ABSTRACT
Ultrafiltration failure is the most frequent alteration of peritoneal transport in peritoneal dialysis (PD) patients, and is a frequent cause of technical withdrawal. At the beginning of the therapy, there is a great functional diversity, but alter the third or fourth years the 20% of patients develop progressive ultrafiltration failure and an increase of the small solute transport. In parallel to this functional alteration, the peritoneum of PD patients shows morphological alterations, such as loss or transformation of mesothelial cells, basal membrane reduplication, submesothelial fibrosis, hyalinazing vasculopathy and neoangiogenesis. There are scant comparative studies of morphofunctional correlation. Most of them have been reported on long-term PD patients and showed a progressive increase of fibrosis and vasculopathy with time on PD, specially in patients with ultrafiltration failure and in those with sclerosing peritonitis. The peritoneal vessel number do not always increase with time on PD, and it is associated with advanced ultrafiltration failure. Some short-term studies have demonstrated that the initial lesion related to the high small solute peritoneal transport is the epithelial to mesenchimal transition of the mesothelial cell (the transformation of mesothelial cell into fibroblastic cell). The higher secretion of extracellular matrix and vascular endothelial growth factor by the transformed mesothelial cells should participated on later development of fibrosis and high peritoneal permeability, not always in relation with higher number of peritoneal vessels.
