Role of transthoracic ultrasound in detecting volume of pleural effusion

Background
Transthoracic ultrasound can help in developing and evaluating an equation for simple quantification of pleural effusion (PE) that enables time and cost-effective decision-making for thoracentesis in those patients.


Objective of the study
The study aims to assess the validity of the second Goecke and Schwerk equation (H+D (both in cm)×70] while H is the lateral height of effusion, and D is the distance between the diaphragm and the lung, which depends on easy calculations to precisely estimate the PE volume in sitting individuals.


Patients and methods
From October 1, 2022 to March 31, 2023, a prospective observational cohort of 30 patients with PE was done at the Chest Department of Ain Shams University. All patients were subjected to thoracic ultrasonography to calculate PE volume using this equation before thoracocentesis or medical thoracoscopy that can be compared with drained volume.


Results
Patients with PE had average age 50.73±14.46 years, more in men (66.7%), smokers (53.3%), right-side PE (56.7%), and malignant PE (70%). Measured PE 1724.29±405.06 ml was significantly lower than drained fluid 1992.67±684.88 ml. There is a highly significant positive correlation of the total measured volume via this equation and drained volume (r=0.697; P=0.0001, 95%), age (r=0.649; P=0.0002). Measured PE volume was highly significantly correlated with drained PE volume through thoracoscopy (P=0.001). There is a highly significant positive correlation of the drained volume with measured volume (r=0.697; P=0.0001), age (r=0.499; P=0.005), and thoracoscopy-drained volume (r=0.848; P=0.0002), Volume through thoracoscopy is the most highly significant factor that can predict the measured PE volume (P=0.001). This equation was accurate in predicting PE volume (intraclass correlation coefficient 0.76). Measured PE volume was very significant (P<0.001) higher in malignant PE. It is highly significantly (P=0.001) higher in anechoic PE than in homogenous echogenic PE.


Conclusion
The second Goecke equation (H+D (both in cm)×70) is a valid method with 76.1% accuracy and it could predict the actual volume in seated patients admitted in wards


Study limitations
Although small sample size of this study, further studies with a higher number of patients may add value to this study.