ammonia cirrhosis clinicalmedicine complications congresses control diagnosis diseases donorselection etiology extracellularmatrix fibrosis gastroenterology genetherapy hepaticencephalopathy hepatitisc hepatitiscvirus liver livertransplantation medicine metabolism methods molecularaspects pathophysiology pharmacokinetics physiopathology postoperativecomplications prevention secondaryprevention therapy toxicology transplantation treatment urea wc536 wi725