Effects of oxalate-rich vegetable on urinary stone formation in experimental rat

This study was aimed to observe the effects of an oxalate-rich vegetable, Cha Plu (Paper sarmentosum), on risk of urinary stone formation.  Sixty rats were used as experimental animal models and were divided into 3 equal groups.  While group 1 was fed with normal food without the vegetable, group 2 and group 3 were fed with food containing 1% and 5% dry vegetable leaves, respectively.  Twenty-four-hour urine specimens were collected and analyzed for calcium, oxalate, phosphate and creatinine.  The analysis was carried out once every fortnight for 26 consecutive weeks.  The rats were killed and urinary tract examination for the existence of stone was performed on the 26 th week.  The results showed that the patterns of growth, food and water intake, collected urine volume as well as urine composition among the 3 groups of rat were similar.  In urinary tract exploration, a one-millimeter-size stone was found in renal pelvis of one rat in group 3 Chemical analysis, however, reealed that the stone was not the calcium stone type (calcium oxalate and/or calcium phosphate as the main components).  If absorption processess are similar between the rats and the men, our results are not consistent with the propose that ingestion of oxalate-rich vegetable posts a high risk to urinary stone formation.