Abstract Background and Aims The evaluation of hydration status in dialysis patients is a crucial aspect of their care. Focused lung ultrasound has garnered attention as a cost-effective and accessible tool for assessing hydration status, particularly through the detection of B-lines. Despite its potential, there is a lack of comprehensive systematic reviews addressing the clinical utility of lung ultrasound in fluid assessment for dialysis patients. Method A systematic search was conducted on PubMed, MEDLINE, EMBASE, Cochrane, and Web of Science. Two independent reviewers screened titles, abstracts, and full texts, with a third reviewer consulted in cases of discrepancy. Inclusion criteria encompassed papers utilizing lung ultrasound to evaluate fluid status in dialysis patients. Exclusion criteria were: abstracts or posters and papers not investigating at least one of the following endpoints: B-type natriuretic peptide, cardiovascular events, inferior vena cava, preload, NYHA classification, ultrafiltration/weight reduction, blood pressure, total body water/bioimpedance, hospitalization, mortality, and clinical evaluations. A modified QUADAS2-score was employed for assessment of risk of bias and applicability by two independent investigators. The protocol was registered at Prospero (CRD42022334147). Results A total of 2543 papers were identified of which 156 underwent full-text screening. Of these, 49 papers were included in the review, comprising seven randomised controlled trials and 41 observational studies. The most common study aim was impact assessment of ultrafiltration on the quantity of B-lines. However, numerous studies investigated the correlation between lung ultrasound and various endpoints such as bioimpedance, chest x-ray, and clinical examination. Overall, the included papers were characterized by noteworthy heterogeneity in terms of ultrasound protocol, encompassing differences in number of scanning zone (8-28), B-lines cut-off points, and definitions of endpoint. The QUADAS assessment revealed risk of bias in the included studies, most commonly related to a lack of blinding and, consequently, an impact on the interpretation of index test results. Only n=24 studies (49%) scored “low” risk of bias. Regarding patient selection, the numbers were even lower with only n=17 studies (34%) scoring “low” on risk of bias. Conclusion The collective evidence on clinical utility of lung ultrasound for fluid assessment of dialysis patients is characterised by notable heterogeneity and risk of bias, precluding meta-analysis. Well-designed large scale studies are still warranted to determine the optimal ultrasound protocol. Future studies should establish guidelines for scanned zones and consensus cut-offs to enhance homogeneity.
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