Refeeding syndrome (RFS) describes potentially fatal shift in electrolytes in severe malnourished patients receiving rapid and excessive food re-introduction. It is a result of hormonal and metabolic disturbances.

There are various clinical and laboratory features with hypophosphatemia being the most common one. Elevation in liver function tests is also frequently seen. Patients with anorexia are a high-risk group for developing RFS. The aim of the study was to investigate the incidence and clinical features of RFS among hospitalized patients, as well as severity of malnutrition (Z-score, BMI).

This study is a retrospective analysis of medical documentation of patients diagnosed with anorexia nervosa (restricting (ANRT) and binge eating/purging

(ANBP) subtype), eating disorder NOS (EDNOS) and avoidant/restrictive food intake disorder (ARFID) who were admitted to our Centre for eating disorders in children and adolescents during a 5 year period (2014-2018). We analyzed the age, gender, duration of the disease before admittance, anthropometric data (BMI and Z-score), average weight loss, the need for nasogastric (NG) tube feeding and phosphate supplementation. For statistical analysis we used t-test.

256 patients (232 female) aged 6-20 years (median 15+/-2.06) of which 43% were diagnosed with ANRT, 10% ANBP, 8% ARFID, 39% with EDNOS were included in the study. The average duration of the disease at the time of admittance was 13.25+/-13.43 months. Average BMI Z-score was -1.97+/-1.63 average weight loss was 20+/-9.76% initial body weight (IBW).

Hypophosphatemia was found in 15.6% patients, of which 65% received phosphate supplements by oral or intravenous route depending of phosphate serum concentration. Elevated liver enzymes due to RFS were found in 9.3% of patients. In total RFS in some form developed in 23% patients.

Average BMI Z-score of patients that developed RFS was -2.6+/-1.89, average weight loss was 23.9+/-9.85% of IBW. Both variables were significantly different (p<0.05) in comparison with non-RFS group which had BMI Z-score of

-1.76+/-1.47 and average weight loss of 18.7+/-9.3% of IBW. The average duration of the disease was similar in both groups (13 months) (p=0.84).

NG tube feeding was needed in 27% of all patients, 24% patients in non-RFS group and 37% in patients with RFS.

Our study reported that even in controlled hospital conditions and with careful realimentation RFS has a high incidence. We found statistically significant difference when it comes to BMI Z-score and average weight loss between two groups of patients.