Effect of intestinal surgery on the risk of urinary stone formation.

The prevalence of urinary stone disease in 426 patients who had undergone bowel surgery at the General Infirmary at Leeds from 1958 to 1978 was found by postal questionnaire to be 9.4%. The risk of urinary stone formation was determined from the composition of 24 hour urines from 61 unselected patients, in whom intestinal resections had been performed. There were 27 patients with an ileostomy, 17 patients with an ileostomy and a small bowel resection, and 17 patients with a small bowel resection, or bypass, and an intact colon. Of this group of 61 patients, 9.8% gave a history of urinary stones after surgery. Compared with normal control subjects ileostomy patients had significantly lower urinary pH and volume, higher concentrations of calcium, oxalate, and uric acid, and increased risk of forming uric acid and calcium stones: a small bowel resection combined with an ileostomy increased the ileostomy output, lowered the urinary volume further, and reduced urinary calcium excretion. The concentration of urinary oxalate increased and the risk of both uric acid and calcium stones was high. Patients with small bowel resection and intact colon had hyperoxaluria and an increased risk of calcium stones despite a low urinary calcium. There was no increased risk of uric acid stones in this sub-group. It is concluded that the risk of forming urinary stones after this type of surgery is considerable. The follow-up of patients with ileostomies and with small bowel resections should include an assessment of faecal losses and urinary composition to identify the patients who have a high risk of forming urinary stones.     

Urolithiasis risk factors in continent reservoir ileostomy patients

Conventional ileostomy patients are at an increased risk to urinary stone formation compared to normal controls. This study was designed to evaluate any further risk factors to urinary stone formation in patients with Kock ileostomies. Nine Kock ileostomy patients were matched for age, sex, and body weight with nine conventional ileostomy patients and nine controls. Two 24-hour urine samples from each patient were analyzed for volume, pH, Na⁺/K⁺ ratio, oxalate, and uric acid concentration. Both ileostomy groups demonstrated reduced urinary volume and Na⁺/K⁺ ratio as compared to the control groups (P<0.05). The Kock ileostomy group had the lowest urinary volume. There was no significant reduction in urinary pH or elevation in urine uric acid concentration in the Kock ileostomy group. The results suggest that there is no significantly added risk to uric acid stone formation in Kock ileostomy patients     

Stones from bowel disease.

Kidney stones are increased in patients with bowel disease, particularly those who have had resection of part of their gastrointestinal tract. These stones are usually CaOx, but there is a marked increase in the tendency to form uric acid stones, as well, particularly in patients with colon resection. These patients all share a tendency to chronic volume contraction due to loss of water and salt in diarrheal stool, which leads to decreased urine volumes. They also have decreased absorption, and therefore diminished urinary excretion, of citrate and magnesium, which normally act as inhibitors of CaOx crystallization. Patients with colon resection and ileostomy form uric acid stones, as loss of bicarbonate in the ileostomy effluent leads to formation of an acid urine. This, coupled with low urine volume, decreases the solubility of uric acid, causing crystallization and stone formation. Prevention of stones requires treatment with alkalinizing agents to raise urine pH to about 6.5, and attempts to increase urine volume, which increases the solubility of uric acid and prevents crystallization. Patients with small bowel resection may develop steatorrhea; if the colon is present, they are at risk of hyperoxaluria due to increased permeability of the colon to oxalate in the presence of fatty acids, and increased concentrations of free oxalate in the bowel lumen due to fatty acid binding of luminal calcium. EH leads to supersaturation of urine with respect to CaOx, in conjunction with low volume, hypocitraturia and hypomagnesuria. Therapy involves a low-fat, low-oxalate diet, attempts to increase urine volume, and agents such as calcium given to bind oxalate in the gut lumen. Correction of hypocitraturia and hypomagnesuria are also helpful.     

Renal function in patients with urinary stones of varying compositions

Kidney stones are a potential risk factor for chronic kidney disease. The impact of different urinary stone components on renal function is unknown. In this study, we retrospectively reviewed 1,918 medical records of patients with urolithiasis. The renal function was evaluated as estimated glomerular filtration rate. All the stones were analyzed by Fourier transform infrared spectroscopy. The patients were divided into five groups according to the stone components. Statistical analysis was performed with analysis of variance. All the patients with stones had Stage 2-3 chronic kidney disease. The patients with uric acid and struvite stones had significantly lower estimated glomerular filtration rate compared with those having other stone components (p<0.01). Furthermore, the patients with calcium-containing stones (calcium oxalate and calcium phosphate) had significantly better renal function than those with non-calcium-containing stones (struvite and uric acid, p<0.01). Patients with urolithiasis had decreased renal function, and the impact of renal function varied depending on the stone components. We conclude that stone analysis is important in predicting the change in renal function in patients with urolithiasis. Moreover, the patients with non-calcium-containing stones, such as struvite and uric acid stones, should be carefully evaluated and treated to preserve their renal function.     

不同体质指数尿路结石患者结石化学成分分析（附850例报告）

目的观察不同体质指数（BMI）尿路结石患者结石化学成分。方法根据我国BMI标准,将850例尿路结石患者分为正常组（BMI〈24）245例、超重组（BMI24—27）327例、肥胖组（BMI≥28）278例。采用傅立叶红外光谱法分析其结石化学成分。结果850例中,结石成分为草酸钙、磷酸钙、尿酸、磷酸镁铵者分别为645（75．9％）、128（15．1％）、52（6．1％）、25（2．9％）例。其中尿酸结石患者平均年龄均高于其他结石成分患者（P〈0．05）,男性比例显著高于女性（P〈0．05）;磷酸铵镁结石男性比例低于女性（P〈0．01）。正常组、超重组、肥胖组中,草酸钙结石者分别为70．2％、78．0％、78．4％（P〈0．05）,尿酸结石者分别为2．9％、7．0％、7．9％（P〈0．05）,磷酸镁铵结石者分别为7．3％、1．2％、1．1％（P〈0．01）,三组磷酸钙结石比例相近（P〉0．05）。结论BMI对结石成分有一定的影响;超重及肥胖的结石患者中,尿酸、草酸钙结石比例显著高于BMI正常的结石患者;尿酸、草酸钙结石患者应注意控制体质量。     

Risk factors for the formation of urinary calcium-containing stones in diabetics

Levels of 24-hour urinary calcium, magnesium, oxalate, citrate, uric acid, phosphorus and creatinine as well as urinary volume were determined in 85 patients and 81 normal subjects. Among the patients, 43 were diabetics without stone, 5 diabetics with stone and 37 with idiopathic calcium stone formation in the urinary tract. It is shown that the main risk factors involved in urinary calcium-containing stone formation are the levels of calcium, oxalate, uric acid and citrate and the volume of 24-hour urine. With the data obtained, the authors calculated the ion-activity products index of calcium oxalate and the relative probability of stone formation in the three groups of patients and the control group of normal subjects. The index in normal subjects, diabetics without stone, diabetics with stone and patients with idiopathic urinary calcium stone was 3.07 +/- 0.16, 2.90 +/- 0.25, 3.90 +/- 0.58 and 5.11 +/- 0.38 respectively. The upper limit of the relative probability in normal subjects was 0.54. Most of the patients with idiopathic urinary calcium stone (32/37) and all the 5 diabetics with stone had higher probability value than this, while most of the normal subjects (73/81) and of the diabetics without stone (39/43) had value lower than this. The results indicate that though the diabetics have higher level of urinary calcium and higher value of the product of calcium x oxalate x uric acid, they have also inhibitive factors for stone formation, such as increased level of urinary citrate. As a result, urinary stone formation will not be a frequent occurrence.     

Role of genital mycoplasmata and other bacteria in urolithiasis

Urease-producing bacteria have been shown to affect the formation of infection stones by splitting urea into ammonia, bicarbonate and carbonate. An increase in alkaline pH results in urinary supersaturation of the ions. The increase in ammonia also causes injury to the urothelial glycosaminoglycan layer. Non-urease-producing bacteria have been speculated to form urinary stones. Midstream voided bladder urine and fractured stone nidus samples from 72 patients undergoing surgery for urolithiasis were cultured on specific media for genital mycoplasmata and on conventional media. Urine samples were obtained from a control group of 40 healthy subjects. Genital mycoplasmata and other bacteria were evaluated with regard to the composition of urinary stones. Compared with other origins of stones, the relation between isolation of Ureaplasma urealyticum and infection stone disease was statistically proven. Isolation of genital mycoplasmata was significantly higher in women than in men in the study group. The urinary stones comprised 84.7% calcium stones, 8.3% uric acid stones and 6.9% infection (magnesium ammonium phosphate) stones. Coagulase-negative Staphylococci, Escherichia coli, Corynebacterium spp., Enterobacterium spp. and U. urealyticum were cultured from stone samples. The results suggests that non-urease-producing bacteria, as well as urease-producing bacteria, may influence the formation of urinary stones.     

Comparison of secondary signs as shown by unenhanced helical computed tomography in patients with uric acid or calcium ureteral stones

Unenhanced helical computed tomography (UHCT) has evolved into a well-accepted diagnostic method in patients with suspected ureterolithiasis. UHCT not only shows stones within the lumen of the ureter, it also permits evaluation of the secondary signs associated with ureteral obstruction from stones. However, there we could find no data on how secondary signs might differ in relation to different compositions of ureteral stones. In this study, we compared the degree of secondary signs revealed by UHCT in uric acid stone formers and in patients forming calcium stones. We enrolled 117 patients with ureteral stones who underwent UHCT examination and Fourier transform infra-red analysis of stone samples. Clinical data were collected as follows: age, sex, estimated glomerular filtration rate (eGFR), urine pH, and radiological data on secondary signs apparent on UHCT. The uric acid stone formers had significantly lower urine pH and eGFR in comparison to calcium stone formers, and on UHCT they also had a higher percentage of the secondary signs, including rim sign (78.9% vs. 60.2%), hydroureter (94.7% vs. 89.8%), perirenal stranding (84.2% vs. 59.2%) and kidney density difference (73.7% vs. 50.0%). The radiological difference was statistically significant for perirenal stranding (p=0.041). In conclusion, we found that UHCT scanning reveals secondary signs to be more frequent in patients with uric acid ureteral stones than in patients with calcium stones, a tendency that might result from an acidic urine environment.     

Risk factors for nephrolithiasis in patients with familial idiopathic hypercalciuria

PURPOSE: About 40% of patients with nephrolithiasis have idiopathic hypercalciuria, sometimes associated with a family history of kidney stones. In these families, little is known about the frequency of, and risk factors for, stone formation among hypercalciuric patients. We therefore conducted a prospective study of 216 subjects from 33 families with idiopathic hypercalciuria. MATERIALS AND METHODS: We recorded the age, weight, and history of calcium stones in all subjects, and measured 24-hour urine volume and excretion of calcium, uric acid, sodium, magnesium, urea, citrate, phosphate, and sulfate on a nonrestricted diet. We performed a more complete metabolic evaluation in many of the hypercalciuric subjects (calciuria/weight >0.1 mmol/kg/d). Multivariate logistic regression analysis was performed to identify independent risk factors for stone formation. RESULTS: The prevalence of self-reported nephrolithiasis was 46% (61/132) in hypercalciuric subjects and 11% (7/63) in normocalciuric subjects (P <0.0001). In multivariate analysis, age (odds ratio [OR] per 10 years of age = 1.3; 95% confidence interval [CI]: 1.1 to 1.6), urine calcium excretion (OR = 1.3 per mmol/d increase; 95% CI: 1.2 to 1.5), and uric acid excretion (OR = 3.3 per mmol/d increase; 95% CI: 1.4 to 7.5) were independent risk factors for nephrolithiasis. The risk of nephrolithiasis increased progressively with greater levels of hypercalciuria. CONCLUSION: We found a significant dose-effect association between calciuria and stone disease in patients with familial hypercalciuria. Other factors associated with stone formation included higher uric acid excretion, probably reflecting higher food intake, and age, probably reflecting the length of exposure to hypercalciuria and hyperuricosuria.     

Effect of prolonged bedrest on the propensity for renal stone formation

The effect of prolonged bedrest immobilization on urinary risk factors for stone formation and on the propensity for the crystallization of calcium salts was examined in eight normal subjects. During 5 weeks of bedrest, the mean urinary calcium excretion rose during the first week and remained elevated (from 5.68 to approximately 7.50 mmol/day). Mean urinary phosphorus excretion increased by the second week of bedrest and remained elevated (from 2.70 to approximately 30.6 mmol/day). Urinary sodium and uric acid excretion rose slightly, as did urinary magnesium. Urinary pH, oxalate, and citrate changed slightly or not at all. Owing to these biochemical alterations, urinary saturation of calcium phosphate, calcium oxalate, and monosodium urate increased significantly during bedrest, but that of uric acid did not change. The inhibitor activity against the spontaneous nucleation of brushite (CaHPO4.2H2O) and calcium oxalate was not altered significantly by bedrest. Thus, the propensity for the crystallization of stone-forming calcium salts was enhanced by bedrest, suggesting that immobilization may confer increased risk for the formation of calcium-containing renal stones.     

痛风及高尿酸患者易患尿路结石机制

痛风和高尿酸血症患者是尿路结石的高发人群。现有的结石治疗方法难以解决结石反复复发的难题,为充分改善患者生活质量,在结石形成之前对可控的危险因素进行控制十分必要。尿酸和草酸钙结石是最常见的结石类型,痛风和高尿酸血症患者尿pH、尿酸排泄量及尿量对这两种结石的形成起到复杂的影响,本文对痛风及高尿酸血症患者易患结石的机制进行综述,以指导临床诊治,减少结石的形成风险。     

Dietary aspects of uric acid stone disease

Kidney stones composed of uric acid present a treatment challenge, particularly in terms of successful prevention of recurrence over the long term. Between 5-12% of all stone patients form calculi composed partially or completely of uric acid. These stones have traditionally been treated with a combination of pharmacological and surgical techniques. The role of diet and fluids in the pathogenesis and management is gradually being recognized and there is potential for dietary intervention to become a major treatment modality for this type of stone. This paper discusses the stone formation process, the metabolism or uric acid and its physical and chemical properties. Specific risk factors for uric acid calculi formation are covered. Dietary protein is reviewed in detail. A comprehensive strategy for the dietary management of uric acid renal calculi disease is suggested.     

Stone Composition as a Function of Age and Sex

Background and objectives

Kidney stones are heterogeneous but often grouped together. The potential effects of patient demographics and calendar month (season) on stone composition are not widely appreciated.

Design, setting, participants, & measurements

The first stone submitted by patients for analysis to the Mayo Clinic Metals Laboratory during 2010 was studied (n=43,545). Stones were classified in the following order: any struvite, any cystine, any uric acid, any brushite, majority (≥50%) calcium oxalate, or majority (≥50%) hydroxyapatite.

Results

Calcium oxalate (67%) was the most common followed by hydroxyapatite (16%), uric acid (8%), struvite (3%), brushite (0.9%), and cystine (0.35%). Men accounted for more stone submissions (58%) than women. However, women submitted more stones than men between the ages of 10–19 (63%) and 20–29 (62%) years. Women submitted the majority of hydroxyapatite (65%) and struvite (65%) stones, whereas men submitted the majority of calcium oxalate (64%) and uric acid (72%) stones (P<0.001). Although calcium oxalate stones were the most common type of stone overall, hydroxyapatite stones were the second most common before age 55 years, whereas uric acid stones were the second most common after age 55 years. More calcium oxalate and uric acid stones were submitted in the summer months (July and August; P<0.001), whereas the season did not influence other stone types.

Conclusions

It is well known that calcium oxalate stones are the most common stone type. However, age and sex have a marked influence on the type of stone formed. The higher number of stones submitted by women compared with men between the ages of 10 and 29 years old and the change in composition among the elderly favoring uric acid have not been widely appreciated. These data also suggest increases in stone risk during the summer, although this is restricted to calcium oxalate and uric acid stones.     

Using computed tomography to predict in vivo stone chemical composition

OBJECTIVES. Several authors hypothesized the usefulness of the non-contrast helical computed tomography (NCHCT) with the determination of stone Hounsfield Unit (HU) values in order to predict urinary stone compositions. Preoperative knowledge of stone composition might be interesting in pre-operative decision-making process. The aim of this study was to evaluate the possible correlation between stone chemical composition and correspondent stone HU value in an in-vivo experience. METHODS. Forty patients with urinary stones were preoperatively studied with abdominal NCHCT, where stone HU values were reported. Stone chemical composition was obtained in each patient, using the colorimetric method. The HU value of each stone was compared with the correspondent chemical analysis. Results. The median HU values of calcium oxalate (n=10), mixed calcium oxalate and phosphate (n=19), calcium phosphate (n=2), uric acid (n=6) and mixed uric acid and calcium oxalate (n=3) stones were 1060 HU [interquartile range (IQR) 743.75-1222.5]; 900 HU (IQR 588.5-1108.5); 774 HU (range 720-828); 371 HU (IQR 361.25-436.25) and 532 HU (range 476-626), respectively. CONCLUSIONS. Our results confirmed a statistically significant difference of the HU values between calcium and pure uric acid calculi, suggesting a correlation between stone chemical composition and CT-density. Hounsfield unit.     

Management of uric acid calculi in the elderly patient

Uric acid stones are more common in older patients. Their formation usually requires a persistently acid urine. Conversely, they can be dissolved and their re-formation prevented by the use of alkaline salt therapy. This paper discusses the spectrum of uric acid stone disease including the frequent presentation as a recurrent gravel/colic syndrome. It reviews the clinical situations in which uric acid stones often form and outlines an approach to dissolution of stones using either oral therapy or urinary tract irrigation. Prophylaxis of further stone formation is often possible with only alternate day, single dose treatment with alkaline potassium salts.     

Bariatric Surgery and Effects on Calcium and Bone Metabolism

With the increasing epidemic of obesity in the United States as well as abroad, bariatric surgery has emerged as the most effective and sustained treatment for reduction. This treatment modality has been well recognized to diminish the risk of cardiovascular morbidity and mortality and ameliorate diabetes mellitus. However, with time, derangement in mineral metabolism has emerged as a major complication in this population. Population-based study has shown increased prevalence of bone fractures and kidney stone formation following bariatric surgery. The risk appears to be more specific after Roux-en-Y gastric bypass procedures, the most common surgical approach among this population. Over the past decade, there have been advances in the understanding of pathophysiologic mechanisms of both bone loss and kidney stone disease in these patients. The understanding of these underlying pathophysiologic mechanisms may lead to the development of drug therapies that ameliorate this complication. Unfortunately, at the present time, there is no hard data on any specific treatment showing decreased incidence of fragility fractures or kidney stone passage. However, some studies suggest that calcium and vitamin D supplementation may decrease bone loss and bone turnover, and as a result, increase bone mineral density in this population. However, there is concern with the development of kidney stone formation following such an approach. A novel treatment approach would be the use of effervescent potassium calcium citrate that not only prevents complications of bone loss but may diminish the risk of kidney stone formation. Despite preliminary results showing the effectiveness of this drug in the reduction in the parathyroid hormone, bone turnover, and improvement in the urinary saturation marker showing effectiveness against calcium oxalate and uric acid stones, there is no hard data available to support the effectiveness of this treatment in the reduction in fragility fractures or kidney stone incidence. Such studies to explore this effect must be considered in the future.     

Increased frequency of ultrasonographic findings suggestive of renal stones in patients with ankylosing spondylitis

OBJECTIVE: To determine the frequency of hypercalciuria and renal stones in ankylosing spondylitis (AS) sufferers. METHODS: This study involved 83 consecutive AS patients (21 female, 62 male; mean age 36.7 yr), 72 consecutive Behcet's disease (BD) patients (29 female, 43 male; mean age 37.7 yr) as disease control and 92 healthy control (HC) (26 female, 66 male; mean age 32.9 yr.) Twenty-four hour urine analyses for urinary calcium and uric acid levels were performed in each patient. Likewise, blood samples for erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), parathyroid hormone (PTH), calcium and uric acid evaluation were taken. Renal ultrasonography to evaluate the presence of renal stone was performed in patients with AS, as well as in the BD patients and HC individuals after a fasting period of 12 hours. RESULTS: 20 of the 80 (25%) patients with AS were diagnosed with renal stones. Only 4/72 (5.5%) BD patients, and 3/98 (3.3%) HC individuals had renal stones by ultrasonography. AS patients had a significantly higher frequency of renal stones compared with BD (p < 0.001) and HC (p < 0.0001). AS patients with renal stones were much older and their disease duration was much longer in comparison with AS patients without renal stones. Ultrasonographic and laboratory findings did not correlate. The number of AS patients with hypercalciuria who had renal stones was higher than that of AS patients who did not have renal stones (p < 0.01). There was a negative correlation between acute phase response and spinal mobility. CONCLUSION: Renal stone prevalence was found to increase in AS patients. The likelihood of renal stone formation was also found to increase with the extension of the disease duration of AS sufferers.     

泌尿系结石成分与代谢异常的临床研究

目的探讨泌尿系结石患者的结石成分与代谢异常的关系。 方法选择2012年6月至2016年10月在佛山市南海区第二人民医院泌尿外科确诊为泌尿系结石的200例患者的临床资料,200例患者入选并参加该研究,平均年龄（36.2±3.4）岁,男女比例2:1。收集泌尿系结石患者的结石标本和血清及尿液样本,测定结石成分和血/尿代谢情况,具体测定指标为pH值、肌酐、尿酸、钙离子、磷酸盐、草酸盐、枸橼酸盐和镁离子浓度等。 结果有86（43%）例患者结石成分分析为草酸钙结石;90.5%患者存在代谢异常,最常见是高草酸尿症（64.5%）,其次是高钙尿症,高钙血症,低枸橼酸尿症和高尿酸血症。高草酸尿症易发草酸钙结石、草酸钙/磷酸钙及草酸钙/尿酸混合成分结石;低枸橼酸尿症易发草酸钙、磷酸钙结石;高钠血症及高尿酸血症都易发草酸钙结石;高胱氨酸血症易发胱氨酸结石。 结论代谢异常在泌尿系结石患者中常见,大多数为高草酸尿症、高钙尿症、高钙血症、低枸橼酸尿症、高尿酸血症。代谢异常容易诱发结石,结石成分和代谢异常分析有助于选择合适的医学治疗和调整饮食习惯来预防结石复发。     

Mechanisms of Stone Formation

We have reviewed the general mechanisms involved in kidney stone formation, with reference to those composed of calcium oxalate or phosphate, uric acid, and cystine. These processes include nucleation of individual crystals, aggregation or secondary nucleation to produce small intrarenal multicrystalline aggregates, fixation within the kidney, and further aggregation and secondary nucleation to produce the clinical stone. The factors regulating these processes have been discussed as well as the effects of tubular fluid or urine pH and promoters or inhibitors, including urate or uric acid in the case of calcium oxalate stones, citrate, pyrophosphate, phytate, and urinary proteins. We also discuss the potential for macromolecular inhibitors to actually promote stone formation when they are fixed to some intrarenal structure or if they themselves become aggregated into protein?Cprotein complexes.     

Pathogenesis, pathophysiology, and classification

In this article, we discuss kidney stones from the perspectives of the factors that produce excessive urinary supersaturation of the stone-forming elements that comprise clinical calcium (oxalate and phosphate), uric acid, struvite, cystine, or drug stones. These factors include low urine volume, hypercalciuria, hyperoxaluria, hypocitraturia, hyperuricosuria, the presence of bacterial urease, cystinuria, the effects of urine pH, excessive phosphaturia, and the excessive excretion of drugs or metabolites. We describe the various locations of stones throughout the urinary tract and discuss their development from initial single crystal formation and attachment through the clinically appreciable stone. In particular, we present the major competing hypotheses of stone initiation: intratubular crystallization and attachment vs interstitial formation of Randall's plaques. Finally, we discuss in some depth the role of various urine macromolecules, osteopontin, Tamm-Horsfall protein, urninary prothrombin fragment 1, and serum inter-α-inhibitor, as modulators of crystallization processes and stone formation.