BACKGROUND: Acute liver disease may progress to fulminant hepatic failure, as a result of which a very high proportion of patients will die unless liver transplantations are performed.Therefore, timely and accurate assessment of the degree of liver damage in acute liver disease outweighs specific disease etiologies with regard to treatment and prognosis.However, current methods of disease severity assessment in patients with acute liver disease are far from optimal.The 13C-methacetin breath test (13C-MBT) has been proposed as a promising tool for non-invasively assessment of metabolic liver function in the setting of chronic liver disease.However, evidence on acute liver injury was scanty and typically anecdotal.In the present study, we evaluated the role of 13C-MBT in assessment of acute liver injury in rat model.METHODS: Rat model of acute liver injury was induced by a single intraperitoneal injection of D-gal (450mg/kg), which was dissolved in saline (0.6ml/100g of body weight).Forty-eight male Sprague-Dawley rats were randomly assigned to one control group (n=8) and five model groups (each n=8) according to different time points after D-gal injection (6h, 12h, 24h, 48h, 72h).The rats in control group received same volume of saline as a substitute for D-gal.13C-MBT, biochemical tests, 15-minute retention rate of indocyanine green (ICGR15), and liver biopsy were also performed for each group.Parameters were compared between control group and each model group.Continuous variables were described as mean ± SD and were analyzed by Students two-independent-sample t test for normal distribution or Mann-Whitney non-parametric U test for skewed distribution.Normality of distribution was determined using the Kolmogorov-Smirnov test (cut-off at P=0.01).Correlations of parameters of 13C-MBT (Tmax, MVmax, CUM120 and DOBmax), biochemical tests, ICGR15 with liver necrosis score were also analyzed using Spearman s correlation analysis.RESULTS: The mean value of Tmax(min) in control group and model groups at time point of 6h, 12h, 24h, 48h, and 72h were 18.3 ± 4.1, 21.7 ± 4.7, 23.3 ± 5.16, 33.3 ± 4.3, 28.3 ± 3.83, and 23.3 ± 5.16, respectively.Compared with the control group, the Tmax in the model groups at time points of 12h, 24h, 48h and 72h were significantly higher than that in the control group.The MVmax (%), CUM120 (%) and DOBmax (%) in control group were 5.06 ± 0.78, 4.21 ± 1.44, and 75.1 ± 9.57, respectively.These three parameters, following a similar pattern, decreased simultaneously and reached lowest value at time point of 24h, and then recovered toward normal after injection of D-gal.Compared with control group, MVmax, CUM120 and DOBmax in model groups at time points of 6h, 12h, 24h and 48h were significantly lower than that in control group.At time point of 72h, the differences of these three parameters between control group and model group were no longer significant.The changes of parameters of 13C-MBT preceded most of other traditional methods, including liver biopsy.In addition, Tmax, MVmax, CUMIn and DOBmax, as well as most of other traditional methods, were correlated with liver necrosis score (r=0.493, P<0.05; r=-0.731, P<0.01; r=0.618, P<0.01; r=-0.592, P<0.01, respectively).CONCLUSIONS: 13C-MBT was a sensitive tool for timely detection of acute liver injury and early prediction of recovery in rat model.Further clinical studies were warranted to validate its role in real patients with acute liver injury.