Application of the pleural effusion ratio in diagnosing freshwater drowning: A comparative study

Drowning is a leading cause of unintentional death globally, with diagnosis remaining challenging due to the non-specific nature of postmortem findings. This prospective study aimed to evaluate the diagnostic utility of the pleural effusion (PE) ratio in differentiating freshwater drowning from other causes of death. A total of 179 medico-legal autopsies conducted between July 2022 and April 2023 at a tertiary centre in Northern India were analysed, comprising 75 cases of freshwater drowning, 64 sudden cardiac deaths and 40 hangings. PE and lung weights were recorded, and the PE ratio was calculated as the weight of PE divided by the combined weight of the lungs and PE, multiplied by 100. Statistically significant differences were observed in PE ratios among the three groups (p < 0.001). The mean PE ratio was markedly elevated in drowning cases (30.07) compared to cardiac (2.75) and hanging deaths (3.21). Receiver operating characteristic curve analysis yielded an area under the curve of 1.0, identifying 7.4 as the optimal PE ratio threshold for diagnosing drowning, with 100% sensitivity and specificity. This study, based on freshwater drownings in a uniform glacier-fed river environment, supports the PE ratio as a reliable adjunct in diagnosing drowning deaths. A PE ratio exceeding 7.4 strongly indicates freshwater drowning and may aid forensic pathologists in differentiating it from postmortem submersion. It should be used in conjunction with circumstantial evidence and only after the exclusion of all other possible causes of death.