HYPERAMMONEMIA IN STARVATION FOLLOWING BARIATRIC SURGERY Estrella J 1 , Tchan M 1 , Bhattarchaya K 1 , Carpenter K 1 , Wilcken B 1 1 West Syd Gen Prog, WMH and CHW, Westmead, Australia Hyperammonemia complicating bariatric surgery has been only rarely described1-3. After exclusion of a urea cycle defect, the mechanism underlying this remains unclear. We describe a 52 year old woman with a BMI of 31 who underwent billary pancreatic bypass (duodenal switch) Following operation she had several months of very poor oral intake and developed recurrent episodes of hyperammonemic encephalopathy. Empirical antibiotic therapy for bacterial overgrowth was not beneficial. Amino acid profile showed uniformly very low levels of amino acids including glutamine. Plasma acylcarnitines were normal. Urinary orotic acid profile was below detection limit on a number of occasions. Gene analysis for possible CPS and NAGS deficiency was undertaken with no pathogenic mutations identified. Because of the persistence of her symptoms she underwent reversal of her gastric surgery and had a dramatic improvement, with a normalized amino acid profile and an improved appetite. There have been no further hyperammonenic episodes. We hypothesize that this nutritionally deficient patient developed substrate deprivation of urea cycle intermediates and tissue depletion of glutamine, impairing its use as an ammonia shuttle to the liver, both leading to decreased urea cycle activity. Phenylketonuria (PKU) adults modify diet by phenylalanine restriction, protein restriction, or relaxation of diet, potentially affecting body composition. We measured body composition in PKU adults (33 F, 9 M) aged 32.2± 9.5 years (mean±SD), and body mass index (BMI) 27.9±6.4 kg/m2 using air-displacement plethysmography (ADP) for total body fat (TBF), prompt gamma neutron activation analysis (IVNAA) for total body protein (TBP), and total body dual-energy x-ray absorptiometry (DEXA) for both bone mineral density (BMD) and skeletal muscle mass (SMM). In females, %TBF was 37.1±9.1, TBP using age and sex adjusted nitrogen index (normal NI=1.00±0.10) was 0.98±0.12, and SMM measured as height-adjusted appendicular lean tissue mass (ALTM) was 5.77±2.35 kg/m2. BMD z-scores were −0.27±1.26 (lumbar spine), -0.01±1.01 (femoral neck) and +0.07±1.15 (total body). In males, %TBF was 20.3±8.2, NI was 1.13± 0.13, and ALTM was 8.24±0.45 kg/m2. BMD z-scores were −0.75±1.22 (lumbar spine), -0.23±1.47 (femoral neck) and −0.09±1.32 (total body). PKU adults treated longterm with protein-modified but often high-energy diets have normal TBP and BMD, but adiposity is increased in women.