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Aim: The Cockcroft and Gault formula is a quick and reliable method for calculating creatinine clearance without a 24-hour urine collection (CG-cl). In obese subjects an excess of fat mass provokes a reduction in daily creatinine urine excretion per body kilo weight and is responsible for overestimated renal function when calculated by CG-cl. The aim of this study was to devise a simple correction method which could also make use of CG-cl in obese subjects., Patients and Methods: In 52 subjects with a body mass index (BMI) > 25, renal function was assessed by simultaneously determining creatinine clearance using 24-hour urine collection (Cr-cl) and the CG-cl. The percentage difference between the 2 clearances (delta %) was correlated with BMI for each patient using simple linear regression analysis. The estimated regression model (delta% = 1.217 BMI-- 24.81) provided the following CG-cl correction formula for obese subjects: Corrected CG-cl = CG-cl (1.25 - 0.012 BMI). Its validity was evaluated in another group of 20 subjects with BMI > 25 by comparing the results obtained with Corrected CG-cl to those obtained by CG-cl and MDRD formula (MDRD-cl) using the clearance of 51Cr-EDTA (5 Cr-EDTA-cl) as the GFR measurement gold standard., Results and Conclusion: Linear regression analysis of CG-cl, MDRD-cl and Corrected CG-cl compared to 5tCr-EDTA-cl (considered as the independent variable) resulted in the following determination coefficients (R2): 0.687; 0.818; 0.947, respectively. In conclusion, this formula can be considered a quick and reliable method for CG-cl correction in obese subjects.

Central diabetes insipidus (CDI) arising in the puerperal period has been attributed mainly to Sheehan's syndrome or to lymphocytic infundibulo-neurohypophysitis. We report the case of a 24-year-old woman who came to our observation for the appearance, 3 weeks after a normal delivery, of a polyuric-polydipsic syndrome. Measurements of urinary volumes, plasma osmolality and urinary osmolality, in conditions of free water intake, water deprivation and a water deprivation-vasopressin administration test, demonstrated CDI. Brain magnetic resonance imaging showed a normal morphology of the adenohypophysis and total absence of the neurohypophysis. Assays of the pituitary hormones were found to be within normal limits. These results, incompatible with a diagnosis of Sheehan's syndrome and lymphocytic infundibulo-neurohypophysis, excluded all the other known causes of acquired CDI. Our diagnosis was therefore of post-gravid idiopathic CDI. Thus, it is possible that in the puerperal period other diseases of the posterior hypophysis may develop, of unknown etiopathogenesis but equally responsible for CDI.