Electronic search strategies, using clearly reported search terms, were developed in December 2022 and updated in March 2023. It involved 4 databases: namely PubMed, Web of science, Scopus and Embase. Additionally, the references of eligible studies and the first 100 relevant articles retrieved from Google Scholar and the Open Access Theses and Dissertations were screened. This SR included observational studies that compared the fluids present in the paranasal sinuses of drowning and non-drowning subjects. Case reports, case series with less than 10 cases and studies with suspected overlap in the population were all excluded. For a study to be included, one of the following parameters should have been reported; fluid presence, fluid density or volume in the one or more of the paranasal sinuses. Two reviewers participated in the selection, based on the eligibility criteria, in the data extraction and quality assessment processes. They worked independently and in duplicate. Disagreements between them were resolved by discussion or by the involvement of a third reviewer.

In this SR the validity of finding fluids in the paranasal sinuses for identifying drowning as the cause of death, was investigated. These fluids could be either detected by computed tomography (CT) or by aspiration. New Castle Ottawa Scale was used for quality assessment of the included articles. Missing means and standard deviations were clarified by contacting the authors, estimating them using indirect methods, or collected through WebPlotDigitizer. All meta-analyses were conducted using the inverse-of-variance method and a random-effects model. Publication bias was also assessed using funnel plot.

The primary outcome in this review was fluid presence in the paranasal sinuses as detected by CT or by aspiration and reported using odds ratio to identify or refute drowning as a cause of death. Subgrouping based on the method of fluid detection was performed to identify the impact of the method on the results. Other outcomes were fluid density and volume. The latters were reported using the mean and standard deviation.

Out of 510 identified articles, only 14 studies were included, comprising 1044 subjects, 489 drowned and 555 non-drowned. The post-mortem interval in the included studies extended from 3 hours to 17 days, and the age of the subjects ranged from 6 to 97 years. Ten of the studies had a quality assessment score of 5-6. Twelve studies were included in a meta-analysis. The latter revealed a strong correlation between the presence of fluid in the paranasal sinuses and drowning (OR = 17.1; 95% CI 7.2 to 40.5; p<.001), with a moderate heterogeneity (I2 = 54%). No potential for publication bias was also detected.

Based on the results of this SR, the authors concluded that the paranasal sinus fluid analysis is a valuable diagnostic method when drowning is suspected, but cannot be definitively confirmed through traditional approaches.