HLA-DR. (A and B are class 1 MHC/HLA antigens and DR is class II MHC/HLAantigen). Matching at these 6 loci is the most important for successful long term transplant. The degree of HLA matching does NOT impact the risk of acute rejection though.

Question 23

Why is HLA matching important

Answer 23

•Unless donor/recipient are HLA identical, recipient T cells will recognize foreign donor HLA antigens as “non-self” and mount a response (rejection).

Question 24

Treatment of transplant rejection

Answer 24

If T cell mediated, IV steroids, anti-thymocyte globulin. If antibody/B cell mediated, plasmapheresis or IVIG/rituximab to inhibit antibody production

Question 25

Immunosuppresion regimen for transplant

Answer 25

triple therapy: Calcineurin inhibitor + proliferation inhibitor + prednison

Question 26

calcineurin inhibitors examples and side effects

Answer 26

cyclosporin and tacrolimus. Nephrotoxicity (vasoconstriction of afferent arteriole, then interstitial fibrosis and sclerosis, gingival hyperplasia, neurotoxicity

Question 27

Proliferation inhibitor examples

Answer 27

1) Mycophenolate Mofetil (MMF, cellcept, myfortic, MPA)- inhibit purine synthesis. 2) mTOR Inhibitors (sirolimus, everolimus)

Question 28

cancer and transplant

Answer 28

Increased risk of cancer after transplant due to immunosuppression

Question 29

Pre-renal causes of AKI in transplant

Answer 29

• Volume depletion from post-operative fluid shifts, blood loss, etc. • Thrombosis of the transplanted renal artery or vein (surgical emergency)• Calcineurin inhibitor effects on the afferent arteriole

Question 30

Post-renal causes of AKI in transplant

Answer 30

• Transplant ureter obstruction due to fluid collection: requires surgical drainage o Lymphocele o Hematoma • Urine leak: due to break down of transplant ureter to bladder anastomosis. Creatinine rises due to absorption through peritoneal membrane (Cr concentration is much higher in urine vs. serum). Requires ureteral stenting and often surgical repair.
• Transplant ureter obstruction due to fluid collection: requires surgical drainage o Lymphocele o Hematoma • Urine leak: due to break down of transplant ureter to bladder anastomosis. Creatinine rises due to absorption through peritoneal membrane (Cr concentration is much higher in urine vs. serum). Requires ureteral stenting and often surgical repair.

Question 31

Renal causes of AKI in transplant

Answer 31

Delayed graft function, acute rejection, recurrent primary kidney disease, infection (UTI, polyoma virus)

Question 32

Which primary renal diseases are likely to re-occur in a transplant

Answer 32

Primary focal segmental glomerulosclerosis, myeloproliferative glomerulonephropathy II (100% recurrance), atypical HUS (100% recurrence). Membranous nephropathy IgA nephropathy, SLE, diabetic nephropathy tend to recur though are often not clinically significant

Question 33

Imaging/labs for suspect AKI

Answer 33

a. Ultrasound to evaluate for post-renal obstruction/fluid collections. b. Calcineurin inhibitor drug level to evaluate for potential toxicity. c. Urinalysis for infection, proteinuria. d. Serum for bacterial/viral (BK) culture or PCR, antibodies against donor HLA antigens