Evolución de la litiasis residual post-LEOC en función del tipo de cálculo y de la composición de la orina

Summary.- OBJECTIVES: Extracorporeal shock wave lithotripsy (ESWL) is one of the most commonly used procedures for removal of renal calculi from the upper urinary tract, but complete expulsion of the fragments generated is not always achieved. This can lead to new lithiasic episodes, and it is considered that 10-26% of fragmented calculi can undergo regrowth. This in vitro study investigated the influence of fragment and urinary composition on post-ESWL growth of fragments, with the aims of establishing the effect and importance of these parameters, and identifying effective prophylactic mea- sures. METHODS: Fragments collected from patients immedia- tely following expulsion after ESWL treatment were se- lected for regrowth experiments. The particles included 24 calcium oxalate monohydrate (COM) fragments, 48 calcium oxalate dihydrate (COD), 24 hydroxyapatite (HAP), and 16 uric acid. RESULTS: In all treatments, calculi fragments showed a considerable capacity to induce growth of calcium oxalate and calcium phosphate. Under normocalciuria conditions, new COM crystals formed; both COM and COD crystals developed under hypercalciuria conditio- ns at a urinary pH 6.0 both HAP and brushite (BRU) crystals were formed. The highest growth rates were observed for COD calculi fragments under hyper- calciuria conditions and at a urinary pH of 6.5, follo- wed by growth on COM and HAP fragments under the same conditions; growth rates under other conditions tested were similar but 10-fold lower. With regard to the role of crystallization inhibitors, phytate exhibited inhibi- tory effects under all assay conditions. However, citrate had little effect, even at the highest concentration tested (1,000 mg/L). CONCLUSIONS: This study demonstrates the importan- ce of avoiding heterogeneous nucleant retention (pre- existing solid microparticles) in renal cavities, as these can act as very efficient inducers of the formation of new calculi, the composition of which is mainly dependant on the urine composition.