Urinary tract calculi--a comparison of chemical and crystallographic analyses

Scanning electron microscopy in analysis of urinary stones

Urolithiasis is a frequent and in many cases serious disease. Proper analysis of kidney stone composition is crucial for appropriate treatment and prevention of disease recurrence. In this work, scanning electron microscopy (SEM) coupled with energy-dispersive spectroscopy was applied for a study of 30 samples covering the most common types of human kidney stones. The results are analyzed and evaluated in terms of applicability of the method for both routine kidney stone analysis as well as collecting of specific data. The method provides complex information about studied samples including morphology of the stones and of the present crystals or their aggregates. It also brings information on elemental composition of the phases. After application of standardization, quantitative microanalysis with detection limits of 400 ppm (Mg, P, S, Cl, K, Ca), 500 ppm (Na) and 1200 ppm (F) was obtained. Compositional mapping with EDS shows the elemental distribution within a sample. This study demonstrated that information on morphology and chemistry acquired by these methods was highly reliable for identification of phases, even when present in small amounts. It provided information on kidney stone structure, relationships between phases, major and minor element content, and variations in chemical composition related to the growth of the stones. SEM represents a powerful tool in urinary stone analysis, since a single facility can produce a wide spectrum of information. It can be suggested as a basic method used for routine urinary stone identification, whilst bringing additional detailed information that cannot be obtained by other methods.

Renal geology (quantitative renal stone analysis) by 'Fourier transform infrared spectroscopy'

AIM

To prospectively determine the precise stone composition (quantitative analysis) by using infrared spectroscopy in patients with urinary stone disease presenting to our clinic. To determine an ideal method for stone analysis suitable for use in a clinical setting.

METHODS

After routine and a detailed metabolic workup of all patients of urolithiasis, stone samples of 50 patients of urolithiasis satisfying the entry criteria were subjected to the Fourier transform infrared spectroscopic analysis after adequate sample homogenization at a single testing center.

RESULTS

Calcium oxalate monohydrate and dihydrate stone mixture was most commonly encountered in 35 (71%) followed by calcium phosphate, carbonate apatite, magnesium ammonium hexahydrate and xanthine stones.

CONCLUSIONS

Fourier transform infrared spectroscopy allows an accurate, reliable quantitative method of stone analysis. It also helps in maintaining a computerized large reference library. Knowledge of precise stone composition may allow the institution of appropriate prophylactic therapy despite the absence of any detectable metabolic abnormalities. This may prevent and or delay stone recurrence.

Urinary calculi: microbiological and crystallographic studies

Although referred to as "urinary calculus disease", the formation of stone in the urinary tract is not caused by a single etiological agent. As such, diverse clinical investigations to diagnose the cause of stone formation must be carried out and the course of management after diagnosis must inevitably be different in each case. This review will cover all aspects of calculus formation, but will give particular attention to calculi caused by infection of the urinary tract with urease-producing bacteria. This is a recurrent, potentially life-threatening disease which has led clinicians to refer to the condition as "stone cancer". Because the etiology of infection stones is so different from stones caused by metabolic disorders, the two disease patterns should be considered separately, a fact often overlooked in epidemiological studies of stone formation. The importance of analysis of calculi as an aid to management is thus emphasized; identification of stone type will help to indicate appropriate therapy. A review of methods of analysis will be covered, particularly crystallographic analysis. Inhibition of bacterial urease as a means of management of infection stones will be discussed together with problems encountered and brighter hopes for the future.

Reduction in urinary oxalate values by allopurinol

A variety of substances have been used to prevent recurrence of stone disease. Recently there has been considerable interest in the ability of allopurinol to prevent stone recurrence. This article discusses the effect of allopurinol on the urinary oxalate in a group of stone formers. A significant reduction was obtained especially in subjects in whom the blood urate levels exceeded 300 mumol./L. Possible mechanisms explaining the mode of action of the drug are discussed.