Wet vs. dry chemical analysis of renal stones

Microwave dielectric property based classification of renal calculi: Application of a kNN algorithm

The proper management of renal lithiasis presents a challenge, with the recurrence rate of the disease being as high as 46%. To prevent recurrence, the first step is the accurate categorization of the discarded renal calculi. Currently, the discarded renal calculi type is determined with the X-ray powder diffraction method which requires a cumbersome sample preparation. This work presents a new approach that can enable fast and accurate classification of discarded renal calculi with minimal sample preparation requirements. To do so, first, the measurements of the dielectric properties of naturally formed renal calculi are collected with the open-ended contact probe technique between 500 MHz and 6 GHz with 100 MHz intervals. Cole-Cole parameters are fitted to the measured dielectric properties with the generalized Newton-Raphson method. The renal calculi types are classified based on their Cole-Cole parameters as calcium oxalate, cystine, or struvite. The classification is performed using k-nearest neighbors (kNN) machine learning algorithm with the 10 nearest neighbors, where accuracy as high as 98.17% is achieved.

Biochemical composition of salivary stones in relation to stone- and patient-related factors

BACKGROUND

Salivary stones are calcified structures most often found in the main duct of the submandibular or parotid salivary gland. They contain of a core surrounded by laminated layers of organic and inorganic material.

MATERIAL AND METHODS

Submandibular and parotid sialoliths (n=155) were collected at the department of Oral and Maxillofacial surgery of a general hospital between February 1982 and September 2012. The weight of the sialoliths was determined and the consistency was subjectively classified. Subsequently, the biochemical composition of the stones was determined by wet chemical methods or FT-IR spectrometry. Age and gender of the patients were retrieved from their medical records. Data were statistically analyzed using Fisher's exact tests.

RESULTS

Sialoliths are mainly composed of inorganic material. Carbonate apatite was identified in 99% of the stones, phosphate in 88%, calcium in 87%, magnesium in 68%, struvite in 44%, oxalate in 38% and carbonate in 35%. Solid salivary stones contain more frequently struvite than stones with a soft consistency (p=0.05). Larger stones (>100mg) contain more frequently carbonate (p=0.05). Stones from older patients (≥38years) showed an almost significant trend towards more frequent presence of phosphate (p=0.083).

CONCLUSIONS

The biochemical composition of submandibular and parotid sialoliths is related to stone-related factors, probably to age but not to the gender of the patient.

The systematic classification of urinary stones combine-using FTIR and SEM-EDAX

BACKGROUND

To explore underlying mechanism of urinary stones formation, the composition and microstructure of urinary stones were analyzed systematically with a large sample study from China.

MATERIALS AND METHODS

A total of 2437 urinary stones were obtained from the urology department at our Hospital. The composition of the stones was analyzed by Fourier transform infrared spectroscopy (FTIR). Meanwhile, the microstructure and element distribution were observed with scanning electron microscopy combined with element distribution analysis (SEM-EDAX).

RESULTS

Urinary stones were classified into eight types, that were consisted of calcium oxalate stones (1301/2437, 53.39%), calcium phosphate stones (131/2437, 5.38%), anhydrous uric acid stones (434/2437, 17.81%), magnesium ammonium phosphate stones (12/2437, 0.49%), sodium urate stones (5/2437, 0.21%), brushite stones (4/2437, 0.16%), cystine stones (3/2437, 0.12%) and mixed stones (547/2437, 22.45%, ten subtypes were included). Under SEM, they displayed distinct microstructures: plank-like, brick-like, polyhedron or paliform crystals for calcium oxalate stones, similar sized echin-sphere or rough bulbiform or tree bark-like crystals for calcium phosphate stones, rotten-wood-like or petrous crystals for anhydrous uric acid stones, globular or gallet-like crystals for magnesium ammonium phosphate stones, sawdust-like crystals for sodium urate stones, broken-wood-like crystals for brushite stones, stacking hexagonal cystine crystals for cystine stones, and two or more of the above crystals for mixed stones. Meanwhile, they also presented distinct elemental composition and distribution by EDAX.

CONCLUSIONS

Urinary stones can be classified into eight types, and exhibit a diversity of microstructure and elemental compositions in China. The formation process of different types of urinary stones may be diverse.

Interpreting the results of chemical stone analysis in the era of modern stone analysis techniques

INTRODUCTION AND OBJECTIVE

Stone analysis should be performed in all first-time stone formers. The preferred analytical procedures are Fourier-transform infrared spectroscopy (FT-IR) or X-ray diffraction (XRD). However, due to limited resources, chemical analysis (CA) is still in use throughout the world. The aim of the study was to compare FT-IR and CA in well matched stone specimens and characterize the pros and cons of CA.

METHODS

In a prospective bi-center study, urinary stones were retrieved from 60 consecutive endoscopic procedures. In order to assure that identical stone samples were sent for analyses, the samples were analyzed initially by micro-computed tomography to assess uniformity of each specimen before submitted for FTIR and CA.

RESULTS

Overall, the results of CA did not match with the FTIR results in 56 % of the cases. In 16 % of the cases CA missed the major stone component and in 40 % the minor stone component. 37 of the 60 specimens contained CaOx as major component by FTIR, and CA reported major CaOx in 47/60, resulting in high sensitivity, but very poor specificity. CA was relatively accurate for UA and cystine. CA missed struvite and calcium phosphate as a major component in all cases. In mixed stones the sensitivity of CA for the minor component was poor, generally less than 50 %.

CONCLUSIONS

Urinary stone analysis using CA provides only limited data that should be interpreted carefully. Urinary stone analysis using CA is likely to result in clinically significant errors in its assessment of stone composition. Although the monetary costs of CA are relatively modest, this method does not provide the level of analytical specificity required for proper management of patients with metabolic stones.

FT-IR analysis of urinary stones: a helpful tool for clinician comparison with the chemical spot test

Background. Kidney stones are a common illness with multifactorial etiopathogenesis. The determination of crystalline and molecular composition and the quantification of all stone components are important to establish the etiology of stones disease but it is often laborious to obtain using the chemical method. The aim of this paper is to compare chemical spot test with FT-IR spectroscopy, for a possible introduction in our laboratory. Methods. We analyzed 48 calculi using Urinary Calculi Analysis kit in accordance with the manufacturer's instructions. The same samples were analyzed by FT-IR using the Perkin Elmer Spectrum One FT-IR Spectrometer. All FT-IR spectra of kidney stones were then computer matched against a library of spectra to generate a report on the various components. Results. On the basis of FT-IR analysis, the 48 calculi were divided into three groups: pure stone, mixed stone, and pure stone with substances in trace. Results of each group were compared with those obtained with chemical spot test. A general disagreement between methods was observed. Conclusions. According to our data, the introduction of the FT-IR technique in clinical chemistry laboratory may be more responsive to clinician expectations.