Accurate stone analysis: the impact on disease diagnosis and treatment

Abstract

This manuscript reviews the requirements for acceptable compositional analysis of kidney stones using various biophysical methods. High-resolution X-ray powder diffraction crystallography and Fourier transform infrared spectroscopy (FTIR) are the only acceptable methods in our labs for kidney stone analysis. The use of well-constructed spectral reference libraries is the basis for accurate and complete stone analysis. The literature included in this manuscript identify errors in most commercial laboratories and in some academic centers. We provide personal comments on why such errors are occurring at such high rates, and although the work load is rather large, it is very worthwhile in providing accurate stone compositions. We also provide the results of our almost 90,000 stone analyses and a breakdown of the number of components we have observed in the various stones. We also offer advice on determining the method used by the various FTIR equipment manufacturers who also provide a stone analysis library so that the FTIR users can feel comfortable in the accuracy of their reported results. Such an analysis on the accuracy of the individual reference libraries could positively influence the reduction in their respective error rates.

Physiology of Hyperuricemia and Urate-Lowering Treatments

“…Up to 20% of patients with gout develop kidney stones although stone formation may also occur in patients with normal urinary and serum levels of urate (reviewed in ( 147 )). MSU crystal deposits have been detected in the renal medulla of patients with gout and furthermore renal function has been shown to be improved after successful urate-lowering treatment in gout patients (reviewed in ( 150 )). This implies that the presence of MSU crystals in the kidneys and the associated inflammation may contribute to renal insufficiency.…”

“…Over the last decade, we have seen an accumulating body of evidence which implicates gout and/or uric acid elevation as an independent predictor for hypertension, atrial fibrillation and cardiovascular disease ( 150 , 155 , 168 – 171 ). However, clearly not all patients with hyperuricemia go on to develop cardiovascular disease and many of those who do also exhibit one or more other established risk factors.…”

“…This finding is supported by the observation that the nonsynonymous variant in SLC2A9 , rs16890979 (Val253Ile) is significantly associated both with a reduction in both uric acid and in blood pressure in an Amish cohort exposed to sodium-controlled diets ( 158 ). Finally, a number of studies have confirmed that people with elevated sUA are at risk of having high blood pressure, even if they otherwise appear to be perfectly healthy ( 152 , 176 ) and reviewed in Richette et al ( 150 ).…”

The Way from Renal Calcifications and Urinary Crystals to Kidney Stones: An Important Aspect in the Pathogenesis of Calcium Nephrolithiasis

“…Modern urological endoscopy which allows the inspection of the whole renal cavity showed that calcium oxalate and phosphate stones comprising about 80% of all concretions [8] generally start by a fixed growth on papillary calcifications, which were already described as potential source of nephrolithiasis in 1937 by Randall [9]. Recently much work was done to elucidate the pathogenesis of these calcifications being present either as interstitial deposits of calcium phosphate (Randall's plaques) or as intratubular accumulation of calcium oxalate crystals (Randall's plugs) [10][11][12].…”

“…Therefore, the question raises whether special crystallization conditions in urine might be responsible for stone formation by the apposition of new crystals on Randall's plaques and plugs. This question stimulated us to an intensive study of the formation and especially the AGN of calcium oxalate crystals being with 60% the most frequent stone compound [8]. Experiments were directly performed in urine where like in other biological mediums, crystals as well as Randall's plaques and plugs always are coated by proteins [14].…”