Abstract
BackgroundPatients with idiopathic calcium oxalate stones are advised to consume a low-oxalate diet to prevent recurrence. In this study, on patients with calcium oxalate stones we have attempted to determine the effect of calcium content of diet on the formation of calcium oxalate crystals in urine by in vitro supersaturation study of fresh postprandial urine samples and observing the morphology of the crystals formed using polarized optical microscopy.MethodsThe trial was conducted as a prospective interventional randomised crossover clinical trial in a repeated measures design. Sixty patients with calcium oxalate stones and no metabolic abnormalities in urine treated by lithotripsy at a tertiary care centre during the period May 2016 to May 2019 were recruited. Following a 14 h overnight fasting, urine samples were collected after providing the patient with either a low- or high-calcium meal for breakfast followed four hours later, by high-oxalate meal for lunch. Urine was tested for multiple parameters including urine pH, specific gravity, calcium/creatinine ratio and supersaturation of urine with sodium oxalate followed by optical density measurement by spectrophotometry and microscopic analysis of crystals formed.ResultsOptical density values and calcium/creatinine ratio of urine samples obtained after high-calcium meal are significantly higher than in corresponding sample obtained after low-calcium meal (p < 0.001). These findings were reflected in the morphology of formed crystals in their size, shape and number. When urinary calcium levels were low, no crystals were formed during supersaturation study of postprandial urine samples following a high-oxalate diet.ConclusionsHigh calcium content in diet significantly contributes to kidney stone formation. There is a lower risk of kidney stone formation with a low-calcium meal even on consumption of a high-oxalate diet.
Highlights
Patients with idiopathic calcium oxalate stones are advised to consume a low-oxalate diet to prevent recurrence
Gopala and Joe Afr J Urol (2021) 27:124 for preventing recurrence [6]. Such diets may be high in calcium content, and there is a strong correlation between intake of calcium and urinary calcium excretion, with one study reporting a mean urinary calcium increase in 55–72 mg associated with every 1000 mg increase in daily calcium [7]
Sixty patients in the age group between 19 and 60 years with calcium oxalate stones in the kidney or upper ureter who were evaluated for their stone and treated by extracorporeal shock wave lithotripsy (ESWL) in the urology department of our tertiary care hospital during the period May 2016 to May 2019 were recruited
Summary
Patients with idiopathic calcium oxalate stones are advised to consume a low-oxalate diet to prevent recurrence. Gopala and Joe Afr J Urol (2021) 27:124 for preventing recurrence [6]. Such diets may be high in calcium content, and there is a strong correlation between intake of calcium and urinary calcium excretion, with one study reporting a mean urinary calcium increase in 55–72 mg associated with every 1000 mg increase in daily calcium [7]. This study was conceptualized to determine whether the calcium content of diet can independently affect the tendency for stone formation in calcium oxalate stone formers
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