24-hour urinary sodium and albumin excretion in the obese and the effects of bariatric surgery

Obesity and renal parameters
Obesity has acquired epidemic proportions in the United States, with nearly 65%
of the adult population overweight and obese. In the Netherlands, the total
percentage of overweight and obese people has increased from 44.1% of the
population in 2000 (47.9% of all men and 40.4% of all women) to 47.2% of the
population in 2009 (52.5% of all men and 41.9% of all women). 9.4% of the
population belonged to the obese group in 2000 (8.6% of all men and 10.2% of
all women) and this increased to 11.8% in 2009 (11.2% of all men and 12.4% of
all women). This has led to an increase in the rate of bariatric procedures,
with about 300 procedures performed in a year at the Slotervaart Hospital in
Amsterdam, the Netherlands where the most common bariatric procedure is the
Roux-en Y-gastric bypass.

Extreme obesity is associated with cardiovascular disease, type 2 diabetes,
dyslipidemia, and hypertension. The steady increase in the prevalence of
obesity contributes to the increase in the prevalence of chronic kidney
disease, through renal damage associated with type-2 diabetes and hypertension.
Obesity is an independent risk factor for the kidney, since it is associated
with an increased risk of albuminuria and glomerulosclerosis, and worsens the
course of chronic kidney disease regardless of the primary renal disease. The
relationship between massive obesity and nephritic-range proteinuria was first
reported in 1974. After that, increased evidence demonstrated that
obesity-related glomerulopathy should be identified as an isolated complication
of obesity.

Obesity is associated with glomerular hyperfiltration in animal models. Human
studies also revealed abnormal renal haemodynamics in obese subjects, showing
increased glomerular filtration rate, increased renal blood flow or both. Since
one of the major determinants of proximal tubular reabsorption is the pressure
gradient determined by Starling forces, the augmented oncotic pressure of the
plasma entering the peritubular capillaries is expected to promote proximal
tubular sodium reabsorption, salt retention and in increase in systemic
arterial pressure.

Bariatric surgery produces greater weight loss and is more effective in
controlling hypertension, diabetes, dyslipidemia, and other cardiovascular risk
factors. However, its effect on renal parameters (e.g. changes in GFR,
albuminuria, proteinuria and natriuresis) scarcely are described in the
literature especially studies on the long-term evaluation of these effects
after 2 years of follow-up. Therefore, the aim of this study was to evaluate
the effect of weight loss on renal parameters in obese patients who have
undergone bariatric surgery.

The objective of this study was to evaluate the effect of weight loss after
bariatric surgery on blood pressure, renal parameters and renal function in
obese patients.

Observational study of patients who have undergone bariatric surgery in
Slotervaart Hospital, Amsterdam, the Netherlands.

There are no risks expected for patients participating in this study.