The Short-Term Effects of Roux-en-Y Gastric Bypass on Renal Excretion of Sodium and Its Association with Blood Pressure.

INTRODUCTION: Bariatric surgery has been shown to be effective in reducing weight and has benefits, such as lowering blood pressure. An increase in urinary sodium excretion has been suggested as a possible mechanism. This study explored changes in sodium excretion and their correlation with blood pressure after Roux-en-Y gastric bypass. MATERIALS AND METHODS: This study was conducted on 28 obese participants with body mass index (BMI) of 44.54 ± 7.81 kg/m2 who underwent gastric bypass. Before surgery and at the third and sixth months after gastric bypass, blood pressure, urinary sodium concentration, 24-hour (24-h) urinary sodium excretion, and fractional excretion of sodium were evaluated. In addition, serum sodium and potassium levels were determined. Nonparametric tests were used to analyze the data. RESULTS: Blood pressure decreased after surgery and remained at low levels over the 3- and 6-month periods. The urinary sodium concentration increased at 3 months after surgery; however, the 24-h urinary sodium excretion and urine volume decreased. Interestingly, although some associations between variables were observed, significant correlations between the 24-h urinary sodium excretion and the systolic, diastolic, and mean blood pressures were found. In addition, the urine volume was higher in the sixth month than in the third month following surgery. CONCLUSIONS: In the months immediately following surgery, a low-salt and low-volume diet favors decreases in urine volume and 24-h urinary sodium excretion. In addition, in the sixth month after surgery, an association between blood pressure and 24-h urinary sodium excretion was observed.

Validation of a predictive index of neoplasia in unexplained weight loss / Validación de un índice predictivo de neoplasia en pérdida de peso inexplicada

Background: Involuntary weight loss (IWL) is associated with a bad prognosis. A causal diagnosis is difficult and the priority is to identify those patients at risk of a serious underlying disease, such as malignant neoplasia. Objective: External validation of a prognostic index of neoplasia in patients with IWL. Methods: Patients referred for IWL from 2005 to 2014 to the Department of Internal Medicine, of a specialty care hospital in Mexico City were studied. Al of them underwent an evaluation consisting of medical history, physical examination and basic laboratory studies, those patients without an apparent cause of IWL, were included. A probability of neoplasia according to Hernández prognostic index was calculated. Complementary diagnostic studies were performed until a causal diagnosis was reached, or the cases were classified as "unknown cause", if the etiology was not possible to find after one year of follow-up. A binarian logistic model was constructed with five variables age, leucocyte count, albumin, lactic dehydrogenase and alkaline phosphatase levels, and a prediction rule was developed. Results: 130 Patients were included and 45 of them (30%) had a neoplastic cause of IWL. The prediction rule according to Hernández criteria, correctly classified 65% of the patients (sensitivity 29%, Specificity 85%, positive predictive value 50% and negative predictive value 69%). When the original index was modified in two categories (high and low probability), it showed a sensitivity of 84.4% and a negative predictive value of 85.7%. Conclusion: The Hernández index has a limited value as a screening tool.

Introducción: la pérdida involuntaria de peso es un factor de mal pronóstico. Su diagnóstico causal es difícil y es prioritario identificar los casos que tienen una enfermedad grave subyacente. Objetivo: validar un índice pronóstico de neoplasia en pacientes con pérdida involuntaria de peso. Métodos: pacientes referidos por pérdida involuntaria de peso de 2005 a 2014, fueron evaluados mediante historia clínica y exámenes básicos de laboratorio; en el estudio fueron incluidos los pacientes sin causa aparente después de la evaluación. Se calculó la probabilidad de neoplasia, según el índice de Hernández. Se realizaron estudios complementarios hasta identificar una causa o fueron clasificados como "causa desconocida", si no se encontró la etiología después de un año de seguimiento. Se construyó un modelo de regresión logística binaria con las variables edad, cifras de leucocitos, albúmina, deshidrogenasa láctica y fosfatasa alcalina; con la ecuación resultante se predijo neoplasia como causa de pérdida involuntaria de peso. Resultados: se incluyeron 130 pacientes, 45 tuvieron causa neoplásica (30%). La ecuación de predicción clasificó correctamente a 65% de los sujetos analizados (especificidad 85%, sensibilidad 29%, valor predictivo positivo 50%, valor predictivo negativo 69%). Al modificarse el índice original en dos categorías (probabilidad alta y baja), mostró una sensibilidad del 84.4% y un valor predictivo negativo del 85.7%. Conclusión: el índice tuvo baja sensibilidad, lo que limita su uso como prueba de tamizaje.