[Clinician and researcher at the time. Is it possible?] / Clínico e investigador a la vez, ¿se puede?

Research in clinical practice arises as a constant need for improvement to provide better care to patients, train better human resources and make a daily reflection on the amount of scientific information we receive every day. We want to reflect on how the Centro de Adiestramiento en Investigación Clínica (CAIC) from our healthcare activity changed our practice.

La investigación en la práctica clínica surge como una necesidad constante de mejora, a fin de dar una atención de mayor calidad a los pacientes, formar recursos humanos más preparados y hacer una reflexión diaria ante la cantidad de información científica que recibimos todos los días. Queremos hacer una reflexión de como el Centro de Adiestramiento en Investigación Clínica (CAIC) desde nuestra actividad asistencial cambió nuestra práctica.

[Interobserver agreement in the diagnosis of bladder outlet obstruction in women]. / Variabilidad interobservador en el diagnóstico de obstrucción del tracto de salida vesical en mujeres.

Background: The diagnosis of bladder outlet obstruction (BOO) in women is a challenge for functional urology. In Mexico there are few data that report the prevalence of OTSV in women, being up to 24% in a group of patients. Objective: The aim of this study is to compare six different definitions of bladder outlet obstruction and evaluate the interobserver agreement in an educational setting. Material and Methods: Urodynamic studies (UDS) of women with and without diagnosis of BOO were retrospectively assesed. Farrar, Chassagne, Lemack, Defreitas, Blavais and Groutz, Solomon-Greenwell definitions were evaluated. All UDS were independently reviewed by 5 observers. The easiest, the hardest and the fastest were chosen. Interobserver agreement to classify the patients as obstructed was assessed by kappa reliability statistical analysis. We classified the type of mistakes the participants made; error of interpretation and miscalculation. Results: A total of 28 urodynamic studies were reviewed. All observers had a substantial agreement (0.64-0.78) to classify BOO using all but Lemack and Solomon-Greenwell definitions. A total 120 errors from 840 responses were found; 45.8% errors of interpretation of UDS and 54.1% miscalculation of the equation. Finally, all the participants chose the Solomon-Greenwell was the most difficult definition. Conclusion: Chassagne, Defreitas and Farrar definitions proved substantial interobserver agreement. Solomon-Greenwell and Lemack´s definitions had the highest number of pitfalls and the lowest level of agreement.

Introducción: el diagnóstico de obstrucción de tracto de salida vesical (OTSV) en mujeres supone un reto para la urología funcional. En México existen pocos datos que reporten la prevalencia de OTSV en mujeres, siendo de hasta el 24% en un grupo de pacientes. Objetivo: comparar seis definiciones diferentes de obstrucción de tracto de salida vesical (OTSV) en mujeres y evaluar la concordancia entre observadores en un entorno educativo. Material y métodos: evaluación retrospectiva de estudios urodinámicos de mujeres con y sin diagnóstico de OTSV. Se evaluaron las definiciones de Farrar, Chassagne, Lemack, Defreitas, Blavais y Groutz y Solomon-Greenwell. A todos los participantes se les brindó un taller teórico-práctico para analizar los estudios urodinámicos en su fase de flujo-presión y diagnosticar la OTSV. Los estudios urodinámicos fueron revisados de forma independiente por cinco observadores. La concordancia interobservador para clasificar a los pacientes como obstruidos se evaluó mediante análisis estadístico de confiabilidad kappa. Se clasificó el tipo de errores que cometieron los participantes, error de interpretación de estudios urodinámicos y error de cálculo en los criterios. Resultados: se revisaron en total 28 estudios urodinámicos. Todos los observadores tuvieron una concordancia buena de (0.64-0.78) para clasificar OTSV usando todas las definiciones excepto las de Lemack y Solomon-Greenwell. Se encontraron un total de 120 errores de 840 respuestas, 45.8% errores de interpretación y 54.1% error de cálculo de la ecuación. Los participantes eligieron la definición de Solomon-Greenwell, la más difícil. Conclusión: las definiciones de Chassagne, Defreitas y Farrar demostraron una concordancia sustancial entre observadores. Las definiciones de Solomon-Greenwell y Lemack tuvieron el mayor grado de dificultad y el menor nivel de acuerdo.

[ROC curves: general characteristics and their usefulness in clinical practice]. / Curvas ROC: características generales y su uso en la práctica clínica.

The use of diagnostic tests to determine the presence or absence of a disease is essential in clinical practice. The results of a diagnostic test may correspond to numerical estimates that require quantitative reference parameters to be transferred to a dichotomous interpretation as normal or abnormal and thus implement actions for the care of a condition or disease. For example, in the diagnosis of anemia it is necessary to define a cut-off point for the hemoglobin variable and create two categories that distinguish the presence or absence of anemia. The method used for this process is the preparation of diagnostic performance curves, better known by their acronym in English as ROC (Receiver Operating Characteristic). The ROC curve is also useful as a prognostic marker, since it allows defining the cut-off point of a quantitative variable that is associated with greater mortality or risk of complications. They have been used in different prognostic markers in COVID-19, such as the neutrophil/lymphocyte ratio and D-dimer, in which cut-off points associated with mortality and/or risk of mechanical ventilation were identified. The ROC curve is used to evaluate the diagnostic performance of a test in isolation, but it can also be used to compare the performance of two or more diagnostic tests and define which one is more accurate. This article describes the basic concepts for the use and interpretation of the ROC curve, the interpretation of an area under the curve (AUC) and the comparison of two or more diagnostic tests.

El uso de pruebas diagnósticas para determinar la presencia o ausencia de una enfermedad es esencial en la práctica clínica. Los resultados de una prueba diagnóstica pueden corresponder a estimaciones numéricas que requieren parámetros cuantitativos de referencia para trasladarse a una interpretación dicotómica como normal o anormal y así, implementar acciones para la atención de una condición o una enfermedad. Por ejemplo, en el diagnóstico de anemia es necesario definir un punto de corte para la variable hemoglobina y crear dos categorías que distingan la presencia o no de anemia. El método utilizado para este proceso es la elaboración de curvas de rendimiento diagnóstico, mejor conocidas por sus siglas en inglés como ROC (Receiver Operating Characteristic). La curva ROC además es útil como marcador pronóstico, ya que permite definir el punto de corte de una variable cuantitativa que se asocia a mayor mortalidad o riesgo de complicaciones. Se han usado en distintos marcadores pronósticos en COVID-19, como el índice neutrófilos/linfocitos y dímero D, en los que se identificaron puntos de corte asociados a mortalidad y/o riesgo de ventilación mecánica. La curva ROC se utiliza para evaluar el rendimiento diagnóstico de una prueba de forma aislada, pero también se puede usar para comparar el rendimiento de dos o más pruebas diagnósticas y definir aquella que es más precisa. En este artículo se describen los conceptos básicos para el uso e interpretación de la curva ROC, la interpretación de un área bajo la curva (ABC) y la comparación de dos o más pruebas diagnósticas.

Diagnosis and treatment of urethral stricture in men with neurogenic lower urinary tract dysfunction: A systematic review.

AIM: To summarize available data focused on diagnosis and management of urethral stricture in men with neurogenic lower urinary tract dysfunction by a systematic review of the literature. MATERIALS AND METHODS: A systematic review of the literature was carried out through an extensive electronic database search performed in PubMed/MEDLINE and Scopus databases for full texts, and International Continence Society, American Urology Association, and European Association of Urology abstracts for citations related to urethral structure. This review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis. RESULTS: A total of 316 articles were identified, 48 of which were selected for this review. Different strategies are currently being used for the management of urethral strictures, such as clean intermittent catheterization (CIC) which reduces stricture by up to 68%; direct vision internal urethrotomy which shows lower rates of renarrowing; urethroplasty which shows a success rate up to 70%; urinary diversion is the treatment of choice when reconstruction is not possible. CONCLUSIONS: Further studies are needed in this population because of the heterogeneity of the outcomes and the lack of a standardized definition and classification of this population.

Factores de riesgo preoperatorios en pacientes con pielonefritis xantogranulomatosa sometidos a nefrectomía.

OBJETIVO: Identificar factores de riesgo asociados a complicaciones mayores en pacientes con pielonefritis xantogranulomatosa sometidos a nefrectomía. MÉTODO: Análisis retrospectivo de expedientes clínicos de pacientes con pielonefritis xantogranulomatosa sometidos a nefrectomía. Se analizaron el sexo, el índice de masa corporal, el índice de comorbilidad de Charlson, la clasificación del estado físico de la American Society of Anesthesiologists, la etapa de Malek, el conteo leucocitario y los valores de creatinina. Las complicaciones se estratificaron en menores y mayores según la clasificación de Clavien-Dindo. Se realizó análisis univariado y bivariado usando las pruebas exacta de Fisher y ji al cuadrado de Pearson, y se establecieron medidas de riesgo utilizando la odds ratio (OR). RESULTADOS: Se analizaron 72 pacientes con una edad media de 50 años, el 83% mujeres, el 58.3% con urocultivo positivo y el 66% con litiasis renal. El 32% tuvieron alguna complicación mayor y el 15% requirieron admisión a la unidad de cuidados intensivos. Los valores elevados de creatinina (OR: 3.8; intervalo de confianza del 95% [IC95%]: 1.1-13; p = 0.02) y la etapa Malek II-III (OR: 4.5; IC95%: 1.2-17.5; p = 0.02) se asociaron con complicaciones mayores. CONCLUSIÓN: El estadio de Malek y los valores elevados de creatinina incrementan el riesgo de desarrollar complicaciones mayores en los pacientes con pielonefritis xantogranulomatosa sometidos a nefrectomía. OBJECTIVE: To identify preoperative risk factors associated with major complications in patients with xanthogranulomatous pyelonephritis undergoing total nephrectomy. METHOD: Retrospective analysis of patient's charts with xanthogranulomatous pyelonephritis who underwent nephrectomy. Risk factors included for analysis were gender, body mass index, Charlson comorbidity index, American Society of Anesthesiologists physical status classification, Malek's stage, leukocyte count and creatinine levels. Postoperative complications were stratified in minor and major according to Clavien-Dindo's classification. Univariate and bivariate analysis using Fisher's exact test, Pearson's chi-squared and odds ratio (OR) was performed. RESULTS: 72 patients were analyzed, 83% women, mean age of 50 years, 58.3% positive urine cultures and 66% kidney stones. Major complications were present in 32% of cases, and 15% were admitted to the intensive care unit. Elevated creatinine (OR: 3.8; 95% confidence interval [95%CI]: 1.1-13; p = 0.02) and Malek's stage II to III (OR: 4.5; 95%CI: 1.2-17.5; p = 0.02) were associated with major complications. CONCLUSION: The Malek Stage and elevated creatinine increases the risk of major complications in patients undergoing nephrectomy due to xanthogranulomatous pyelonephritis.

Is there a role for sacral neuromodulation in patients with neurogenic lower urinary tract dysfunction?

ABSTRACT Purpose To review current literature regarding sacral neuromodulation (SNM) for neurogenic lower urinary tract dysfunction (NLUTD) focused on indications, barriers and latest technological developments. Material and Methods A PubMed database search was performed in April 2020, focusing on SNM and various neuro-urological conditions. Results SNM has been increasingly indicated for lower urinary tract dysfunction (LUTD) in neuro-urological patients. Most studies are cases series with several methodological limitations and limited follow-up, lacking standardized definition for SNM clinical success. Most series focused on neurogenic overactive bladder in spinal cord injured (incomplete lesions) and multiple sclerosis patients. Barriers for applying this therapy in neurogenic LUTD were mainly related to magnetic resonance imaging incompatibility, size of the implantable pulse generator (IPG), and battery depletion. Newer technological advances have been made to address these limitations and will be widely available in the near future. Conclusions SNM seems a promising therapy for neurogenic LUTD in carefully selected patients with incomplete lesions. Further studies are still needed to define which subgroups of neurological patients benefit the most from this minimally invasive technique.

Is there a role for sacral neuromodulation in patients with neurogenic lower urinary tract dysfunction?

PURPOSE: To review current literature regarding sacral neuromodulation (SNM) for neurogenic lower urinary tract dysfunction (NLUTD) focused on indications, barriers and latest technological developments. MATERIAL AND METHODS: A PubMed database search was performed in April 2020, focusing on SNM and various neuro-urological conditions. RESULTS: SNM has been increasingly indicated for lower urinary tract dysfunction (LUTD) in neuro-urological patients. Most studies are cases series with several methodological limitations and limited follow-up, lacking standardized definition for SNM clinical success. Most series focused on neurogenic overactive bladder in spinal cord injured (incomplete lesions) and multiple sclerosis patients. Barriers for applying this therapy in neurogenic LUTD were mainly related to magnetic resonance imaging incompatibility, size of the implantable pulse generator (IPG), and battery depletion. Newer technological advances have been made to address these limitations and will be widely available in the near future. CONCLUSIONS: SNM seems a promising therapy for neurogenic LUTD in carefully selected patients with incomplete lesions. Further studies are still needed to define which subgroups of neurological patients benefit the most from this minimally invasive technique.

[Lower urinary tract symptoms in medical residents as reflection of a stressful work environment.] / Síntomas del tracto urinario inferior como reflejo del ambiente laboral hospitalario en médicos residentes.

OBJECTIVE: To determine if the presence of moderate to severe lower urinary tract symptoms in medical resident are associated with workplace bullying. MATERIAL AND METHODS: Cross-sectional study conducted in medical residents. Moderate to severe lower urinary tract symptoms were defined as greater than 8 points on the International Prostate Symptom Score. Residents were classified as bullied if their total score on the Negative Acts Questoinnarie-Revised, was above 41 points. Perceived bullying was considered as present when any positive answer was documented in a specific question to measure this variable. Bivariate analysis to determine statistical differences between presence of lower urinary tract symptoms and exposure to both types of bullying was performed using χ² . The magnitude and directions of all associations were determined by calculating the Odds Ratio with 95% level of confidence. RESULTS: 209 residents were included, 63% men; 68% reported at least one lower urinary tract symptom, of which, 56% were mild, 10% moderate and 2% severe. The prevalence of bullying was 42% while perceived bullying was present in 39%. Residents with ≥8 points on the International Prostate Symptom Score had higher risk of being exposed to bullying (OR: 2.8, 95% CI: 1.1-6.7, p=0.01) and/or perceived bullying (OR: 3.1 95% CI: 1.3-7.5, p=0.00). Female gender had greater risk than man for presenting lower urinary tract symptoms at basal state (OR: 2.8, 95% CI: 1.1-6.6, p=0.01). CONCLUSIONS: Medical residents with moderate or severe urinary tract symptoms may be related to bullying. Being a woman is associated with an increased risk of developing LUTS.

OBJETIVO: Determinar si la presencia de síntomas del tracto urinario inferior moderados a severos en médicos residentes se asocian con la exposición a bullying laboral.MATERIAL Y MÉTODOS: Estudio transversal realizado en médicos residentes. Se definió síntomas del tracto urinario inferior moderados a severos como más de 8 puntos en el Índice Internacional de Síntomas Prostáticos. Los residentes se consideraron como expuestos a bullying si el puntaje total en la Escala de Conductas Negativas era mayor a 41 puntos. Se consideró como bullying percibido cualquier respuesta positiva en una pregunta específica para medir esta variable. Se realizó un análisis bivariado utilizando la χ² para determinar diferencias estadísticas entre la presencia de síntomas del tracto urinario inferior y la exposición a ambos tipos de bullying. La magnitud y dirección de las asociaciones se establecieron calculando el Odds Ratio con un intervalo de confianza al 95%. RESULTADOS: Se incluyeron 209 residentes, 63% hombres; 68% refirieron algún síntoma del tracto urinario, de los cuales, 56% fueron leves, 10% moderados y 2% severos. La prevalencia de bullying fue de 42% y el bullying percibido se presentó en el 39%. Los residentes con ≥8 puntos en el Índice Internacional de Síntomas Prostáticos tuvieron mayor riesgo de estar expuestos a bullying (OR: 2,8, IC 95%: 1,1-6,7, p=0,01) y bullying percibido (OR: 3,1 95% CI: 1,3-7,5, p 0,00). Ser mujer se asoció con mayor riesgo de presentar síntomas del tracto urinario inferior (OR: 2,8, IC 95%: 1,1-6,6, p=0,01). CONCLUSIONES: Los médicos residentes con síntomas del tracto urinario moderados o severos pueden estar relacionados a bullying. Ser mujer se asocia a mayor riesgo de presentar STUI.

[The relevance and irrelevance of charts in clinical research]. / Pertinencia e impertinencia de los gráficos en la investigación clíni-ca.

Charts are a visual aid that is used in articles in order to highlight the results of an investigation. They allow illustrating the results with the purpose of making them clearer. Charts, just like statistical tests, are selected based on the objective of the study, the types of variable, and the statistical analyzes to be illustrated. Some of the most commonly used charts in clinical practice are frequency histograms, which illustrate qualitative variables or frequencies; also error charts, that are used for normally distributed quantitative variables; box plots or violin plots are used for distribution-free quantitative variables, and survival curves are for variables that include the person-time variable. The aforementioned charts can be used to illustrate the comparisons between maneuvers and outcome depending on the type of variable that is being analyzed. When two groups are compared and the dependent variable is dichotomous, forest plots are used; for multivariate models, the chart depends on the type of analysis. As for logistic regression and linear regression, tree diagrams are used; and scatter plots are used for linear regression. Survival plots are used for Cox proportional hazards. Although charts can be very useful, if they are misused, they can show differences where there are none, which leads to a misinterpretation of the studies. In this article, we will use examples to complement the topics that were previously addressed in the articles of this series.

Los gráficos constituyen una ayuda visual que usan los artículos para resaltar los resultados de una investigación. Estos permiten ilustrar los resultados con el fin de hacerlos más claros. Los gráficos, al igual que las pruebas estadísticas, se seleccionan a partir del objetivo del estudio, de los tipos de variable y de los análisis estadísticos que se desee ilustrar. Algunos de los gráficos más usados en la práctica clínica son los histogramas de frecuencia que ilustran las variables cualitativas o frecuencias, los gráficos de error se usan para variables cuantitativas con distribución normal, el gráfico de cajas o gráfico de violín para variables cuantitativas de libre distribución y las curvas de supervivencia para las variables que incluyen la variable tiempo/persona. Estos mismos gráficos pueden ser usados para ilustrar las comparaciones entre maniobras y desenlace dependiendo del tipo de variable que se analice. Cuando se comparan dos grupos y la variable dependiente es dicotómica se usan gráficos de bosque. Para los modelos multivariados los gráficos dependen del tipo de análisis, en el caso de la regresión logística se utilizan gráficos de árbol y para la regresión lineal, de dispersión; y para los riesgos proporcionales de Cox, gráficos de supervivencia. Si bien los gráficos son de gran utilidad, mal utilizados pueden mostrar diferencias donde no las hay, provocando una errónea interpretación de los estudios. En este artículo complementaremos con ejemplos los temas abordados con anterioridad en los artículos de esta misma serie.

Factores predictores del estado libre de cálculos en la primera ureteroscopia flexible con litotricia láser.

INTRODUCTION: Flexible ureteroscopy and laser fragmentation (FURSL) is a minimally invasive modality for surgical treatment of renal stones. Inadequate selection of patients for this treatment generates a cost-effectiveness unbalance. OBJECTIVE: To know the stone-free rate predictors in a single surgical time in patients undergoing FURSL. METHOD: Retrospective cohort of patients undergoing FURSL. Global and gender-categorized univariate and multivariate (logistic regression) analyses were performed to identify stone-free predictors at first FURSL. RESULTS: Stone-free rate at first FURSL was 73.62%. Predictors in males were patient age and stone size, density and multiplicity; in females, body mass index and multiplicity of stones. CONCLUSIONS: Stone-free rate predictors at first FURSL are different in males and females. Women with overweight and obesity probably have easy-to-fragment and easy-to-extract stones associated with uric acid.

INTRODUCCIÓN: La ureteroscopia flexible con litotricia láser (URSLL) es una modalidad mínimamente invasiva de tratamiento quirúrgico de cálculos renales. La selección inadecuada de pacientes para este procedimiento genera un desbalance de costo-efectividad. OBJETIVO: Conocer los factores predictores de estado libre de litos en un solo tiempo quirúrgico en pacientes sometidos a URSLL. MÉTODO: Cohorte retrospectiva de pacientes sometidos a URSLL. Se realizó un análisis univariado y multivariado (regresión logística) de los predictores de estado libre de cálculos en la primera URSLL, global y categorizado por sexo. RESULTADOS: EL estado libre de cálculos en la primera URSLL fue de 73.62 %. Los predictores de estado libre de cálculos en hombres fueron edad y tamaño, densidad y multiplicidad del cálculo; en las mujeres, el índice de masa corporal y la multiplicidad del cálculo. CONCLUSIONES: Los factores pronósticos de estado libre de cálculos en la primera URSLL son distintos en hombres y mujeres. Las mujeres con obesidad y sobrepeso probablemente tengan cálculos de fácil fragmentación y extracción asociados con ácido úrico.

Factores predictores del estado libre de cálculos en la primera ureteroscopia flexible con litotricia láser / Predictors of stone-free status in the first flexible ureteroscopy with laser lithotripsy

Resumen Introducción: La ureteroscopia flexible con litotricia láser (URSLL) es una modalidad mínimamente invasiva de tratamiento quirúrgico de cálculos renales. La selección inadecuada de pacientes para este procedimiento genera un desbalance de costo-efectividad. Objetivo: Conocer los factores predictores de estado libre de litos en un solo tiempo quirúrgico en pacientes sometidos a URSLL. Método: Cohorte retrospectiva de pacientes sometidos a URSLL. Se realizó un análisis univariado y multivariado (regresión logística) de los predictores de estado libre de cálculos en la primera URSLL, global y categorizado por sexo. Resultados: EL estado libre de cálculos en la primera URSLL fue de 73.62 %. Los predictores de estado libre de cálculos en hombres fueron edad y tamaño, densidad y multiplicidad del cálculo; en las mujeres, el índice de masa corporal y la multiplicidad del cálculo. Conclusiones: Los factores pronósticos de estado libre de cálculos en la primera URSLL son distintos en hombres y mujeres. Las mujeres con obesidad y sobrepeso probablemente tengan cálculos de fácil fragmentación y extracción asociados con ácido úrico.

Abstract Introduction: Flexible ureteroscopy and laser fragmentation (FURSL) is a minimally invasive modality for surgical treatment of renal stones. Inadequate selection of patients for this treatment generates a cost-effectiveness unbalance. Objective: To know the stone-free rate predictors in a single surgical time in patients undergoing FURSL. Method: Retrospective cohort of patients undergoing FURSL. Global and gender-categorized univariate and multivariate (logistic regression) analyses were performed to identify stone-free predictors at first FURSL. Results: Stone-free rate at first FURSL was 73.62%. Predictors in males were patient age and stone size, density and multiplicity; in females, body mass index and multiplicity of stones. Conclusions: Stone-free rate predictors at first FURSL are different in males and females. Women with overweight and obesity probably have easy-to-fragment and easy-to-extract stones associated with uric acid.

[Tasa libre de litos sin complicación mayor como definición de éxito en nefrolitotomía percutánea].

Introduction: Success in percutaneous nephrolithotomy (PCNL) is defined as a stone-free status; however, major complications are highly common and have been reported as a secondary outcome. Objective: To propose a new definition of PCNL success that comprises a stone free rate without major complications and a risk scale to predict this outcome. Methods: Historical cohort of patients undergoing PCNL. The included variables were age, gender, urine culture, Charlson's comorbidity index (CCI) and complex stones. Success was defined as a stone free status with or without Clavien grade ≤ 2 complication; intermediate success: with stones, with or without Clavien grade ≤ 2 complication; and failure: with or without stones with Clavien grade ≤ 2 complication. Bivariate analysis was performed to identify which factors are associated with the outcome. The independent weight of each factor was calculated by multiple logistic regression analysis. Results: 568 procedures were included, 59% of which were in females. Median age was 49 years; 65%, 22% and 13% of cases were classified as success, intermediate success and failure, respectively. Female sex, positive urine culture, complex stones and severe CCI were associated with failure. Conclusions: The likelihood of success was directly proportional to the number of risk factors.

Introducción: El éxito en nefrolitotomía percutánea (NLP) se define como estatus libre de litos, sin embargo, las complicaciones mayores se presentan con alta frecuencia y han sido reportadas como resultado secundario. Objetivo: Presentar una nueva definición de éxito en NLP que comprenda la tasa libre de litos sin complicaciones mayores y una escala de riesgo para predecir este desenlace. Método: Cohorte histórica de pacientes sometidos a NLP. Las variables incluidas fueron edad, sexo, urocultivo, índice de comorbilidad de Charlson (ICC) y lito complejo. Se definió éxito: sin litos, sin o con complicación Clavien ≤ 2; éxito intermedio: con litos sin o con complicación Clavien ≤ 2; fracaso: con o sin litos con complicación Clavien > 2. Se realizó análisis bivariado para identificar los factores asociados con el desenlace. Por regresión logística múltiple se calculó el peso independiente de cada factor. Resultados: Se incluyeron 568 procedimientos, 59 % en el sexo femenino. La mediana de edad fue de 49 años; 65, 22 y 13 % de los casos tuvieron éxito, éxito intermedio y fracaso. El sexo femenino, urocultivo positivo, lito complejo e ICC severo se asociaron con fracaso. Conclusión: La probabilidad de éxito fue directamente proporcional al número de factores de riesgo.

Tasa libre de litos sin complicación mayor como definición de éxito en nefrolitotomía percutánea / Stone-free rate without major complication as a definition of success in percutaneous nephrolithotomy

Resumen Introducción: El éxito en nefrolitotomía percutánea (NLP) se define como estatus libre de litos, sin embargo, las complicaciones mayores se presentan con alta frecuencia y han sido reportadas como resultado secundario. Objetivo: Presentar una nueva definición de éxito en NLP que comprenda la tasa libre de litos sin complicaciones mayores y una escala de riesgo para predecir este desenlace. Método: Cohorte histórica de pacientes sometidos a NLP. Las variables incluidas fueron edad, sexo, urocultivo, índice de comorbilidad de Charlson (ICC) y lito complejo. Se definió éxito: sin litos, sin o con complicación Clavien ≤ 2; éxito intermedio: con litos sin o con complicación Clavien ≤ 2; fracaso: con o sin litos con complicación Clavien > 2. Se realizó análisis bivariado para identificar los factores asociados con el desenlace. Por regresión logística múltiple se calculó el peso independiente de cada factor. Resultados: Se incluyeron 568 procedimientos, 59 % en el sexo femenino. La mediana de edad fue de 49 años; 65, 22 y 13 % de los casos tuvieron éxito, éxito intermedio y fracaso. El sexo femenino, urocultivo positivo, lito complejo e ICC severo se asociaron con fracaso. Conclusión: La probabilidad de éxito fue directamente proporcional al número de factores de riesgo.

Abstract Introduction: Success in percutaneous nephrolithotomy (PCNL) is defined as a stone-free status; however, major complications are highly common and have been reported as a secondary outcome. Objective: To propose a new definition of PCNL success that comprises a stone free rate without major complications and a risk scale to predict this outcome. Methods: Historical cohort of patients undergoing PCNL. The included variables were age, gender, urine culture, Charlson's comorbidity index (CCI) and complex stones. Success was defined as a stone free status with or without Clavien grade ≤ 2 complication; intermediate success: with stones, with or without Clavien grade ≤ 2 complication; and failure: with or without stones with Clavien grade ≤ 2 complication. Bivariate analysis was performed to identify which factors are associated with the outcome. The independent weight of each factor was calculated by multiple logistic regression analysis. Results: 568 procedures were included, 59% of which were in females. Median age was 49 years; 65%, 22% and 13% of cases were classified as success, intermediate success and failure, respectively. Female sex, positive urine culture, complex stones and severe CCI were associated with failure. Conclusions: The likelihood of success was directly proportional to the number of risk factors.

Rearrangement of the Guy's stone score improves prediction of stone-free rate after percutaneous nephrolithotomy.

OBJECTIVE: We propose a modification of the original Guy's Stone Score (GSS) to hold on 20 % of prognostic discrimination among groups which makes this score a more reliable resource for risk assessment in patients undergoing percutaneous nephrolithotomy (PCNL). MATERIAL AND METHODS: Historical cohort of 126 patients undergoing PCNL from December 2010 to November 2014 was included in the survey. Every patient was classified according to the original GSS. For the new classification of Guy Stone Score (GSS-M) all of the subgroups included in the scale were analyzed individually and then ranked from better to worst according to the postoperative stone- free rates (SFRs). This ranking led us to reclassify all the original subgroups, clustering them in three new categories according to their SFRs as subgroups of good, intermediate and poor prognosis, trying to achieve at least 20% of prognostic discrimination among the groups. RESULTS: Hundred and twenty-six PCNL procedures were evaluated, but only 124 were included for statistical analysis and classified based on SFR according to the GSS as follows: 76% for grade 1, 71% for grade 2, 55% for grade 3 and 20% for grade 4. The SFRs were also assessed for the GSS-M obtaining the following predictive values as 93%, 67% and 44% for the good, intermediate and poor prognostic groups, respectively. The prognostic difference among the GSS-M groups was always >20% (p<0.05). CONCLUSION: The original GSS has limitations to predict SFR because of its poor discrimination power among prognostic groups. This rearrangement improves prediction of SFR and better discriminates risk groups in PCNL.