Hypocitraturia as a risk factor for nephrocalcinosis after kidney transplantation

Calcium-oxalate crystal deposition in kidney transplant biopsy specimen led us to investigate the impact of calcineurin inhibitor treatment on urinary excretion of lithogenic and stone inhibitory substances in 53 children after successful kidney transplantation (KTx) receiving cyclosporine A (CsA) or tacrolimus. We compared the values obtained with those of 12 patients with recurrent nephrotic syndrome under CsA and of 6 patients with Rasmussen encephalitis (RE) under tacrolimus therapy. Renal ultrasound examinations were repeatedly performed. Hypocitraturia was found in 69% of patients, with KTx patients having a significantly lower urinary citrate excretion than those receiving calcineurin inhibitors for other reasons. Secondly, we found hyperoxaluria in 35% of patients, again especially in those after KTx. No significant difference in urinary substances was seen comparing CsA with tacrolimus treatment. Urolithiasis was found in one and calcium-oxalate crystal deposition in biopsy specimen of three KTx patients. Calcineurin inhibitor treatment can lead to significant hypocitraturia, especially in patients after KTx receiving the highest dose of medication. Hyperoxaluria is primarily the result of a removal of significant body oxalate stores, deposited during dialysis, but may not be suspected as a specific side effect of calcineurin inhibitor therapy. Both findings can increase the risk for urolithiasis or nephrocalcinosis.

PHYSICOCHEMICAL METABOLIC CHARACTERISTICS FOR CALCIUM OXALATE STONE FORMATION IN PATIENTS WITH GOUTY DIATHESIS

PURPOSE

We determined why calcium oxalate stones instead of uric acid stones form in some patients with gouty diathesis.

MATERIALS AND METHODS

Gouty diathesis was diagnosed from absence of secondary causes of uric acid stones or low urinary pH, and reduced fractional excretion of urate with discriminant score of the relationship between urinary pH and fractional excretion of urate less than 80. From the stone registry 163 patients with gouty diathesis were identified, including 62 with uric acid stones (GD + UA) and 101 patients with calcium oxalate stones (GD + Ca). Metabolic data and 24-hour urinary chemistry study were compared between the 2 groups.

RESULTS

Compared with GD + UA, GD + Ca had significantly greater urinary calcium (196 +/- 96 mg per day vs 162 +/- 82 mg per day, p <0.05) and significantly lower urinary citrate (430 +/- 228 vs 519 +/- 288 mg per day, p <0.05), resulting in higher urinary saturation of calcium oxalate. Both groups had low urinary pH (less than 5.5) and high urinary undissociated uric acid (greater than 100 mg/dl). Urinary calcium post-oral calcium load was significantly higher in GD + Ca than in GD + UA (0.227 vs 0.168 mg/dl glomerular filtrate, p <0.001).

CONCLUSIONS

Calcium oxalate stones may form in some patients with gouty diathesis due to increased urinary excretion of calcium and reduced excretion of citrate. Relative hypercalciuria in GD + Ca may be due to intestinal hyperabsorption of calcium.

Urolithiasis in adults. Clinical and biochemical aspects

Urolithiasis is a multifactorial recurrent disease of world-wide distribution in rural, urban, industrial and non-industrial regions. Changes in urinary pH is a risk factor especially with hyperuricosuria, hypercalciuria or hyperoxaluria. With recurrence, hypercalcuria and higher urinary oxalate levels are more frequent. Hypercalciuria and hyperuricosuria showed correlation with family history of stones. The ionic relations between various stone forming salts in urine of patients are opposite to that in controls and are well represented in stone composition. Obesity is a risk factor in both genders. Over eating a diet rich in all nutrients was associated with hyperuricosuria while a diet high only in fat was associated with other urinary disturbances. High protein and fat intake are risk factors. High or low calcium diet was associated with urolithiasis and supplemental calcium is not a risk factor. Potassium and magnesium citrate are potent in inhibiting the growth of stone fragments after extracorporeal shock wave lithotripsy. Whether in patients or normal subjects, drinking hard water should be avoided; tap water or low calcium content water is preferable. Seasonal variations in temperature affected urinary volume, pH and relative saturation of uric acid. To prevent recurrence, patients should maintain high fluid intake achieving a urine volume of 2 liters per day.

The relationship of magnesium intake to serum and urinary calcium and magnesium levels in Trinidadian stone formers

BACKGROUND

The present study was undertaken to investigate the relationship between the dietary intake of magnesium and the serum and urinary levels of calcium and magnesium in a group of Trinidadian stone formers.

METHODS

A group of 102 confirmed stone formers presenting to urological clinics were interviewed using a questionnaire designed to obtain a semi-quantitative estimate of their oral magnesium intake. Patients were invited to give blood samples for serum calcium and magnesium levels and to provide 24-h urine specimens for the measurement of urinary levels of these minerals, as well as total urinary volumes. A group of 102 controls was subjected to a similar interview and blood and urinary testing. Chi-square tests and Student's t-tests were used to examine group demographic differences. The Mann-Whitney test investigated differences in biochemical indices. Binary logistic regression was used to identify predictors of stone formation.

RESULTS

Blood samples were obtained from 60 patients and 98 controls. Urine samples were returned by 34 patients and 97 controls. Only 10 stones were retrieved from patients. Patients had a significantly lower magnesium intake, but higher median serum and urinary calcium levels, and higher serum calcium to magnesium ratios than controls. Independent variables capable of predicting stone formation included total magnesium intake and serum and urinary calcium levels.

CONCLUSIONS

Increased serum and urinary calcium levels, calcium to magnesium ratios, and a low magnesium intake were predictive of stone formation in this Trinidadian population.

Role of urinary supersaturation in the evaluation of children with urolithiasis

Timed urine collections are a standard part of the evaluation for predisposition to stone formation in children with urolithiasis. Supersaturation is defined as the ratio of the concentration of dissolved salt to its solubility in urine. The purpose of the present study was to determine if adding supersaturation to the standard timed urine collection increased the ability to detect a metabolic predisposition to stone formation. Thirty-two children with urolithiasis had 24-hour urine measurements of calcium, oxalate, citrate, uric acid, and cystine (the "traditional" evaluation), as well as supersaturation for calcium oxalate, calcium phosphate, and uric acid, on the same urine sample. Nine (28%) of the 32 were hypercalciuric, 2 (6%) hyperoxaluric, and 4 (12%) hypocitraturic. In total, 14 (44%) had a metabolic predisposition that was detected by the traditional evaluation. Supersaturation was elevated in 18 (56%), including nine who did not have metabolic predisposition detected by traditional evaluation. Urine volume was low in 17 (53%) of 32 children, including eight of nine children with abnormal supersaturation but normal traditional evaluation. Only one child with normal traditional evaluation and normal urine volume had elevated supersaturation. These results show that the benefit of adding supersaturation to the traditional evaluation was largely negated by consideration of urine volume.

Risk factors determining active urinary stone formation in patients with urolithiasis

AIMS

The goal of clinical and metabolic evaluation of patients with urinary stones is to identify patients at high risk for recurrent stone formation and as such, to allow the practitioner to suggest preventive therapies. However, knowledge about risk factors for active stone formation in patients with urolithiasis is limited. This study was initiated to assess the significance of several metabolic and clinical parameters for the determination of the risk of active stone formation.

METHODS

Study in 320 consecutive outpatients referred to our clinic for metabolic analysis. Clinical and metabolic parameters were determined by standardized procedures of questionnaires, serum biochemical profiles and urinalysis.

RESULTS

In 21.5% of 284 patients with complete data stone formation was active. Hypercalciuria, hypocitraturia and urinary tract infections had odds ratios for active stone formation above 2.5, whereas the odds ratio of a positive family history was 0.38. Hyperuricosuria, hyperoxaluria and a low urinary volume did not influence the risk for active stone formation.

CONCLUSION

The risk profile for active stone formation differs from the risk profile for urolithiasis in general. Metabolic evaluation and determination of those risk factors in patients with urolithiasis might improve the estimation of the risk of future stone formation.

2,8-dihydroxyadeninuria: Are there no cases in scandinavia?

Homozygosity or mixed heterozygosity for mutations in the adenine phosphoribosyltransferase gene cause enzyme deficiency directing adenine through an alternative metabolic pathway. This results in the production of 2,8-dihydroxyadenine, which is actively secreted into the urine. 2,8-dihydroxyadenine is insoluble at physiological urinary pH but as marked supersaturation is possible the manifestations differ: there may be minimal consequences, there may be infiltration of the tubulointerstitial tissue with acute or chronic damage or there may be stone formation in the urinary tract. Effective treatment can be offered and therefore the prognosis depends upon the renal function at diagnosis. Treatment consists of adequate fluid intake, a low-purine diet and administration of allopurinol. Urinary 2,8-dihydroxyadenine crystals are easily recognized under a microscope. The diagnosis of 2,8-dihydroxyadeninuria can be confirmed by estimation of adenine phosphoribosyltransferase activity in erythrocyte lysates. More than 300 cases of 2,8-dihydroxyadeninuria have been diagnosed worldwide, most of them in Japan, France and Iceland. One case has been reported in Finland but there have been no reports from the Scandinavian peninsula or from Denmark. The relevant mutations may be very rare in these countries but underdiagnosis is also possible.

Effect of antiepileptic drug polytherapy on crystalluria

Urolithiasis is a rare side effect of antiepileptic drugs. To clarify the risk factors for urolithiasis induced by antiepileptic drugs, the effect of antiepileptic drug monotherapy on crystalluria was studied, and zonisamide or sulthiame therapy and alkaline urine were demonstrated to be risk factors. In the next investigation, the effect of antiepileptic drug polytherapy on crystalluria was retrospectively studied in epilepsy patients treated for more than 1 month during the last 7 years. A total of 278 urine specimens from epilepsy patients aged between 7 months and 36 years were enrolled in this study. The mean age was 12.3 years. There were 109 samples from females and 169 from males. Antiepileptic drugs administered in this study were valproate (174 urinary samples), zonisamide (139), carbamazepine (138), phenobarbital (65), phenytoin (52), acetazolamide (17), clonazepam (15), sulthiame (6), ethosuximide (6), nitrazepam (4), and clobazam (4). Epilepsy patients treated with antiepileptic drug polytherapy were frequently found to have crystalluria in patients demonstrating alkaline urine and taking acetazolamide, zonisamide (particularly with high serum levels), or many antiepileptic drugs in combination. Regular urinalysis seems to be necessary in these patients, and the evaluation for urolithiasis should be performed if persistent crystalluria is demonstrated.

Structural and functional modification of THP on nitration: comparison with stone formers THP

OBJECTIVE

The crucial steps involved in the lithogenic process are governed by the macromolecular components of urine, of which proteins play a major role. Structurally abnormal proteins have been reported to be present in the urine of stone formers. Free radical injury has come a long way in explaining some of the pathophysiological events of renal lithiasis. Thus, our present work was designed to study the impact of the potent oxidant peroxynitrite on the biochemical components of the urinary Tamm-Horsfall glycoprotein (THP).

MATERIALS AND METHODS

Nitration on THP was carried out using peroxynitrite (ONOO(-)). After nitration, biochemical components like thiols, S-nitrosothiol, hexose, hexosamine and sialic acid were determined and these factors were compared with those of stone formers and normal THP. Crystallization behavior of control, nitrated NS-THP and stone formers THP was studied.

RESULTS

There was a significant decrease in thiol, hexose, hexosamine and sialic acid contents in stone formers and nitrated NS-THP, when compared to that of the control THP. In contrast to this, S-nitrosothiol content was significantly increased in stone formers and nitrated NS-THP (p < 0.001) when compared with the control THP. NO(x) metabolites were significantly elevated in stone formers THP when compared with that of control THP. When subjected to CaOx crystallization, stone formers THP and nitrated NS-THP promoted both CaOx nucleation and aggregation, while normal THP was found to be an inhibitor of the above processes.

CONCLUSION

From our results we conclude that nitration of THP could represent one of the prime events in modifying kinetic behavior of THP, thus converting THP into a heterogeneous nucleator of renal calculi formation.

Acute felbamate overdose with crystalluria

A 3-year-old child developed vomiting, ataxia, and crystalluria after ingestion of approximately 232 mg/kg of felbamate elixir. High-powered polarization microscopy of the urine revealed sharp, needle-like crystals. The analysis of the urine crystals showed unchanged felbamate (80.9%), monocarbamate felbamate (18.8%), and trace amounts of mercapturic acid conjugates of the metabolite 2-phenylpropenal (0.1%). The serum felbamate level 15 h after ingestion was 138 mg/L. Crystalluria and hematuria resolved with intravenous fluid therapy, and the child recovered within 24 h.

EFFECTS OF URINARY PROTHROMBIN FRAGMENT 1 IN THE FORMATION OF CALCIUM OXALATE CALCULUS

PURPOSE

We investigated the effects of urinary prothrombin fragment 1 in the formation of calcium oxalate urolithiasis.

MATERIALS AND METHODS

Fresh urine and renal parenchyma from patients with calcium oxalate calculus and normal controls were collected. Urinary prothrombin fragment 1 was isolated and purified from urine. It was identified by sodium dodecyl sulfide-polyacrylamide gel electrophoresis and analysis of its first 13 N-amino acids. The inhibitory activity of urinary prothrombin fragment 1 on calcium oxalate crystal growth was tested by the seeded crystallization technique. Meanwhile, the gamma-carboxyglutamic acid composition of urinary prothrombin fragment 1 was analyzed by a previously described method and genetic mutation of the gamma-carboxyglutamic acid domain of urinary prothrombin fragment 1 from renal parenchyma was detected by polymerase chain reaction-single strand conformational polymorphism sequencing.

RESULTS

The gamma-carboxyglutamic acid composition of urinary prothrombin fragment 1 was significantly decreased from normal (24.4 to 1.7 mol/1,000 amino acids) in patients with calcium oxalate calculus. The mean growth index +/- SD of urinary prothrombin fragment 1 to calcium oxalate crystals was 42.3 +/- 4.2 compared with the normal index of 19.2 +/- 2.8 (p <0.01). The polymerase chain reaction-single strand conformational polymorphism sequencing technique revealed no genetic mutation of the gamma-carboxyglutamic acid domain of urinary prothrombin fragment 1 in patients with calcium oxalate calculus.

CONCLUSIONS

The gamma-carboxyglutamic acid composition of urinary prothrombin fragment 1 as well as its ability to inhibit calcium oxalate crystal growth was significantly decreased in patients with calcium oxalate calculus. This was not caused by genetic mutation of the gamma-carboxyglutamic acid domain of urinary prothrombin fragment 1. It is important to elucidate the mechanisms of calcium oxalate stones in view of urinary prothrombin fragment 1.

Surface-enhanced laser desorption/ionization-time of flight-mass spectrometry (SELDI-TOF-MS): a new proteomic urinary test for patients with urolithiasis

SELDI-TOF-MS is a highly sensitive protein-analysis tool capable of detecting minute protein profile differences between biological samples. As proteins have been associated with urinary tract calculi, protein-based urinalysis may offer insights into their diagnosis. The purpose of this study was to evaluate SELDI-TOF-MS as a potential method for identifying urinary biomarkers of urolithiasis. Midstream sterile urine samples were obtained from 25 male patients with a confirmed diagnosis of urolithiasis (test group) and 25 male subjects with no known history of the disease (controls). Urinary levels of oxalate, total protein, albumin, and osteopontin were determined. Protein profiles were generated using SELDI-TOF-MS.SELDI-TOF-MS profiling revealed a relationship between protein peak intensities at 67 and 24 kDa that differed between the two groups. The ratio of p67:p24 was found to be less than 1.0 in all of the control samples (mean 0.26), while 18 out of 25 (72%) of the test group samples displayed a ratio greater than 1.0 (total group mean 4.75, P<0.001). Albumin, total protein, and oxalate levels were higher in the test group than the controls. Although SELDI-TOF-MS is not yet in widespread use in hospital and diagnostic laboratories, this system represents a promising new method for rapidly identifying patients with urolithiasis.

Analysis of calcium, oxalate, and citrate interaction in idiopathic calcium urolithiasis in children

The majority of urinary stones in children are composed of calcium oxalate. To investigate the interaction between urinary calcium, oxalate, and citrate as major risk factors for calcium stones formation, their 24-h urinary excretion was determined in 30 children with urolithiasis and 15 normal healthy children. The cutoff points between children with urolithiasis and healthy children, accuracy, sensitivity, and specificity for each risk factor alone as well as for all three taken together were determined. OneR and J4.8 classifiers as parts of the larger data mining software Weka, based on machine learning algorithms, were used for the determination of the cutoff points for differentiation of the children. The decision tree based on J4.8 classifier analysis of all three risk factors together proved to be the best for differentiating stone formers from normal children. In comparison to the accuracy of the differentiation after calcium and oxalate of 80% and 75.6%, respectively, the decision tree showed an accuracy of 97.8%. Even when its stability was tested by the leave-one-out cross-validation procedure, the accuracy remained at a very acceptable percentage of 93.2% correctly classified patients. J4.8 classifier analysis gave a look inside urinary calcium, oxalate, and citrate interaction. Urinary calcium excretion was shown as the most informative in discrimination of the children with urolithiasis from healthy children. However, it was shown that oxalate and citrate excretions might influence the stone formation in a subpopulation of the stone formers. In patients with low urinary calcium, a major role in lithogenesis belongs to oxalate, in some of them alone and in others in conjunction with citrate. Decreased urinary citrate excretion in the presence of increased oxalate excretion may lead to stone formation.

STONE FORMING RISK OF CALCIUM CITRATE SUPPLEMENTATION IN HEALTHY POSTMENOPAUSAL WOMEN

PURPOSE

We evaluated the effect of calcium citrate supplementation alone or in combination with potassium citrate on the stone forming propensity in healthy postmenopausal women.

MATERIALS AND METHODS

A total of 18 postmenopausal women without stones underwent a randomized trial of 4 phases comprised of 2 weeks of treatment with placebo, calcium citrate (400 mg calcium twice daily), potassium citrate (20 mEq twice daily), and calcium citrate and potassium citrate (at same doses). During the last 2 days of each phase urine was collected in 24-hour pools for complete stone risk analysis.

RESULTS

Compared to placebo, calcium citrate increased urinary calcium and citrate but decreased urinary oxalate and phosphate. Urinary saturation of calcium oxalate, brushite and undissociated uric acid did not change. Potassium citrate decreased urinary calcium, and increased urinary citrate and pH. It decreased urinary saturation of calcium oxalate and undissociated uric acid, and did not change the saturation of brushite. When calcium citrate was combined with potassium citrate, urinary calcium remained high, urinary citrate increased even further and urinary oxalate remained reduced from the calcium citrate alone, thereby marginally decreasing the urinary saturation of calcium oxalate. Urinary pH increased, decreasing urinary undissociated uric acid. The increase in pH increased the saturation of brushite despite the decrease in urinary phosphorus.

CONCLUSIONS

Calcium citrate supplementation does not increase the risk of stone formation in healthy postmenopausal women. The co-administered potassium citrate may provide additional protection against formation of uric acid and calcium oxalate stones.

Determination of the calcium oxalate crystallization risk from urine samples: the BONN Risk Index in comparison to other risk formulas

PURPOSE

Regular risk evaluation and risk monitoring during stone therapy are recommended measures to ensure reduction of recurrence of crystal formation. This strategy optimizes the patient treatment by a more individual approach and decreases expensive over treatment. We evaluated the BONN Risk Index (BRI) through data actualization and evaluation refinement. The BRI was compared with the most common methods of risk evaluation, namely calculation of relative urinary calcium oxalate (CaOx) supersaturation (RS) and of the urine activity product (AP)CaOx index to estimate the urine AP with respect to CaOx.

MATERIALS AND METHODS

A total of 201, 12 and 24-hour urine samples were collected from 95 healthy volunteers and from 106 CaOx stone formers. Crystallization experiments following the BRI method were performed. RS and APCaOx were calculated from urinalysis. Data were indexed and individually grouped into 8 classes, and frequency distributions were plotted. A calculation scheme for the BRI based estimation of the statistical probability of a clinically healthy person being a (still nondetected) CaOx stone former is provided.

RESULTS

Logarithmically arranged BRI groups from healthy subject and patient data showed Gaussian frequency distributions. Compared with RS and APCaOx BRI allowed optimum distinction between healthy subjects and stone formers. The healthy subject probability of already being a CaOx stone former strongly increased with increasing BRI.

CONCLUSIONS

The BRI for evaluating CaOx crystallization risk allows reliable distinction between healthy subjects and CaOx stone formers. Although RS and APCaOx require much more analytical efforts for determination, their results do not show higher reliability.

[What foods should stone formers avoid?]

Urolithiasis is a disease that has a high recurrence rate. We think that dietary guidance is necessary for the prevention of urolithiasis. It is important that stone formers eat a well-balanced diet and proper quantity of foods.

[Clinical value of crystalluria study]

Crystalluria is a marker of urine supersaturation present in both normal and pathological conditions. Indeed, nature and characteristics of the spontaneous crystalluria are of clinical interest for detecting and following biological disorders involved in renal diseases. Method. Crystalluria examination should preferably be performed on first morning urine or fresh fasting voiding samples by polarised microscopy in a Malassez cell. Urine samples must be stored at 37 degrees C or at room temperature and examined within two hours following voiding. Results and discussion. Crystalluria should be interpreted according to various criteria: 1) chemical nature of crystals for abnormal crystals such as struvite, ammonium urate, cystine, dihydroxyadenine, xanthine or drugs; 2) crystalline phase of common chemical species as calcium oxalates, calcium phosphates and uric acids; 3) crystal morphology (calcium oxalates); 4) crystal size (calcium oxalates); 5) crystal abundance (calcium oxalates, calcium phosphates, uric acids, cystine); 6) crystal aggregation (calcium oxalates); 7) frequency of crystalluria assessed on serial first morning urine samples, a very useful tool for long-term surveillance of patients. Within calcium oxalate crystalluria, presence of whewellite is a marker of elevated oxalate concentration (urine oxalate > 0.3 mmol/L); a crystal number > 200/mm 3 is highly suggestive of heavy hyperoxaluria of genetic or absorptive origin. Predominant weddellite crystalluria is most often indicative of an excessive urine calcium concentration (> 3.8 mmol/L); a dodecahedric aspect of the crystals is a marker for heavy hypercalciuria (> 6 mmol/L) while an increased crystal size (>or= 35 microm) is indicative of simultaneous hypercalciuria and hyperoxaluria. Calculation of the global crystal volume, especially when applied to calcium oxalates or cystine, is a clinically useful tool for the monitoring of patients suffering from primary hyperoxaluria or cystinuria. Lastly, presence of crystalluria in more than 50% of serial first voided morning urine samples is in our experience the most reliable biological marker for detecting the risk of stone recurrence in lithiasic patients. Conclusion. Crystalluria examination is an essential laboratory test for detecting and following pathological conditions, which may induce renal stone disease or alter kidney function due to urine crystals.

Phyllanthus niruri normalizes elevated urinary calcium levels in calcium stone forming (CSF) patients

Phyllanthus niruri is a plant used for years in Brazil to treat urinary calculi. We prospectively evaluated the effect of P. niruri intake on 24 h urinary biochemical parameters in an attempt to assess its in vivo effect in calcium stone forming (CSF) patients. A total of 69 CSF patients (39 males and 30 females, 38+/-8 years old) were randomized to take either P. niruri ( n=33) (450 mg capsules, td) or placebo ( n=36) for 3 months. Blood calcium, uric acid, citrate, magnesium, oxalate, sodium and potassium were determined at baseline and at the end of the study. A subset analysis was made in patients classified according to the presence of metabolic abnormalities (hypercalciuria, hyperuricosuria, hyperoxaluria, hypocitraturia and hypomagnesiuria). Overall, there were no significant differences in the mean values of urinary parameters between the urine samples before and after P. niruri intake, except for a slight reduction in mean urinary magnesium after P. niruri, which was within the normal range. However, in the subset analysis, we observed that P. niruri induced a significant reduction in the mean urinary calcium in hypercalciuric patients (4.8+/-1.0 vs 3.4+/-1.1 mg/kg/24 h, P<0.05). In this short-term follow-up, no significant differences in calculi voiding and/or pain relief between the groups taking P. niruri or the placebo were detected. Our data suggest that P. niruri intake reduces urinary calcium based on the analysis of a subset of patients presenting with hypercalciuria. Larger trials including primary hypercalciuric stone formers should be performed in order to confirm these findings and to determine the possible clinical consequences of urinary calcium reduction during P. niruri administration.

Changes in urinary parameters after oral administration of potassium-sodium citrate and magnesium oxide to prevent urolithiasis

OBJECTIVES

To examine urinary parameters among normal individuals and patients with calcium oxalate (CaOx) stones after oral administration of potassium-sodium citrate (KNa-Cit) and magnesium oxide (MgO). Urinary citrate and magnesium have been known as the inhibitors of CaOx stone formation. Supplementation with potassium-magnesium citrate prevents the recurrence of CaOx stones.

METHODS

Twenty-five male volunteers aged 21 to 42 years without a history of urinary stones were given either KNa-Cit or MgO, or both. Fourteen patients with recurrent CaOx stones were also given both supplements, and 24-hour urine samples were collected to determine the urinary parameters.

RESULTS

The administration of both KNa-Cit and MgO to the normal individuals increased the excretion of citrate, magnesium, and potassium by 70.0%, 44.2%, and 50.0%, respectively. These parameters increased less when KNa-Cit or MgO was administered individually. After administration of both supplements to the patients with stones, the citrate, magnesium, and potassium levels increased by 62.1%, 63.3%, and 25.3%, respectively, and oxalate decreased by 66.5%. In both normal individuals and patients, the ion activity product index of CaOx decreased significantly more after administration of the combination than with either compound alone or before administration.

CONCLUSION

The combination of KNa-Cit and MgO is more effective than either supplement alone in inhibiting the crystallization of CaOx stones. The combination may improve the urinary parameters of patients with stones accompanied by hypocitraturia and/or hypomagnesuria.

Comparison of cytology and nuclear matrix protein 22 (NMP 22) for the detection and follow-up of bladder-cancer

OBJECTIVES

This study was designed to determine the clinical usefulness of the Nuclear Matrix Protein 22 (NMP 22) Test for the detection of bladder cancer in comparison to urine cytology.

METHODS

One hundred sixty-four patients suffering from or being suspicious for bladder cancer and 64 healthy controls participated in a prospective study. Freshly voided spot urine samples were taken for cytological examination and determination of NMP 22-levels by enzyme-linked immunoassay.

RESULTS

Sensitivity to the NMP 22 Test according to the tumor grading was (results of cytology in parentheses): GI 25.0% (20.0%), G2 68.2% (59.1%), and G3 100.0% (66.7%); overall sensitivity was 62.5% (45.0%). Sensitivity according to superficial bladder cancer was 46.7% (36.7%), and to invasive bladder cancer 90.0% (70.0%). Specificity was 65.9% (88.9%).

CONCLUSIONS

NMP 22 is a reliable tool for detecting invasive bladder cancer. Results for the well-differentiated superficial bladder cancer occurring frequently are as poor as those obtained with cytology. In addition, benign lesions such as urolithiasis or urinary tract infection lead to false positive results. Therefore, cystoscopy has to be performed when trying to detect and follow-up bladder cancer.

The effect of a vegetarian and different omnivorous diets on urinary risk factors for uric acid stone formation

BACKGROUND

About 10-15% of all urinary stones are composed of uric acid. A high urinary uric acid excretion, a low urine volume and an acidic urinary pH value are suggested to be the most important risk factors for uric acid stone formation.

AIM OF THE STUDY

The effect of a vegetarian diet and different omnivorous diets on the risk of uric acid crystallization was investigated.

METHODS

Ten healthy male subjects ingested a self-selected meat-containing diet (SD) for two weeks, and three different standardized diets for a period of 5 days each. The Westerntype diet (WD) was representative of the usual dietary habits,whereas the balanced omnivorous diet (OD) and the ovo-lacto-vegetarian diet (VD) were calculated according to the requirements.

RESULTS

The risk of uric acid crystallization was highest on the ingestion of diets SD and WD, due to the high urinary uric acid excretion and the acidic urinary pH. The relative supersaturation with uric acid declined significantly by 85% on the intake of diet OD, consequent to the decrease in uric acid excretion and concentration and the increase in urinary pH value. The ingestion of the vegetarian diet VD led to a further significant reduction in the risk of uric acid crystallization by 93% compared to diet WD.

CONCLUSIONS

The results indicate that the intake of a balanced vegetarian diet with a moderate animal protein and purine content, an adequate fluid intake and a high alkali-load with fruits and vegetables results in the lowest risk of uric acid crystallization compared to the omnivorous diets.

Renal Tubular Alteration by Crystalluria in Stone Disease – An Experimental Study by Means of MDCK Cells

OBJECTIVES

Physicochemical properties of urine do not explain the formation of urinary stones. Clinical findings and results of animal experiments suggest that alteration to the renal tubular cell plays a key role in the initiation of urinary stone formation. It is not clear whether this is a primarily intracellular alteration of metabolic origin which, after lysis of the renal tubular cell in the lumen, presents a nucleus for the formation of concretions, or whether in the lumen it is tubular cell damage induced by crystalluria that triggers the formation of urinary stones.

MATERIALS AND METHOD

Using Madin-Darby canine kidney cells, the influence of crystalluria on the renal tubular cell was tested in cell cultures. The influence of parathyroid hormone, vitamin D(3), oxalate and calcium concentrations and the extent to which these processes can be inhibited by allopurinol and selenium were investigated.

RESULTS

Calcium oxalate monohydrate crystals produced reproducible damage to the renal tubular cell which was independent of parathyroid hormone and vitamin D(3). The crystalluria-induced effects were unrelated to the oxalate and calcium concentration or the pH. Allopurinol and selenium were able to inhibit the processes.

CONCLUSION

The results indicate secondary involvement of the renal tubular cell in lithogenesis as a result of luminal alteration caused by calcium oxalate crystals. Mechanical damage and interaction between crystal and tubular cell lead to the apposition of crystals. The nephroprotective effect of allopurinol and selenium as antioxidants might explain the benefit of allopurinol found clinically in terms of stone metaphylaxis.

Screening for biochemical abnormalities in urolithiasis patients

BACKGROUND

The significance of biochemical screening in stone formers has been a debated topic. This study was conducted to investigate the frequency of biochemical abnormalities in our urolithiasis patients and to compare the abnormality between the first time and recurrent stone formers so that this information would help in assessing the value of biochemical screening in our practice.

METHODS

Over a twenty-one month period, new and recurrent stone disease patients had one random blood specimen and two random 24-hour urine collections analysed for biochemical abnormalities. Serum was checked for calcium, urate, phosphate and creatinine. The urines were measured for volumes, calcium, oxalate, urate, citrate, cystine and pH.

RESULTS

Out of total of 113 patients, 83 (73%) had some urinary or blood abnormality. Highest number of abnormalities were in urine. Low volume 33 (39.76%), hypercalciuria 33 (39.76%) and hyperoxaluria 20 (24.1%) were the main urinary abnormalities. Elevated serum creatinine in 10 (12.05%) was commonest blood abnormality. Females had significantly higher frequencies of low urinary volume (48% vs 21%, p=0.001), hyperoxaluria (38% vs 11%, p=0.002) and hypocitraturia (37% vs 0%, p<0.001). There was no significant difference of abnormality rate between first time and recurrent stone formers.

CONCLUSION

A high frequency of urinary biochemical abnormality and equal abnormality frequencies among first time and recurrent stone formers highlights the significance of biochemical screening even in cases of initial stone presentation. We feel such diagnostic evaluation would help in providing precise treatment and efficient prophylaxis.