Studies of urinary risk factors in urolithiasis

Urinary excretions of calcium, oxalate and uric acid were estimated in 160 stone-formers (male 118, female 42) and 257 healthy controls (male 207, female 50). Stone-formers were divided into two groups according to their stone analysis: calcium containing stone-formers and non-calcium stone-formers. Calcium stone-formers were divided again into those who had a single stone episode and multiple or recurrent stone episodes. Urinary calcium and oxalate showed significant increases in calcium stone-formers, while urinary uric acid increased only in male calcium stone-formers. Recurrent calcium stone-formers demonstrated significant high levels of urinary calcium excretion especially in males, whereas no difference of urinary oxalate excretion between recurrent and single stone-formers. The frequency distributions on the excretion of three subjects were estimated respectively in patients with calcium stone and in controls. Relative risks, risk curves and stone probabilities were proposed and compared. The higher excretion values of urinary calcium and oxalate closely related to higher risks of forming calcium stones. On the other hand, urinary uric acid did not have such a relation to calcium stone formation. We defined the states which urinary excretions exceeded 95% upper confidence limits of normal controls as hyperexcretions. Hypercalciuria was more than 200 mg/day in male and female, hyperoxaluria was 50 mg/day in male and 45 mg/day in female and hyperuricosuria was 850 mg/day in male and 650 mg/day in female according to our definition. Among male calcium stone-formers, hypercalciuria was found in 45.3%, hyperoxaluria in 26.4% and hyperuricosuria in 15.1%. While in female calcium stone-formers, hypercalciuria in 23.7%, hyperoxaluria in 26.3% and hyperuricosuria in 13.2%. Of the male calcium stone-formers 57.5% showed either or both hypercalciuria and hyperoxaluria, and recurrent stone-formers also demonstrated a higher incidence among them. Excretion products of urinary calcium and oxalate were calculated and compared in each group. Calcium stone-formers showed significant high values especially in male recurrent stone-formers. The estimation by combining some risk factors will provide more useful means of assessing severity of urinary calculous diseases and therapeutic effects of their various treatments.     

Prediction of stone disease by discriminant analysis and artificial neural networks in genetic polymorphisms: a new method

OBJECTIVE: To use information from genetic polymorphisms and from patients (drinking/exercise habits) to identify their association with stone disease, the main analytical and predictive tools being discriminant analysis (DA) and artificial neural networks (ANNs). PATIENTS, SUBJECTS AND METHODS: Urinary stone disease is common in Taiwan; the formation of calcium oxalate stone is reportedly associated with genetic polymorphisms but there are many of these. Genotyping requires many individuals and markers because of the complexity of gene-gene and gene-environmental factor interactions. With the development of artificial intelligence, data-mining tools like ANNs can be used to derive more from patient data in predicting disease. Thus we compared 151 patients with calcium oxalate stones and 105 healthy controls for the presence of four genetic polymorphisms; cytochrome p450c17, E-cadherin, urokinase and vascular endothelial growth factor (VEGF). Information about environmental factors, e.g. water, milk and coffee consumption, and outdoor activities, was also collected. Stepwise DA and ANNs were used as classification methods to obtain an effective discriminant model. RESULTS: With only the genetic variables, DA successfully classified 64% of the participants, but when all related factors (gene and environmental factors) were considered simultaneously, stepwise DA was successful in classifying 74%. The results for DA were best when six variables (sex, VEGF, stone number, coffee, milk, outdoor activities), found by iterative selection, were used. The ANN successfully classified 89% of participants and was better than DA when considering all factors in the model. A sensitivity analysis of the input parameters for ANN was conducted after the ANN program was trained; the most important inputs affecting stone disease were genetic (VEGF), while the second and third were water and milk consumption. CONCLUSIONS: While data-mining tools such as DA and ANN both provide accurate results for assessing genetic markers of calcium stone disease, the ANN provides a better prediction than the DA, especially when considering all (genetic and environmental) related factors simultaneously. This model provides a new way to study stone disease in combination with genetic polymorphisms and environmental factors.     

The association between gout and nephrolithiasis in men: The Health Professionals' Follow-Up Study

Approximately 10 million adults in the United States have experienced the passage of a kidney stone, and up to 5 million have been diagnosed with gout by a physician. Previous reports have suggested that gout increases the risk for the development of kidney stones, but there are no prospective data. We used data from a cohort of 51,529 male health care professionals to examine the independent association between gout and kidney stone disease. In a cross-sectional analysis of gout and kidney stone disease reported on the 1986 baseline questionnaire, the prevalence of kidney stone disease was almost twofold higher in men with history of gout compared to those without (15% vs. 8%). After adjusting for age and body mass index (BMI), a history of gout remained significantly associated with kidney stone disease (OR 1.88; 95% CI 1.68 to 2.11). We then prospectively examined the risk of incident kidney stones in men with and without a confirmed diagnosis of gout after excluding men who reported a history of kidney stone disease or gout on the baseline questionnaire. A confirmed diagnosis of gout increased the multivariate relative risk of incident kidney stones (RR 2.12; 95% CI 1.22 to 3.68). In contrast, a history of kidney stone disease was not associated with increased risk of gout (RR 1.05; 95% CI 0.54 to 2.07). In conclusion, a history of gout independently increases the risk for incident kidney stones in men. Physicians should provide dietary counseling, such as increasing fluid intake and decreasing salt consumption, to subjects with gout in addition to other risk factors, such as family history of kidney stones, in order to decrease the likelihood of stone formation.     

Metabolic risk factors and the impact of medical therapy on the management of nephrolithiasis in obese patients

PURPOSE: Previous studies have demonstrated that obesity can increase the risk of stone formation as well as recurrence rates of stone disease. Yet appropriate medical management can significantly decrease the risk of recurrent stone disease. Therefore, we analyzed our obese patient population, assessing the risk factors for stone formation and the impact of selective medical therapy on recurrent stone formation. MATERIALS AND METHODS: A retrospective chart review was performed to identify obese patients with stone disease from our Stone Center. Metabolic risk factors for stones were identified as well as patient response to medical therapy. A similar analysis was performed on a group of age and sex matched nonobese stone formers. RESULTS: Of 1,021 patients 140 (14%) were identified as obese (body mass index greater than 30). Of these patients complete metabolic evaluations were available in 83 with an average followup of 2.3 years. The most common presenting metabolic abnormalities among these obese patients included gouty diathesis (54%), hypocitraturia (54%) and hyperuricosuria (43%), which presented at levels that were significantly higher than those of the nonobese stone formers (p <0.05). Stone analysis was available in 32 obese patients with 63% having uric acid calculi. After initiating treatment with selective medical therapy obese and nonobese patients demonstrated normalization of metabolic abnormalities, resulting in an average decrease in new stone formation from 1.75 to 0.15 new stones formed per patient per year in both groups. CONCLUSIONS: Obesity, as a result of dietary indiscretion, probable purine gluttony and possible type II diabetes, appears to have a significant role in recurrent stone formation. Appropriate metabolic evaluation, institution of medical therapy and dietary recommendations to decrease animal protein intake can significantly improve the risk of recurrent stone formation in these often difficult to treat patients.     

Time trends in reported prevalence of kidney stones in the United States: 1976-1994

BACKGROUND: A body of evidence establishes that the occurrence of kidney stone disease has increased in some communities of industrialized countries. Information on recent temporal trends in the United States is lacking and population-based data on epidemiologic patterns are limited. Study objective was to determine whether kidney stone disease prevalence increased in the United States over a 20-year period and the influence of region, race/ethnicity, and gender on stone disease risk. METHODS: We measured the prevalence of kidney stone disease history from the United States National Health and Nutrition Examination Survey (II and III), population-based, cross-sectional studies, involving 15,364 adult United States residents in 1976 to 1980 and 16,115 adult United States residents in 1988 to 1994. RESULTS: Disease prevalence among 20- to 74-year-old United States residents was greater in 1988 to 1994 than in 1976 to 1980 (5.2% vs. 3.8%, P < 0.05), greater in males than females, and increased with age in each time period. Among 1988 to 1994 adults, non-Hispanic African Americans had reduced risk of disease compared to non-Hispanic Caucasians (1.7% vs. 5.9%, P < 0.05), and Mexican Americans (1.7% vs. 2.6%, P < 0.05). Also, age-adjusted prevalence was highest in the South (6.6%) and lowest in the West (3.3%). Findings were consistent across gender and multivariate adjusted odds ratios for stone disease history, including all demographic variables, as well as diuretic use, tea or coffee consumption, and dietary intake of calcium, protein, and fat did not materially change the results. CONCLUSION: Prevalence of kidney stone disease history in the United States population increased between 1980 and 1994. A history of stone disease was strongly associated with race/ethnicity and region of residence.     

Diagnostic value of colour Doppler twinkling artefact in sites negative for stones on B mode renal sonography

The aim of the study was to investigate the diagnostic value of the colour Doppler twinkling artefact (TA) in renal stone disease. To enhance the evidence of TA, a preliminary in vitro study was performed to optimise the setting of colour Doppler sonography. In the in vitro study, an oxen kidney was examined using an high-frequency (12.5 MHz) linear array probe in a water bath before and after the inoculation of an aliquot of powder obtained by fragmentation of a calcium oxalate stone. In the clinical study, 67 patients with diagnosis of urinary stone based on B-mode sonography and 67 matched control subjects were examined with colour Doppler sonography using a low-frequency (2.5 MHz) curvilinear phased array probe. In vitro, the injection of calcium oxalate powder in a bovine kidney sample induced the appearance of spots without any back shadowing appearance on B mode but with a large number of TA on colour Doppler. In vivo, TA was much more frequent in patients with stone disease (95.5%) compared to controls (9.0%) (P < 0.001). TA was highly associated to renal stone disease and was also present in renal areas where a stone was undetected with B mode approach suggesting its diagnostic role although further studies are needed to confirm its accuracy. The type of instrumentation and its setting is crucial to obtain reproducible results.     

Biochemical characterization of primary hyperparathyroidism with and without kidney stones

The exact metabolic-physiological background for kidney stone formation in primary hyperparathyroidism (PHPT) is unclear. To obtain clarification, this retrospective data analysis was conducted in 131 patients with PHPT who had undergone a detailed ambulatory evaluation on a random diet since 1980. The baseline biochemical presentation of 78 patients with PHPT with stones was compared with that of 53 patients without stones. Compared to those without stones, the stone-forming patients had a more marked hypercalciuria (343 ± 148 vs. 273 ± 148 mg/day, P < 0.01). Urinary saturation of calcium oxalate and brushite was significantly higher in stone-formers. Serum PTH and fasting urinary calcium were similar between the two groups, but serum phosphorus was significantly lower in stone-formers. Serum calcitriol (available in some patients) showed a slightly higher mean value in stone-formers but the difference was not significant. The increment in urinary calcium after oral load of 1-g calcium was twofold higher among stone-formers. Radial shaft and L2–L4 bone mineral densities resided within the normal ranges. Stone-formers with PHPT display exaggerated urinary calcium excretion due to intestinal hyperabsorption of calcium, contributing to a greater enhancement of the saturation of stone-forming calcium salts.     

Incidence of Urolithiasis in Northeast Thailand

Background :
Urolithiasis is a major health problem in the northeast part of Thailand. In this study, we examined the prevalence of renal stone disease and differences of urinary components between stone formers and healthy control subjects in northeastern rural areas of Thailand.
Methods :
We selected 3 villages in the rural areas of Khon Kaen province in northeast Thailand. Three hundred and sixty-seven persons were asked questions relating to urolithiasis and were examined by abdominal ultrasound (US). We collected a spot urine sample from stone formers and healthy control subjects from each village.
Results :
Abnormal findings by US were detected in 39 individuals (10.6%), and included 31 individuals with renal calculi (8.4%), 16 with hydronephrosis (4.4%), and 1 individual with a renal cyst (0.3%). This yielded a disease rate of urinary stones in this study of 16.9%. The male/female ratio was 2/1 and the average age of the individuals examined was 40.3 + 13.9 years. However, there was no significant difference between the urinary parameters of stone formers and the healthy control subjects. Conclusion: There was a high incidence of renal stone disease in the northeast part of Thailand, but the tendency for hypocitraturia was only found in stone formers.     

GERIATRIC UROLITHIASIS

Purpose

We define the differences between geriatric patients with urinary stone disease compared to a younger cohort.

Materials and Methods

A data base, including serum biochemical profiles, 24-hour urinalyses and standardized questionnaires, was retrospectively evaluated from more than 6,000 consecutive patients with urinary stone disease.

Results

Geriatric stone formers comprised 12% (721) of all stone patients. Two-thirds of these elderly patients had aberrant urinary values and 29% had isolated hypocitraturia compared to 17% in the younger group. Of geriatric stone forming patients 76% had recurrent urinary stones (mean 3.5 stone episodes), which was similar to the younger comparable group (77%, mean 3.3 stone episodes). The severity of urinary stone disease was similar between the 2 groups based on the need for urological intervention. Geriatric stone patients, in general, experienced the first stone episode later in life (after age 50 years) compared with younger patients. Elderly patients had an increased incidence of uric acid stones, but had a similar incidence of struvite calculi. Geriatric stone patients underwent parathyroid surgery more frequently (2.7 versus 0.7%). Geriatric stone forming patients rarely had renal failure.

Conclusions

The incidence, recurrence and severity of recurrent urinary stone disease were similar between geriatric and younger stone forming patients. Geriatric stone patients had an increased incidence of isolated hypocitraturia, uric acid calculi and previous parathyroidectomy. The geriatric stone population is not merely an extension of younger stone forming patients presenting at an older age. Rather, geriatric patients commonly experience the first symptomatic stone episode later in life.     

Association of E-cadherin gene 3'-UTR C/T polymorphism with calcium oxalate stone disease

INTRODUCTION: Urinary stone disease is one of the most commonly seen urological diseases in Taiwan. Single nucleotide polymorphisms (SNPs) are commonly used for the investigation of genetic markers for stone disease. E-cadherin (CDH-1) is one of the cellular junction proteins related to the integrity of epithelial cells. Our aim was to investigate a polymorphism of the CDH-1 gene 3'-UTR as a possible genetic marker in the search for the genetic causes. MATERIALS AND METHODS: 148 patients with calcium oxalate stone were compared with 103 healthy controls for the frequency of CDH-1 3'-UTR polymorphisms. The polymorphism was detected by polymerase chain reaction-based restriction analysis (PML I endonuclease). RESULTS AND CONCLUSIONS: The results revealed significant differences between normal individuals and calcium stone disease patients (p = 0.0013). The distribution of genotype TT homozygote was higher in stone patients (51.5%) than in the control group (43.4%). The odds ratio for T allele compared to C allele was 2.0. We have concluded that polymorphisms of CDH-1 3'-UTR is a valid genetic marker for calcium stone disease.     

TAP 2 gene Msp-I polymorphism might be associated with calcium oxalate stone disease

INTRODUCTION: Inflammation might be one of the causes of stone disease. The function of the transporter associated with antigen-processing protein (TAP) is related to immune response and inflammation. Our aim was to investigate the relationship between stone disease and 5 polymorphic sites of the TAP gene (TAP1-1, 1-2, 2-1, 2-2, 2-3). MATERIALS AND METHODS: We compared the frequencies of 5 polymorphisms in the TAP gene between 208 patients with recurrent calcium oxalate stone and 210 healthy controls. The polymorphism was detected by polymerase chain reaction-based restriction analysis. RESULTS: Significant differences in the frequency of the polymorphism at the TAP2-2 site were detected between normal individuals and calcium stone disease patients (p<0.0001). The distribution of the genotype AA homozygote was higher in stone patients (33.3%) than in the control group (16.3%). The odds ratio for the A allele compared with the G allele was 2.097 (95% CI 1.571-2.802). CONCLUSIONS: We conclude that the TAP2-2 MspI polymorphism might be associated with calcium stone disease.     

Changing gender prevalence of stone disease

PURPOSE: Recent studies suggest that the incidence of renal stone formation has been increasing and the male predominance of nephrolithiasis is decreasing, which may be due to changes in diet and lifestyle. We examined changes in the prevalence by gender of inpatient hospital discharges for urinary stone disease. MATERIALS AND METHODS: The Nationwide Inpatient Sample was used for analysis. Discharges with an International Classification of Diseases, 9th revision, Clinical Modification principal diagnosis of 592.0 (calculus of kidney) or 592.1 (calculus of ureter) from 1997 to 2002 were included in the investigation. RESULTS: An estimated mean+/-SE 1,013,621+/-19,310 discharges for stone disease occurred from 1997 to 2002. Discharges for renal calculus increased by 18.9% during the study period (p<0.001), while discharges for ureteral calculus remained relatively constant. After adjusting for population changes discharges for renal calculi increased by 14.2% (p=0.002). In females discharges for renal calculi increased by 21.0% and discharges for ureteral calculi increased by 19.2% (each p<0.001). After adjusting for population changes renal calculus and ureteral calculus discharges in females increased by 22.0% (p=0.001) and 14.5% (p=0.005), respectively. CONCLUSIONS: In this nationally representative sample the population adjusted rate of discharges for stone disease in females dramatically increased from 1997 to 2002. This alteration represents a change in the prevalence by gender of treated stone disease from a 1.7:1 to 1.3:1 male-to-female ratio. It may reflect variations in the underlying prevalence by gender of stone disease. We speculate that the increasing incidence of nephrolithiasis might be due to lifestyle associated risk factors, such as obesity.     

Are we overstressing water quality in urinary stone disease?

A door to door survey of 38,805 persons from urban (9527) and rural (nontribal −19,716; tribal −9562) areas was carried out from 59 localities of Udaipur region to find out the prevalence of urinary stone disease. Simultaneously 118 water samples were also collected. The three sources of drinking water in these localities were tap, handpump and well and the prevalence of urinary stone disease in relation with the source of drinking water was 548.3, 303.4 and 189.9/1,00,000 population, respectively. All the samples were analysed for total hardness, Ca, Mg, Na, K, iP, SiO₃, SO₄, Cl, F, Cu, Zn and Mn. The tap water was softest with highest prevalence. The chi-square test revealed that prevalence was unassociated with any of these constituents. We feel that overstress should not be given to quality of drinking water in the management of stone disease.     

Stone disease in the Hmong of Minnesota: initial description of a high-risk population

BACKGROUND AND PURPOSE: The Hmong are an ethically distinct refugee population from the highlands of Laos. Metropolitan Minneapolis-St. Paul, Minnesota is home to the largest population of Hmong ( 40,000) outside Asia. A clinical impression that the Hmong have a high rate of uric acid stone disease was evaluated. PATIENTS AND METHODS: A retrospective chart review was performed. All adult Hmong patients seen between January 1, 2000, and December 31, 2001, by a large urology group practice (N = 205) were compared with a similar number of non-Hmong patients (N = 204). RESULTS: Of these patients, 94 Hmong (46%) and 23 non-Hmong (11%) patients had stone disease (P < 0.001). After addition of 75 non-Hmong stone patients to create a suitable comparison group, a total of 86 Hmong and 88 non-Hmong stone patients had complete records. Sex (57% v 60% male) and mean age (47.9 v 47.3 years) were similar. Staghorn calculi were found in 21 Hmong (24%) and 0 non-Hmong patients (P < 0.001). Surgical treatments differed between Hmong and non-Hmong (P = 0.004): SWL (16 v 35), ureteroscopy (24 v 29), percutaneous nephrolithotomy (19 v 7), and nephrectomy (5 v 0). Treatment for staghorn calculi was refused by 9 Hmong patients (43%). Stone composition was available in 40 Hmong and 39 non-Hmong. Uric acid (>10%) was found in 50% of Hmong and 10% of non-Hmong stones (P < 0.001). CONCLUSIONS: Hmong patients who come to urologic attention tend to do so for stone disease and tend to have uric acid calculi. The frequent requirement for invasive therapy, including nephrectomy, in the Hmong is of concern.     

Urinary citrate excretion in stone-formers and normal controls.

A specific method was used for the estimation of citrate in 24-hour urine collections from 108 young adult controls, 158 patient controls and 164 stone-formers. Stone-formers excreted significantly less citrate in 24 hours than either patient controls or young adult controls. Stone-formers had a lower concentration of citrate in their urine than either of the control groups. The young adult females exhibited a much greater excretion of citrate relative to calcium than the young males. Because of the ability of citrate to complex with calcium ions and keep them in solution, the relatively low incidence of calcium-containing stones in females under 50 years of age could well be the result of their high excretion of citrate and their increased excretion of this substance relative to calcium.     

Screening renal stone formers for distal renal tubular acidosis

A group of 110 consecutive renal stone formers were screened for distal renal tubular acidosis (RTA) using morning fasting urinary pH (mfUpH) levels followed by a short ammonium chloride loading test in patients with levels above 6.0. In 14 patients (12.7%) a renal acidification defect was noted; 13 had incomplete and 1 had complete distal RTA. Distal RTA was found particularly in recurrent stone formers (17%), and especially in those with bilateral stone disease, where a distal renal tubular acidification defect was found in 50%. We have been unable to differentiate primary from secondary RTA in renal stone formers. Regardless of whether the acidification defect is primary or secondary to stone formation, however, all renal stone formers with distal RTA can expect to benefit from prophylactic alkaline therapy and it is recommended that the screening procedure, which is easy to use in daily clinical practice, is applied to all stone formers and not restricted to patients with recurrent stone disease.     

合肥地区胆囊疾病的流行病学调查

目的 通过合肥地区6946位健康人群的体检探讨各种良性胆囊疾病的发生情况（包括已行胆道手术者）以及高脂血症与胆囊结石的关系。方法 采用腹部彩色多普勒B超检查发现胆囊疾病。以血液生化检测对比胆囊结石组（1051例）与无胆囊结石的（5133例）对照组高血脂的发生率。结果 6946例被检人群中良性胆囊疾病发生率21.55％；胆囊结石、胆囊息肉样病变、胆囊胆固醇沉着症、慢性胆囊炎、肝内胆管及总胆管结石发生率分别为15.13%、3.39%、1.35%、0.96%、0.70%；胆囊结石占良性胆囊疾病的70．2％；胆囊结石组与对照组的高血脂发生率分别为56.9%、32.3%，P＜0.001差异有显著意义。结论 本组工作提示，合肥地区工薪群体良性胆囊疾病特别是胆囊结石的发病率较高且与高血脂关系密切，高血脂可能是胆囊结石形成的另一高危因素。     

DIFFERENTIAL EXPRESSION OF URINARY INTER-alpha-TRYPSIN INHIBITOR TRIMERS AND DIMERS IN NORMAL COMPARED TO ACTIVE CALCIUM OXALATE STONE FORMING MEN

Purpose

We determine if the immunoreactive profile of urinary inter-alpha-trypsin inhibitor can be used to distinguish between normal individuals and individuals with calcium oxalate stone disease.

Materials and Methods

Urinary proteins were dialyzed against water (15 kDa. molecular weight cutoff), lyophilized and resolved by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (6% acrylamide, reducing conditions) followed by Western blot. Inter-alpha-trypsin immunoreactive proteins were detected by enhanced chemiluminescence. Stone formation was confirmed to be active radiologically or passed as stone or gravel within 12 months of the sample. Stone composition was confirmed crystallographically. Normal individuals had no personal or familial history of urolithiasis and matched stone forming patients regarding race (white) and age (23 to 71 years old). Urine from a total of 101 individuals was analyzed.

Results

The intact inter-alpha-trypsin trimer ([approximately] 220 to 240 kDa.) and heavy chain (HC) 2-bikunin/HC1-bikunin dimers ([approximately] 115 to 130 kDa.) were detected more often in stone forming men (23 of 26 [89%] and 26 of 26 [100%], respectively) than in normal individuals (6 of 26 [23%] and 5 of 26 [19%], respectively, p < 0.0001). In those normal individuals who expressed inter-alpha-trypsin trimer and HC-bikunins the relative intensities were 5.3 +/− 1.4% and 16.3 +/− 17.1% of the stone forming controls, respectively. The identity of high molecular weight-inter-alpha-trypsin immunoreactive bands was confirmed using antibodies against the individual subunits (HC1, HC2, HC3, bikunin). In contrast to men high molecular weight-inter-alpha-trypsin's were readily detected in normal and stone forming women with equal frequency (inter-alpha-trypsin-trimer p = 0.1337, HC-bikunins p = 0.2836): inter-alpha-trypsin-trimer 17 of 18 [94%] and 9 of 13 [77%]; HC-bikunins 17 of 18 [94%] and 10 of 13 [85%]). Inter-alpha-trypsin-trimer and HC-bikunins, respectively, were detected in 2 and 5 of 10 patients with chronic renal disease. Expression was not related to hematuria or proteinuria.

Conclusions

Immunoreactive profiles of urinary proteins may be able to be developed into a useful diagnostic tool to identify active stone formation, although a separate panel may be required for men and women. It is possible that these differences may provide clues as to why the incidence of stone disease is higher in men than women.     

Progression of nephrolithiasis: long-term outcomes with observation of asymptomatic calculi

BACKGROUND AND PURPOSE: Observation is often recommended for patients presenting with asymptomatic renal calculi. This study evaluated the natural history of asymptomatic calculi and the risk of progression of disease. PATIENTS AND METHODS: We conducted a retrospective evaluation of 300 male patients average age 62.8 years who were followed for a mean of 3.26 years for asymptomatic renal calculi in an outpatient urology clinic. At presentation, the mean cumulative stone diameter was 10.8 mm; 56% were lower-pole stones, and 48% of the patients had multiple calculi. Patients underwent annual radiographic imaging and clinic visits with standardized questions regarding the development of symptoms or complications from calculi. Progression of disease was defined as the need for surgical intervention, the development of pain, or stone growth on serial imaging. RESULTS: Overall, 77% of patients experienced disease progression, with 26% requiring surgical intervention. Stone size was positively associated with progression: those with an isolated stone >/=4 mm on presentation were 26% more likely to fail observation than patients with smaller solitary calculi (P = 0.012). Stone growth was less common in those with upper-pole and middle-pole stones (47% v 61%) for lower-pole stones; P = 0.002). Urine uric acid concentration correlated positively with the rate of stone growth (P = 0.05). Likewise, serum uric acid concentration predicted stone growth (odds ratio = 3.6). CONCLUSIONS: Stratification of risk of progression according to presenting stone size, location, and composition may facilitate discussions with the patient regarding the alternatives of observation versus intervention. Specifically, small non-uric acid calculi in the upper pole may be most amenable to observation.     

新疆南部维吾尔族尿石症患者病例对照研究

目的探讨新疆南部维吾尔族泌尿系结石发病的危险因素。方岳采用问卷调查的方式，研究了阿克苏地区90例维吾儿族泌尿系结石患者一般情况及生活习惯、饮食习惯，并对其结石成分进行分析。结果21—50岁为尿结石高发年龄组（74．4％），男性略多于女性，结石患者较对照组多口味偏咸，饮水量较少，差异有统计学意义（P〈0．001）；结石成分以草酸钙为主者81例（90．0％），磷酸钙结石1例（1．1％），尿酸结石5例（5．6％），磷酸镁铵结石2例（2．2％），胱氨酸结石1例（1．1％）。结论泌尿系结石发病主要受饮食习惯和饮水量的影响。