The kidney in children with tyrosinemia: sonographic, CT and biochemical findings

Background. Tyrosinemia relates to a deficiency of fumarylacetoacetate hydr olase and presents early in life with central nervous system and liver abno rmalities. Renal function is often impaired. Little is known about the arch itecture and function of the kidneys. Objective. Imaging changes on US and CT are compared to the function of the kidneys in children with tyrosinemia, and followed after liver transplanta tion. Materials and methods. Renal sonography, CT and renal function tests in 32 children were reviewed. Renal length, volume, echogenicity and nephrocalcin osis were evaluated. Renal function was assessed by glomerular filtration r ate, and the presence of aminoaciduria, acidosis and calciuria. Seventeen c hildren had open renal biopsy during time of liver transplantation. Histolo gy was reviewed. Statistical analyses relating renal structure to function were performed, and repeated after transplantation. Results. The kidneys were enlarged (47 %), hyperechogenic (47 %) and showed nephrocalcinosis (16 %). There was delayed excretion of contrast medium at CT in 64 %. Aminoaciduria was present in 82 % of children, hypercalciuria in 67 %, tubular acidosis in 59 %, and low GFR in 48 %. Delayed excretion o f contrast was associated with low GFR (P < 0.05). Renal biopsies showed di lated tubules (81 %), interstitial fibrosis (56 %), glomerulosclerosis (56 %) and tubular atrophy (56 %). During a mean observation period of 3 years following liver transplantation, GFR improved in 50 %, tubular acidosis in 50 % and hypercalciuria in 70 %. No change was noted in renal size or sonog raphic architecture. Conclusion. Renal architecture and function are abnormal in the majority of children with tyrosinemia. Liver transplantation improves renal function i n about 50 % of patients, but abnormal renal size and architecture persist.