Objective II: This part of the study is a double-blind crossover study to compare optimized doses of TUDCA with optimized doses of ursodiol in 15 patients stratified according to age (less than 10 vs 10-20 vs more than 20 years). Patients are randomized to receive either TUDCA or ursodiol orally for an initial 3 month period, followed by a 3 month washout period in which no drug is administered. Patients then receive the alternate drug for 3 months.