Ammonium acid urate calculi: a reevaluation of risk factors

PURPOSE: We reevaluate the demographic and metabolic risk factors for ammonium acid urate stones. MATERIALS AND METHODS: Since 1986, 23 women and 21 men ranging in age from 20 to 81 years (mean 48.7) were treated for stones partly composed of ammonium acid urate. Stone composition ranged from 2 to 60% ammonium acid urate (mean 24.1) of the total stone mass. No patient had a pure ammonium acid urate stone, although 11 (25%) had stones with ammonium acid urate as the predominant crystal. RESULTS: In the 44 patients 1 or more potential risk factors for ammonium acid urate were identified. Of the patients 11 (25%) had a history of inflammatory bowel disease with 10 (22.7%) having undergone ileostomy diversion, 6 (13.6%) admitted to a history of significant laxative use or abuse, 18 (40.9%) were morbidly obese, 16 (36.4%) had a history of recurrent urinary tract infections and 9 (20.5%) had a history of recurrent uric acid stones. CONCLUSIONS: Patients clearly at risk for stones with an ammonium acid urate component include those with a history of inflammatory bowel disease and ileostomy diversion or laxative abuse. Other factors that may potentially enhance ammonium acid urate stone formation include morbid obesity, recurrent uric acid calculi and recurrent urinary tract infection. A careful history followed by further metabolic evaluation is warranted in these patients.     

Analysis of stone disease in morbidly obese patients undergoing gastric bypass surgery

BACKGROUND AND PURPOSE: Recent studies have demonstrated a higher incidence of nephrolithiasis in the morbidly obese. Nephrolithiasis also has been described as a potential outcome after gastric bypass surgery. This is the first study to our knowledge that examines the incidence of nephrolithiasis in the morbidly obese in the setting of gastric bypass surgery at a tertiary referral center. PATIENTS AND METHODS: We retrospectively reviewed the records of patients undergoing laparoscopic gastric Roux-en-Y bypass surgery for morbid obesity at our institution for the incidence of nephrolithiasis preoperatively, de novo stones postoperatively, and both preoperative and postoperative stone formation. RESULTS: Of the 972 patients who underwent a laparoscopic gastric bypass for the treatment of morbid obesity between 1990 and the present, 85 (8.8%) were found to have upper urinary-tract calculi preoperatively, and 32 (3.2%) had de novo stones postoperatively. Of those 85 who had stones preoperatively, 26 (31.4%) developed recurrent stones postoperatively. CONCLUSIONS: These results support findings in the current literature that nephrolithiasis has a higher incidence in the morbidly obese population. The combination of preoperative stone history and gastric bypass surgery may place patients at a higher risk of future stone formation. This latter group of patients should be screened for postoperative stone formation.     

High incidence of kidney stones in Icelandic children

All children less than 18 years of age who were diagnosed with a first episode of kidney stones at pediatric referral centers in Iceland during the years 1995–2000 were studied retrospectively. The diagnosis was based on clinical features and results of imaging studies. Patients were invited for evaluation at the end of the study period. Twenty-six patients (15 females, 11 males), median age 9.4 (range 0.2–14.9) years, experienced 34 episodes of kidney stones. The annual incidence was 5.6 and 6.3 per 100,000 children less than 18 and 16 years of age, respectively. Abdominal pain was the most common symptom (N=17; 69%) and urinalysis revealed hematuria in 21 patients (80.8%), sterile pyuria in 17 (65%), and 2,8-dihydroxyadeninuria in two. Six patients (23%) had positive urine cultures at the time of diagnosis and five (20%) had urinary tract anomalies. Family history of kidney stones was positive in one third of patients. Metabolic risk factors for stone formation were identified in 22 of 23 patients (96%) who underwent evaluation. Hypercalciuria, the most common metabolic risk factor, was identified in 18 patients (78%). Stones passed spontaneously in nine patients (35%) and six patients had recurrent stone episodes. The incidence of kidney stones in Icelandic children is high compared with other Western populations, affecting females more than males. Underlying metabolic risk factors were identified in most patients.     

Calcium stone disease: a multiform reality

In calcium renal stones, calcium oxalate and calcium phosphate in various crystal forms and states of hydration can be identified. Calcium oxalate monohydrate (COM) or whewellite and calcium oxalate dihydrate (COD) or weddellite are the commonest constituents of calcium stones. Calcium oxalate stones may be pure or mixed, usually with calcium phosphate or sometimes with uric acid or ammonium urate. The aim of this study was to compare the clinical and urinary patterns of patients forming calcium stones of different composition according to infrared spectroscopic analysis in order to obtain an insight into their etiology. The stones of 84 consecutive calcium renal stone formers were examined by infrared spectroscopy. In each patient, a blood sample was drawn and analysed for serum biochemistry and a 24-h urine sample was collected and analysed for calcium, phosphate, oxalate, citrate and other electrolytes. We classified 49 patients as calcium oxalate monohydrate (COM) stone formers, 32 as calcium oxalate dihydrate (COD) stone formers and three as apatite stone formers according to the main component of their stones. Patients with COM stones were significantly older than patients with COD stones (P<0.002). Mean daily urinary calcium and urinary saturation with respect to calcium oxalate were significantly lower in patients with COM than in those with COD stones (P<0.000). Patients with calcium oxalate stones containing a urate component (10%) presented with higher saturation (P<0.012) with respect to uric acid in their urine (and lower with respect to calcium oxalate and calcium phosphate, respectively P<0.024 and P<0.003) in comparison with patients without a urate component in the stone. Patients with calcium oxalate stones with a calcium phosphate component (15%) showed higher (P<0.0016) urinary saturation levels with respect to calcium phosphate (and lower with respect to uric acid (P<0.009), compared with patients forming stones without calcium phosphate or with a low calcium phosphate component. Patients with calcium stones mixed with urate had a significantly lower urinary pH (P<0.002) and urinary calcium (P<0.000), and patients with calcium phosphate >15%, higher urinary pH (P<0.004) and urinary calcium (P<0.000). In conclusion, in the evaluation of the individual stone patient, an accurate analysis of the stone showing its exact composition and the eventual presence of minor components of the stone is mandatory in order to plan the correct prophylactic treatment. Patients with calcium stones could require various approaches dependent on the form and hydration of the calcium crystals in their stones, and on the presence of minor crystalline components that could have acted as epitaxial factors.     

Role of stone analysis in metabolic evaluation and medical treatment of nephrolithiasis

BACKGROUND AND PURPOSE: Comprehensive metabolic evaluation has become an important aspect of the management of recurrent nephrolithiasis, yet the role of stone analysis is often neglected or perhaps underestimated. The purpose of this study was to determine the role of stone analysis in medical decision making in patients with recurrent nephrolithiasis. MATERIALS AND METHODS: We evaluated 100 consecutive stone-forming patients who had undergone compositional stone analysis as well as comprehensive metabolic evaluation at our institution. An analysis of stone composition in relation to metabolic disturbances was performed. Patients were stratified into two groups: calcium and non-calcium stone formers. RESULTS: Patients having non-calcium stones were found to have a metabolic analysis reflecting specific metabolic disorders. Alternatively, patients with calcium stones were heterogeneous with regard to metabolic disorders, but there was a significant likelihood of renal tubular acidosis in those patients with calcium phosphate calculi. On the basis of these results, a simplified metabolic evaluation and nonselective medical therapy based on stone composition was formulated to facilitate assessment, management, and monitoring of stone disease. CONCLUSIONS: Compositional stone analysis should be an integral part of the metabolic evaluation of patients with nephrolithiasis. Moreover, stone analysis alone may provide guidance for therapeutic treatment and obviate a formal metabolic evaluation.     

Clinical and biochemical profile of patients with “pure” uric acid nephrolithiasis compared with “pure” calcium oxalate stone formers

The purpose of the present study was to compare the clinical characteristics of “pure” uric acid (UA) stone formers with that of “pure” calcium oxalate (CaOx) stone formers and to determine whether renal handling of UA, urinary pH, and urinary excretion of promoters and inhibitors of stone formation were different between the two groups. Study subjects comprised 59 patients identified by records of stone analysis: 30 of them had “pure” UA stones and 29 had “pure” CaOx nephrolithiasis. Both groups underwent full outpatient evaluation of stone risk analysis that included renal handling of UA and urinary pH. Compared to CaOx stone formers, UA stone formers were older (53.3 ± 11.8 years vs. 44.5 ± 10.0 years; P = 0.003); they had higher mean weight (88.6 ± 12.5 kg vs. 78.0 ± 11.0 kg; P = 0.001) and body mass index (29.5 ± 4.2 kg/m² vs. 26.3 ± 3.5 kg/m²; P = 0.002) with a greater proportion of obese subjects (43.3% vs. 16.1%; P = 0.01). Patients with “pure” UA lithiasis had significantly lower UA clearance, UA fractional excretion, and UA/creatinine ratio, with significantly higher serum UA. The mean urinary pH was significantly lower in UA stone formers compared to CaOx stone formers (5.17 ± 0.20 vs. 5.93 ± 0.42; P < 0.0001). Patients with CaOx stones were a decade younger, having higher 24-h urinary calcium excretion (218.5 ± 56.3 mg/24 h vs. 181.3 ± 57.1 mg/24 h; P = 0.01) and a higher activity product index for CaOx [AP (CaOx) index]. Overweight/obesity and older age associated with low urine pH were the principal characteristic of “pure” UA stone formers. Impairment in urate excretion associated with increased serum UA was also another characteristic of UA stone formers that resembles patients with primary gout. Patients with pure CaOx stones were younger; they had a low proportion of obese subjects, a higher urinary calcium excretion, and a higher AP index for CaOx.     

Biochemical profile of idiopathic uric acid nephrolithiasis

BACKGROUND: The objective of this study was to elucidate a biochemical profile of patients with idiopathic uric acid nephrolithiasis, without secondary causes (such as dehydration or diarrhea). Study subjects comprised 56 patients with idiopathic uric acid nephrolithiasis (UA stone group) who underwent a full outpatient evaluation. The control group was composed of 54 with absorptive hypercalciuria and 2 normal subjects, matched with the UA stone group according to age, body mass index, and gender. METHODS: Urinary pH and ammonium and serum and urinary uric acid were measured. The fractional excretion of urate was calculated. RESULTS: Compared with the control group, the UA stone group had a significantly higher serum uric acid and significantly lower urinary uric acid, pH (5.34 +/- 0.23 vs. 6.17 +/- 0.36, P < 0.001), and fractional excretion of urate (0.052 +/- 0.028 vs. 0.080 +/- 0.029, P < 0.001), but individual values overlapped considerably between the two groups. Discriminant analysis of the relationship between urinary pH and fractional excretion of urate yielded a "discriminant score," which provided a much better separation between the two groups, with a correct classification in 95.5% of subjects. In contrast, urinary ammonium, citrate, sulfate, and potassium did not differ between two groups. CONCLUSIONS: In idiopathic uric acid nephrolithiasis, urinary pH and fractional excretion of urate are significantly lower than in control subjects, suggestive of defects in urinary acidification and urate excretion. Since these impairments are believed to be associated with primary gout, the underlying disturbance in idiopathic uric acid nephrolithiasis may be primary gout.     

Nephrolithiasis associated with renal insufficiency: factors predicting outcome

BACKGROUND AND PURPOSE: Renal calculous disease may be associated with various degrees of renal insufficiency secondary to a combination of obstruction, urinary infection, frequent surgical intervention, and coexisting medical disease. Herein, we present our data on the progression of renal function in patients with stones associated with renal insufficiency and assess the significance of various factors that could predict postoperative renal function deterioration. PATIENTS AND METHODS: Data were obtained from 4400 patients undergoing treatment for calculous disease at our institute since 1991. Renal insufficiency, defined as a baseline serum creatinine >1.5 mg/dL, was present in 84 (1.9%). Predictive factors evaluated for renal function deterioration were preoperative (age, duration of symptomatology and nephrolithiasis, urinary tract infection, coexistent medical diseases, baseline serum creatinine, and stone burden), intraoperative (number of percutaneous tracts), and postoperative (recurrent infection, proteinuria, cortical atrophy, residual fragments, and stone recurrence). RESULTS: Over a mean follow-up of 2.2 years (range 6 months-6 years), 33 patients (39.3%) showed improvement, 24 (28.6%) showed stabilization, and 27 (32.1%) showed deterioration in their renal function. Higher baseline serum creatinine, proteinuria >300 mg/day, renal cortical atrophy, stone burden >1500 mm(2), recurrent urinary infection, and age <15 years were significant predictors of subsequent renal function deterioration. CONCLUSIONS: Patients with nephrolithiasis and mild to moderate renal insufficiency warrant aggressive treatment aimed at complete stone clearance and prevention of recurrence of stones and urinary infection. A higher baseline preoperative serum creatinine, proteinuria >300 mg/day on follow-up, renal cortical atrophy, stone burden >1500 mm(2), recurrent urinary infection, and age <15 years are associated with a significantly higher likelihood of renal function deterioration after treatment of the calculous disease.     

Recurrent stone‐forming patients have high visceral fat ratio based on computed tomography images compared to first‐time stone‐forming patients

Objectives

To compare various fat parameters based on computed tomography images between recurrent stone‐forming patients and patients forming stones for the first time.

Methods

Included in the present study were 300 patients with upper urinary tract calculi who had undergone active stone removal in our hospital. Using pretreatment computed tomography images, we measured visceral fat area and volume, subcutaneous fat area and volume, visceral fat area ratio and visceral fat volume ratio. We compared patient backgrounds and these fat parameters between those who recurrently formed stones and those who formed stones for the first time. We also performed logistic regression analysis to identify factors that contribute to severe stones.

Results

A total of 148 (49.3%) patients were recurrent stone‐forming patients. Recurrent stone‐forming patients were statistically significantly younger (P < 0.01) and there were more male patients (P < 0.01). In addition, visceral fat area ratio and visceral fat volume ratio in recurrent stone‐forming patients were significantly higher than those in first‐time stone‐forming patients (P = 0.03 and P = 0.01, respectively). On the other hand, there was no significant difference in visceral fat area (P = 0.32), subcutaneous fat area (P = 0.36), visceral fat volume (P = 0.38) or subcutaneous fat volume (P = 0.23). Receiver operating characteristics analysis showed that area under the curve of visceral fat volume ratio (0.583) for recurrent stones was larger than that of visceral fat area ratio (0.571). In multivariate analysis, increasing visceral fat volume ratio was an independent significant predictor of recurrent stones (P = 0.04).

Conclusions

Recurrent stone‐forming patients have high visceral fat ratios compared to first‐time stone‐forming patients, shown here for the first time.

     

The etiology of urolithiasis in HIV infected patients

PURPOSE: It is commonly thought that urinary lithiasis in HIV infected patients on protease inhibitor therapy is composed primarily of the protease inhibitor itself. Since many HIV infected patients on protease inhibitors presenting to our institution had nonprotease inhibitor stones, we investigated potential underlying metabolic abnormalities that may account for the lithogenesis. MATERIALS AND METHODS: We retrospectively reviewed all HIV infected patients on protease inhibitors with renal colic and evidence of nephrolithiasis who presented to our institution between June 1996 and January 2001. Patients were evaluated for stone composition and metabolic abnormalities of blood and urine when possible. RESULTS: A total of 24 patients were identified, and all were or had been on protease inhibitors (indinavir 14, ritonavir 3, nelfnavir 2, unspecified 5). Of the 14 patients on indinavir only 4 (28.6%) had indinavir containing stones. The remaining stones in this group and in those not on indinavir contained various amounts of calcium oxalate monohydrate and dihydrate, ammonium acid urate and uric acid. Of 10 patients who underwent 24-hour urine collection for metabolic evaluation 8 (80%) had abnormalities, including hypocitraturia in 5, hyperoxaluria in 4, hypomagnesuria in 4, hypercalciuria in 3, increased supersaturation of calcium oxalate in 3 and hyperuricosuria in 2. Abnormalities in the levels of urinary phosphate and sodium were also observed. CONCLUSIONS: HIV infected patients form many types of stones, which probably are attributable to underlying metabolic abnormalities rather than the use of protease inhibitors. A complete metabolic evaluation is warranted in these patients, as a means of guiding treatment to prevent future stone episodes, while avoiding the need to alter antiretroviral regimens.     

Serum phosphate in stone formers: what does a low serum phosphate level mean?

PURPOSE: Metabolic evaluation is indicated in stone formers to identify and subsequently modify risk factors for nephrolithiasis. Some believe that serum phosphate may be an important indicator of nephrolithiasis risk. We determined whether serum phosphate is an independent risk factor for recurrent calcium stone formation and whether it may be used as an early marker for occult disease, such as hyperparathyroidism. MATERIALS AND METHODS: The charts of all patients with regular long-term stone clinic followup were reviewed. Initial serum phosphate levels were compared with stone recurrence, complications due to stones, initial visit urinary laboratory values and the medical diagnoses made during followup. Unpaired 2-sample t tests, and correlation and logistic regression analyses were performed with statistical significance at p <0.05. RESULTS: Data were available on 51 men and 25 women 22 to 74 years old (mean age 52). Of the patients 50 were recurrent and 26 were single stone formers. Serum phosphate levels were lower in women than in men. No consistent associations existed between initial or future serum phosphate levels and stone recurrence, complications from stones, urinary values or other medical diagnoses made during followup. CONCLUSIONS: Serum phosphate does not appear to be an independent risk factor for urinary tract stone recurrence or complications, or a reliable early predictor of occult disease.     

10-year experience with extracorporeal shockwave lithotripsy in the state of Colorado

PURPOSE: To evaluate trends in the utilization of extracorporeal shockwave lithotripsy (SWL) and the potential need for medical prophylaxis of urolithaisis in the state of Colorado. MATERIALS AND METHODS: We examined patient and stone characteristics of individuals undergoing SWL for renal or upper-ureteral stones over a 10-year period (1987-1996) at the Kidney Stone Center of the Rocky Mountains. There were no significant changes in the in-state physician referral patterns nor SWL treatment criteria over this time interval. All patients were treated on the Dornier HM3 lithotripter. From September 1999 to December 1999, 198 consecutive patients undergoing SWL filled out a 10-point questionnaire regarding their interest in medical prophylaxis of urolithiasis. RESULTS: The number of patients from Colorado rose 32.5%: from 15.7 per 100,000 population in 1987 to 20.8 per 100,000 in 1996. Patient demographics such as sex, race, age, and history of nephrolithiasis did not change. Furthermore, there were no significant changes in the treated stone size or stone location. The overall increase in treatment numbers was attributable equally to increases in the number of upper ureteral and renal stones. Of the 198 patients questioned, 114 (58%) were recurrent stone formers, but only 52 (45%) of these had been offered a metabolic evaluation. CONCLUSIONS: Over the 10 years since the introduction of WSL in Colorado, there has been a gradual increase in its utilization. This higher utilization is probably multifactorial. Patients undergoing SWL have a strong desire to prevent future stone episodes and are very interested in medical prophylaxis of their stone disease.     

Infrared spectroscopic analysis of urinary stones (including stones induced by melamine-contaminated milk powder) in 189 Chinese children

Aim

The aim of the study was to investigate the composition of the stones in Chinese children with urolithiasis, including peculiar stones induced by melamine-contaminated milk powder.

Materials and Methods

Between 1999 and 2009, 189 urinary stones from children of East China were received at our institution. Among them, 12 stones were received from pediatric stone formers with a history of consuming melamine-contaminated milk powder in 2008; and the remaining stones were defined as “natural” stones. All stones were analyzed by Fourier transform infrared spectroscopy.

Results

Among 177 “natural” stones, whewellite stone (49.72%) was observed most frequently followed by weddellite stone (15.25%), uric acid anhydrous stone (9.6%), carbapatite stone (9.04%), cystine stone (9.04%), ammonium acid urate stone (4.52%), struvite stone (2.26%), and sodium urate stone (0.56%). Twelve young children who consumed melamine-contaminated milk powder were younger than 3 years, and their stones were composed of a mixture of uric acid dihydrate and ammonium acid urate based on Fourier transform infrared spectroscopy. In addition, the stones were radiolucent and could be dissolved by urine alkalinization.

Conclusions

Our study emphasizes the relatively high rate of calcium oxalate stones and cystine stones, and the relatively low rate of struvite stones in Chinese children with urolithiasis. The stones caused by melamine-contaminated milk powder are composed of the mixture of uric acid dihydrate and ammonium acid urate.     

Lithogenic activity and clinical relevance of lipids extracted from urines and stones of nephrolithiasis patients

We investigated contents and classes of urinary and stone matrix lipids, and evaluated their clinical relevance in nephrolithiasis patients. Lithogenic role of major lipid classes was explored. Urine (24 h) and stone samples were collected from 47 patients with nephrolithiasis. Control urines were obtained from 29 healthy subjects. Urinary 8-hydroxy-deoxyguanosine (8-OHdG), malondialdehyde (MDA), N-acetyl-β-glucosaminidase (NAG) activity and total proteins were measured. Total lipids were extracted from centrifuged urines (10,000 rpm, 30 min) and stones by chloroform/methanol method. Major classes of lipids were identified using multi-one-dimensional thin-layer chromatography (MOD-TLC). Influence of each lipid class purified from stone matrices on stone formation was evaluated using crystallization and crystal aggregation assays. Urinary NAG activity and 8-OHdG were significantly elevated in nephrolithiasis patients. Total lipids in centrifuged urines of the patients were not significantly different from that of controls. In nephrolithiasis, urinary excretion of total lipids was linearly correlated to urinary MDA, 8-OHdG, NAG activity and total proteins. Lipid contents in stone matrices varied among stone types. Uric acid stone contained lower amount of total lipids than calcium oxalate and magnesium ammonium phosphate stones. MOD-TLC lipid chromatograms of healthy urines, nephrolithiasis urines and stone matrices were obviously different. Triacylglyceride was abundant in urines, but scarcely found in stone matrices. Stone matrices were rich in glycolipids and high-polar lipids (phospholipids/gangliosides). Partially purified glycolipids significantly induced crystal aggregation while cholesterol was a significant inducer of both crystal formation and agglomeration. In conclusion, total lipids in centrifuged urines did not differ between nephrolithiasis and healthy subjects. Our finding suggests that the significant sources of lipids in patients’ urine may be large lipids-containing particles, which are removed in centrifuged urines. However, urinary lipid excretion in nephrolithiasis patients was associated with the extent of oxidative stress and renal tubular injury. Triacylglyceride was abundant in urines, but rarely incorporated into stones. Glycolipids were principal lipid constituents in stone matrices and functioned as crystal aggregator. Cholesterol purified from stone matrices bared crystal nucleating and aggregating activities.     

Flexible ureteroscopy and holmium laser lithotripsy for treatment of upper urinary tract calculi in patients with autosomal dominant polycystic kidney disease

The objective of the study was to investigate the safety and efficacy of flexible ureteroscopy and holmium laser lithotripsy for the management of patients with autosomal dominant polycystic kidney disease (ADPKD) and associated nephrolithiasis. Between 2005 and 2010, flexible ureteroscopic stone treatment was attempted in 13 patients with ADPKD. Two patients had bilateral renal stones. Most of the stones were located in the renal pelvis and/or calices with a stone size 1.7 cm in the largest diameter. The success rate and morbidity and complications were recorded. A total of 45 intrarenal calculi with a mean stone size of 5.6 mm (range 3–17) were identified. The mean number of stones per patients was 3.2 (range 2–5). The mean number of primary procedures was 1.2 (range 1–2). The overall stone-free rates after one and two procedures were 84.5 and 92.3%, respectively. Complications occurred in three procedures and consisted of low-grade fever in one procedure, flank pain in another procedure and stent pain in another procedure. No patient died. Flexible ureteroscopy with holmium laser lithotripsy is a safe and effective method for the treatment of patients with ADPKD and associated nephrolithiasis.     

A prospective study of nonmedical prophylaxis after a first kidney stone.

OBJECTIVE: To assess, in a multicentre prospective randomized study, the effectiveness of specific nonmedical prophylaxis and nonspecific dietary prophylaxis in patients treated after experiencing their first idiopathic calcium-containing kidney stone. PATIENTS AND METHODS: From 1991 to 1994, 242 patients with idiopathic calcium urinary stones from three urological centres were randomly assigned into two groups. In group 1 (intervention, 113 patients), a specific dietary regimen was recommended and thereafter corrected according to a comprehensive metabolic evaluation. Group 2 (control, 94 patients) underwent only minimal metabolic screening and used general dietary measures, with no regular follow-up. An increased fluid intake was recommended in both groups. After 3 years, the effectiveness of the prophylactic and dietary regimens was evaluated in 207 patients. RESULTS: At entry, the clinical characteristics were comparable in the two groups, with only extracorporeal lithotripsy being more frequent in group 2. Almost 80% of patients reported a high intake of meat and a low intake of dairy products. In group 1 and 2, a recurrent stone was encountered in seven (6%) and 18 (19%) patients, respectively; recurrent and growing stones were found in eight (8%) and 22 (23%) patients, respectively (P<0. 01). There was a higher incidence of bilateral residual (or untreated) stones, and Weddellite stones (P<0.001) among patients with a recurrent or growing stone. An analysis of the dynamics of the metabolic variables indicated the significance of repeated dietary counselling. CONCLUSION: Specific dietary therapy, adjusted according to a metabolic evaluation, is more effective than nonspecific general dietary recommendations in preventing the formation of a second urinary stone.     

The severity of infection stones compared to other stones in the upper urinary tract

A retrospective study of the case records of 391 adult patients with spontaneously passed or surgically removed concrements from the upper urinary tract during the period 1982-1983 was performed. According to chemical analysis, 66% of the stones were calcium stones, 30% were infection stones, 4% were uric acid/urate stones and 1% were cystine stones. Of the infection stones 12 (10%) were staghorn calculi. The infection stones placed a greater strain on the patients than the calcium stones. Thus, infection stones were significantly more often recurrent stones and required surgery significantly more often than the calcium stones. Only 6% of the patients with infection stones had proved abnormalities predisposing to upper urinary tract infection. Urinary tract infection with a urease-producing microorganism was detected in only 52% of the patients with infection stones. As infection with a urease-producing microorganism is a prerequisite for the formation of infection stones in the urinary tract a careful microbiological investigation to find and treat the infection responsible for the stone formation is mandatory.     

A study of allopurinol in the prevention of recurrent calcium oxalate stones

We studied the effect of allopurinol on the prevention of stone recurrence in 134 patients with recurrent, idiopathic calcium nephrolithiasis. They consisted of 113 male patients and 21 female, between 16 and 72 years with an average age of 42.7. The patients were divided into two groups according to the type of stone occurrence; those with multiple stones without previous stone episodes (multiple stone group), and the those with recurrent stones (stone episode group). Twenty three patients belonged to the multiple stone group and 111 patients belonged to the stone episode group. The stones in 19 of the 23 patients in the multiple stone group remained stable throughout the study, while stones in 4 grew. Fifty-nine of the 111 patients in the stone episode group were free from recurrence, but the others showed recurrence. Statistical analyses was done on the stone episode group. The stone recurrence rate of all of the 111 cases showed significant decrease during prophylactic treatment with allopurinol (p less than 0.01), although the observation period before treatment was 73.0 +/- 65.8 months and that during and after treatment was 28.2 +/- 12.1 months. During the two years before and after prophylaxis 79 patients also showed a significantly decreased recurrence rate. Moreover, regarding 37 cases without any stones at the start of treatment, stone recurrence rate decreased significantly after the administration of allopurinol. Throughout this study, we used a new method for evaluating reasonable stone recurrence. It did not calculate the number of stones recurred, but the stone-forming circumstance in each kidney.(ABSTRACT TRUNCATED AT 250 WORDS)     

African American ESRD patients have a high pre-dialysis prevalence of kidney stones compared to NHANES III

If nephrolithiasis (NL) promotes progression to end stage renal disease (ESRD), requiring renal replacement therapy, one might expect a higher prevalence of pre-ESRD stones among ESRD versus non-ESRD subjects. We compared the prevalence of pre-ESRD stones in an African-American (AA) hemodialysis (HD) population to the estimated stone prevalence in a nationally representative cohort of AA persons as obtained by the Third National Health and Nutrition Survey (NHANES III). Face-to-face questionnaires were administered to a sample of 300 AA HD patients undergoing dialysis therapy at the University of Chicago to determine pre-ESRD NL prevalence. All data on pre-ESRD stone prevalence was confirmed by documented medical history, radiology and laboratory findings, where available. Prevalence of pre-ESRD NL in AA HD patients was 8.3% versus 2.8% in the age, race and sex adjusted NHANES III population (P < 0.001). After adjustment for age and sex, it was estimated that the prevalence of pre-ESRD kidney stones among AA HD patients is significantly higher than the prevalence of kidney stones found in the general AA population.     

Gender Differences among Hispanics and Caucasians in symptomatic presentation of kidney and ureteral stones

PURPOSE: We determined gender differences in the symptomatic presentation of kidney and ureteral stones among the Hispanic population and compared it with presentation in the Caucasian population. PATIENTS AND METHODS: A retrospective chart review was performed on 443 patients seen in our Emergency Department or Urgent Care Center for symptomatic kidney or ureteral stones over a 5-year period. Demographic information was obtained, including sex, race, age, location of stone, stone size, and type of urologic intervention. Of the 443 patients, 263 (59%) were Hispanic, and 180 (41%) were Caucasian. RESULTS: The male-to-female ratio of the symptomatic patients with kidney stones was 1.48 for both Hispanic and Caucasian patients. The male-to-female ratio for ureteral stones was 1.06 and 2.48 for the Hispanic and Caucasian patients, respectively (P < 0.05). The rate of urologic intervention was similar among Caucasian males and females and Hispanic females (approximately 33%) but significantly lower among Hispanic males (18%). CONCLUSIONS: The relative symptomatic presentation of ureteral stones of men and women among the Hispanic population is nearly 1:1, whereas the ratio in Caucasian men and women approaches the previously reported 2.5:1. No significant racial or sex differences were noted in the symptomatic presentation of kidney stones. In comparison with Hispanic men, Hispanic women undergo significantly more urologic interventions for symptomatic urolithiasis.