Metabolic basis of renal-stone disease

Effects of drinking water quality on urinary parameters in men with and without urinary tract stones

OBJECTIVE

There is some controversy regarding the impact of water hardness on stone risk. Our study addresses this issue in a controlled setting.

MATERIAL AND METHODS

Fifteen stone-former (SF) and 14 non-stone-former (NSF) males participated in this study in 3 intervals of 2 days each. Subjects collected a 24-hour urine sample while consuming a self-selected diet. They were then administered controlled diets. During the first 2 days, patients consumed water of minimal hardness (WMH), followed by tap water (TW) with moderate hardness on days 3 and 4, and mineral water (MW) on the final 2 days. Calcium (Ca), phosphorus, uric acid, oxalate, citrate, magnesium (Mg), sodium, potassium, and creatinine (Cr) content were measured in 24-hour urine samples on days 2, 4, and 6.

RESULTS

Differences in water hardness and analytes were statistically significant among the different water types (P < .05). Urinary output in both groups increased during intervention with all 3 varieties of water (P < .05). Specific gravity of urine decreased in both groups drinking WMH and TW (P < .05) but not with MW. Mg/g Cr level was higher in NSF at baseline (P < .01), WMH (P < .05), and TW (P < .05). With the increase in drinking water hardness, Ca/g Cr ratio increased in SF but not in NSF (P < .05).

CONCLUSIONS

NSF had significantly higher urinary Mg/g Cr excretion rate before intervention than SF (P < .01). Increasing drinking water hardness while controlling for all other factors increased Ca/g Cr ratio in SF, rendering them at least theoretically more inclined to stone formation.

Ethylene glycol induces calcium oxalate crystal deposition in Malpighian tubules: a Drosophila model for nephrolithiasis/urolithiasis

Several animal species are used to study calcium oxalate urolithiasis; however, an ideal model has yet to be identified. We used Drosophila as a model organism and fed the flies lithogenic agents such as ethylene glycol, hydroxyl-L-proline, and sodium oxalate. At different times, the Malpighian tubules, the kidney equivalent of insects, were dissected and a polarized light microscope used to highlight the birefringent crystals. Scanning electron microscopy and energy-dispersive X-ray spectroscopy confirmed that the crystal composition was predominately calcium oxalate. Furthermore, administration of potassium citrate successfully reduced the quantity of and modulated the integrity of the ethylene glycol-induced crystals. Thus, the Drosophila model of bio-mineralization produces crystals in the urinary system through many lithogenic agents, permits observation of crystal formation, and is amenable to genetic manipulation. This model may mimic the etiology and clinical manifestations of calcium oxalate stone formation and aid in identification of the genetic basis of this disease.

Management of Cystinuria

Cystinuria is a monogenic disorder in which there is a transepithelial transport defect of di-basic amino acids, including cystine, ornithine, lysine, and arginine (COLA). This results in diminished reabsorption of these amino acids in both the intestine and renal proximal tubule. This article describes the disorder, reviews the mechanisms of normal COLA renal transport, and summarizes issues related to the disorder, such as the role of mutations, associated diseases, clinical manifestations, therapies, the renal impact, and handling of pediatric patients.

Cystine calculi. Diagnosis and management

The genetics, pathophysiology, diagnosis, and treatment of cystinuria are discussed in this article. Newer chemotherapeutic and surgical options that are used to treat this disease process also are reviewed. The authors suggest a multimodal approach in the treatment of cystinuria and cystine calculi.

Human bladder cancer: evidence for a potential irritation-induced mechanism

Bladder cancer is one of the most common human cancers, constituting about 6% and 2% of all cancers among males and females, respectively. Over 90% of all bladder cancers are transitional cell carcinomas, with most of the remainder being squamous cell carcinomas. Smoking and occupational exposure to aromatic amines and other agents are most prominent among the risk factors identified. Inflammation of the bladder, largely by infection but also by stones or a combination of the two, may play some role in human bladder cancer development. The association between inflammation and cancer appears to be stronger for squamous cell than for transitional cell carcinoma. Stones and infection can be important factors in the development of bladder tumours in rodents, but the tumours are predominantly transitional cell rather than squamous cell carcinomas.

The influence of banana stem extract on urinary risk factors for stones in normal and hyperoxaluric rats

OBJECTIVE

To study the effect of banana stem (Family Musaceae) extract on urinary risk factors in an animal model of hyperoxaluria.

MATERIALS AND METHODS

Thirty male rats were divided into five groups of six rats each. The rats in Group I acted as the control, in Group II rats hyperoxaluria was induced using sodium glycollate, Group III were given aqueous banana stem extract alone, Group IV were given both sodium glycollate and aqueous banana stem extract and Group V were given sodium glycollate alone followed by aqueous banana stem extract. Urine analysis (24 h) was carried out to determine the levels of calcium, phosphorous, oxalate, glycollic acid and glyoxylic acid in each of the five groups.

RESULTS

In the rats treated with aqueous banana stem extract, urinary oxalate excretion was significantly reduced when compared with the controls. The extract reduced urinary oxalate, glycollic and glyoxylic acid and phosphorus excretion in the hyperoxaluric rats. The extract appeared to have no effect on urinary calcium excretion.

CONCLUSION

Banana stem extract from the Musaceae family may be a useful agent in the treatment of patients with hyperoxaluric urolithiasis.

The frusemide test: simple screening test for renal acidification defect in urolithiasis

Urinary pH was first labelled as a risk factor for patients with recurrent calcium stone disease of the renal tract in 1978. The standard diagnostic test for patients with a history of stones, who appear to have urinary acidification defects is the ammonium chloride test. However, the performance of this test results in significant morbidity, particularly nausea and vomiting, and as a result there is little enthusiasm for screening for such defects. We describe a screening test that may be used to determine which patients require more definitive testing. It involves an oral dose of frusemide (40 mg) followed by half-hourly urine sampling for pH. For the detection of a renal tubular acidification defect, the frusemide test had sensitivity = 100%, specificity = 82%, predictive value of a positive result = 40%, predictive value of a negative result = 100%, screening efficiency = 84%, and there was no morbidity. During the ammonium chloride test 80% of the patients vomited or felt very nauseated.

Hyperoxaluria in patients with recurrent calcium oxalate calculi: dietary and other risk factors

The presence of mild hyperoxaluria in recurrent calcium oxalate stone formers is controversial. The aim of this study was to identify recurrent stone formers with mild hyperoxaluria and to classify them further by assessing their response to a low oxalate diet. In addition, the prevalence of other risk factors for stone formation in this group of patients was investigated. A total of 207 consecutive patients with recurrent renal calculi were screened and 40 (19%) were found to have mild hyperoxaluria. Of these, 18 (45%) responded to dietary oxalate restriction by normalising their urinary oxalate. The remaining 22 patients were classified as having idiopathic hyperoxaluria and were subdivided into those in whom urinary oxalate excretion was consistently elevated in all specimens measured and those in whom the elevation was intermittent in nature. Dietary oxalate restriction had a partially beneficial effect in lowering oxalate excretion in the patients with persistent hyperoxaluria. No difference in urinary oxalate excretion was found after dietary restriction in the patients with intermittent hyperoxaluria. Other risk factors, including dietary, absorptive and renal hypercalciuria and hypocitraturia, were documented, the prevalence of which (65%) was not significantly different from that (62.5%) found in 40 age- and sex-matched calcium stone formers without hyperoxaluria. The prevalence of hyperuricosuria was significantly greater in patients with hyperoxaluria when compared with stone controls. Further studies are required to elucidate the underlying mechanisms of hyperoxaluria in recurrent stone formers.

Urinary calcium excretion in healthy adolescents

To establish normative data for urinary calcium excretion in healthy adolescents, we measured calcium-creatinine ratios (UCa/Cr) in urine samples collected from 222 middle school teenagers of diverse racial and socioeconomic backgrounds. Median UCa/Cr were: white girls, 0.23 mmol/L per mmol/L (0.08 as mg/dl per mg/dl); black girls, 0.14 (0.05); white boys, 0.14 (0.05); and black boys, 0.08 (0.03). The 95th percentile values for UCa/Cr were: white girls, 0.54 (0.19); black girls, 0.59 (0.21); white boys, 0.68 (0.24); and black boys, 0.50 (0.18). By nonparametric analysis, girls had significantly higher UCa/Cr than boys (p less than 0.01), and whites had significantly higher urinary UCa/Cr than blacks (p less than 0.01). No significant correlation was found between Tanner stage and UCa/Cr in either sex. This study provides data for detecting adolescents with high urine calcium excretion, which should be useful clinically and in studies designed to evaluate the significance of persistent hypercalciuria.

Urinary volume in children with urolithiasis

Urinary volume in 24-hour urine collections was examined in 50 children with hypercalciuria and urolithiasis or hematuria, 12 with idiopathic calcium oxalate urolithiasis and 36 healthy children. Urinary volume was 22.2 +/- 2.0 ml. per kg. per day in healthy children and 25.4 +/- 2.0 ml. per kg. per day in children with hypercalciuria, and it was similar in children with absorptive and renal hypercalciuria, and significantly lower in children with idiopathic calcium oxalate urolithiasis (12.2 +/- 1.4 ml. per kg. per day, p less than 0.001 from controls and children with hypercalciuria). Volume was not statistically different in hypercalciuric children with and without urolithiasis. Urinary sodium excretion in children with idiopathic calculi was not statistically different from controls. Urine osmolality was similar among the groups. Urinary volume represents a risk factor in children with idiopathic calcium oxalate urolithiasis, and increased fluid intake should be emphasized in such patients.

Clinical and laboratory approaches for evaluation of nephrolithiasis

The initial part of this presentation deals with the sensitivity of tests commonly used in the diagnosis of primary hyperparathyroidism. Total serum calcium levels often are normal in patients with small parathyroid adenomas but levels of serum ultrafilterable and/or ionized calcium usually are elevated in these patients. The recent introduction of improved radioimmunoassays for measurement of circulating parathyroid hormone has led to greatly improved sensitivity of this test for the diagnosis of primary hyperparathyroidism. However, measurement of total urinary cyclic adenosine monophosphate, even when expressed as a function of glomerular filtration rate, is an extremely insensitive test in patients who have parathyroid adenomas weighing less than 1 gm. Consequently, this test no longer is used for diagnostic purposes in our laboratory. Data relating to the prevalence and causes of hyperoxaluria in patients with idiopathic calcium oxalate stones also are presented. Hyperoxaluria (more than 450 mumol. per 24 hours) was found in 21 of 99 consecutive untreated male patients. Approximately a third of the patients with high normal or increased urinary oxalate excretion also have increased urinary glycolate excretion, which is indicative of increased endogenous oxalate production. This metabolic abnormality was unresponsive to pyridoxine administration but preliminary findings suggest that it may be corrected by restricting dietary protein.

Cystinuria

Cystinuria is an inherited metabolic disease resulting in renal stone formation. An incidence of 1 in 7000 makes it a relatively common genetic disease. The biochemical defect is a carrier protein in the epithelial cells of certain organs. This carrier protein is responsible for the transport of cystine and the dibasic amino acids. Cystine is a poorly soluble compound which precipitates in acid urine and results in renal calculi. Cystine stones account for 1 to 2% of all renal calculi. Homozygotes are detected by the high concentration of cystine in their urine. Treatment consists of sulfhydryl compounds that form more soluble compounds with cystine through sulfhydryl exchange as well as alkalinization of urine and hydration to make cystine more soluble.

Urolithiasis in childhood

Urolithiasis occurs less frequently in children than it does in adults living in contemporary industrialized nations. However, renal calculi continue to be identified with greater frequency in certain children: those who live in some areas of North America (e.g., the Southeastern United States), in those with relatively common metabolic disorders such as idiopathic hypercalciuria or with congenital urinary tract malformations, and in patients who have remained immobilized for long periods. Evaluation of children with suspected urolithiasis should include a careful history and physical examination to identify associated symptoms and signs and factors known to predispose to calculus formation, appropriate radiographic and blood studies, and timed urine collections. Appropriate management varies with etiology but should include maintaining adequate fluid intake, and long-term monitoring of the activity of the stone disease.

Canine primary hyperparathyroidism and its association with urolithiasis

Primary hyperparathyroidism results from autonomous secretion of parathyroid hormone by a single or multiple parathyroid glands. Clinical signs result from various combinations of hypercalcemia, hypercalcemic nephropathy, urolithiasis, or mobilization of calcium and phosphorus from bone. Following parathyroidectomy, the prognosis for dogs with primary hyperparathyroidism is good if the disorder is diagnosed before renal disease is advanced.

New drug therapy for kidney stones: a review of cellulose sodium phosphate, acetohydroxamic acid, and potassium citrate

Kidney stones have an overall incidence of two to three percent in western countries. In many patients, the disease process is difficult to control and recurrence rates are high: 20 to 50 percent over the subsequent ten years. The pathogenesis and standard methods of treatment for the five major types of stones (i.e., calcium oxalate, struvite, calcium phosphate, uric acid, and cystine) are reviewed. Three new drugs are reviewed in the context of their roles in the selective treatment of kidney stones. Cellulose sodium phosphate (Calcibind) is a nonabsorbable ion-exchange resin with a limited indication for the treatment of calcium stones associated with absorptive hypercalciuria Type I. Acetohydroxamic acid (Lithostat) is an urease-inhibitor that is indicated as adjunctive therapy in patients with chronic urea-splitting urinary tract infections and struvite stones. Potassium citrate (Urocit) is an investigational agent that has clinical efficacy in patients with calcium oxalate and calcium phosphate stones who are hypocitraturic. In addition, potassium citrate is an alkalinizing agent that can be used in patients with uric acid stones.

Response to a physiologic dose of pyridoxine in type I primary hyperoxaluria

We measured urinary oxalate and glycolate excretion before and during pyridoxine administration (2 to 200 mg per day) in four patients with primary hyperoxaluria. In two patients with type I primary hyperoxaluria, urinary oxalate and glycolate excretion fell markedly in response to a physiologic dose of pyridoxine of 2 mg per day and became completely normal when the dose was increased to 25 mg per day. In the other two patients, who had a different type of primary hyperoxaluria (normal urinary glycolate excretion), there was no response to 2 mg of pyridoxine per day. In one of these patients, doses of 25 and 50 mg per day were also ineffective, but a moderate reduction in oxalate excretion took place with 200 mg per day; in the other patient there was a moderate reduction in oxalate excretion with 25 mg of pyridoxine per day. Our findings suggest that the degree of hyperoxaluria in this disorder may be only slight or moderate if the patient has been ingesting a pyridoxine-rich diet or multivitamin tablets containing small amounts of pyridoxine. Our results also suggest that smaller doses of pyridoxine than those heretofore employed should be tried in patients with primary hyperoxaluria.

Cholestatic jaundice associated with D-penicillamine therapy

Cholestatic jaundice is a rare complication of penicillamine therapy. We report here a 35-year-old patient who developed fever, a rash and cholestatic jaundice 16 days after commencing treatment with penicillamine for cystinuria. The jaundice subsided slowly after discontinuation of the drug and with prolonged therapy with prednisone. The literature on penicillamine-induced liver injury is reviewed.

Nephrolithiasis: current concepts in medical management

Advances in renal lithiasis research have contributed to a better understanding of the many varied factors that contribute to renal calculus formation. Utilizing the newer techniques of ambulatory metabolic evaluation, we can establish a specific diagnosis in 95% of recurrent stone-formers. Since a significant percentage of initial stone-formers will never have a second episode, it is essential to establish the natural history of the patient's stone disease prior to initiating potentially life-long medical therapy. The majority of initial stone-formers can be managed with education concerning modest dietary restrictions and increased fluid intake. For the recurrent stone-former with metabolically active stone disease, it is probably best to design medical therapy to treat the specific urinary chemical abnormality or disease process.

Thiol-disulfide interchange between cystine and N-2-mercaptoethyl-1, 3-diaminopropane as a potential treatment for cystinuria

The radioprotective compound WR2721 is a thiophosphate, which, when administered orally, is activated at the acid pH of the stomach to its free thiol (MDP). The free thiol is a mucolytic compound which acts via the reduction of disulfide bonds of mucin molecules. An equimolar mixture of MDP and cysteine, in urine at pH 6.0 and 37 degrees C, when oxidized by molecular oxygen, preferentially forms the soluble mixed disulfide between MDP and cysteine. The disulfide cystine will undergo thiol-disulfide interchange with MDP; as a result, cystine crystals are effectively dissolved. Moreover, in the presence of catalytic amounts of free thiol, the disulfide of MDP will undergo thiol-disulfide interchange with cystine to dissolve cystine crystals. The mixed disulfide of MDP with cysteine is soluble in urine at pH 6.0 and 37 degrees C to at least 100 mg/ml. Chromatographic procedures which permit the analysis of MDP and its mixed disulfide derivatives as MDP-sulfonic acid are described. By these procedures, it was demonstrated that 20% of a single oral dose of WR2721 was excreted as MDP derivatives in the urine of normal volunteers. These procedures will permit the evaluation of WR2721 in the treatment of cystinuria.

The stone clinic effect in patients with idiopathic calcium urolithiasis

The "stone clinic effect" refers to the effect of encouraging a high intake of fluid and avoiding dietary excesses on stone formation and growth in patients with urolithiasis. To determine the extent of this effect we reviewed the clinical courses of 108 patients with idiopathic calcium urolithiasis and indeterminant metabolic activity. There was no evidence of stone growth or new stone formation (metabolic inactivity) after a mean followup of 62.6 months in 63 of the 108 patients (58.3 per cent), including 12 of 17 (70.6 per cent) with hypercalciuria and 7 of 15 (46.7 per cent) with hyperuricosuria. Comparison of initial and followup 24-hour urine volumes demonstrated a significant increase in patients who were metabolically inactive at followup (p less than 0.0005), while no increase was detected in patients who were metabolically active at followup. We recommend that specific drug therapy should not be given to patients with idiopathic calcium urolithiasis until the stone clinic effect has been evaluated.

Urinary excretion of urate in patients with calcium oxalate stone disease

The diurnal variation in excretion and concentration of urinary urate was studied in 31 patients with calcium oxalate stone disease. Urate excretion was highest during the day-time, decreased in the evening and was low during the night. Meal-related peaks were observed. The concentration of urate reached the highest levels during the morning hours and, attributable to a low pH in morning urine, most samples were at this time super-saturated with respect to uric acid. In addition, many urines appeared to be at high risk of exceeding the uric acid formation product. Concerning the ion-activity product of sodium urate, supersaturated samples were frequently found, but the risk of exceeding the formation product for sodium urate at a normal urate excretion was apparently low.

Investigation and treatment of renal calculi associated with hypercalciuria

Thirty-four patients presenting to a urology clinic over a five-year period with renal calculi and either hypercalciuria or hypercalcemia were investigated by measurements of serum parathyroid hormone and urinary calcium and cAMP. Ten patients were hypercalcemic and were found to have primary hyperparathyroidism. Of the remaining patients all but one had excessive urine calcium excretion after an oral calcium load. In addition, 9 patients were shown to have elevated fasting urinary calcium levels while on a low-calcium diet, raising the possibility of impaired renal calcium conservation as one factor causing their hypercalciuria. The measurement of urinary cAMP levels did not contribute to the accuracy of diagnosis and did not permit further subclassification into different types of hypercalciuria. There was a decrease in urinary calcium excretion and a marked reduction in stone-related events in 10 patients with severe renal stone disease during treatment with hypocalciuric agents.

The long-term outcome of restorative operation in Crohn's disease: influence of location, prognostic factors and surgical guidelines

The course of all 113 patients with Crohn's disease whose initial procedure involved an anastomosis operated upon from 1942 to 1972 was followed through 1980. The calculated cumulative 30-year total mortality was 23.4%, 16.7% disease-related. The cumulative recurrence rate was 29% at five years, 52% at ten years, 64% at 15 years and 84% at 25 years, with no important differences between disease locations and types of operation. Sex, age, duration, granulomas, enteral or perirectal fistulas and length of the resection, the disease, and the proximal resection margin had no significant influence on the rates of development of recurrent disease or on functional outcome. By far the most common site of recurrence was the neo-terminal ileum, but in ileocolitis compared with ileitis, recurrence was 5.2 times more likely (p = 0.0001) to involve the adjacent or remote colon as well. Moreover, only 1/63 ileitis patients eventually required ileostomy, whereas 15/47 patients with ileocolitis or colitis ultimately required this procedure (p less than 0.001). The current status of the patients was excellent or good in 64% and unwell or dead related in 24%. Urolithiasis developed in 19%.

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 less than 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.

Urine screening for aminoacidopathies: is it beneficial? Results of a long-term follow-up of cases detected bny screening one millon babies

One million 6-week-old infants were screened for aminoacidurias and the long-term follow-up analyzed to assess the benefits of the screening program. Apart from phenylketonuria, now normally detected by blood screening at five days, the most frequent abnormalities identified were cystinuria, histidinemia, Hartnup disease, and iminoglycinuria. Other disorders occurred less frequently than 1:100,000. Early diagnosis provided unequivocal clinical benefit only for phenylketonuria. There was probable benefit to patients with cystinuria, homocystinuria, argininosuccinic aciduria, and to some patients with Hartnup disease. However, benefit of early diagnosis in these disorders, of which the combined incidence was 1:10,000, was not clear-cut; for example, in 68 cystinuric children, four had already developed renal stones despite close medical supervision and a regimen of increased fluid intake to the limits of tolerance. No patient detected with any other condition benefited, either because the condition appeared benign and was not treated, or because the disorder was serious or lethal and there was a bad outcome despite early diagnosis and treatment. Existing urine screening programs should explore the incidence and clinical significance of further biochemical abnormalities detectable in the newborn infant, but there is no indication at present for the initiation of new urine screening programs designed to detect only aminoacidurias.