INTRATUBULAR CRYSTALLIZATION EVENTS

Can urolithiasis start as an intratubular event? Under severe hyperoxa luric conditions in animal models at least crystal formation can. Rece ntly models have been presented that assess the chances of crystal for mation under more normal conditions. These models describe changes in fluid composition as this passes through the nephron, these conditions being simulated in in vitro experiments. It appears that under natura lly occurring intratubular conditions calcium-salt crystallization tak es place within the time tubular fluid normally spends in the nephron. Precipitation starts with a calcium-phosphate phase under conditions found in the thin limbs. This crystalline phase then (partly) dissolve s when collecting duct conditions are used, thereby inducing formation of calcium oxalates. Under these conditions the latter increase in si ze by way of crystal growth and agglomeration. Large particle formatio n and cell adhesion can eventually result in particle retention and su bsequent stone formation. Viewing urolithiasis as originally an intrat ubular event has consequences for in vitro experiments and treatments, which are discussed in this paper.