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Urinary saturation: casual or causal risk factor in urolithiasis?
Author(s) -
Rodgers Allen L.
Publication year - 2014
Publication title -
bju international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.773
H-Index - 148
eISSN - 1464-410X
pISSN - 1464-4096
DOI - 10.1111/bju.12481
Subject(s) - urinary system , medicine , uric acid , calcium oxalate , casual , demography , sociology , materials science , composite material
Objective To assess (i) the extent to which urinary supersaturation ( SS ) has successfully discriminated between stone formers and healthy individuals ( N ), (ii) whether absolute SS has diagnostic worth and (iii) whether high SS is the fundamental cause of stone formation per se.Materials and Methods Google Scholar was used to identify studies in which urinary compositional data had been determined. In those cases where SS values were not given, or where other risk indices had been reported, they were (re‐)calculated. Collected data were termed ‘global’ but were then ‘filtered’ according to stone type and protocols used for SS calculations. SS distribution plots for calcium oxalate, brushite and uric acid were constructed. Data were statistically analysed using the unpaired t ‐test and M ann– W hitney test.Results In all, 47 studies yielded 123 SS values for healthy individuals and 122 values for stone formers. The mean and median SS values were significantly greater in stone formers compared with healthy individuals in all but one of the comparisons. Wide variations in SS occurred for healthy individuals and stone formers. The two groups could not be separated.Conclusions Absolute SS has no diagnostic worth. It is impossible to quantify the meaning of a ‘high’ SS value. Urines cannot be identified as originating from healthy individuals or stone formers based on their SS . SS should be determined in clinical and research settings for relative comparisons during the assessment of treatment efficacies. This study provides a compelling argument for SS being a casual factor rather than a causal one.