The diagnosis and follow-up of stone forming patients is usually performed by analysis of 24-h urine samples. However, crystallization risk varies throughout the day, being higher at night. The main objective of this study is to evaluate the urinary crystallization risk in adults and children by calculating risk indexes based on different collection periods.
The study included 149 adults (82 healthy and 67 stone-formers) and 108 children (87 healthy and 21 stone-formers). 24-h urine was collected, divided into 12-h daytime sample (8 am to 8 pm), and 12-h overnight sample (8 pm to 8 am next morning). Solute concentrations, the calcium to citrate ratio (Ca/Cit), and the ion activity product of calcium oxalate (AP[CaOx]) and calcium phosphate (AP[CaP]) were calculated in each 12-h sample and in overall 24-h urine. Assessments were also related to stone type.
Ca/Cit and AP(CaOx) were significantly higher in stone forming patients than in healthy subjects. The 12-h overnight samples had the highest values for both risk indexes, confirming a greater risk for crystallization at night. The AP(CaP) index was significantly higher in patients with pure hydroxyapatite stones than healthy controls, but was not significantly different between stone-formers overall and healthy controls.
The calculation of risk indexes is a simple method that clinicians can use to estimate crystallization risk. For this purpose, the use of 12-h overnight urine may be a reliable alternative to 24-h collections.
BMC urology. 2018 Dec 19*** epublish ***
Adrian Rodriguez, Concepcion Saez-Torres, Concepcion Mir, Paula Casasayas, Nuria Rodriguez, Dolores Rodrigo, Guiem Frontera, Juan Manuel Buades, Cristina Gomez, Antonia Costa-Bauza, Felix Grases
Laboratory of Renal Lithiasis Research, University Institute of Health Sciences Research (IUNICS-IdISBa), University of Balearic Islands, Ctra Valldemossa, km 7.5, 07122, Palma de Mallorca, Spain., Laboratory of Renal Lithiasis Research, University Institute of Health Sciences Research (IUNICS-IdISBa), University of Balearic Islands, Ctra Valldemossa, km 7.5, 07122, Palma de Mallorca, Spain. ., Department of Urology, Son Llatzer Hospital, 07198, Palma de Mallorca, Spain., Research Unit, Son Espases Universitary Hospital, 07020, Palma de Mallorca, Spain., Department of Nephrology, Son Llatzer Hospital, 07198, Palma de Mallorca, Spain., Clinical Analysis Service, Son Espases Universitary Hospital, 07020, Palma de Mallorca, Spain.