Renal changes and estimation of glomerular filtration rate using different equations in morbidly obese Egyptian patients

Obesity is a worldwide pandemic with multiple consequences including kidney affection. This study aimed to assess the effects of obesity on renal functions and to detect the most reliable formula of estimated glomerular filtration rate (eGFR) in morbidly obese patients. A cross-sectional, observational study was conducted on 82 morbidly obese patients. Anthropometric measurements were done for all patients and body adiposity (BAI) and visceral adiposity (VAI) indices were calculated after assessment of abdominal fat tissue analysis by computerized tomography (CT). Serum creatinine was incorporated into six different formulae of eGFR, then eGFR was compared with the 24-h measured creatinine clearance (CLcr) values. The mean body mass index was 55.8 ± 9.5 kg/m2. Proteinuria and glomerular hyperfiltration (CLcr > 130 ml/min/1.73 m2) were detected in 68.3% and 91.5% of the patients, respectively. Cockcroft–Gault formula using total (CCG-TBW-eGFR) and adjusted body water (CCG-AjBW-eGFR) had the nearest values to measured CLCr. These two formulae had a moderate reliability and the lowest percentage of error (30% and 23%, respectively). Visceral and total abdominal fat tissue surface area and volume assessed by CT were directly correlated to the 24-h urinary protein excretion (r = 0.32, 0.24, 0.37 and 0.34, respectively; p = 0.02, 0.03, 0.004 and 0.002, respectively). Glomerular hyperfiltration and proteinuria are highly prevalent in morbidly obese patients. There is no ideal formula for GFR estimation in morbidly obese patients, however, TBW and AjBW incorporated into the Cockcroft–Gault can be helpful in those patients. •Glomerular hyperfiltration and proteinuria affect the majority of morbidly obese individuals.•Obesity itself, not adipose tissue distribution, is responsible for glomerular hyperfiltration.•24-h urine collection is the method of choice to assess of glomerular filtration rate in morbidly obese individuals.•Total and adjusted body water integrated in Cockcroft–Gault equation are moderately reliable in morbidly obese individuals.