Alkaline Water: Help or Hype for Uric Acid and Cystine Urolithiasis?

PURPOSE: The consumption of alkaline water, water with an average pH of 8 to 10, has been steadily increasing globally as proponents claim it to be a healthier alternative to regular water. Urinary alkalinization therapy is frequently prescribed in patients with uric acid and cystine urolithiasis, and as such we analyzed commercially available alkaline waters to assess their potential to increase urinary pH. MATERIALS AND METHODS: Five commercially available alkaline water brands (Essentia, Smart Water Alkaline, Great Value Hydrate Alkaline Water, Body Armor SportWater, and Perfect Hydration) underwent anion chromatography and direct chemical measurements to determine the mineral contents of each product. The alkaline content of each bottle of water was then compared to that of potassium citrate (the gold standard for urinary alkalinization) as well as to other beverages and supplements used to augment urinary citrate and/or the urine pH. RESULTS: The pH levels of the bottled alkaline water ranged from 9.69 to 10.15. Electrolyte content was minimal, and the physiologic alkali content was below 1 mEq/L for all brands of alkaline water. The alkali content of alkaline water is minimal when compared to common stone treatment alternatives such as potassium citrate. In addition, several organic beverages, synthetic beverages, and other supplements contain more alkali content than alkaline water, and can achieve the AUA and European Association of Urology alkali recommendation of 30 to 60 mEq per day with ≤ 3 servings/d. CONCLUSIONS: Commercially available alkaline water has negligible alkali content and thus provides no added benefit over tap water for patients with uric acid and cystine urolithiasis.

[Dissolution of uric acid stones in the ureter].

INTRODUCTION: Uric acid stones (UA), consisting of uric acid/uric acid dihydrate, occur in 6.1-15.1% of all cases of urolithiasis in industrialized countries. At the same time, the frequency of these stones is directly dependent on age. Thus, the incidence of UA reaches 40% in men over 80 years of age and 27.3% in women over 90 years of age. UA are the only stones that are amenable to dissolution therapy with the use of citrate salts that alkalinize urine pH. A number of authors and European Association of Urology guidelines consider stone dissolution as a first-line therapy in the treatment of patients with UA, both as monotherapy and in combination with surgical procedures. MATERIALS AND METHODS: The results of conservative treatment of 86 patients aged 28 to 78 years with radiolucent ureteral stones ranging in size from 3 to 25 mm and a density of 133 to 728 HU, who underwent 89 courses of stone dissolution therapy from 2011 to 2018, are presented in the article. They had no obstruction or were prestented. There were 52 men (n=55 courses) and 34 women (n=34 courses). RESULTS: In 78 out of 89 clinical cases (87.6%), stone-free status was obtained within 14 to 181 days. Most often the duration of therapy was 30 days. In 11 (12.4%) cases the treatment was considered ineffective. However, only in 4 (4.5%) patients the stone size did not change, while in 7 (7.9%) cases it decreased. The results of the study suggest the high efficiency of citrate therapy in patients with ureteral stones in case of unobstructed urine outflow (including those with stents), which is comparable to surgical treatment.

The role of third-generation dual-source dual-energy computed tomography in characterizing the composition of renal stones with infrared spectroscopy as the reference standard.

Purpose: The aim of our study was to prospectively evaluate the role of third-generation, dual-source, dual-energy computed tomography (DECT) in the characterization of renal calculi, with ex vivo renal stone evaluation using Fourier transform infrared spectroscopy (IS) as the reference standard. Material and methods: In our study 50 patients with history suggestive of renal calculi were subjected to DECT using 100 kVp and Sn150 kVp. With DECT, renal stone attenuation at low and high kVp was attained, and the attenuation ratios were measured. The result of DECT was compared with IS to identify the chemical composition of the extracted renal stones. IBM SPSS version 22 was used for statistical analysis. Results: In our study, the mean attenuation ratio of the renal stone was 1.57 ± 0.25. Out of 50 patients, the stones of 39 patients were predicted as calcium-containing stones, in 4 patients as cystine stones, and in 7 as uric acid stones on DECT. In IS analysis, 43 patients had calcium-containing stones, and 7 patients had uric acid stones. The accuracy rate of DECT for detecting calcium and uric acid stones in our study were 90% and 100%, respectively. The positive predictive value for the DECT to assess the chemical composition of renal calculi was found to be 92%. Conclusions: Third-generation DECT scan had 100% accuracy in differentiating uric acid stones from non-uric acid stones in our study. Because the treatment is different for different chemical compositions of stones, identification of specific chemical components is very important, and it can be accurately done by DECT.

Targeted renal knockdown of Na+/H+ exchanger regulatory factor Sip1 produces uric acid nephrolithiasis in Drosophila.

Nephrolithiasis is one of the most common kidney diseases, with poorly understood pathophysiology, but experimental study has been hindered by lack of experimentally tractable models. Drosophila melanogaster is a useful model organism for renal diseases because of genetic and functional similarities of Malpighian (renal) tubules with the human kidney. Here, we demonstrated function of the sex-determining region Y protein-interacting protein-1 (Sip1) gene, an ortholog of human Na+/H+ exchanger regulatory factor (NHERF1), in Drosophila Malpighian tubules and its impact on nephrolithiasis. Abundant birefringent calculi were observed in Sip1 mutant flies, and the phenotype was also observed in renal stellate cell-specific RNA interference Sip1 knockdown in otherwise normal flies, confirming a renal etiology. This phenotype was abolished in rosy mutant flies (which model human xanthinuria) and by the xanthine oxidase inhibitor allopurinol, suggesting that the calculi were of uric acid. This was confirmed by direct biochemical assay for urate. Stones rapidly dissolved when the tubule was bathed in alkaline media, suggesting that Sip1 knockdown was acidifying the tubule. SIP1 was shown to collocate with Na+/H+ exchanger isoform 2 (NHE2) and with moesin in stellate cells. Knockdown of NHE2 specifically to the stellate cells also increased renal uric acid stone formation, and so a model was developed in which SIP1 normally regulates NHE2 activity and luminal pH, ultimately leading to uric acid stone formation. Drosophila renal tubules may thus offer a useful model for urate nephrolithiasis.

Systemic analysis of urinary stones from the Northern, Eastern, Central, Southern and Southwest China by a multi-center study.

BACKGROUND: To provide some basis for the prevention of urinary stones in general population, we did a systemic analysis of urinary stones from Northern, Eastern, Central, Southern and Southwest China by a multi-center study. METHODS: A total of 11,157 urinary stones from Northern, Eastern, Central, Southern and Southwest China were obtained and analyzed by Fourier transform infrared spectroscopy. Combined with scanning electron microscopy and X-ray energy spectrometer, urinary stones were classified into different types. Furthermore, the correlation between stone types and clinical characteristics, as well as their regional distribution were elucidated. RESULTS: Calcium oxalate stones were the most common type in each region, followed by calcium oxalate-calcium phosphate mixed stones, uric acid stones and calcium phosphate stones. The distribution of calcium oxalate stones were highest prevalence in Southwest China (67.9%, P < 0.05), followed by Eastern and Northern China. Anhydrous uric acid stones, with a constituent ratio of 19.3% in Southern China, and 13.7% in Central China, were significantly higher than that in other regions (P < 0.05). Elements analysis indicated varieties among stone types as well as distribution regions. Moreover, the clinical characteristics were highly correlated with stone types and anatomical locations but not their distribution regions. CONCLUSIONS: The material and elements composition of urinary stones among different regions showed some varieties. Calcium oxalate stone has the highest constituent ratio in Southwest China, while anhydrous uric acid stone has the highest constituent ratio in Southern China. Moreover, the clinical characteristics were highly correlated with stone types and anatomical locations but not their distribution regions.

Uric acid stones, clinical manifestations and therapeutic considerations.

Uric acid stones account for 10%-15% of all urinary stones. Changes in dietary habits, environment or both can result in the increase of uric acid stones. The formation of uric acid stones is related to hyperuricosuria, low urinary volume and persistently low urinary pH. Diabetes and obesity also significantly increase the risk of stone formation. Dual-energy CT provides a convenient and reliable method for diagnosis. Stone composition analysis and 24-hour urine metabolic evaluations should be considered for further evaluation. Most small uric acid stones (diameter <2 cm) can be treated by pharmacotherapy or extracorporeal shock wave lithotripsy. However, ureteroscopy and other minimally invasive procedures should be reserved for larger stones (diameter ≥2 cm), or patients with concomitant urinary tract obstruction and/or infections. Additionally, adjustment of potential pathophysiologic defects by pharmacotherapy and dietary modification is strongly recommended for the prevention of uric stone recurrence.

Dual energy can accurately differentiate uric acid-containing urinary calculi from calcium stones.

PURPOSE: To retrospectively evaluate the accuracy of dual-energy CT (DECT) in the detection of the chemical composition of urinary calculi in correlation with infrared spectroscopic stone analysis. METHODS: We reviewed the CT scans of 255 patients who underwent DECT due to a clinical suspicion of urolithiasis. Out of this group, we included 64 patients with clinically symptomatic urolithiasis requiring stone removal. After surgical removal of the stone by ureterorenoscopy, chemical composition was analyzed with infrared spectroscopy. We correlated DECT stone characterization results with chemical stone composition based on dual-energy indices (DEI). A total of 213 renal and ureteral stones could be removed and chemically analyzed. RESULTS: A total of 213 calculi were evaluated. Thirty eight out of sixty four (59 %) patients had >1 stone. DECT was used to differentiate stones by using DEI. Stones harboring calcium (CA) were color-coded in blue, while stones containing uric acid (UA) were colored red. Median DEI in UA-containing stones were 0.001. Non-UA-containing stones had a DEI between 0.073 for pure CA stones and 0.077 containing CA and other substances (p = 0.001; p = 0.03, respectively). Sensitivity of DECT was 98.4 % for differentiation of UA from non-UA-containing calculi. Specificity was 98.1 %. Mean effective radiation dose of DECT was 4.18 mSv (0.44-14.27 mSv), thus comparable to conventional CT scans of the abdomen. Conventional measurement of Hounsfield units did not correlate with stone composition. CONCLUSION: DECT with image post-processing reliably discriminates UA-containing calculi from all other stones, but the study offered limitations. Discrimination within the non-UA stones cannot be reliably achieved but is clinically insignificant.

Radiation Dose Reduction in Dual-Energy CT: Does It Affect the Accuracy of Urinary Stone Characterization?

OBJECTIVE: The purpose of this article is to assess the effect of radiation dose reduction in dual-energy CT (DECT) on the performance of renal stone characterization using a patient cohort. MATERIALS AND METHODS: CT data from 39 unenhanced DECT examinations performed for stone characterization were retrospectively analyzed in this study. Reduced-dose images were simulated at 75%, 50%, and 25% of the routine dose using a previously validated noise-insertion algorithm. Differentiation between uric acid (UA) and non-UA stones was performed using a fixed cutoff value for the dual-energy ratio. ROC analysis was performed to determine optimal cutoff values and the associated sensitivity and specificity. RESULTS: Of the 206 stones found, 43 were UA and 163 were non-UA. The mean (± SD) volume CT dose index (CTDIvol) was 16.0 ± 4.0 mGy at the 100% dose level. The mean noise in 100-kV images increased from 40.9 ± 6.8 HU at 100% dose to 46.8 ± 8.8 HU, 57.7 ± 12.5 HU, and 85.4 ± 22.9 HU at 75%, 50%, and 25% dose levels, respectively. Using the default cutoff value, for stones 10 mm(3) or larger, the sensitivity/specificity were 100.0%/98.8%, 82.8%/98.8%, and 89.3%/98.7%, at 75%, 50%, and 25% dose levels, respectively. ROC analysis showed varying optimal cutoff values at different dose levels. The sensitivity and specificity improved with use of these optimal cutoff values. Differentiation capability decreased for stones smaller than 10 mm(3). CONCLUSION: At 75% of the 16-mGy routine dose, the sensitivity and specificity for differentiating UA from non-UA stones were minimally affected for stones 10 mm(3) or larger. The use of optimal cutoff values for dual-energy ratio as dose decreased (and noise increased) provided improved performance.

Protein Intake and High Uric Acid Stone Risk.

Rationale & Objective: We evaluated the metabolic differences between pure and impure uric acid stone formers in this retrospective study of uric acid kidney stone formers diagnosed between 1996 and 2021. Study Design: Demographics and medical history were compared by χ2 tests. Twenty-four-hour urine chemistries were compared using logistic regressions while controlling for demographics and comorbid conditions. Setting & Participants: Patients from Yale Urology and Nephrology Clinics with a documented kidney stone analysis containing uric acid were included. In total, 4,294 kidney stone formers had a stone analysis, and 722 (16.8%) contained uric acid. Patients with all stone analyses  ≥ 50% uric acid were allocated to the pure group, while patients with ≥1 stone analysis <50% uric acid were allocated to the impure group. Results: Among kidney stone formers, the prevalence of uric acid nephrolithiasis was 16.8%. Pure uric acid stone formers were more likely to be older, heavier, and were 1.5 times more likely to have chronic kidney disease. When controlling for age, sex, race, ethnicity, and body mass index, pure uric acid stone formers had lower urinary pH and lower urine citrate normalized for creatinine. Additionally, they had a higher protein catabolic rate, urine urea nitrogen, and urine sulfur normalized for creatinine, all markers of dietary protein intake. These findings persisted after controlling for chronic kidney disease. Limitations: This is a retrospective study from a single center. Conclusions: Pure uric acid stone formation is more common with diminished kidney function; however, after controlling for kidney function, pure uric acid stone formation is associated with protein intake, suggesting that modifying protein intake may reduce risk.

Gas formation during chemolysis.

Uric acid stones account for approximately 10 % of renal stone disease. These are the only crystals that can be managed with an oral treatment called chemolysis. Chemolysis also known chemolitholysis was first described in the late 60's, but was accepted as a medical treatment for uric acid stone disease in mid 80's. During this process, depending on the stone burden, CO2 can sometimes be produced, resulting in gas formation.

The effect of calcium oxalate stones and uric acid stones on male sexual function.

PURPOSE: This study compared the effects of calcium oxalate stones and uric acid stones on male sexual function. METHODS: We enrolled 100 patients with ureteral stones. According to the composition of the stones, they were divided into the calcium oxalate stone group and the uric acid stone group. All patients underwent ureteroscopic holmium laser lithotripsy. General data such as age, body mass index, course of disease, stone diameter, and degree of renal hydronephrosis were compared. Sperm parameters, including sperm density, sperm viability, and sperm deformity rate, as well as International Index of Erectile Function-5 questionnaire (IIEF-5) scores, and Quality of Life (QOL) scores, were measured and compared before and 6 weeks after the surgery. RESULTS: There were no statistically significant differences in general data and sperm parameters between the two groups before the surgery (P > 0.05). However, there were significantly lower IIEF scores but significantly higher QOL scores in the uric acid stone group. In the calcium oxalate stone group, there were no statistically significant differences in sperm parameters, IIEF score, and QOL score before and after the surgery (P > 0.05). In the uric acid stone group, there were no statistically significant differences in sperm parameters before and after surgery (P > 0.05), whereas there were significantly higher IIEF scores but significantly lower QOL scores after the surgery (P < 0.05). The prevalence of erectile dysfunction (ED) in the uric acid stone group was 38.18% (21/55), which was significantly higher compared to 20.00% (9/45) in the calcium oxalate stone group (P < 0.05). The multivariate binary logistic regression analysis showed that the independent risk factor related to ED was uric acid stones (odds ratio: 2.637, 95% confidence interval 1.040-6.689, P = 0.041). No statistically significant differences were found in sperm parameters between patients with and without ED. CONCLUSION: Compared with the calcium oxalate stone group, patients with uric acid stones had a higher prevalence of ED and poorer sexual performance.

A combined model based on CT radiomics and clinical variables to predict uric acid calculi which have a good accuracy.

The aim of this study was to develop a CT-based radiomics and clinical variable diagnostic model for the preoperative prediction of uric acid calculi. In this retrospective study, 370 patients with urolithiasis who underwent preoperative urinary CT scans were enrolled. The CT images of each patient were manually segmented, and radiomics features were extracted. Sixteen radiomics features were selected by one-way analysis of variance (ANOVA) and least absolute shrinkage and selection operator (LASSO). Logistic regression (LR), random forest (RF) and support vector machine (SVM) were used to model the selected features, and the model with the best performance was selected. Multivariate logistic regression was used to screen out significant clinical variables, and the radiomics features and clinical variables were combined to construct a nomogram model. The area under the receiver operating characteristic (ROC) curve (AUC), etc., were used to evaluate the diagnostic performance of the model. Among the three machine learning models, the LR model had the best performance and good robustness of the dataset. Therefore, the LR model was used to construct the nomogram. The AUCs of the nomogram model in the training set and validation set were 0.878 and 0.867, respectively, which were significantly higher than those of the radiomics model and the clinical feature model. The CT-based radiomics model based has good performance in distinguishing uric acid stones from nonuric acid stones, and the nomogram model has the best diagnostic performance among the three models. This model can provide an effective reference for clinical decision-making.

Comprehensive Nomogram for Prediction of the Uric Acid Composition of Ureteral Stones as a Part of Tailored Stone Therapy.

BACKGROUND: Oral chemolitholysis is a noninvasive therapy for uric acid (UA) stones. Proper patient selection is crucial for success of the therapy. OBJECTIVE: To develop a nomogram for prediction of UA stones using parameters gathered during emergency work-up for flank pain. DESIGN, SETTING, AND PARTICIPANTS: A single-center cohort (459 patients) with singular ureteral stones and available stone analysis was retrospectively reviewed for radiological, urinary, and serological findings indicating UA stones. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: A Mann-Whitney U test or Kruskal-Wallis test was applied for univariate analysis. Categorical variables were compared using a χ2 test. Binary logistic regression of significant parameters was performed to design the nomogram. RESULTS AND LIMITATIONS: Univariate analysis revealed statistically significant differences in parameters between predominantly UA and non-UA groups, including median age (60 yr, interquartile range [IQR] 51.5-70.5 vs 51 yr, IQR 39-62; p < 0.001), body mass index (30.0 kg/m2, IQR 27.25-35.0 vs 26.6 kg/m2, IQR 24.0-30.467; p < 0.001), stone density (435.0 HU, IQR 329.0-528.0 vs 750.0 HU, IQR 548.0-995.0; p < 0.001), serum UA (437.5 µmol/l, IQR 374.25-478.0 vs 321.0 µmol/l, IQR 273.0-377.0; p < 0.001), and urine pH (5.5, IQR 5.0-5.5 vs 6.0, IQR 5.5-6.5; p < 0.001). Radiolucency was more frequent in the predominantly UA group (88.60% vs 32.70%; p < 0.001). Multivariate binary logistic regression confirmed age, body mass index, stone density, serum UA, urine pH, and radiolucency as independent predictors of UA stones and these parameters were used to design the nomogram. CONCLUSIONS: We present a nomogram for the prediction of uric acid stones. PATIENT SUMMARY: We developed a nomogram as a simple tool with potential to be useful in patient counseling regarding chemolitholysis as a tailored stone treatment for uric acid urinary stones.

Introduction of a Standardized Approach of Electronic Urinary pH Monitoring to Assist Alkalization Therapy: A Uric Acid Urolithiasis Patient's Perspective.

Introduction: This study evaluates the introduction of an electronic pH meter to measure the urinary pH in patients with uric acid (UA) urolithiasis and assess patient's perspective. Materials and Methods: Patients known with UA urolithiasis were included in this single-center, nonrandomized, prospective feasibility study, IDEAL stage 2a. Their experience with urolithiasis and satisfaction with the method of urinary pH monitoring before inclusion was evaluated. All patients received an electronic pH meter and standardized instructions. After a period of 6-12 weeks their experience and satisfaction with this pH meter and new regimen was assessed. Patient satisfaction was scored on a Likert scale 1-5. Results: Eighteen patients were included. Median age was 63 years and median body mass index was 30 kg/m2. The cohort consisted of 67% men and 33% women. In their medical history, 55% had unilateral stones, whereas 45% had bilateral stones. The median estimated glomerular filtration rate was 58 mL/minute/1.73 m2. Eighty-nine percent took medication to alkalize their urine, median 3.5 years. Fifteen patients used paper reagent strips and three used an electronic pH meter to assess urinary pH before this study. Satisfaction with the method of urinary pH measurement at inclusion was reasonable (median score 3; interquartile range [IQR] 1-4). Satisfaction with the new electronic pH meter was good (median score 4; IQR 3-5), as was the overall satisfaction (median score 4; IQR 3-5). The new electronic pH meter was slightly easier to use (median 3.5; IQR 1.75-5), as easy in maintenance (median 3; IQR 2-4), and significantly easier to read (median 5; IQR 4-5). The new electronic pH meter was better (median score 4; IQR 2.75-5) than their previous method. Conclusion: The introduction of a standardized approach of urinary pH monitoring for UA urolithiasis patients with an electronic pH meter leads to an easier interpretable outcome and higher patient satisfaction.

Influence of Age and Geography on Chemical Composition of 98043 Urinary Stones from the USA.

BACKGROUND: Urolithiasis is a growing issue globally, but it is heterogeneous, with a different epidemiology and pathophysiology for each different stone composition. OBJECTIVE: The purpose of this study is to describe the incidence of urinary stones in the USA from 2016 to 2019 by chemical composition and to investigate the influence of age and geography on these stone types. DESIGN SETTING AND PARTICIPANTS: We obtained compositional analyses for all urinary stones submitted to a national laboratory over an approximately 3-yr period. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: Data collected included the chemical constituents of a stone, patient age, and geographical origin. We describe the incidence of each stone type by frequency. Statistical testing was performed to determine the influence of age and geographical region on overall incidence of each stone composition. RESULTS AND LIMITATIONS: In total, 99 908 specimens were analyzed. When pure stones were ordered by frequency, we found that the most common stone type was calcium oxalate (CaOx) (79.2%), followed by uric acid (UA; 14.3%), calcium phosphate (CaPO4; 3.7%), cystine (0.51%), drug induced (0.12%), and magnesium ammonium phosphate (0.04%). CaOx, UA, and CaPO4 were often mixed with one another. Among CaOx stones, the plurality (28.0%) was made of pure calcium oxalate monohydrate (COM), and only 0.002% was pure calcium oxalate dihydrate. There was an overall association between stone composition and both geographical distribution and age (p < 0.001). CONCLUSIONS: CaOx stones comprise the majority of urinary stones in the USA, of which almost 28% were pure COM. Additionally, age and geographical region are significantly associated with variations in stone composition. PATIENT SUMMARY: We evaluated the incidence of urinary stones in the USA based on their chemical composition. The most common stone type was calcium oxalate, the majority of which was pure calcium oxalate monohydrate. We also found age and geographical region to be significantly associated with variations in stone composition.

Uric acid nephrolithiasis: An update.

Uric acid nephrolithiasis appears to increase in prevalence. While a relationship between uric acid stones and low urinary pH has been for long known, additional association with various metabolic conditions and pathophysiological basis has recently been elucidated. Some conditions such as diabetes and metabolic syndrome disease, excessive dietary intake, and increased endogenous uric acid production and/or defect in ammoniagenesis are associated with low urinary pH. In addition, the phenomenon of global warming could result in an increase in areas with greater climate risk for uric acid stone formation. There are three therapeutic steps to be taken for management of uric acid stones: identification of urinary pH profiles, assessment of urinary volume status, and identification of disorders leading to excessive uric acid production. However, the most important factor for uric acid stone formation is acid urinary pH, which is a prerequisite for uric acid precipitation. This article reviews recent insights into the pathophysiology of uric acid stones and their management.

Kidney stones diseases and glycaemic statuses: focus on the latest clinical evidences.

Diabetes and obesity are already recognized as potential risk factors for nephrolithiasis, especially for uric acid stones. Insulin resistance and hyperinsulinemia actively contribute to impaired ability to excrete an acid load and altered ammonium production, leading to a lower urinary pH compared to non-diabetic controls. All these electrolytic disorders play an important role in stone formation and aggregation, especially in uric acid stones. There are still missing points in scientific evidence if the increased risk in stone formation is already existing even in the prediabetic statuses (isolated impaired glucose tolerance, isolated impaired fasting glucose, and associated impaired glucose tolerance/impaired fasting glucose) as well as it is worth to consider the same level of risk. Urolithiasis is the most frequent urological cause of hospitalization in diabetic patients and its cost is usually higher compared to non-diabetic patients, but less is known in others altered glycaemic diseases. The aim of this review article is to focus on the association between stone formation and altered glycaemic statuses, beyond the already known link between nephrolithiasis and diabetes mellitus.

Epidemiology, pathophysiology, and management of uric acid urolithiasis: A narrative review.

An in-depth comprehension of the epidemiology as well as pathophysiology of uric acid urolithiasis is important for the identification, treatment, and prophylaxis of calculi in these patients. Persistently low urinary pH, hyperuricosuria, and low urinary volume are the most important factors in pathogenesis of uric acid urolithiasis. Other various causes of calculus formation comprises of chronic diarrhea, renal hyperuricosuria, insulin resistance, primary gout, extra purine in the diet, neoplastic syndromes, and congenital hyperuricemia. Non-contrast-enhanced computed tomography is the radiologic modality of choice for early assessment of patients with renal colic. Excluding situations where there is acute obstruction, rising blood chemistry, severe infection, or unresolved pain, the initial management ought to be medical dissolution by oral chemolysis since this method has proved to be effective in most of the cases.

Type 2 diabetes mellitus and renal stones.

BACKGROUND: The incidence of urinary stone disease has shown a steep rise in recent decades along with marked modifications in dietary habits and life- style. There has been an increased prevalence of urinary stone disease in patients with diabetes. We took up this study to determine the association of diabetes mellitus with kidney stones in patients undergoing surgical treatment. MATERIALS AND METHODS: Patients presenting with renal stones for surgical management formed the study group. Body mass index (BMI) was calculated by noting the weight and height of the patient. The extracted stone/stone fragments were analyzed to determine the chemical composition. Urinary pH was similarly noted in all. RESULTS: The mean BMI among the diabetics was 26.35 ± 5.20 (range 17.75-35.60), whereas the mean BMI among the non-diabetics was 23.41 ± 2.85 (range 17.71-31.62) (P < 0.0004). The incidence of uric acid calculi in the diabetics was significantly high (P < 0.03). The mean urinary pH among the diabetics was 5.61 ± 0.36 and among the non-diabetics was 6.87 ± 0.32, which was significantly lower (P < 0.000044). CONCLUSIONS: There is a strong association between type 2 diabetes and uric acid stone formation. There is also a strong association between diabetes mellitus, BMI, and also with lower urinary pH.

Impact of urinary stone volume on computed tomography stone attenuations measured in Hounsfield units in a large group of Austrian patients with urolithiasis.

INTRODUCTION: To investigate retrospectively the impact of urinary stone volume on computed tomography stone attenuations measured in Hounsfield units in 253 patients with urolithiasis. MATERIAL AND METHODS: CT scans were performed in 253 patients with suspected urinary stone disease from 2008 to 2010 using CT-Scanner Siemens, SOMATOM, Sensation 64. One experienced radiologist (A.L) who was blinded to the chemical composition of the stones retrospectively reviewed images and analyzed data to determine the composition of the stones. The results were compared with the biochemical analysis results obtained by infrared spectroscopy (100 FTIR, PerkinElmer). RESULTS: 253 consecutive patients from 2008 to 2010 were included into analysis: 189 males, and 64 females. Mean age was 51.2. According to stone volume, stones were divided into 2 groups: 126 stones with volume of 4.3 mm or more, 127 stones with volume less than 4.3 mm. There was a significant relationship between stone volume and its CT attenuation only in stones with a volume 4.3 mm or more (p <0.05). CONCLUSIONS: We failed to show a significant relationship between stone volume and its attenuations in Hounsfield units. We could not distinguish uric acid stones from non uric acid stones.