Renal function in pediatric liver transplant patients

Actuarial five-year patient survivals after pediatric orthotopic liver transplantation (OLT) of 75 to 80% are now commonplace. However, renal dysfunction after pediatric OLT remains a serious complication and maybe broadly divided into four categories. The first is pre-existing renal disease in association with liver disease. This includes tyrosinemia with Fanconi syndrome, congenital cystic disease of the liver with associated polycystic disease of the kidney, Alagille's syndrome and primary hyperoxaluria. Second is hepatorenal syndrome. Resolution is dependent on successful OLT, although short-term dialysis may be required. Children with renal failure prior to transplantation have a significantly increased mortality. Third is peri- and early post-transplant renal impairment. The four major influences on early renal function after OLT are: (i) pretransplant renal function; (ii) early liver graft function; (iii) induction therapy with cyclosporine and tacrolimus; (iv) use of other nephrotoxic drugs. Fourth is long-term nephrotoxicity of cyclosporine and tacrolimus (FK-506). Both of these essential immunosuppressives carry the risk of long-term irreversible toxicity. In one study children, treated with cyclosporine, surviving > one year after OLT, 73% had a true GFR < 77 ml/min/1.73 m2. Children treated for > or = 24 months had a significantly lower GFR than those treated from 12 to 24 months. Half the children with a GFR < or = 50 ml/min/1.73 m2 had hypertension. Another study showed that 46% of pediatric OLT patients had a > or = 20% decrease in GFR over two to four years. FK-506 nephrotoxicity is comparable to that of cyclosporine. In a randomized control trial comparing FK-506 and cyclosporine, there was a 52% decrease in GFR over the first year in the FK-506 group, which was not significantly different to that of the cyclosporine group. In 60% of patients converted from cyclosporine to FK-506 one study showed a 50% or more drop in GFR. Both FK-506 and cyclosporine are associated with hypertension, hyperkalemia, hypomagnesemia and metabolic acidosis. In conclusion, the prognosis for long-term renal function in pediatric OLT patients is as yet unknown. Debate continues as to whether the impairment is static or progressive. Long-term follow-up studies of GFR are essential.