Abstract: Thirty-seven trials were identified; only one was at low risk of bias. Most of the analyses failed to find any significant differences. The significant findings that were found were the following: 1) icteric medical patients receiving parenteral nutrition had a reduced serum bilirubin (mean difference (MD) -2.86 mg%, 95% CI -3.82 mg% to -1.89 mg%, 3 trials) and better nitrogen balance (MD 3.60 g/day, 95% CI 0.86 g/day to 6.34 g/day, 1 trial); 2) surgical patients receiving parenteral nutrition had a reduced incidence of postoperative ascites only in the fixed-effect model (RR 0.65, 95% CI 0.48 to 0.87, 2 trials, I2 = 70%) and one trial demonstrated a reduction in postoperative complications, especially infections (pneumonia in particular); 3) enteral nutrition may have improved nitrogen balance in medical patients (although a combination of the three trials was not possible); 4) one surgical trial of enteral nutrition found a reduction in postoperative complications; and 5) oral nutritional supplements had several effects in medical patients (reduced occurrence of ascites (RR 0.57, 95% CI 0.37 to 0.88, 3 trials), possibly (significant differences only seen in the fixed-effect model) reduced rates of infection (RR 0.49, 95% CI 0.24 to 0.99, 3 trials, I2 = 14%), and improved resolution of hepatic encephalopathy (RR 3.75, 95% CI 1.15 to 12.18, 2 trials, I2 = 79%). While there was no overall effect of the supplements on mortality in medical patients, the one low risk of bias trial found an increased risk of death in the recipients of the supplements. Three trials of supplements in surgical patients failed to show any significant differences. No new information was derived from the various subgroup or sensitivity analyses. The exploratory analyses were also unrevealing except for a logical conundrum. There was no difference in mortality when all of the trials were combined, but the trials of parenteral nutrition found that those recipients had better survival (RR 0.53, 95% CI 0.29 to 0.98, 10 trials). Either the former observation represents a type II error or the latter one a type I error. The data do not compellingly justify the routine use of parenteral nutrition, enteral nutrition, or oral nutritional supplements in patients with liver disease. The fact that all but one of these trials were at high risks of bias even casts doubt on the few benefits that were demonstrated. Data from well-designed and executed randomised trials that include an untreated control group are needed before any such recommendation can be made. Future trials have to be powered adequately to see small, but clinically important, differences.

Plain-language summary: Since the best way to make such a determination is to undertake randomised trials, in which patients are assigned by chance to receive, or not receive, one or another of these treatments, this systematic review was undertaken to identify and summarise this information. Randomised trials comparing patients with liver diseases who were assigned to receive parenteral nutrition, enteral nutrition, or oral nutritional supplements to similar patients assigned not to receive any nutritional intervention were collected. The three nutritional interventions were considered separately. In addition, within each category of nutritional intervention, patients with medical conditions were compared separately from patients with surgical conditions. Thus there were six primary analyses, medical patients receiving or not receiving parenteral nutrition, surgical patients receiving or not receiving parenteral nutrition, medical patients receiving or not receiving enteral nutrition, surgical patients receiving or not receiving enteral nutrition, medical patients receiving or not receiving supplements by mouth, and surgical patients receiving or not receiving supplements by mouth. The outcomes of interest were mortality, hepatic morbidity (ascites, gastrointestinal bleeding, encephalopathy), quality of life, adverse events, infections, cost, duration of hospitalisation, jaundice, postoperative complications (only for the surgical trials), and nutritional outcomes (for example, body weight). A total of 37 randomised trials were identified. All but one had a high risk of systematic error (bias, that is overestimation of benefits and underestimation of harms). When the data were combined, most of the analyses failed to demonstrate a difference. There were some significant differences observed. These were that 1) parenteral nutrition reduced serum bilirubin more rapidly and improved one type of nutritional outcome (nitrogen balance) in medical patients with jaundice, and may have reduced some postoperative complications; 2) enteral nutrition may have improved nitrogen balance in medical patients, and reduced postoperative complications in surgical patients; and 3) supplements reduced the occurrence of ascites and also may have decreased the number of infections. Furthermore, the receipt of supplements (especially ones containing branched-chain amino acids) may have been helpful in the treatment of patients with hepatic encephalopathy. No significant effects were seen from the use of supplements in surgical patients. None of these observed benefits can be said to be definitively present because of the presence of methodologic flaws in the trials, which may have produced an overestimation of the observed effect. Moreover, due to too few patients included in the trials with two few outcome measures, both spurious significant findings and spurious insignificant findings cannot be excluded. The data are not strong enough to justify a recommendation to use these nutritional interventions routinely. We need well-designed and well-conducted randomised trials to prove that such therapy is indeed efficacious.