Determinants and risk factors for renal damage: where do patients hospitalized for severe anorexia nervosa stand? A multi-center study

Although renal damage is increasingly reported among the most undernourished patients with Anorexia Nervosa (AN), it remains underestimated in current practice, and often associated with acute dehydration. The purpose of our study was to evaluate the frequency, the extent, and the risk factors of renal involvement among adolescents and adults hospitalized in specialized units for AN. In this multi-center study, 197 consecutive participants were included, aged 13-65, from 11 inpatient eating disorder psychiatric units. Information on the course of AN, clinical characteristics, biological data, and medication were collected. At admission, mean BMI was 13.1 (± 1.6) kg/m for a mean age of 20.74 (± 6.5) years and the z-score was - 3.6 (± 1.33). Six participants (3.0%) had hyponatremia, four (2.0%) had hypokalemia, and nine (4.5%) had hypochloremia. The Blood Urea Nitrogen/Creatinine ratio was over 20 for 21 (10.6%) participants. The mean plasma creatinine was 65.22 (± 12.8) µmol/L, and the mean eGFR was 74.74 (± 18.9) ml/min. Thirty- five participants (17.8%) had an eGFR > 90 ml/min, 123 (62.4%) from 60 to 90 ml/min, 35 (17.8%) from 45 to 60 ml/min, and 4 (2%) under 45 ml/min. In multivariate analysis, only BMI on admission was a determinant of renal impairment. The lower the BMI the more severe was the renal impairment. When eGFR is calculated, it highlights renal dysfunction found in severe AN requiring hospitalisation in specialized units. The severity of undernutrition is an independent associated factor. Kidney functionality tests using eGFR, in addition to creatinine alone, should be part of routine care for patients with AN to detect underlying renal dysfunction.