Medical therapy to facilitate urinary stone passage: a meta-analysis

BACKGROUND

Medical therapies to ease urinary-stone passage have been reported, but are not generally used. If effective, such therapies would increase the options for treatment of urinary stones. To assess efficacy, we sought to identify and summarise all randomised controlled trials in which calcium-channel blockers or alpha blockers were used to treat urinary stone disease.

METHODS

We searched MEDLINE, Pre-MEDLINE, CINAHL, and EMBASE, as well as scientific meeting abstracts, up to July, 2005. All randomised controlled trials in which calcium-channel blockers or alpha blockers were used to treat ureteral stones were eligible for inclusion in our analysis. Data from nine trials (number of patients=693) were pooled. The main outcome was the proportion of patients who passed stones. We calculated the summary estimate of effect associated with medical therapy use using random-effects and fixed-effects models.

FINDINGS

Patients given calcium-channel blockers or alpha blockers had a 65% (absolute risk reduction=0.31 95% CI 0.25-0.38) greater likelihood of stone passage than those not given such treatment (pooled risk ratio 1.65; 95% CI 1.45-1.88). The pooled risk ratio for alpha blockers was 1.54 (1.29-1.85) and for calcium-channel blockers with steroids was 1.90 (1.51-2.40). The proportion of heterogeneity not explained by chance alone was 28%. The number needed to treat was 4.

INTERPRETATION

Although a high-quality randomised trial is necessary to confirm its efficacy, our findings suggest that medical therapy is an option for facilitation of urinary-stone passage for patients amenable to conservative management, potentially obviating the need for surgery.

Modulators of urinary stone formation

Urine contains compounds that modulate the nucleation, growth and aggregation of crystals as well as their attachment to renal epithelial cells. These compounds may function to protect the kidneys against: 1, the possibility of crystallization in tubular fluid and urine, which are generally metastable with respect to calcium salts, 2, crystal retention within the kidneys thereby preventing stone formation and 3, possibly against plaque formation at the nephron basement membrane. Since oxalate is the most common stone type, the effect of various modulators on calcium oxalate (CaOx) crystallization has been examined in greater details. Most of the inhibitory activity resides in macromolecules such as glycoproteins and glycosaminoglycans while nucleation promotion activity is most likely sustained by membrane lipids. Nephrocalcin, Tamm-Horsfall protein, osteopontin, urinary prothrombin fragment 1, and bikunin are the most studied inhibitory proteins while chondroitin sulfate (CS), heparan sulfate (HS) and hyaluronic acid (HA) are the best studied glycosaminoglycans. Crystallization modulating macromolecules discussed here are also prominent in cell injury, inflammation and recovery. Renal epithelial cells on exposure to oxalate and CaOx crystals produce some of the inflammatory molecules such as monocyte chemoattractant protein-1 (MCP-1) with no apparent role in crystal formation. In addition, macrophages surround the CaOx crystals present in the renal interstitium. These observations indicate a close relationship between inflammation and nephrolithiasis.

Helical CT of urinary calculi: effect of stone composition, stone size, and scan collimation

OBJECTIVE

Helical CT has become the preferred methodology for identifying urinary calculi. However, the ability to predict stone composition, which influences patient treatment, depends on the accurate measurement of the radiographic attenuation of stones. We studied the effects of stone composition, stone size, and scan collimation width on the measurement of attenuation in vitro.

MATERIALS AND METHODS

One hundred twenty-seven human urinary calculi of known composition and size were scanned at 120 kVp, 240 mA, and a 1:1 pitch at different collimations. A model, based on the physics of helical CT, was used to predict the effect of scan collimation width and stone size on measured attenuation.

RESULTS

At a 1-mm collimation, stone groups could be differentiated by attenuation: the attenuation of uric acid was less than that of cystine or struvite, which overlapped; these were less than the attenuation of calcium oxalate monohydrate, which was in turn lower than that of brushite and hydroxyapatite, which overlapped and showed the highest values. At a wider collimation, attenuation was lower and the ability to differentiate stone composition was lost. Attenuation also decreased with smaller stones. At a 10-mm collimation, some uric acid stones (<approximately 6 mm) and other stones (< approximately 4 mm) had very low attenuation, so low that they could remain undetected on helical CT. The model predicted well the degree that attenuation was affected by stone size and collimation width.

CONCLUSION

Stone composition and stone size, relative to CT collimation, independently influenced CT attenuation. The effect of stone size and collimation generally conformed to the model's predictions. We determined that small stones with low attenuation can be overlooked on helical CT.

Randall's plaque: Pathogenesis and role in calcium oxalate nephrolithiasis

The purpose of these studies was to test the hypothesis that Randall's plaque develops in unique anatomical sites of the kidney and their formation is conditioned by specific stone-forming pathophysiologies. We performed intraoperative papillary biopsies from kidneys of idiopathic-calcium oxalate (CaOx), intestinal bypass for obesity, brushite (BR) and cystine stone formers (SF) during percutaneous nephrolithotomy. Tissues were examined by infrared analysis and light and electron microscopy. Our analysis revealed a distinct pattern of mineral deposition and papillary pathology for each type of SF. CaOx SF had interstitial apatite crystals beginning at thin loops of Henle. These deposits termed Randall's plaque are thought to serve as sites for stone attachment. No tubular injury was noted. Intestinal bypass patients possessed intraluminal apatite deposits in inner medullary collecting ducts (IMCD) with associated cell injury. BR SF showed the most severe form of cortical and medullary changes with sites of Randall's plaque, and yellowish intraluminal deposits of apatite in IMCD. Cystine SF had plugging of ducts of Bellini with cystine crystals and apatite deposits in IMCD and loops of Henle. Intratubular sites of crystalline deposits were always associated to adjacent regions of interstitial fibrosis. The metabolic, anatomic, and surgical pathologic findings in four distinct groups of SF clearly show that 'the histology of the renal papilla from a stone former, is particular to the clinical setting'. We believe our approach to studying stone disease will provide insights into the pathogenesis of stone formation for each type of SF that will lead to improved clinical treatment.

Epidemiology and risk factors in urolithiasis

Stone formation in the urinary tract affects about 5-10% of the population in industrialized countries, although it is very rare in other countries such as Greenland or Japan. The high incidence and recurrence rate contribute to making the urolithiasis a serious social problem. Nowadays, urolithiasis must be considered a 'disease in evolution' for several reasons, such as epidemiological changes, evolution of the methods used for diagnosis, and the treatment and prophylaxis of the population considered 'at risk' of stone disease. Some features of stone disease have changed over the last few years due to many social, economical and cultural factors that are described here. The increased prevalence of small urinary calculi has brought about a change in clinical symptoms, with frequent episodes of renal-ureteral colic, persistent pain and hydronephrosis. Similarly, the presence of residual fragments after extracorporeal shock wave lithotripsy has induced a radical change in the management of small calculi through the use of mini-invasive surgical techniques.

Urinary tract stones in pregnancy

The presence of stones during an otherwise uneventful pregnancy is a dramatic and potentially serious issue for the mother, the fetus, and the treating physicians alike. The incidence and predisposing factors are generally the same as in nonpregnant, sexually active, childbearing women. Unique metabolic effects in pregnancy such as hyperuricuria and hypercalciuria, changes in inhibitors of lithiasis formation, stasis, relative dehydration, and the presence of infection all have an impact on stone formation. The anatomic changes and physiologic hydronephrosis of pregnancy make the diagnosis and treatment more challenging. Presenting signs and symptoms include colic, flank pain, hematuria, urinary tract infection, irritative voiding, fever, premature onset or cessation of labor, and pre-eclampsia. The initial evaluation and treatment are again similar to those used for the nonpregnant population. The most appropriate first-line test is renal ultrasonography, which may, by itself, allow the diagnosis to be made and provide enough information for treatment. Radiographic studies, including an appropriately performed excretory urogram, give specific information as to size and location of the stones, location of the kidneys, and differential renal function and can be used safely, but the ionizing radiation risks should be considered. All forms of treatment with the exception of extracorporeal shock wave lithotripsy and some medical procedures are appropriate in the pregnant patient. Close coordination by the urologist, the obstetrician, the pediatrician, the anesthesiologist, and the radiologist is required for the appropriate care of these patients.

Disruption of the caveolin-1 gene impairs renal calcium reabsorption and leads to hypercalciuria and urolithiasis

Using LoxP/Cre technology, we generated a knockout mouse homozygous for a null mutation in exon 2 of Cav1. In male Cav1-/- animals, we observed a dramatic increase in the incidence of urinary calcium stone formation. In 5-month-old male mice, the incidence of early urinary calculi was 67% in Cav1-/- mice compared to 19% in Cav1+/+ animals. Frank stone formation was observed in 13% of Cav1-/- males but was not seen in Cav1+/+ mice. Urine calcium concentration was significantly higher in Cav1-/- male mice compared to Cav1+/+ mice. In Cav1-/- mice, distal convoluted tubule cells were completely devoid of Cav1 and the localization of plasma membrane calcium ATPase was disrupted. Functional studies confirmed that active calcium absorption was significantly reduced in Cav1-/- compared to Cav1+/+ male mice. These results demonstrate that disruption of the Cav1 gene promotes the progressive steps required for urinary calcium stone formation and establish a new mouse model for urinary stone disease.

Cultures of exfoliated epithelial cells from different locations of the human urinary tract and the renal tubular system

Exfoliated human urinary tract epithelial cells and renal tubular cells from urinary sediments of healthy adults, of urological patients and of internal patients were isolated and cultured. Cells started proliferating within 1 week after seeding a sediment. Proliferating cells formed colonies of different morphologies, designated as type-1 or type-2 cell colonies. Type-1 cell colonies showed irregular contours and spindle-like cells within the colonies. Subcultivation of type-1 cells for up to six passages was possible. Type-2 cell colonies showed smooth-edged contours and subcultivation was not possible. The epithelial character of type-1 cells was demonstrated by positive immunohistochemical staining for cytokeratin-7. In contrast to carbonic anhydrase-positive stained Madin Darby canine kidney cells (MDCK), which were used as positive controls for renal tubular cells, type-1 cells were carbonic anhydrase-negative on staining with the cobalt phosphate method. This indicates that type-1 cells were not of renal tubular origin. Type-2 cells were positively stained for carbonic anhydrase, indicating that type-2 cells were renal tubular cells. Type-2 cell colonies could be assigned to two subgroups with different cell forms. Colonies of cobblestone-like cells more often occurred than type-2 cell colonies with spindle-like cells, which are described in this study for the first time. Colonies with cobblestone-like cells formed domes (hemicysts), whereas spindle-like type-2 cell colonies did not. Cultures of urinary sediments from healthy adults, elderly multimorbid patients treated with furosemide, and urological patients with urolithiasis treated with sulfamethoxazole/trimethoprim and/or with a percutaneous nephrostomy catheter were compared. In 52% of all cultured sediments from healthy adults, in 30% of those from multimorbid patients, and in 75-80% of those from urological patients cells proliferated to colonies. The ratios of type-1 to type-2 cell colonies were 3.3:1 (healthy adults), 1.4:1 (urological patients with urolithiasis), and 1.8:1 (urological patients with urolithiasis, urine was directly collected from the renal pelvis with a percutaneous nephrostomy catheter). Successful cultures of the urinary sediments from these three groups revealed means of 3 or 4 colonies, 14 colonies, and 21 colonies, respectively. Differences in the number of colonies in relation to sex were observed only for the group of urological patients. It was shown that type-1 cells were urothelial cells, which did not show morphological differences due to their locations of origin within the urinary tract, whereas type-2 cells were probably renal tubular cells. These findings offer new aspects in the culturing of human urothelial or kidney epithelial cells with a method based on noninvasive collecting of specimens and requiring only minimal culture effort. The cultures obtained by this method can be used for in vitro studies in toxicological and clinical research.

The pathobiology of Schistosoma haematobium infection in humans

Schistosoma haematobium infection is a common occurrence in Africa and the Middle East and is the world's leading cause of hematuria. Since more North Americans are venturing into endemic areas and more residents of endemic areas are seeking medical care in North America, pathologists must be able not only to diagnose urinary schistosomiasis but also to provide advice as to further therapy. These endeavors mandate knowledge of the pathobiologic features of the disease. The severity and frequency of the sequelae of urinary schistosomiasis (hydroureter, hydronephrosis, bladder ulcer, and polyposis) and of its complications (bacterial urinary tract infection, renal failure, urothelial cancers) depend on the intensity of infection, i.e., worm burden and tissue egg burden, and the duration of infection. Significant differences in gross and microscopic morphology, clinical laboratory findings, and optimal mode of treatment exist between active (during active egg deposition) and inactive (after cessation of oviposition) disease. Moreover, nearly half of the severe sequelae and complications occur during the inactive phase of the disease, when diagnosis is most difficult. The manifestations of this disease are manifold and complex, and firm understanding of the pathobiologic features is necessary if pathologists are to understand their role in the direction of treatment.

Slc7a9-deficient mice develop cystinuria non-I and cystine urolithiasis

Cystinuria is a common recessive disorder of renal reabsorption of cystine and dibasic amino acids that results in urolithiasis of cystine. Cystinuria is caused by defects in the amino acid transport system b0,+ (i.e. the rBAT/b0,+AT heteromeric complex). Mutations in SLC3A1, encoding rBAT, cause cystinuria type A, characterized by a silent phenotype in heterozygotes (phenotype I). Mutations in SLC7A9, encoding b0,+AT, cause cystinuria type B, in which heterozygotes in most cases hyperexcrete cystine and dibasic amino acids (phenotype non-I). To facilitate in vivo investigation of b0,+AT in cystinuria, Slc7a9 knockout mice have been generated. Expression of b0,+AT protein is completely abolished in the kidney of Slc7a9-/- mice ('Stones'). In contrast, Stones expressed significant amounts of rBAT protein, which is covalently linked to unidentified light subunit(s). Stones mice present a dramatic hyperexcretion of cystine and dibasic amino acids, while Slc7a9+/- mice show moderate but significant hyperexcretion of these amino acids (phenotype non-I). Forty-two per cent of Stones mice develop cystine calculi in the urinary system. Calculi develop during the first month of life and grow throughout the life span of the animals. Histopathology in kidney reveals typical changes for urolithiasis (tubular and pelvic dilatation, tubular necrosis, tubular hyaline droplets and chronic interstitial nephritis). The fact that some Stones mice, generated in a mixed genetic background, develop cystine calculi from an early age, while others do not develop them in their first year of life, suggests the involvement of modifier genes in the lithiasis phenotype. Thus, Stones provide a valid model of cystinuria which can be used in the study of genetic, pharmacological and environmental factors involved in cystine urolithiasis.

Urolithiasis in the horse - a review of 13 cases

The presenting signs, treatment and postoperative progress of 13 horses with vesical and urethral calculi are reviewed. Single, discrete stones were present in 10 animals in which the results of treatment were generally good. In three horses with sabulous cystic deposits, urolithiasis was associated with bladder paralysis and the response to treatment was poor.

Response of the rat to saccharin with particular reference to the urinary bladder

Male and female Wistar rats were administered sodium saccharin for life (2 yr) either in the drinking water or diet. The maximum palatable dose of saccharin in the drinking water was found to be 2 g/kg/day and, even then, there was some voluntary restriction of fluid intake in the males. By contrast, double this dose--namely 4 g/kg/day, was palatable in the diet. A control group of rats of both sexes received saccharin-free diet and drinking water. Mild urothelial hyperplasias developed from 85 weeks in rats of both sexes receiving saccharin either in the drinking water or diet; the incidence was statistically significant in both the bladders and kidneys of rats receiving the higher dose of saccharin in the diet, but in the kidneys only of rats receiving the lower dose of saccharin in the drinking water. Telangiectasia of the vasa recta was significant in saccharin-treated rats of both sexes at both doses. A very low incidence of bladder tumours, exclusively in males receiving the higher saccharin dose in the diet was seen from 95 weeks. No consistent relationship between bladder epithelial hyperplasias and crystalluria could be demonstrated, although all 3 bladder tumours were associated with some form of mineralisation. Results suggest a particular susceptibility of males to saccharin treatment. The possibility that saccharin may promote, or enhance, the development of latent tumour cells already present in the experimental population, rather than initiate carcinogenesis per se is considered.

Pathology of diseases in wild desert tortoises from California

Twenty-four ill or dead desert tortoises (Gopherus agassizii) were received between March 1992 and July 1995 for necropsies from the Mojave and Colorado deserts of California (USA). Diseases observed in these animals included cutaneous dyskeratosis (n = 7); shell necrosis (n = 2); respiratory diseases (n = 7); urolithiasis (n = 3); and trauma (n = 5). In tortoises with cutaneous dyskeratosis the horn layer of shell was disrupted by multiple crevices and fissures and, in the most severe lesions, dermal bone showed osteoclastic resorption, remodeling, and osteopenia. In tortoises with shell necrosis, multiple foci of necrotic cell debris and heterophilic inflammation within the epidermal horn layer were subtended by necrotic dermal bone colonized by bacteria and fungi. Of the seven tortoises with respiratory disease, five were diagnosed with mycoplasmosis. The diagnosis of mycoplasmosis was based on the presence of chronic proliferative rhinitis and positive serologic tests and/or isolation of Mycoplasma sp. Chronic fungal pneumonia was diagnosed in one tortoise with respiratory disease. In the three tortoises with urolithiasis, two were discovered dead, and the live tortoise had renal and articular gout. Traumatic injuries consisted of one tortoise entombed within its burrow, one tortoise burned in a brush fire, two tortoises struck by moving vehicles, and one tortoise attacked by a predator. While the primary cause of illness could be attributed to one or two major disease processes, lesions were often found in multiple organ systems, and a variety of etiologies were responsible for morbidity and mortality.

A mouse model for cystinuria type I

Cystinuria, one of the most common inborn errors of metabolism in humans, accounts for 1-2% of all cases of renal lithiasis. It is caused by defects in the heterodimeric transporter system rBAT/b0,+AT, which lead to reduced reabsorption of cystine and dibasic amino acids through the epithelial cells of the renal tubules and the intestine. In an N-ethyl-N-nitrosourea mutagenesis screen for recessive mutations we identified a mutant mouse with elevated concentrations of lysine, arginine and ornithine in urine, displaying the clinical syndrome of urolithiasis and its complications. Positional cloning of the causative mutation identified a missense mutation in the solute carrier family 3 member 1 gene (Slc3a1) leading to an amino acid exchange D140G in the extracellular domain of the rBAT protein. The mouse model mimics the aetiology and clinical manifestations of human cystinuria type I, and is suitable for the study of its pathophysiology as well as the evaluation of therapeutic and metaphylactic approaches.

Ultrastructural microbial ecology of infection-induced urinary stones

With advanced techniques of scanning and transmission electron microscopy we studied the ultrastructural ecology of bacteria associated with struvite calculi on catheter surfaces, and in the bladder, ureter and renal pelvis. These detailed morphological data indicate that the interstices, core and external surface of such struvite aggregates contain large numbers of bacterial cells that grow as microcolonies and thick biofilms within extensive fibrous organic matrices. These bacterial cells and their secreted products (glycocalyx or biofilm matrix) appear to provide initial foci for crystal development and aggregation of crystals to form macroscopic struvite stones. The protective glycocalyx-enclosed microcolonial mode of bacterial growth also may explain the relative resistance to antibiotics observed in bacteria associated with infection stones.

Urinary macromolecular inhibition of crystal adhesion to renal epithelial cells is impaired in male stone formers

BACKGROUND

Retention of microcrystals that form in tubular fluid could be a critical event in kidney stone formation. This study was performed to determine if urinary macromolecules from stone-forming (SF) individuals have reduced ability to inhibit crystal adhesion to renal cells.

METHODS

A first morning whole urine (WU) sample was obtained from 24 SF subjects (17 males and 7 females) and 24 age-, race-, and sex-matched controls (C). An aliquot of urine was centrifuged and an ultrafiltrate (UF) free of macromolecules >10 kD and 10x concentrate (U(conc)) were prepared.

RESULTS

Supplementing UF with increasing amounts of U(conc) to return the macromolecule concentration to 0.25x, 0.5x, or 1x of baseline progressively decreased crystal binding to cells. This effect was blunted in the male SF group compared to controls (P < 0.05, SF vs. C, for UF plus 0.25x macromolecules). No difference was apparent in the female groups. In order to identify responsible macromolecule(s), calcium oxalate monohydrate (COM) crystals were coated with U(conc) and adherent proteins then released and probed by Western blot. Coated COM crystals from male controls contained 3.5-fold more Tamm-Horsfall protein (THP) than SF subjects (P < 0.01). COM crystal coating with other proteins did not consistently differ between the groups. COM crystal coating by urinary prothrombin fragment 1 (UPTF1, P < 0.05) and crystal adhesion inhibitor (CAI) (P= 0.09) correlated with decreased crystal binding to cells, whereas coating with osteopontin (OPN) correlated with increased adhesion tendency (P < 0.05).

CONCLUSION

Urinary macromolecules >10 kD coat COM crystals and block their adhesion to renal cells. This capacity appears to be blunted in male but not female SF individuals. Multiple urinary proteins may play a role in renal cell-urinary crystal interactions, and THP appears to be one of the more important ones.

The use of a ureteral access sheath does not improve stone-free rate after ureteroscopy for upper urinary tract stones

PURPOSE

To evaluate the impact of a ureteral access sheath (UAS) on stone-free (SF) rate after flexible ureteroscopy for upper urinary tract stones.

MATERIALS AND METHODS

We retrospectively reviewed 280 patients who underwent flexible ureteroscopy (URS) for upper urinary tract stone between 2009 and 2012. Patients were divided into two groups based on whether a UAS was used (n = 157) or not (n = 123). SF rate was evaluated at one and three months after surgery by abdominal imaging. Quantitative and qualitative variables were compared with Student's t test and χ2 test, respectively. A logistic regression model was used to determine the predictive factors of SF status.

RESULTS

Stone size was similar in both groups (15.1 vs. 13.7 mm, p = 0.21). SF rates at one and 3 months were comparable in UAS and non-UAS groups (76 vs. 78% and 86 vs. 87%, p = 0.88 and 0.89, respectively). Complication rates were similar in both groups (12.7 vs. 12.1%, p = 0.78). In multivariable analysis, stone size was the only predictive factor of SF rate (p = 0.016).

CONCLUSION

The routine use of a UAS did not improve SF rate in patients undergoing flexible URS for upper urinary tract calculi.

Localization of tamm-horsfall protein and osteopontin in a rat nephrolithiasis model

The possibility of more than one urinary protein being simultaneously associated with calcium oxalate (CaOx) crystallization in vivo was investigated by examining the localization of Tamm-Horsfall protein (THP) and osteopontin (Opn) in a rat model of nephrolithiasis. CaOx crystal deposits were induced in male Sprague-Dawley rats by feeding 0.75% ethylene glycol in drinking water. THP and Opn were localized on kidney sections by immunoperoxidase technique, using specific polyclonal antibodies. When only occasional crystal deposits were seen in the kidney, THP showed a similar to normal pattern of distribution, with positive staining in the thick ascending limbs of the loop of Henle. Opn was localized in some nephrons in the thin limb of loop of Henle and on the papillary surface in the calyceal fornix. In contrast, in samples with a significantly increased number of deposits in the kidneys, the staining for both THP and Opn was strikingly enhanced and altered, with positive staining around the crystals as well as abnormal localization in the papilla. Interestingly, the occurrence of Opn was, however, more consistent than that of THP. This is a first study showing that in this nephrolithiasis model, normal localization of THP and Opn is altered and they are closely and concurrently associated with crystal deposits in vivo.

Urolithiasis in childhood

A retrospective review was performed of the records of 85 children with urinary-tract calculi evaluated and treated during a 12-year period. The study evaluated the patients' age, sex, initial complaints, etiology, relevant pathological factors, stone location, mode of treatment, and stone analysis. There were 68 boys and 17 girls, a ratio of 4:1. Patient age ranged from 10 months to 16 years (average 8.2 years). Flank pain was the most common manifestation. Seventy patients had calculi in the upper urinary tract and 31 in the lower urinary tract; 16 had stones in more than one site and 15 had bilateral stones. Hypercalciuria was the most common metabolic disorder. Most patients underwent open surgical procedures for removal of their calculi; 5 stones were successfully removed endoscopically. In 3 cases, the stones passed spontaneously. Calcium oxalate and calcium phosphate stones were present in 32 cases, struvite in 5, cystine in 2, and uric acid in 1 Urolithiasis is still one of the most common pediatric urologic problems in Turkey, but as living standards improve, the incidence of the disease has tended to decline in recent years. Anatomic anomalies and metabolic disorders are of great importance in the etiology of stone disease.

Phyllanthus niruri inhibits calcium oxalate endocytosis by renal tubular cells: its role in urolithiasis

We investigated the in vitro effect of an aqueous extract of Phyllanthus niruri L. on a model of CaOx crystal endocytosis by Madin-Darby canine kidney cells. The extract exhibited a potent and effective non-concentration-dependent inhibitory effect on the CaOx crystal internalization. This response was present even at very high (pathologic) CaOx concentrations and no P. niruri L.-induced toxic effect could be detected. Biochemical analysis of culture media containing P. niruri L. did not provide any clues for the elucidation of the cellular pathways affected by this natural product. Although further studies are necessary for a better understanding of the role of P. niruri L. in urolithiasis, our findings show that this natural product could be an attractive alternative for the treatment of urinary stones.

Calcium oxalate crystal localization and osteopontin immunostaining in genetic hypercalciuric stone-forming rats

BACKGROUND

The inbred genetic hypercalciuric stone-forming (GHS) rats develop calcium phosphate (apatite) stones when fed a normal 1.2% calcium diet. The addition of 1% hydroxyproline to this diet does not alter the type of stone formed, while rats fed this diet with 3% hydroxyproline form mixed apatite and calcium oxalate stones and those with 5% hydroxyproline added form only calcium oxalate stones. The present study was designed to determine the localization of stone formation and if this solid phase resulted in pathologic changes to the kidneys.

METHODS

GHS rats were fed 15 g of the standard diet or the diet supplemented with 1%, 3%, or 5% hydroxyproline for 18 weeks. A separate group of Sprague-Dawley rats (the parental strain of the GHS rats), fed the standard diet for a similar duration, served as an additional control. At 18 weeks, all kidneys were perfusion-fixed for structural analysis, detection of crystal deposits using the Yasue silver substitution method, and osteopontin immunostaining.

RESULTS

There were no crystal deposits found in the kidneys of Sprague-Dawley rats. Crystal deposits were found in the kidneys of all GHS rats and this Yasue-stained material was detected only in the urinary space. No crystal deposits were noted within the cortical or medullary segments of the nephron and there was no evidence for tubular damage in any group. The only pathologic changes occurred in 3% and 5% hydroxyproline groups with the 5% group showing the most severe changes. In these rats, which form only calcium oxalate stones, focal sites along the urothelial lining of the papilla and fornix of the urinary space demonstrated a proliferative response characterized by increased density of urothelial cells that surrounded the crystal deposits. At the fornix, some crystals were lodged within the interstitium, deep to the proliferative urothelium. There was increased osteopontin immunostaining in the proliferating urothelium.

CONCLUSION

Thus in the GHS rat, the initial stone formation occurred solely in the urinary space. Tubular damage was not observed with either apatite or calcium oxalate stones. The apatite stones do not appear to cause any pathological change while those rats forming calcium oxalate stones have a proliferative response of the urothelium, with increased osteopontin immunostaining, around the crystal deposits in the fornix.

Renal tubular injury induced by hyperoxaluria: evaluation of apoptotic changes

In order to evaluate the injurious effect of hyperoxaluria on renal tubular epithelium, as judged by apoptotic changes in the renal parenchyma, we performed an experimental study in 20 rabbits. In the experimental group animals (n = 10) severe hyperoxaluria was induced by continuous ethylene glycol (EG; 0.75%). Histologic alterations, including crystal formation, together with apoptotic changes were evaluated after 7 and 28 days. Control group animals (n = 10) received normal distilled drinking water. Following 7- and 28-day periods, tissue sections obtained from kidneys were examined histopathologically under light microscopy for the presence and the degree of crystal deposition in the tubular lumen. Apoptotic changes in renal tubular cells were examined using the terminal deoxynucleotidyl transferase (TdT)-mediated dUTP in situ nick and labeling (TUNEL) method during the same follow-up period. Crystal deposition was evident in the tubular lumen of tissue sections obtained during the 7-day examination period. During the 28-day examination period, however, these findings were found to be either limited or to have disappeared. In relation to apoptotic changes, the percentage of positive nuclei stained using the TUNEL method was from 11 to 20% in the experimental group and 5.6% in the control group. Our findings indicate that both calcium oxalate (CaOx) crystals and hyperoxaluria itself may be injurious to renal tubular cells, as indicated by apoptotic changes. These changes may be responsible for the pathologic course of urolithiasis.