RESUMO
INTRODUCTION: Immunonutrition (IN) is used in major visceral surgery to reduce postoperative complications. This umbrella review (review of reviews) collects and analyses data on the efficacy of perioperative IN. METHODS: The review was conducted in accordance with PRISMA 2020 guidelines. Inclusion criteria were meta-analyses comparing IN with normal diet or isocaloric isonitrogenous feeding. The primary outcome was infectious complications. Secondary outcomes were overall morbidity, hospital length of stay and mortality. Methodological quality was evaluated using AMSTAR-2. Overlap and certainty of evidence (GRADE) were assessed. RESULTS: Twenty meta-analyses (MAs) were included in the umbrella review: eleven on various abdominal surgeries (one MA was considered twice) and eight on pancreatic, oesophageal, hepatic, or colorectal surgeries. Overall, IN was associated with significantly fewer postoperative infectious complications (OR 0.60 [0.54-0.65], random effect model) but with substantial heterogeneity (I2 = 64%), and less postoperative morbidity (OR 0.78 [0.74-0.81], I2 = 30.3%). Excluding three MAs with heterogeneity did not alter the results. The overlap between the MAs was slight, with a corrected covered area of 0.13. There was no significant difference in the timing of IN (preoperative, postoperative or perioperative). CONCLUSION: This umbrella review confirms the beneficial effect of IN in visceral surgery. Some practical questions remain unanswered: optimal timing of IN, in which surgical speciality it is best used, and its utility in enhanced recovery programmes. REGISTRATION IN PROSPERO: CRD42021255177.