Abstract
A high fluid intake is still the most evidence-based measure for the prevention of idiopathic stone disease. The recommendation of current guidelines on urolithiasis to increase diuresis to 2–2.5 L/day is mainly based on a single clinical study. The present paper shows the influence of diuresis on calcium oxalate (CaOx) crystallization and especially aggregation (AGN) which can explain the initial development of Ca stones on papillary calcifications as well as stone growth in the renal pelvic system. Diuresis determines the urinary transit time (UT) through the kidney and together with the afflux of Ca and Ox the state of urinary saturation with respect to CaOx being the most frequent stone mineral. High supersaturation inducing crystallization during UT and a high urinary ion concentration interfering with the inhibition of crystal AGN by urinary macromolecules seem to be critical parameters for stone formation. Using data from the literature the influence of diuresis on these parameters is evaluated for short-term recurrent stone formers (RSF), idiopathic stone patients, and healthy controls, the latter two collectives with and without excessive oxalate ingestion. This investigation suggests that a diuresis of 2 L/day may protect from stone formation even after dietary Ox excesses and in RSF. However, in RSF with a continuously high Ca and Ox afflux into urine a permanent high diuresis is required which is difficult to sustain over 24 hours.
Highlights
Kidney stones are often accompanied by painful colic and can lead to severe renal damage or even loss of a kidney
In this paper we investigate the influence of diuresis on the formation and especially the aggregation of calcium oxalate (CaOx), this being with 60% the most frequent stone compound [6]
Kidney calcifications being an important source of stones are a frequent finding even without stone disease
Summary
Kidney stones are often accompanied by painful colic and can lead to severe renal damage or even loss of a kidney. To obtain comparable results Na concentration essential for ionic strength was always adapted to an identical value of 100 mM before performing crystallization tests Under this condition urine showed in 19 of 30 HC and in 10 of 30 SF inhibition of CaOx AGN (p< 0.05). At high IS the extension of electronegative surface potentials responsible for the inhibition of AGN is compressed to a few nanometers by the accumulation of cations like Na on particle surfaces [26] Under these conditions the Van der Waals forces despite their limited reach of action can overwhelm the electrostatic repulsion exerted by the identically charged UM coats of the crystals. The plaques consisted of HAP deposits within an osteopontin matrix whereas the adherent stone mainly contained CaOx crystals
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