Classification of Stones According to Michel Daudon: A Narrative Review.

CONTEXT: Morphoconstitutional analysis of urinary stones is perhaps the most important examination in the evaluation of a patient with urolithiasis. OBJECTIVE: A comprehensive stone classification system was developed in the early 1990s by Michel Daudon, which included the main types of stones and their possible physiopathogenic origin. EVIDENCE ACQUISITION: A narrative review of the articles published about this classification was conducted, without time limit. EVIDENCE SYNTHESIS: Two analytical steps are needed for the classification process: the microscopic examination, which gives the stone morphology, and the physical analysis, which provides the stone constitution. Upon completion of a full analysis, knowledge of the principal crystal species of the stone is acquired. In addition, this analysis highlights the possible causes of the lithogenic process, taking in account less frequent, but severe, pathologies. CONCLUSIONS: The aim of this report is to summarize the principal etiological causes for urinary stone formation thanks to the morphoconstitutional analysis and to present its contribution in the field of urinary stones. PATIENT SUMMARY: We looked at all types of stones and found that their origin varies according to the underlying pathology of the patient.

A novel approach to classify urinary stones using dual-energy kidney, ureter and bladder (DEKUB) X-ray imaging.

OBJECTIVES: Detection of urinary stone composition before treatment can help in its management. The purpose of this work is to study the feasibility of classifying the kidney stone compositions in vivo by dual-energy kidney, ureter, and bladder (DEKUB) X-ray imaging. METHODS: Six urinary stone compositions with nine diameters were simulated in a water phantom, and two 70- and 120-kVp images were acquired by radiography tally of the Monte Carlo code. Six image features among 10 were selected for classification of the kidney stones. Four classification algorithms were applied to the dataset using MatLab software. Five-fold cross-validation was applied to the most accurate algorithm for 1000 times and the true and false detection rates were reported. RESULTS: The obtained accuracy of kidney stone classification was 96 ± 2% and this decreased with increasing noise level. The DEKUB was successful in distinguishing brushite, calcium oxalate monohydrate, cystine, and calcium phosphate stones from other types. CONCLUSIONS: Acceptable results achieved by the low-cost, low-dose DEKUB system in detection of kidney stone composition not only obviates a need for complicated imaging systems such as dual-energy computed tomography, but also provides an available and useful aid for physicians to choose between treatment approaches.

Distribution and Characteristics of Hypouricemia within the Japanese General Population: A Cross-Sectional Study.

Background and objectives: There is insufficient epidemiological knowledge of hypouricemia. In this study, we aimed to describe the distribution and characteristics of Japanese subjects with hypouricemia. Materials and Methods: Data from subjects who underwent routine health checkups from January 2001 to December 2015 were analyzed in this cross-sectional study. A total of 246,923 individuals, which included 111,117 men and 135,806 women, met the study criteria. The participants were divided into quartiles according to their serum uric acid (SUA) levels. We subdivided the subjects with hypouricemia, which was defined as SUA level ≤ 2.0 mg/dL, into two groups and compared their characteristics, including their cardiovascular risks. Results: The hypouricemia rates were 0.46% overall, 0.21% for the men and 0.66% for the women (P < 0.001). The number of the subjects with hypouricemia showed two distributions at SUA levels of 0.4⁻1.1 mg/dL (lower hypouricemia group), which included a peak at 0.7⁻0.8 mg/dL, and at SUA levels of 1.4⁻2.0 mg/dL (higher hypouricemia group). The men in the higher hypouricemia group had lower body mass indexes (BMI) and triglyceride (TG) levels and had higher fasting blood glucose levels than those in the lower hypouricemia group. The women in the higher hypouricemia group were younger; had lower BMI, total protein, TG, total cholesterol and low-density lipoprotein cholesterol levels; and had higher estimated glomerular filtration rates levels compared to those in the lower hypouricemia group. Conclusions: The characteristics of the individuals in the lower and higher hypouricemia groups differed significantly, indicating different pathophysiologies within each group.

The Association of Encrustation and Ureteral Stent Indwelling Time in Urolithiasis and KUB Grading System.

PURPOSE: To evaluate the management of prolonged indwelling ureteral stents and the newly developed KUB (kidney, ureter, and bladder) grading system for the classification of encrusted stents in urolithiasis. METHOD: This study involved 69 patients that had indwelling and forgotten ureteral stents for more than 6 months after urolithiasis treatment. They were categorized into 4 groups based on indwelling time and were reviewed retrospectively. Patients whose ureteral stent could not be removed with simple cystoscopy were graded according to stone surface area and the KUB system. RESULTS: The mean stent indwelling time was 23.1 months. Stone burden in KUB and, in proportion to that, total KUB (T) score showed increased association that was directly proportional to indwelling time (p < 0.001, p = 0.008). Surgical intervention was required in 73.9% of patients. Among patients requiring surgery, 78.4% were treated in a single session and multi-modal interventions were performed in 70.5%. K score ? 3 was found to be associated with multiple surgery requirements (odds ratio [OR];11.25, %95 confidence interval [CI]:2.132-59.375),multi-modal procedure requirements (OR;16.50, %95 CI:3.434-79.826 ), and lower stone-free rates (p = 0.04). Bscore ? 3 was associated with multi-modal procedure requirements (OR;8.90, %95 CI:1.052-75.462). U score ? 3and T score ? 9 were associated with an operating time >180 minutes (p < 0.001, p = 0.008). CONCLUSION: Prolonged indwelling time of the ureteral stent in urolithiasis is associated with increased encrustation and stone burden. Since the KUB system specifies stone burden and its particular localization, it can be used as a simple, convenient method for the planning treatment of encrusted ureteral stents.

The systematic classification of urinary stones combine-using FTIR and SEM-EDAX.

BACKGROUND: To explore underlying mechanism of urinary stones formation, the composition and microstructure of urinary stones were analyzed systematically with a large sample study from China. MATERIALS AND METHODS: A total of 2437 urinary stones were obtained from the urology department at our Hospital. The composition of the stones was analyzed by Fourier transform infrared spectroscopy (FTIR). Meanwhile, the microstructure and element distribution were observed with scanning electron microscopy combined with element distribution analysis (SEM-EDAX). RESULTS: Urinary stones were classified into eight types, that were consisted of calcium oxalate stones (1301/2437, 53.39%), calcium phosphate stones (131/2437, 5.38%), anhydrous uric acid stones (434/2437, 17.81%), magnesium ammonium phosphate stones (12/2437, 0.49%), sodium urate stones (5/2437, 0.21%), brushite stones (4/2437, 0.16%), cystine stones (3/2437, 0.12%) and mixed stones (547/2437, 22.45%, ten subtypes were included). Under SEM, they displayed distinct microstructures: plank-like, brick-like, polyhedron or paliform crystals for calcium oxalate stones, similar sized echin-sphere or rough bulbiform or tree bark-like crystals for calcium phosphate stones, rotten-wood-like or petrous crystals for anhydrous uric acid stones, globular or gallet-like crystals for magnesium ammonium phosphate stones, sawdust-like crystals for sodium urate stones, broken-wood-like crystals for brushite stones, stacking hexagonal cystine crystals for cystine stones, and two or more of the above crystals for mixed stones. Meanwhile, they also presented distinct elemental composition and distribution by EDAX. CONCLUSIONS: Urinary stones can be classified into eight types, and exhibit a diversity of microstructure and elemental compositions in China. The formation process of different types of urinary stones may be diverse.

Impact of dual energy characterization of urinary calculus on management.

INTRODUCTION: Dual energy CT (DECT) is a recent technique that is increasingly being used to differentiate between calcium and uric acid urinary tract calculi. The aim of this study is to determine if urinary calculi composition analysis determined by DECT scanning results in a change of patient management. METHOD: All patients presenting with symptoms of renal colic, who had not previously undergone DECT scanning underwent DECT KUB. DECT data of all patients between September 2013 and July 2015 were reviewed. Urinary calculi composition based on dual energy characterization was cross-matched with patient management and outcome. RESULTS: A total of 585 DECT KUB were performed. 393/585 (67%) DECT scans revealed urinary tract calculi. After excluding those with isolated bladder or small asymptomatic renal stones, 303 patients were found to have symptomatic stone(s) as an explanation for their presentation. Of these 303 patients, there were 273 (90.1%) calcium calculi, 19 (6.3%) uric acid calculi and 11 (3.4%) mixed calculi. Of those with uric acid calculi, 15 were commenced on dissolution therapy. Twelve of those commenced on dissolution therapy had a successful outcome, avoiding need for surgical intervention (lithotripsy or stone retrieval). Three patients failed dissolution therapy and required operative intervention for definitive management of the stone. CONCLUSION: Predicting urinary tract calculi composition by DECT plays an important role in identifying patients who may be managed with dissolution therapy. Identification of uric acid stone composition altered management in 15 of 303 (5.0%) patients, and was successful in 12, thereby avoiding surgery and its attendant risks.

National Profiles of Urinary Calculi: a Comparison Between Developing and Developed Worlds.

INTRODUCTION: The incidence of urolithiasis has increased in both the developed and the developing countries during the past decades. Economically, the increase of urolithiasis contributes to the rise of the healthcare burden everywhere. Moreover, this increase has been associated with a change in the epidemiology of urolithiasis in terms of age and sex distribution, and also the location and type of calculi. MATERIALS AND METHODS: We searched the MEDLINE for relevant literature dating back to 1980. This review compared the trends in epidemiological factors affecting urolithiasis in the developed and the developing countries during the past decades. RESULTS: People in the developing countries are more likely to contract kidney calculi at a younger age than in the developed countries. Although calculus disease is still more prevalent in men than in women, the latter are increasingly affected in both worlds. Uric acid calculi are more prevalent in the developing than in industrialized countries. There is a progressive increase in the frequency of calcium oxalate and calcium phosphate calculi in the developing countries where these used to be less frequent. CONCLUSIONS: The incidence and prevalence of urinary calculi is increasing globally. Many factors including aging of the population, changes in diet, global warming, and employment of more accurate diagnostic tools seem to be involved in this increase. An increasing affluence and adaptation of Western diet habits in many developing countries seem likely to contribute to the changes.

[Classification of urinary calculi in a pediatric population from Brittany]. / Proposition de "profils types" des calculs urinaires dans une population pédiatrique bretonne.

INTRODUCTION: Urinary lithiasis in children is relatively seldom in France as in industrialized countries. The determination of their etiology based on their composition may lead to a better treatment. METHOD: One hundred and eight urinary calculi from 6 months through 18-year-old children were analyzed by using spectrophotometry, in order to specify their structure. Six groups were evidenced through a multidimensional analysis based on the presence of components weighing at least 5% of the total. RESULTS: The youngest children affected were mostly boys, and the sex ratio switched after 12.5 years. Above 14 years of age, the number of calculi significantly raised. Their composition varied with the gender, and their localization with the age. Finally a correlation between infection and composition of the calculus was shown in our study. CONCLUSION: The classification of calculi among six groups according to their composition, along with clinical informations and morphologic studies, has proven its value in determining the etiology of the lithiasis. These data help to better understand the kind of lithiasis that may be observed and the physiopathology of the mechanism explaining it from the gender and age.

Using 24-hour urinalysis to predict stone type.

PURPOSE: We determined the accuracy of 24-hour urinalysis in predicting stone type and identify the associations between 24-hour urine elements with stone type. MATERIALS AND METHODS: We performed a retrospective review of 503 stone formers with stone composition analysis and 24-hour urinalysis available. Analysis of 24-hour urine elements across stone types was performed using Fisher's exact test and ANOVA. Multinomial logistic regression was used to predict stone type based on 24-hour urinalysis. RESULTS: A total of 280 (56%) patients had predominantly calcium oxalate, 103 (20%) had uric acid, 93 (19%) had calcium phosphate, 16 (3%) had mixed and 11 (2%) had other stone types. There were several significant patient characteristics and 24-hour urinalysis differences across stone type groups. The statistical model predicted 371 (74%) calcium oxalate, 78 (16%) uric acid, 52 (10%) calcium phosphate, zero mixed and 2 (less than 1%) other stone types. The model correctly predicted calcium oxalate stones in 85%, uric acid in 51%, calcium phosphate in 31%, mixed in 0% and other stone types in 18% of the cases. Of the predicted stone types, correct predictions were 61%, 69%, 56% and 71% for calcium oxalate, uric acid, calcium phosphate and other stones types, respectively. The overall accuracy was 64%. Plots were used to explore the associations between each 24-hour urine element with each predicted stone type adjusted for all the others urinary elements. CONCLUSIONS: A 24-hour urinalysis alone does not accurately predict stone type. However, it may be used in conjunction with other variables to predict stone composition.

El artefacto de centelleo en la caracterización de los cálculos urinarios / Role of twinkling artifact in characterization of urinary calculi

Introducción: La caracterización de los cálculos renales está cada vez cobrando mayor importancia como paso previo a la toma de decisiones terapéuticas tales como la nefrolitotomía percutánea (NLP) y la litotricia extracorpórea por ondas de choque (LEOC). En algunos estudios se ha publicado que el artefacto de centelleo (artefacto de ecografía de flujo en color) puede ser de utilidad en la detección de piedras en el riñón. En este estudio se pretende dilucidar si la presencia o ausencia del artefacto de centelleo tendría alguna relación con la composición química de los cálculos. Material y método: En un estudio prospectivo se incluyó a pacientes con cálculos renales de ≥ 0,5cm. Se examinó a 70 pacientes mediante rayos X, pielografía intravenosa, tomografía computarizada sin contraste y ecografía doppler espectral y a color. El artefacto se consideró de grado 1 si sólo ocupaba una parte de la sombra acústica, considerándose de grado 2 si ocupaba la totalidad de la sombra. Se trató a los pacientes con cálculos de menos de 2cm con LEOC, y a aquellos con piedras de mayor tamaño se les derivó a tratamiento con NLP. Resultados: No se detectó artefacto alguno (grado 0) en 11 sujetos, detectándose el grado 1 en 25 y el grado 2 en 24. Se encontró una relación significativa entre el aumento en artefactos de centelleo y tamaño del cálculo (p<0,001). Al analizar la relación entre composición de los cálculos y artefacto de centelleo se detectó el artefacto en prácticamente todas las piedras de oxalato de calcio —dihidrato y fosfato de calcio, mientras que en el caso de los cálculos de oxalato de calcio— monohidrato y ácido úrico se detectó el artefacto únicamente en algo más de la mitad de ellos. En el grupo LEOC se observó que, al aumentar el grado del artefacto de centelleo, descendía el número de sesiones de LEOC necesario (p<0,001). En el grupo NLP se encontró el artefacto de centelleo en todos los pacientes (100%) con piedras de superficie irregular. Conclusión: La irregularidad de la superficie lítica es el factor más influyente en la formación del artefacto de centelleo en piedras de riñón. Dicho artefacto puede tener utilidad a la hora de prever la predisposición a la fragmentación de los cálculos en pacientes derivados a tratamiento con aplicación de LEOC. Podría pronosticarse que aquellos casos en los que el tamaño de la piedra fuese de más de 2cm y no se detectase artefacto de centelleo serían de oxalato de calcio - monohidrato, que es una de las piedras con mayor predisposición a la fragmentación (AU)

Introduction: Stone characterization is becoming important before decision of treatment such as percutaneous nephrolithotomy (PCNL) and extracorporeal shock wave lithotripsy (ESWL). Some studies have reported that the twinkling artifact (color-flow ultrasonography artifact) may be useful to detect urinary stones. This study aims to determine whether the presence or absence of the twinkling artifact is correlated with the chemical composition of the stones. Material and method: Patients with renal stones > 0.5cm were included in a prospective study. Sixty patients were examined with x-ray film, intravenous pyelography, non-contrast computerized tomography, and color and spectral doppler ultrasonography. The artifact was considered grade 1 when occupied only one portion of the acoustic shadowing and when the artifact occupied the entire acoustic shadowing was considered grade 2. Patients with stones smaller than 2cm were treated with SWL and patients with stones larger than 2cm were treated with PCNL. Results: No artifact (grade 0) was detected in 11 subjects, grade 1 in 25 and grade 2 in 24. Significant relationship was found between the increase in twinkling artifact and stone size (p<0.001). When the relation between the composition of the stones and the twinkling artifact was analyzed, artifact was detected nearly in all of the calcium oxalate dihydrate and calcium phosphate stones; whereas the artifact was detected in more than half of the calcium oxalate monohydrate and uric acid stones. In ESWL group it was observed that as the grade of the twinkling artifact increases, the number of required ESWL sessions decreases (p<0.001). In PCNL group twinkling artifact was found in all of the patients (100%) with roughly surfaced stones. Conclusion: The roughness of stone surface is the most important factor in terms of formation of the twinkling artifact in kidney stones. This artifact can be of use in anticipating the breakability of the stones of those patients to be treated with applied ESWL. One might anticipate that cases where the size of the stone is larger than 2cm but no twinkling artifact is detected are calcium oxalate monohydrate, which is one of the stones with highest level of breakability (AU)

Validity of administrative coding in identifying patients with upper urinary tract calculi.

PURPOSE: Administrative databases are increasingly used for epidemiological investigations. We performed a study to assess the validity of ICD-9 codes for upper urinary tract stone disease in an administrative database. MATERIALS AND METHODS: We retrieved the records of all inpatients and outpatients at Johns Hopkins Hospital between November 2007 and October 2008 with an ICD-9 code of 592, 592.0, 592.1 or 592.9 as one of the first 3 diagnosis codes. A random number generator selected 100 encounters for further review. We considered a patient to have a true diagnosis of an upper tract stone if the medical records specifically referenced a kidney stone event, or included current or past treatment for a kidney stone. Descriptive and comparative analyses were performed. RESULTS: A total of 8,245 encounters coded as upper tract calculus were identified and 100 were randomly selected for review. Two patients could not be identified within the electronic medical record and were excluded from the study. The positive predictive value of using all ICD-9 codes for an upper tract calculus (592, 592.0, 592.1) to identify subjects with renal or ureteral stones was 95.9%. For 592.0 only the positive predictive value was 85%. However, although the positive predictive value for 592.1 only was 100%, 26 subjects (76%) with a ureteral stone were not appropriately billed with this code. CONCLUSIONS: ICD-9 coding for urinary calculi is likely to be sufficiently valid to be useful in studies using administrative data to analyze stone disease. However, ICD-9 coding is not a reliable means to distinguish between subjects with renal and ureteral calculi.

Quantitative analysis of 4468 uroliths retrieved from farm animals, exotic species, and wildlife submitted to the Minnesota Urolith Center: 1981 to 2007.

Knowledge of the mineral composition of uroliths in various species of animals can help veterinarians predict the mineral composition of stones in vivo. This information is important because dissolution of existing uroliths, or minimizing further growth of uroliths in situ, is dependent on knowledge of the mineral composition of uroliths. With this objective in mind, this report summarizes the results of quantitative mineral analysis of uroliths retrieved from 4468 animals sent to the Minnesota Urolith Center. It also encompasses the most extensive database about uroliths from animals other than domesticated dogs and cats found in the literature.

Tratamiento de la litiasis vesical con láser / The treatment of bladder lithiasis with laser

OBJETIVO: El uso del láser para litotricia endoscópica, comienza en 1968 al utilizar Mulvaney un láser de rubí sin éxito, posteriormente se probaron láser de CO2 y Neodymio-YAG. Con el láser pulsado de colorante y el láser de alexandrita se obtienen unos rendimientos energéticos que oscilan de 30 a 200 mJ, su capacidad de fragmentación no es universal y esta limitada a pequeños cálculos, generalmente ureterales, por lo que no han sido alternativa terapéutica en la litiasis vesical. El láser de Holmio genera pulsos de energía de 400-2500 mJ, capaz de fragmentar todo tipo de cálculos. El Objetivo de este trabajo es analizar los resultados de la litotricia vesical endoscópica con láser de holmio YAG. MÉTODOS: En el periodo de 2006-2008 hemos tratado 21 casos de litiasis vesical, con tamaños de 1 a 4 cm. en pacientes de 8-76 años, 6 mujeres y 15 hombres, que corresponden a: Cuatro casos de litiasis infantil, 3 de ácido úrico, 1 caso de cistina, litiasis de oxalato y/o fosfato cálcico en 7 casos, 5 casos de litiasis vesical sobre extremo inferior de doble jota, 1 caso de litiasis en ureterocele intravesical. El tratamiento se ha realizado con un equipo Dornier Medilas de 20 watios de Holmio-YAG como fuente de energía, que se ha aplicado a través de cistoscopios infantil-adulto o ureteroscopios de 7-8.5 Ch. semirrígido y flexible. El control post-operatorio se ha realizado con radiografía simple de aparato urinario y ecografía. Realizamos estudio de factores de riesgo litógeno y análisis de los fragmentos del cálculo. RESULTADOS: Los 21 casos descritos corresponden a litiasis vesical secundaria o tipo II. En todos los casos se ha comprobadola ausencia de litiasis residual con estudios de imagen y se han corregido los factores de riesgo litógeno con procedimientos médicos o quirúrgicos. CONCLUSIONES: Consideramos que hoy, la litotricia vesical endoscópica con láser de holmio si es alternativa terapéutica. A pesar de que existen múltiples opciones de tratamiento endoscópico,la litotricia transuretral con láser de holmio ofrece buenos resultados con un bajo porcentaje de complicaciones (AU)

OBJECTIVES: The use of laser for endoscopic lithotripsy started in 1968 when Mulvaney tried a ruby laser without success; Later on, the CO2 laser and the Nd: YAG were tried. With the pulsed dye and alexandrite lasers energetic performances between 30 and 200 mJ are obtained, their capacity of fragmentation is not universal and is limited to small stones, generally ureteral stones, so that it has not been a therapeutic alternative for bladder lithiasis. The holmium laser generates energy pulses of 400-2500mJ, it is able to fragment every type of stone. The objective of this work is to analyze the results of endoscopic bladder lithotripsy with holmium-YAG laser. METHODS: In the period between 2006-2008 we treated 21 cases of bladder lithiasis, with a stone size between 1 and 4 cm in patients from 8-76 years, six women and 15 men, which correspond to: four cases of infantile lithiasis, 3 of uric acid, one case of cystine, seven cases of calcium oxalate and/or phosphate, five cases of bladder lithiasis growing around a double J catheter, and one case of lithiasis within an intravesical ureterocele. Treatment was performed with a 20W Dornier Medilas holmium-YAG equipment, applied using children/adult cystoscopes or 7-8.5 Ch ureteroscopes, both semirigid and flexible. Post operative control included KUB x-ray and ultrasound. We performed a study of lithogenic risk factors and stone fragments analysis. RESULTS: The 21 cases described are all secondary or type II bladder lithiasis. In all cases the absence of residual lithiasis was checked with imaging studies and the lithogenic risk factors were corrected with medical or surgical procedures. CONCLUSIONS: We consider that today bladder endoscopic lithotripsy with holmium laser is a therapeutic alternative. Despite there are multiple options for endoscopic treatment, transurethral lithotripsy with holmium laser offers good results with a low complication rate (AU)

[Pediatric endourology].

OBJECTIVE: To assess the outcome of pediatric patients treated by an endourological approach for various urinary tract pathologies. METHODS AND MATERIALS: Thirty-seven children (median age 5 years, range 0.3-14 years) were endoscopically treated for ureteropelvic junction obstruction (UPJO) (n= 6), ureteral strictures (n=5), upper urinary tract calculi (n=21) and bladder calculi (n = 5). RESULT: Upper urinary tract calculi were approached by ureteroscopy (n=12), retrograde intrarenal surgery (n=6) and percutaneous nephrolithotomy (n = 3). The average stone burden was 11 mm (range 5-35 mm) and operative time was 40 minutes (range 15-120 minutes). Bladder calculi were treated percutaneously in 3 cases and transurethrally in 2 cases for an average stone burden of 34 mm (range 7-120 mm). The overall stone-free rate after one procedure was 96%. UPJOs were retrogradely approached in an average operative time of 40 minutes (range 30-50 minutes). Successful clinical and functional outcome was maintained after an average follow-up of 15 months (range 6-30 months). The 5 ureteral strictures included 2 located in the middle ureter and 3 at the ureterovesical junction. The success rate in this group was 80% and the average follow-up 24 months (range 6-40 months). The median hospitalization time for the entire series was 1 day (range 0-7 days). There were no intraoperative complications. Three (8%) patients developed post-operative urinary tract infections. Delayed anterior urethral stricture occurred in 1 case. No additional complications occurred after an average follow-up of 11 months (range 4-36 months). CONCLUSION: Endourology in children is safe and highly effective. It appears that the indications for endourological treatment in children emulate those of adults.

A review of urinary stone analysis techniques.

Knowledge of the chemical composition and structure of urinary stones is of great value in the choice of treatment and prevention of recurrence. This is a brief review and a comparative study of the principles and practical application of various chemical and physical techniques used for urinary stone analysis. The different methods of classifying and grouping urinary stones by results of chemical analytic techniques are, also, compared and evaluated. In addition to reviewing various techniques used for the in-vitro analysis of removed stone samples, the newly emerging physical and radiological techniques for the in-vivo intact-stone analysis are, also, evaluated. These in-vivo techniques, particularly the rapidly advancing unenhanced spiral CT scanning, represent an important step forward towards the notion of non- destructive analysis of urinary stones while still in situ before the choice of treatment modality.

Cystine: helical computerized tomography characterization of rough and smooth calculi in vitro.

PURPOSE: The classification of cystine stones into rough and smooth varieties has been suggested as an aid to choosing treatment for these difficult stones. Since the surface of stones is difficult to visualize preoperatively, we tested the hypothesis that the surface morphology of cystine stones correlates with their internal structure, as viewed by helical computerized tomography (CT). MATERIALS AND METHODS: Cystine stones were examined visually and categorized into rough (15 stones) and smooth (16 stones) subpopulations of similar size. Each stone was scanned in a helical CT scanner (GE Quad Scanner) to assess radiological characteristics and to measure attenuation values. Scans were also performed using a microCT 20 high resolution laboratory scanner (Scanco Medical AG, Bassersdorf, Switzerland) at 34 microm voxel size and the percent of internal voids was determined. RESULTS: Mean helical CT attenuation values +/- SD for rough stones were lower than for smooth stones (702 +/- 206 vs 921 +/- 51 HU, p <0.002) and the radiological appearance of rough stones suggested radiolucent voids. Internal voids in rough stones were confirmed using micro CT. Rough cystine stones contained a higher percent of internal voids (0.30% vs 0.06%, p <0.0001). CONCLUSIONS: Rough cystine stones can be distinguished from smooth stones using helical CT in vitro, suggesting that it may be possible to distinguish these stones preoperatively. Since rough cystine stones have been reported to be susceptible to shock wave lithotripsy, the identification of this morphology of cystine stones in the patient using attenuation values and appearance on helical CT could be valuable for planning treatment.

Determination of the chemical composition of urinary calculi by noncontrast spiral computerized tomography.

Various techniques for noncontrast spiral computerized tomography (NCCT) were utilized for the determination of the Hounsefield unit (HU) values of various types of urinary calculi with the aim of determining the best technique for distinguishing various stones compositions. A total of 130 urinary stones, obtained from patients who underwent open surgery, were scanned with a multidetector row scanner using 1.25 mm collimation at two energy levels of 100 and 120 kV at 240 mA. Two post-scanning protocols were used for the HU value assignment, tissue and bone windows, for both kV values. In both protocols, three transverse planes were defined in each stone, one near the top, one in the middle, and one near the bottom. Three regions of interest (ROI) were obtained in each plane. The absolute HU value was determined by three methods: the mean of the nine ROI, the mean of the central three ROI, and the central ROI in the middle plane. Determination of the stones' composition was performed using the absolute HU value measured at 120 kV, the dual CT values (HU values at 100 kV-HU values at 120 kV), and HU values/stone volume ratio (HU density). All stones were analyzed by x-ray diffraction to determine their chemical composition. After the exclusion of groups with few calculi, 47 pure stones [25 uric acid (UA), 15 calcium oxalate monohydrate (COM), seven struvite], and 60 mixed stones [15 COM 60-90%+hydroxyl apatite (HA), 14 COM 40-90%+UA, 21 UA+COM <40%, ten mixed struvite+COM+hydroxyl apatite] were included in the statistical analysis. From the least to the most dense, the pure stone types were UA, struvite, COM. Mixed UA+COM<40% calculi were less dense but insignificantly different from pure UA, while when the COM ratio was > or =40% their density became higher than and significantly different from pure UA, and less than but not significantly differentiated from pure COM. Mixed COM+HA were the most dense stones. Using the absolute HU values at 120 kV and HU density, we could distinguish, with statistical significance, all pure types from each other, pure UA from all mixed calculi except UA+COM <40%, pure COM from mixed UA+COM <40%, and pure struvite from all mixed stones except mixed struvite stones. Dual CT values were not as good as absolute HU values and HU density in the determination of stone composition. These results demonstrate that absolute HU values and HU density derived from CT scanning using a small collimation size could uncover statistically significant differences among all pure and most of the mixed urinary stones. This permits more accuracy in the prediction of stone composition. Moreover, this technique permits diagnostic conclusions on the basis of single CT evaluation.

Recurrence prevention in patients with urinary tract stone disease.

Formation of urinary tract concrements is a common disease and steps should be taken in order to elucidate the underlying mechanisms and to give the patients appropriate advice and medical treatment. This present article summarizes the principles for recurrence preventive measures in patients with uric acid, infection, cystine and calcium stone disease. Categories of stone formers are identified with the aim of providing a basis for an individualised treatment with a reasonable patient's compliance. The recommendations are in line with those given by the EAU guideline group for urolithiasis.