Does renal function decline across multiple hospital admissions? An audit of adolescent and young adults hospitalised with a restrictive eating disorder

Background: Impaired renal function, as indicated by a decline in estimated glomerular-filtration-rate (eGFR), is inadequately investigated in individuals hospitalised with restrictive eating disorders. This study aims to investigate renal function across multiple admissions, as well as the clinical characteristics of this group. Methods: A five-year retrospective audit was conducted of adolescents and young adults admitted to a hospital in Sydney, Australia, with a restrictive eating disorder requiring multiple admissions for nutritional rehabilitation. eGFR was calculated from serum creatinine levels inputted into the Chronic Kidney Disease in Children Under 25 (CKiDU25) equation. A generalised linear-mixed-model was used to evaluate associations between eGFR and purging history, medical instability on admission, percentage mean BMI (%mBMI), protein intake in grams/kilogram/day, time from last admission, length-of-stay and admission number. Results: Analysis included 60 patients over 176 admissions, 93% female, mean age 17.1 ± 1.4 years, admission %mBMI 82.0 ± 9.1. The mean number of admissions was 2.9 ± 2.2, with average length-of-stay 22.7 ± 12.2 days, and discharge %mBMI 92.9 ± 7.4. Impaired renal function (eGFR < 90 ml/min/1.73m²) was identified in 36.4% of admissions, and in 2.8% of patients at discharge. Average protein intake increased from 2.2 ± 0.6 g/kg/day on admission to 3.0 ± 0.7 g/kg/day on discharge. Protein intake (9.587, p < 0.001), %mBMI (0.461, p < 0.001), length-of-stay (0.100, p < 0.001), and number of admissions (1.921, p < 0.001) was positively associated with eGFR. Lower eGFR levels were seen with medical instability (-3.113, p = 0.003) or greater between-readmission times (-0.010, p < 0.001). The relationship with purging history was not significant. Conclusions: Impaired renal function was evident in over one third of adolescent and young adults with restrictive eating disorders requiring multiple admissions and improved with nutritional rehabilitation. Findings of this study indicate that eGFR did not decline during the five-year period of observations in this study, however further research is needed to explore the outcomes of the small subgroup of patients who were discharged from hospital with persisting impaired renal function. Overall, eGFR may be a useful indicator of nutritional status and disease severity in patients hospitalised with restrictive eating disorders.