Non-calcium Stones Research Articles

Autofluorescence spectral analysis for detecting urinary stone composition in emulated intraoperative ambient

The prevalence and disease burden of urolithiasis has increased substantially worldwide in the last decade, and intraluminal holmium laser lithotripsy has become the primary treatment method. However, inappropriate laser energy settings increase the risk of perioperative complications, largely due to the lack of intraoperative information on the stone composition, which determines the stone melting point. To address this issue, we developed a fiber-based fluorescence spectrometry method that detects and classifies the autofluorescence spectral fingerprints of urinary stones into three categories: calcium oxalate, uric acid, and struvite. By applying the support vector machine (SVM), the prediction accuracy achieved 90.28 % and 96.70% for classifying calcium stones versus non-calcium stones and uric acid versus struvite, respectively. High accuracy and specificity were achieved for a wide range of working distances and angles between the fiber tip and stone surface in an emulated intraoperative ambient. Our work establishes the methodological basis for engineering a clinical device that achieves real-time, in situ classification of urinary stones for optimizing the laser ablation parameters and reducing perioperative complications in lithotripsy.

The complex pathophysiology of urolithiasis (kidney stones) and the effect of combinational drugs

Body organs are very crucial when it comes to homeostatically maintaining them. If any changes occur in their function, it may lead to the development of diseases in the body. The kidney is one of the functionalised organs that is connected with the ureter and urinary bladder, which is basically the lower part of the body. The kidney priorly controls the volume of various body fluids, fluid osmolality, acid-base balance, various electrolyte concentrations, and the removal of toxins. Any dis-balance in the function of the kidney can generate a disease like renal calculi (kidney stone), chronic kidney disease (CKD), polycystic kidney disease (PKD), urinary tract infections (UTI), etc. Kidney stones (KS) are prevalent worldwide, affecting 15% of individuals. A stone arranged into various sizes may be micro, macro, and nano or found as mono or polycrystalline forms. The names of the two most common kidney stones, calcium and non-calcium stones (Uric acid stones, struvite stones, cysteine stones, and drug-induced KS), are determined primarily by their composition. Calcium stones are commonly found in individuals, approximately 80% of KS. This review provided recent details on kidney stone symptoms, etiology, psychophysiology, and management perspective.
 Keywords: Kidney disease, calcium stone, renal calculi, chronic kidney disease, Polycystic kidney disease.

Machine Learning Prediction of Kidney Stone Composition Using Electronic Health Record-Derived Features.

Objectives: To assess the accuracy of machine learning models in predicting kidney stone composition using variables extracted from the electronic health record (EHR). Materials and Methods: We identified kidney stone patients (n = 1296) with both stone composition and 24-hour (24H) urine testing. We trained machine learning models (XGBoost [XG] and logistic regression [LR]) to predict stone composition using 24H urine data and EHR-derived demographic and comorbidity data. Models predicted either binary (calcium vs noncalcium stone) or multiclass (calcium oxalate, uric acid, hydroxyapatite, or other) stone types. We evaluated performance using area under the receiver operating curve (ROC-AUC) and accuracy and identified predictors for each task. Results: For discriminating binary stone composition, XG outperformed LR with higher accuracy (91% vs 71%) with ROC-AUC of 0.80 for both models. Top predictors used by these models were supersaturations of uric acid and calcium phosphate, and urinary ammonium. For multiclass classification, LR outperformed XG with higher accuracy (0.64 vs 0.56) and ROC-AUC (0.79 vs 0.59), and urine pH had the highest predictive utility. Overall, 24H urine analyte data contributed more to the models' predictions of stone composition than EHR-derived variables. Conclusion: Machine learning models can predict calcium stone composition. LR outperforms XG in multiclass stone classification. Demographic and comorbidity data are predictive of stone composition; however, including 24H urine data improves performance. Further optimization of performance could lead to earlier directed medical therapy for kidney stone patients.

Alternative Substrates Used for Oyster Reef Restoration: A Review

Oyster populations and reef habitats have notably declined in the last century around the world. The ecological, economic, and cultural values of oysters have led to a variety of restoration efforts seeking to recover these lost benefits. Limitations of the native oyster shell substrate and the large-scale nature of many restoration projects have resulted in the increased use of a variety of alternative, or artificial, substrates to create reef structures. A text mining package was used to conduct a review of alternative substrates used for oyster restoration. Specifically, the review (1) assessed commonly used alternative substrates, (2) locations where alternative substrates are used, and (3) common performance metrics used to evaluate alternative substrates. The review demonstrated that (1) the most common substrates included porcelain, concrete, limestone, noncalcium stone, nonoyster shell, dredged shell, and engineered reefs; (2) oyster restoration with alternative substrates occurs worldwide, but evaluations of alternative substrates were primarily (79%) within the United States of America; and (3) four main categories of performance metrics are used to assess alternative substrates—biological, structural, chemical, and economic acceptability. Within the four performance metrics, however, there exists a substantial variety in terms of specific metrics used and application of metrics to assess alternative substrates. Results highlight the need for common metrics across projects to ease comparison between alternative substrate options.

Diagnosis and management of non-calcium-containing stones in the pediatric population

Compared to adults, urolithiasis is less common in children, with a definite rise in incidence, especially among young adults (Tasian et al. in Clin J Am Soc Nephrol 11:488, 2016). In the last 25years, the incidence in children has increased by approximately 6-10% annually, for reasons still unknown, with an associated significant increase in related health care-related expenditures (Hyams and Matlaga in Transl Androl Urol 3(3):278-83, 2014). It has been shown that there is twice as high a risk of chronic kidney disease (CKD) or end stage renal disease (ESRD) in stone formers compared to non-stone formers (Tasian et al. 2016). While calcium-containing stones are by far the most common category of stone encountered in both children and adults, non-calcium stones are more common in children than adults and have been shown in several studies to be associated with greater morbidity and lower renal function than calcium stones (Issler et al. in BMC Nephrol 18(1):136, 2017; Gambaro et al. in J Urol 198:268-273, 2017). This could be related to the challenges in the management of non-calcium-containing stones due to associated infection or metabolic derangements, further leading to recurrence and loss of renal function. There is currently a gap in our understanding of how to appropriately and effectively encounter and manage patients with non-calcium-containing stones, as such cases are encountered less frequently. Identification of stone composition and appropriate management is very important to reduce serious complications and recurrence, especially in non-calcium stones. We present a review of diagnosis and management of non-calcium-containing stones in the pediatric population, in hopes of providing more clarity to providers and promoting a consideration of non-calcium stone composition with all children presenting with urolithiasis.

Flexible Ureteroscopy with Holmium Laser Lithotripsy: A New Choice for Intrarenal Stone Patients

Objective: To evaluate the efficiency and safety of flexible ureteroscopy (FURS) and holmium lithotripsy for intrarenal stones and to stratify the efficiency and safety by stone burdens of ≤20, 20-40, and ≥40 mm. Methods: Five hundred eighty-two patients with intrarenal stones were treated with FURS and holmium lithotripsy at a single department from August 2008 to October 2013. Stone size was evaluated by calculating the cumulative stone diameter of all intrarenal stones, and stone-free status was defined as the absence of any stone or stone fragment <1 mm in the kidney. Results: Data analysis revealed a mean stone burden of 21.8 ± 7.6 mm. The overall primary stone-free rate (SFR) was 65.3%, which increased to 89.0% 6 months after the first surgery. Complications developed in 6.7% of patients. A significant difference was found between lower-calyx stones and other stones (p < 0.001; p = 0.006), while noncalcium stones had a much higher SFR than calcium stones (p < 0.001; p = 0.04). Conclusion: Our study showed that the overall renal SFR with the use of FURS and holmium lithotripsy was satisfactory, with a relatively low complication rate. We believe that FURS with holmium lithotripsy could be a valuable choice for patients with renal stones, especially for patients with a cumulative stone burden ≤40 mm.

Retreatment After Percutaneous Nephrolithotomy in the Computed Tomographic Era: Long-term Follow-up

To examine the long-term retreatment rates and explore prognostic factors after percutaneous nephrolithotomy (PCNL) in the computed tomographic era. Consecutive patients who underwent PCNL with a standardized technique attempting complete fragment detection and clearance by a single surgeon between September 2000 and June 2004 were identified. Through medical record, review details of procedures and outcomes were collected. A total of 166 renal units in 150 subjects were evaluated. Postoperative computed tomographic scans were conducted in 129 subjects. Median follow-up was 5.4years (interquartile range, 4.2-6.2years). Future ipsilateral procedures were performed in 23 renal units (14%) at a median of 2.9years (interquartile range, 1.7-3.7years). The cumulative retreatment rate at 7years for noncalcium stones (24%) was not significantly higher than for calcium-based stones (14%; P=.07). Stone-free renal units had a lower cumulative retreatment rate (4%) than those with residual fragments<2mm (33%) or≥2mm (30%; P= .001). When controlling for residual fragment size, renal units that were composed of uric acid or struvite had an expected hazard rate of retreatment 3.34 times larger than renal units composed of calcium oxalate/phosphate (P=.02) and renal units that were not stone free had an expected hazard rate 7.87 times larger than renal units that were stone free (P=.001). In this population of complex stone patients treated by PCNL, there appears to be no such thing as an "insignificant fragment." Efforts at initial stone clearance should be maximized.

An individualized weight-based goal urine volume model significantly improves expected calcium concentrations relative to a 2-L goal urine volume

Increased urinary volume decreases recurrence rates of nephrolithiasis. Current recommendations for goal volumes are not adjusted to reflect individual risk factors, such as obesity. Our intent was to develop and evaluate a goal urine volume for stone prevention based on predictive calcium modeling. Stone formers with a 24-h urine study (6/2001-9/2010) were identified. Patients with inadequate collections or non-calcium stones were excluded. Multivariate and univariate predictive models for daily calcium were evaluated and a univariate (weight) model was selected. A target calcium concentration constant (2.5mM) was determined from current recommendations. Individualized weight-based goal urine volumes (WGUV) were calculated. Measured calcium concentration and expected calcium concentrations using a 2-L goal volume and WGUV were compared. 185 of 399 patients met inclusion criteria. Body weight was a strong predictor of calcium excretion in each model (p<0.0001). While a 2-L goal urine volume would be expected to improve mean calcium concentrations for the cohort from 3.53 to 2.96mM, the benefit is unequal between subsets with nearly twofold expected concentration for the highest weight quartile (3.98 vs. 2.10mM) and higher expected concentration for males (3.35 vs. 2.59mM). By contrast, a WGUV model improves expected concentrations for all subsets to <2.9mM and the overall cohort to 2.50mM. This study demonstrates a strong relationship between body weight and urinary calcium excretion in stone formers. We introduce the novel concept of individualized goal urine output using statistical modeling, which may be preferable to current recommendations.

Effect of α1-microglobulin and β2-microglobulin on calcium oxalate urine stone formation

Objective To define the difference of urine analysis result,α1-microglobulin (α1-MG) and β2-microglobulin ( β2-MG) between those patients suffering from calcium oxalate stone,non-calcium oxalate stone and non-urolithiasis controls at the same time period. Methods Data from 100 patients admitted to the Department of Urology,First Affiliated Hospital of Anhui Medical University from July,2010 to September,2010 were reviewed.66 patients (45 men,21 women) suffered from urolithiasis,and 34 patients (22 men,12 women) were non-urolithiasis.Patients' ages in urolithiasis group varied from 13 to 78 years and the male to female ratio was 2.1∶1.0.The patients in non-urolithiasis controlgroup aged from 12 to 80 years and the male to female ratio was 1.8∶1.0.Blood and urine were taken from the patient the next morning after admission.The biochemistry from blood and 24 h urine were measured by automatic biochemistry analyzer.The α 1-MG and β2-MG content were measured by radioimmunoassay.The stone compositions were analyzed by infrared spectroscopy. Results There was difference in the levels of serum creatinine and blood urea nitrogen among three groups ( P ＜ 0.05).In controls,those with calcium oxalate stone had higher level of urinary α1-MG and β2-MG,but there were no differences in the urinary electrolyte levels.Group of non-calcium oxalate stones urinary uric acid levels were higher than calcium oxalate and control groups,the difference was statistically significant. Conclusions In the formation of uric acid stones,uric acid increased as independent risk factors.α1-MG,β2-MG may promote the formation of calcium oxalate stones. Key words: Urinary calculi; Stone analysis; 24 h urine analysis; Electrolytes; M icroglobulin

Imaging-Based Assessment of the Mineral Composition of Urinary Stones: An In Vitro Study of the Combination of Hounsfield Unit Measurement in Noncontrast Helical Computerized Tomography and the Twinkling Artifact in Color Doppler Ultrasound

We evaluated the value of combining noncontrast helical computerized tomography (NCHCT) and color Doppler ultrasound in the assessment of the composition of urinary stones. In vitro, we studied 120 stones of known composition, that separate into the five main types: 18 calcium oxalate monohydrate (COM) stones, 41 calcium oxalate dihydrate (COD) stones, 24 uric acid stones, 25 calcium phosphate stones and 12 cystine calculi. Stones were characterized in terms of their Hounsfield density (HU) in NCHCT and the presence of a twinkling artifact (TA) in color Doppler ultrasound. There were statistically significant HU differences between calcium and non-calcium stones (p < 0.001), calcium oxalate stones and calcium phosphate stones (p < 0.001) and uric acid stones and cystine calculi (p < 0.001) but not between COM and COD stones (p = 0.786). Hence, the HU was a predictive factor of the composition of all types of stones, other than for COM and COD stones within the calcium oxalate class (p > 0.05). We found that the TA does not enable differentiation between calcium and non-calcium stones (p > 0.999), calcium oxalate stones and calcium phosphate stones (p = 0.15), or uric acid stones and cystine calculi (p = 0.079). However, it did reveal a significant difference between COM and COD stones (p = 0.002). The absence of a TA is a predictive factor for the presence of COM stones (p = 0.008). Hence, the association of NCHCT and Doppler enables the accurate classification of the five types of stones in vitro.

Application of LIIR Automatic Analysis System of Infrared Spectroscopy in the determination of urinary stone composition

Objective To determine the value of applying LIIR Automatic Analysis System of Infrared Spectroscopy in analyzing urinary stone composition. Methods 1450 samples of urinary stones were collected from 1032 male and 418 female patients. The age of patients ranged from 6 months to 88 years. The mean ages were 41.7±15.3 and 42.0±15.6 years for male and female pa- tients, respectively. Of 1450 stones, 875 cases were located in kidney （60.34%）, 504 cases in ureter （34.76%） and 71 cases in bladder （4.90%）. All stones were analyzed by LIIR Automatic Analysis System of Infrared Spectroscopy （Tianjin）. Analysis results were reevaluated by the artificial analysis of spectrogram, i{ necessary, with polarization microscope, chemical analysis, and X ray diffraction. Results Calcium oxalate monohydrate stones were found in 714 cases （49. 24%）, carbonate apatite stones in 444 cases （30.62%）, anhydrous uric acid stones in 93 cases （6.41%）, calcium oxalate dihydrate stones in 92 cases （6. 34%）, ammonium magnesium phosphate hexahydrate stones in 28 cases （1. 93%）, cystine stones in 23 cases （1.59%）, ammonium urate stones in 20 cases （1.38%）, uric acid dihydrate stones in 16 cases （1.10%）, brushite stones in 12 cases （0. 83%）, sodium urate monohydrate stones in 2 cases （0. 14%）, calcium carbonate stones in 1 cases （0.07%）, and other stone types in 5 cases （0.34%）. Most urinary stones were composed of 2 or more compositions, and purestones were only observed in 397 cases （27.38%）. Most of the mixed stones contained calcium and non-calcium mixed stone was rarely observed. In addition, 15 stones were found in infants who had consumed melamine-contaminated milk powder. These stones were composed of uric acid dihydrate and ammonium urate. The results of reevaluation by artificial analysis showed the following among pure and mixed stones, false detection occurred in 6 cases （0.41%）, of which the composition was ammonium urate or carbonate apatite determined by automatic system but the true composition was an hydrous uric acid. False negative detection occurred in 9 cases （0.62%）, of which the composition was ammonium magnesium phosphate hexahydrate or carbonate apatite in 7 cases, but in other 2 cases the composition could not be determined by artificial analysis. The false negative detection of compo- nents with relatively low content occurred in 6 cases and 10 cases in stones with 2 components and 3 components, respectively. The undetected composition in these cases was ammonium magnesium phosphate hexahydrate or carbonate apatite. Conclusion Automatic Analysis System of Infrared Spectroscopy has many advantages in accuracy, automation and is quick in analyzing the composition of urinary stones, and is worthy of promotion in clinical use. Key words: Urinary calculi; Spectrophotometry, infrared; Calcium oxalate; Apatites

Combination of Lower Pole Anatomic Features in A Single Infundibulopelvic Index Can Predict the Lower Pole Stone Clearance More Accurately

Purpose To investigate whether the combination of lower pole pelvicaliceal anatomic features in a single index can predict the outcome of shock wave lithotripsy treatment (SWL) of lower caliceal stones in children more accurately in stead of considering every single anatomic feature alone. Material and Methods The clinical records of children with lower caliceal stones who underwent SWL between 2002-2008 were reviewed. After excluding patients with ureteropelvic obstruction, major renal anatomic abnormalities, non-calcium stones, metabolic abnormalities, history of recurrent stone disease, multiple stones and previous renal surgery;25 paediatric patients were enrolled into study. Lower pole infundibulopelvic angle (IPA), infundibular length (IL) and width (IW) were measured from intravenous pyelography. Also, paediatric infundibulopelvic index(IPI) was calculated as [IPA( 0 )xIW(mm)x100]/[IL(mm)xstone size(mm 2 )xPelvicaliceal volume(mm 3 )]. Results The mean stone size was 72,4±49,4 mm 2 . Overall stone-free rate was %80.There were no statistically significant difference in IPA, IL and IW values between patients with residual stones and stone-free patients, respectively (p=0.06,p=0.81,p=0.21). Also no statistically significant difference were found in stone size (p=0.27),total pelvicaliceal volume(p=0.06) and SWL parameters. However IPI index was significantly different between two patient groups (p=0.04). Stone Free (mean±SD) Residual(mean±SD) P value Lower IPA( 0 ) 46,8±15,2 40±7,6 0,06 Lower IL 7,9±4 6,8±2 0,81 Lower IW 4,9±2,6 5,4±1,3 0,21 Lower IP index 0,14±0,18 0,028±0,019 0,04 Stone size 66,2±44,1 96,2±67,1 0,27 Mean number of session 1,6±0,8 1,6±0,58 0,87 Mean energy 16,9±1,2 18,3±1,1 0,06 Mean number of shockwave 2457,5±551,6 2785±786 0,33 Total pelvic volume of stone bearing kidney(range) 2621,2(582-7037) 1850(1505-17138) 0,07 Conclusions Results of this study let us think that although every single anatomic variation might have some effect on the SWL outcome of lower caliceal stones in paediatric patient basis, combination of all these anatomic parameters with the stone size in a single index could be a more accurate predictive tool because every single anatomic feature was a part of whole.

Laterality of Symptomatic Recurrent Calcium Nephrolithiasis

Objective: Although it is presumed that both kidneys excrete similar urinary constituents, it is a general observation that the majority of patients present with unilateral stone disease. The aim of this work was to study the laterality of recurrence in calcium stone formers. Patients and Methods: In a retrospective study of 154 patients treated for recurrent symptomatic nephrolithiasis at our institution between January 1982 and December 2006, the side of stone formation was determined by an analysis of radiographic fi ndings and symptomatic history. Patients with hydronephrosis, major renal anatomic anomalies and non-calcium stones were excluded from the study. The features of unilateral stone forming and bilateral stone forming were compared. Statistical analysis was done using Student\'s t-test. Results: Of the 154 patients, 102 were males and 52 females with a male-to-female ratio of 1:2. One hundred and fourteen patients had unilateral stones (Group A), 64 (56%) on the left and 50 (44%) on the right side. In 40 patients they were bilateral (Group B). Comparing Groups A and B, the mean age at the fi rst stone episode was 41.5 versus 38.3 years, the mean interval between the fi rst stone and recurrence was 9.6 versus 9.9 years, and the mean follow-up was 13.3 versus 14.9 years (differences not statistically signifi cant). In Group A, 101 patients (89%) had unilateral stone recurrence episodes with 86 of these 101 patients (85%) developing stones on the same side as the primary stone. Of the 40 patients with bilateral stone formation, 30 patients (75%) had bilateral stone recurrence episodes. Conclusion: Recurrent stone formers commonly present withcalculi on the same side and the etiology of this phenomenon is unclear, but anatomic and external triggers should be considered. Keywords : Laterality, kidney, renal stones, recurrence, urinary calculi. African Journal Of Urology Vol.14 (3) 2007: pp. 143-146

Significance of Lower-Pole Pelvicaliceal Anatomy on Stone Clearance after Shockwave Lithotripsy in Nonobstructive Isolated Renal Pelvic Stones

To investigate the probable effect of lower-pole pelvicaliceal anatomy on stone clearance after shockwave lithotripsy (SWL) in patients with nonobstructive renal pelvic stones. The clinical records of patients with isolated renal pelvic stones who underwent SWL between 1996 and 2005 were reviewed. After excluding patients with obstruction leading to dilatation, major anatomic abnormalities, noncalcium stones, metabolic abnormalities, history of recurrent stone disease, multiple stones, and previous renal surgery, 153 patients were enrolled in the study. Lower pole infundibulopelvic angle (IPA) and infundibular length and width were measured from intravenous urography. Patients were classified into three groups according to stone burden (group 1, <100 mm(2); group 2, 101-200 mm(2); group 3, 201-400 mm(2)). The mean stone size was 142.08+/-86.3 mm(2). Overall stone-free rate was 53.6%. Localization of clinically significant or insignificant residual fragments was in the lower calix, renal pelvis, and both in 50 (32.6%), 29 (18.9%), and 8 (5.2%) patients, respectively. There was no statistically significant difference in pelvicaliceal anatomic features except narrower IPA (P=0.02) in group 1 patients with residual stones. The falling of stone fragments to the lower calix in spite of the ureter whether clinically significant or not after SWL of pelvic stones initially seems to be related to stone burden rather than lower caliceal anatomy. However, existence of a more narrow IPA in group 1 patients with residual fragments led us to believe that lower-pole IPA can play a role in stone clearance, especially for smaller stones, probably because of smaller residual fragment size or the more mobile nature of the primary stone.

The impact of pelvicaliceal features on problematic lower pole stone clearance in different age groups

Our aim was to evaluate the impact of pelvicaliceal variables in pediatric and adult age groups who underwent SWL for lower caliceal calculi. 25 pediatric and 78 adult patients treated with extracorporeal shock wave lithotripsy (SWL) between 1996 and 2004 were enrolled into the study after exclusion of patients with hydronephrosis, major renal anatomic anomalies, non-calcium stones, history of recurrent stone disease and previous renal surgery. Lower pole infundibulopelvic angle (IPA), infundibular length (IL), infundibular width (IW) and pelvicaliceal volume were measured from pre-SWL intravenous urography. The pelvicaliceal stone load (PSL) index implicating the stone burden of each patient described as the relationship between stone volume and total estimated pelvicaliceal volume for stone-bearing kidney was also calculated. Sixty-eight percent of adult and 80% of pediatric patients became stone-free after SWL. The statistical insignificance between PSL index (p=0.097) of two groups shows that both groups shared a similar stone burden. According to SWL outcome, mean IPA values of stone-free and residual patients were 46.85 degrees and 30 degrees in pediatric group, respectively (p=0.01), whereas these values were 48.08 degrees and 43.06 degrees in the adult group, respectively (p=0.352). In the pediatric age group, stone-free and cumulative success rates increased with increasing IPA but this correlation was statistically insignificant (p: 0.263). Lower caliceal anatomy has a higher impact on stone clearance after SWL in pediatric patients and urologists can expect better SWL outcomes from pediatric population with solitary lower caliceal stone than adults under the same conditions.

Is Stone Clearance after Shockwave Lithotripsy in Patients with Solitary Upper-Caliceal Stone Influenced by Anatomic Differences in the Pelvicaliceal System?

We investigated the effect of pelvicaliceal differences on stone clearance after extracorporeal shockwave lithotripsy (SWL) in patients with solitary upper-caliceal stones. The clinical records of patients with solitary upper-caliceal stones who underwent SWL between 1996 and 2004 were reviewed. After excluding patients with hydronephrosis, significant anatomic abnormalities, non-calcium stones, metabolic abnormalities, recurrent stone disease, multiple stones, and previous renal surgery, 42 patients with a mean stone size of 153.47 mm2 (range 20-896 mm2) were enrolled in this study. They were divided into three groups according to stone burden (group 1 < or =100 mm2, group 2,101 mm2-200 mm2, and group 3 >200 mm2). Upper-pole infundibulopelvic angle (IPA), infundibular length (IL), and infundibular width (IW) were measured from intravenous urograms. Of the total, 29 patients (69%) were stone free after SWL treatment. The differences in the upperpole IPA, IL, and IW of stone-free patients and patients with residual stones were not statistically significant (P = 0.85, P = 0.89, and P = 0.37, respectively). Again, there were no statistically significant differences in terms of upper IPA, IW, and IL in comparing the three groups divided by initial stone size. Upper-caliceal anatomy does not exert a significant impact on stone clearance after SWL for isolated upper-caliceal stones. To best of our knowledge, this is the first study to investigate the effects of pelvicaliceal anatomy on SWL treatment for upper-caliceal stones, so there is a need for further investigations to confirm our findings.

Is pelvicaliceal anatomy a risk factor for stone formation in patients with solitary upper caliceal stone?

Objectives To investigate the effect of pelvicaliceal anatomy on stone formation in patients with solitary upper caliceal stones. Methods The records of patients with solitary upper caliceal stones between 1996 and 2004 were reviewed. After the exclusion of patients with hydronephrosis, major anatomic abnormalities, noncalcium stones, metabolic abnormalities, history of recurrent stone disease, multiple stones, and previous renal surgery, 42 patients (24 male, 18 female) and 42 healthy subjects (22 male, 20 female) with normal results on intravenous pyelography (IVP) were enrolled into the study. With a previously described formula, upper pole infundibulopelvic angle (IPA), infundibular length (IL) and width (IW), and pelvicaliceal volume of the stone-bearing and contralateral normal kidney of patients and bilateral normal kidneys of healthy subjects were measured from IVP. Results Forty-two stone-bearing and 126 normal kidneys (42 contralateral, 84 healthy) were assessed. The mean stone size was 153.47 mm 2 (range, 20 to 896 mm 2). There were no statistically significant differences in terms of upper caliceal specifications between stone-bearing and normal kidneys. The mean (± standard deviation) pelvicaliceal volume of 42 stone-bearing and 126 normal kidneys was 2455.2 ± 1380.2 mm 3 and 1845.7 ± 1454.8 mm 3, respectively ( P = 0.019). These values were 2114 ± 2081.5 mm 3 ( P = 0.34) and 1709.5 ± 989.1 mm 3 ( P = 0.001) for contralateral normal kidneys (n = 42) and normal kidneys of healthy subjects (n = 84), respectively. Conclusions Explanation of the etiology of the upper caliceal stone by the anatomic features is very difficult, and these caliceal anatomic variables (IPA, IL, IW) seem not to be a significant risk factor for stone formation in the upper calyx.

The impact of pelvicaliceal anatomical variation between the stone-bearing and normal contralateral kidney on stone formation in adult patients with lower caliceal stones

We aimed to investigate the effect of pelvicaliceal anatomical differences on the etiology of lower caliceal stones. Records of adult patients between January 1996 and December 2005 with solitary lower caliceal stone were reviewed. After exclusion of patients with hydronephrosis, major renal anatomic anomalies, non-calcium stones, history of recurrent stone disease and previous renal surgery, 78 patients were enrolled into the study. Lower pole infundibulopelvic angle (IPA), infundibulovertebral angle (IVA), infundibular length (IL), width (IW), number of minor calices and cortical thickness of the lower pole together with other caliceal variables obtained from the whole pelvicaliceal anatomy of both stone-bearing and contralateral normal kidneys were measured from intravenous pyelogram of the patients. Total pelvicaliceal volume was also calculated by a previously described formula for both kidneys. There were statistically significant difference between two kidneys in terms of IW (p < 0.001) and IL (p = 0.002) of the upper calyx, IW (p = 0.001) and IVA (p < 0.001) of the lower calyx), pelvicaliceal volume (p < 0.001), IPA of middle calyx (p = 0.006) and cortical thickness over the lower pole (p < 0.001). However there was no difference between stone-bearing and contralateral normal kidneys in terms of lower pole IPA (p = 0.864) and IL (p = 0.568). Pelvicaliceal volume but not lower caliceal properties seem to be a risk factor for stone formation in lower calyx.

Pathophysiology, diagnosis and conservative therapy of non-calcium kidney calculi

While calcium oxalate and calcium phosphate make up at least 80% of all kidney stones, infection-induced and uric acid stones occur in 10% and 8%, respectively. Although any type of stone may become infected, the term "infection stones" means that stone formation exclusively depends on urease-producing bacteria. The splitting of urea leads to a rise in urinary pH which may induce crystallization of struvite (magnesium-ammonium-phosphate), the major constituent of infection stones, or carbonate apatite. Struvite stones account for the majority of staghorn calculi. They can grow quite large and may fill the entire collecting system. Patients with struvite stones may present with acute flank pain or remain completely asymptomatic. The cure of infection stones requires complete removal of the stone material. For uric acid crystallization and stone formation, low urine pH (below 5.5) is a more important risk factor than increased urinary uric acid excretion. Main causes of low urine pH are tubular disorders (including gout), chronic diarrheal states or severe dehydration. Accordingly, the treatment of uric acid stones consists not only of hydration (urine volume above 2000 ml per day), but mainly of urine alkalinization to pH values between 6.2 and 6.8. Urinary uric acid excretion can be reduced by a low-purine diet as well as--in case of recurrent uric acid stones and/or gout--by allopurinol. Cystinuria is a rare hereditary gene disorders with impaired tubular reabsorption of cystine. Stone formation occurs as a consequence of cystine's relatively low solubility at urine pH levels below 8. Only symptomatic diet and drug treatments are currently available, with urine dilution and urine alkalinization being the most efficient ones. Cystine stones respond poorly to shockwave lithotripsy, so that invasive procedures may regularly be necessary. 2,8-dihydroxy-adenine stones occur as a consequence of an enzyme deficiency that involves purine metabolism. These resulting stones are not visible by fluoroscopy and are therefore often misinterpreted as uric acid stones. Low-purine diet and allopurinol reduce the frequency of stone formation.

Hounsfield unit density in the determination of urinary stone composition

Objectives. Noncontrast computed tomography (NCCT) has emerged as the diagnostic study of choice in the evaluation of acute flank pain. Recent in vitro studies have suggested that NCCT can be used to predict the composition of urinary stones on the basis of differences in radiodensity (measured in Hounsfield units, HUs). We sought to determine whether the analysis of in vivo urinary stones seen on NCCT could predict their composition. Methods. Between March 1997 and August 1999, 100 pure stones from patients seen at the Wilford Hall Medical Center in San Antonio, Texas were submitted for analysis. All had been visualized by NCCT before stone passage or retrieval. A General Electric High-Speed Advantage CT scanner evaluated most of these patients by a “flank pain protocol” (ie, helical technique with breath-holding at 120 kV, 200 mA with 5 mm collimation). Each scan was interpreted by one of two staff radiologists who measured the HUs for each stone. A statistical comparison was made between the stone composition and radiodensity. To allow for subsequently observed increases in radiodensity with increasing stone size regardless of composition, the HU value was divided by each stone’s largest transverse diameter in millimeters to give the HU density. A statistical comparison was then made between stone composition and HU density. Results. No significant difference was noted between the HU values of calcium oxalate and calcium phosphate stones, and thus they were analyzed collectively as “calcium stones.” When the HU values of calcium (n = 87), uric acid (n = 7), struvite (n = 4), and cystine (n = 2) stones were compared, the overlap of ranges precluded accurate identification, and the mean HU values were not significantly different from one another. There was less overlap noted when comparing the HU densities of the stones studied, and no noncalcium stone had an HU density greater than 76 HU/mm. Using one-way analysis of variance, significant differences were noted between the mean HU density of calcium (105 ± 43) and uric acid (50 ± 24) stones ( P = 0.006). A trend toward significance was found between the mean HU density of the calcium and struvite stones (53 ± 28, P = 0.073). No significant differences were found among the other stones. Conclusions. HU density compared with the HU value alone better characterized differences in radiodensities among urinary stones; calcium stones can be distinguished from uric acid stones on the basis of this value. However, neither the HU density nor the mean HU value was able to identify urinary stones in vivo.