Objectives

Different morpho-compositional types of kidney stones represent different etiologies. By understanding these, we can achieve a correct therapeutic approach. We expose clinical and analytical particularities among several groups of stones in children.

Material and methods

A national renal lithiasis registry is active in our country since January 2015. A specialized laboratory analyses stones. Physicians provide clinical and analytical data. For this study, similar stone types were grouped in 5 categories, according to main component: calcium oxalate monohydrate (COM, n=8), calcium oxalate dihydrate (COD, n=34), hydroxyapatite (HAP, n=11), magnesium ammonium phosphate (MAP, n=16) and Others (n=14). Clinical and analytical variables were compared.

Results

83 stones from 69 patients were included. Male prevalence ranged from 64% in HAP to 93% in MAP. Mean age at diagnosis varied from COD (10.3 years old) to MAP and HAP (3.1). Highest prevalence of relatives with stones appeared in COM (100%), lowest in MAP (36%). Urinary tract abnormalities ranged between 40-44% in HAP and MAP respectively, and 12-14% in the rest. Past urinary infection appeared from 69% in MAP to 13% in COM. HAP had much more frequently multiple stones at diagnosis (73%) with the lowest spontaneous passage (55%). Lowest urine volumes were observed in COM (0.7 [0.6-1.1] mL/kg/h), highest urine pH in HAP (7,0 [7,0 – 8,5]). Hypercalciuria prevalence was similar among all groups (38-50%) except COM (17%). Hypocitraturia was more common in COM (50%), COD (36%) and HAP (29%). Calcium/citrate ratio>0.33 mg/mg was more frequent in COD (60%) and HAP (57%).

Conclusions

COM showed more frequently low urine volumes, hypocitraturia and stones in relatives. MAP and HAP were associated to urinary tract abnormalities, COD and HAP with high calcium/citrate ratio. HAP had higher urine pH.