Albrecht Hesse

Oxalate degrading bacteria: new treatment option for patients with primary and secondary hyperoxaluria?

Current treatment options in patients with primary and secondary hyperoxaluria are limited and do not always lead to sufficient reduction in urinary oxalate excretion. Intestinal oxalate degrading bacteria are capable of degrading oxalate to CO2 and formate, the latter being further metabolized and excreted via the feces. It is speculated, that both endogenously produced, as well as dietary oxalate can be significantly removed via the intestinal tract. Oxalobacter formigenes, an obligate anaerobic microbe normally found in the intestinal tract has one oxalate degrading enzyme, oxalyl-CoA decarboxylase, which is also found in Bifidobacterium lactis. Other bacteria with possible oxalate degrading potency are lactic acid bacteria, as well as Enterococcus faecalis and Eubacterium lentum. However, specific therapeutic studies on humans are scarce and, except for Oxalobacter, data are not congruent. We found the oral application of Oxalobacter successful in patients with primary hyperoxaluria. However, long-term post-treatment follow-up of 1–2xa0years showed that constant intestinal colonization is not achieved in most patients. In one patient with constant colonization, urinary oxalate excretion normalized over time. Short-term studies with other bacteria such as lactic acid bacteria did not show a specific reduction in urinary oxalate excretion. O. formigenes might be a promising new therapeutic tool in patients with primary and secondary hyperoxaluria.

Absence of Oxalobacter Formigenes in Cystic Fibrosis Patients: A Risk Factor for Hyperoxaluria

Summary Background Patients with cystic fibrosis have an increased risk of hyperoxaluria, and of subsequent nephrocalcinosis and calcium-oxalate urolithiasis. Oxalate homoeostasis is controlled, in part, by the intestinal bacterium, Oxalobacter formigenes. The loss of this bacterium from the gut flora is associated with an increased risk of hyperoxaluria and calcium-oxalate urolithiasis. We investigated whether the absence of O formigenes and the presence of hyperoxaluria are correlated in cystic fibrosis (CF) patients. Methods Stool specimens from 43 patients with CF aged 3–9 years and from 21 similarly aged healthy volunteers were examined for O formigenes by culture and DNA analysis. At the same time, 24 h urine samples were collected and analysed for oxalate and other factors that promote or inhibit stone formation. Findings 15 (71%) of 21 healthy volunteers but only seven (16%) of 43 CF patients were colonised with O formigenes. Detection of O formigenes in six of these seven patients required DNA-based identification, suggesting low numbers of colony-forming units, and the CF patient with normal numbers of O formigenes was the only one of the 43 patients who had not been treated with antibiotics. All seven CF patients colonised with O formigenes had normal urinary oxalate levels, but 19 (53%) of 36 patients not colonised with O formigenes were hyperoxaluric, with the most severe hyperoxaluria occurring in young patients. Interpretation Absence of O formigenes from the intestinal tract of CF patients appears to lead to increased absorption of oxalate, thereby increasing the risk of hyperoxaluria and its complications (eg, nephrocalcinosis, urolithiasis). Prolonged widespread use of antibiotics, and alterations of the gastrointestinal tract that occur in CF, may induce a permanent decolonisation in CF patients.

Importance of Magnesium in Absorption and Excretion of Oxalate

Introduction: Magnesium treatment for calcium oxalate urolithiasis is discussed controversially. The aim of this study was to investigate the influence of magnesium supplementation on the oxalate absorption. Materials and Methods: The [13C2]oxalate absorption test was always performed three times in 6 healthy volunteers under standardized conditions, with one 10-mmol magnesium supplement together with the labeled oxalate and with two 10-mmol magnesium supplements given in 12-hour intervals. Results: The mean intestinal oxalate absorption under standard conditions was 8.6 ± 2.83%. The oxalate absorption with one 10-mmol magnesium supplement was 5.2 ± 1.40% and with two supplements 5.5 ± 1.62%. Both decreases were statistically significant relative to the standard test, however, not significantly different from each other. Conclusions: The results show that magnesium administration decreases the oxalate absorption, when magnesium is taken together with oxalate. However, magnesium administration does not decrease the oxalate absorption, when magnesium and oxalate intake differ by 12 h.

Automated Analysis of Urinary Stone Composition Using Raman Spectroscopy: Pilot Study for the Development of a Compact Portable System for Immediate Postoperative Ex Vivo Application

PURPOSEnWe evaluate a compact portable system for immediate automated postoperative exxa0vivo analysis of urinary stone composition using Raman spectroscopy. Analysis of urinary stone composition provides essential information for the treatment and metaphylaxis of urolithiasis. Currently infrared spectroscopy and x-ray diffraction are used for urinary stone analysis. However, these methods may require complex sample preparation and costly laboratory equipment. In contrast, Raman spectrometers could be a simple and quick strategy for immediate stone analysis.nnnMATERIALS AND METHODSnPure samples of 9 stone components and 159 human urinary calculi were analyzed by Raman spectroscopy using a microscope coupled system at 2 excitation wavelengths. Signal-to-noise ratio, peak positions and the distinctness of the acquired Raman spectra were analyzed and compared. Background fluorescence was removed mathematically. Corrected Raman spectra were used as a reference library for automated classification of native human urinary stones (50). The results were then compared to standard infrared spectroscopy.nnnRESULTSnSignal-to-noise ratio was superior at an excitation wavelength of 532xa0nm. An automated, computer based classifier was capable of matching spectra from patient samples with those of pure stone components. Consecutive analysis of 50 human stones demonstrated 100% sensitivity and specificity compared to infrared spectroscopy (for components with more than 25% of total composition).nnnCONCLUSIONSnOur pilot study indicates that Raman spectroscopy is a valid and reliable technique for determining urinary stone composition. Thus, we propose that the development of a compact and portable system based on Raman spectroscopy for immediate, postoperative stone analysis could represent an invaluable tool for the metaphylaxis of urolithiasis.

A new type of artificial urinary calculi: in vitro study by spiral CT.

Bachmann R, Heimbach D, Kersjes W, et al. A new type of artificial urinary calculi: In vitro study by spiral CT. Invest Radiol 2000;35:672–675. RATIONALE AND OBJECTIVES.Artificial urinary calculi similar to natural stones have long been sought in urologic research. In an experimental study, the authors assessed the CT characteristics of a new type of artificially produced urinary calculus [BON(N)-STONE]. METHODS.Six different types of urinary calculi (uric acid, struvite, cystine, calcium oxalate, brushite, and apatite) were produced by a coating technique in which several layers of a suspension of pure substance were applied around a core and dried. A total of 60 stones (10 per group) were studied by spiral CT at two energy levels (100 and 120 kV, 250 mA) with 1-mm slice thickness. RESULTS.All calculi showed a small hyperdense core surrounded by a homogeneous matrix and a slightly hyperdense outer rim. From the least to the most dense, the stone types were uric acid, struvite, cystine, calcium oxalate, brushite, and apatite. Absolute CT values at 100 and 120 kV could differentiate between all groups of stones at a significance level of P < 0.001 or better. Attenuation values were in a comparable range to reported values for natural stones, with the exception of uric acid and struvite, which were notably lower. CONCLUSION.These artificially produced urinary calculi showed properties similar to those of natural stones. Thus, this seems to be a promising stone model for further investigations.

Is in vivo analysis of urinary stone composition feasible? Evaluation of an experimental setup of a Raman system coupled to commercial lithotripsy laser fibers.

PurposeRaman spectroscopy allows immediate analysis of stone composition. In vivo stone analysis during endoscopic treatment may offer advantages concerning surgical strategy and metaphylaxis. Urinary stone components were evaluated utilizing an experimental setup of a Raman system coupled to commercial laser fibers.MethodsSamples of paracetamol (acetaminophen) and human urinary stones with known Raman spectra were analyzed using an experimental Raman system coupled to common commercial lithotripsy laser fibers (200 and 940xa0µm). Two different excitation lasers were used at wavelengths of 532 and 785xa0nm. Numerical aperture of the fibers, proportion of reflected light reaching the CCD chip, and integration times were calculated. Mathematical signal correction was performed.ResultsBoth the laser beam profile and the quality of light reflected by the specimens were impaired significantly when used with commercial fibers. Acquired spectra could no longer be assigned to a specific stone composition. Subsequent measurements revealed a strong intrinsic fluorescence of the fibers and poor light acquisition properties leading to a significant decrease in the Raman signal in comparison with a free-beam setup. This was true for both investigated fiber diameters and both wavelengths. Microscopic examination showed highly irregular fiber tip surfaces (both new and used fibers).ConclusionsOur results propose that laser excitation and light acquisition properties of commercial lithotripsy fibers impair detectable Raman signals significantly in a fiber-coupled setting. This study provides essential physical and technological information for the development of an advanced fiber-coupled system able to be used for immediate stone analysis during endoscopic stone therapy.

Trace Elements in Urolithiasis

Trace elements are essential substances, whose content in the human tissue is less than 50 ppm (50 mg/kg). These elements, such as zinc, copper, nickel, iron, and strontium, are able to form poorly soluble salts with oxalate and phosphate ions. No pure urinary stones consisting of these compounds are known so far. However, the incorporation of zinc phosphate (hopeite) in layers in a struvite stone has been described. Organic stones, such as uric acid, contain only small amounts of trace elements. Compared to calcium oxalates, the concentration of zinc and other trace elements is higher in calcium phosphate stones. Trace elements can contribute to the stabilization of calcium oxalate dihydrate (weddellite), an unstable compound. The disintegration of calcium oxalate monohydrate (whewellite) by shock wave lithotripsy (SWL) is supposed to be improved by the incorporation of trace elements. An incorporation of trace element compounds in layers or also the replacement of calcium in the crystal lattice of whewellite can be responsible for this effect. In conclusion, depending on the stone type and according to their occurrence in urine, trace elements are incorporated into a urinary stone and can affect its properties.

Comparative Costs of Various Treatment Strategies and Preventive Measures

The impact of urolithiasis as an economic factor in health care systems is steadily increasing. Replacement of open surgery with noninvasive and minimally invasive techniques (i.e., ESWL, PCNL, and URS) for the treatment of stones of different sizes and locations has greatly reduced morbidity and the period of hospitalization. Although ESWL, PCNL, and URS are effective treatment options, direct and indirect costs are substantial. Moreover, severe complications and recurrences may occur with varying frequency. Specific metaphylactic measures, including metabolic evaluation, dietary, and drug therapy, have been demonstrated to be cost-effective and efficacious.

Validating automated kidney stone volumetry in computed tomography and mathematical correlation with estimated stone volume based on diameter

OBJECTIVESnTo validate AutoMated UroLithiasis Evaluation Tool (AMULET) software for kidney stone volumetry and compare its performance to standard clinical practice.nnnMATERIALS AND METHODSnMaximum diameter and volume of 96 urinary stones were measured as reference standard by three independent urologists. The same stones were positioned in an anthropomorphic phantom and CT scans acquired in standard settings. Three independent radiologists blinded to the reference values took manual measurements of the maximum diameter and automatic measurements of maximum diameter and volume. An expected volume was calculated based on manual diameter measurements using the formula: [Formula: see text] Results: Ninety-six stones were analyzed in the study. We had initially aimed to assess 100. Nine were replaced during data acquisition due of crumbling and four had to be excluded because the automated measurement did not work. Mean reference maximum diameter was 13.3u2009mm (5.2-32.1u2009mm). Correlation coefficients among all measured outcomes were compared. The correlation between the manual and automatic diameter measurements to the reference was 0.98 and 0.91, respectively (pu2009<u20090.001). Mean reference volume was 1200u2009mm3 (10-9000u2009mm3). The correlation between the expected volume and automatically measured volume to the reference was 0.95 and 0.99, respectively (pu2009<u20090.001).nnnCONCLUSIONSnPatients kidney stone burden is usually assessed according to maximum diameter. However, as most stones are not spherical, this entails a potential bias. Automated stone volumetry is possible and significantly more accurate than diameter-based volumetric calculations. To avoid bias in clinical trials, size should be measured as volume. However, automated diameter measurements are not as accurate as manual measurements.Abstract Objectives: To validate AutoMated UroLithiasis Evaluation Tool (AMULET) software for kidney stone volumetry and compare its performance to standard clinical practice. Materials and Methods: Maximum diameter and volume of 96 urinary stones were measured as reference standard by three independent urologists. The same stones were positioned in an anthropomorphic phantom and CT scans acquired in standard settings. Three independent radiologists blinded to the reference values took manual measurements of the maximum diameter and automatic measurements of maximum diameter and volume. An “expected volume” was calculated based on manual diameter measurements using the formula: documentclass{aastex}usepackage{amsbsy}usepackage{amsfonts}usepackage{amssymb}usepackage{bm}usepackage{mathrsfs}usepackage{pifont}usepackage{stmaryrd}usepackage{textcomp}usepackage{portland, xspace}usepackage{amsmath, amsxtra}usepackage{upgreek}pagestyle{empty}DeclareMathSizes{10}{9}{7}{6}begin{document}