Evaluation of Transthoracic Ultrasonography in Differentiating Pleural Effusions

Evaluation of Transthoracic Ultrasonography in Differentiating Exudative From Transudative Pleural Effusions

Pleural effusion is a condition where excess fluid builds up in the space between the lungs and the chest wall. To properly treat this condition, doctors must determine if the fluid is a "transudate" (usually resulting from systemic conditions like heart failure or liver disease) or an "exudate" (often resulting from local issues like infections, inflammation, or cancer). The standard method to classify this fluid involves inserting a needle into the chest to draw out a sample for laboratory testing, a procedure known as thoracentesis.

While laboratory fluid analysis is highly accurate, the needle procedure carries some inherent procedural risks. This observational study aims to evaluate whether non-invasive imaging tests, specifically chest ultrasound, can accurately determine if the fluid is a transudate or an exudate.

Researchers will enroll adult patients presenting with pleural effusion at Assiut University Hospital. As part of their diagnostic workup, participants will undergo a chest ultrasound and a standard diagnostic thoracentesis (fluid draw) within 24 to 48 hours of each other. The study will then evaluate the features seen on the ultrasound against the laboratory fluid analysis (the current gold standard) to see how well the non-invasive imaging performs in identifying the specific type of pleural effusion.

Study Overview

• Status: Not yet recruiting
• Conditions: Pleural Effusion; Exudative Pleural Effusion; Transudative Pleural Effusion

Detailed Description

Pleural effusion is a highly prevalent pleural space disorder and a fundamental step in its clinical workup is determining whether the fluid is a transudate or an exudate. The standard biochemical tool for this classification is Light's criteria, which requires invasive thoracentesis. Given the procedural risks of thoracentesis and the fact that Light's criteria can misclassify up to 25% of transudates as exudates in patients on diuretic therapy, there is a need to establish the diagnostic value of non-invasive imaging modalities like thoracic ultrasound (TUS).

All enrolled participants will undergo a systematic clinical evaluation and three primary diagnostic assessments:

1. Clinical Evaluation:

   • Participants will undergo a full medical history assessment (evaluating symptoms, duration, and underlying comorbidities) and a physical examination.
   • Baseline blood investigations will be drawn, including complete blood count (CBC), liver and kidney function tests, serum albumin, serum LDH, serum total protein, serum glucose and C-reactive protein (CRP).

2. Chest Ultrasound (TUS):

   • Imaging will be performed using a high-resolution B-mode ultrasound machine equipped with a convex low-frequency probe (3.5-5 MHz) for deep assessment and a linear high-frequency probe (7.5-12 MHz) for near-field evaluation.
   • Patients will be examined in a sitting or semi-recumbent position.
   • Evaluated sonographic parameters include the echogenicity of the pleural fluid (anechoic, homogenously echogenic, complex non-septated, complex septated, hyperechoic), the presence and number of septations, pleural thickening, surface irregularity, and fluid volume estimation.

3. Reference Standard (Thoracentesis):

   • Diagnostic thoracentesis will be performed under ultrasound guidance using a standard aseptic technique.
   • Pleural fluid will be analyzed for total protein, LDH, glucose, albumin, and cell count (with additional microbiology or cytology if clinically indicated).
   • Simultaneous serum protein, LDH, and albumin will be drawn within 2 hours of the procedure.
   • The effusion will be officially classified as an exudate or transudate based on Light's criteria.

• Study Type: Observational
• Enrollment (Estimated): 90

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: N/A

• Sampling Method: Non-Probability Sample

Study Population

The study population comprises adult patients (18 years or older) of both sexes presenting with a clinically and radiologically confirmed pleural effusion (unilateral or bilateral). Participants will be recruited from patients admitted to the Chest Medicine Department or referred for imaging at Assiut University Hospital. Eligible participants are those scheduled to undergo diagnostic thoracentesis and ultrasound of the chest as part of their standard clinical diagnostic workup.

Description

Inclusion Criteria:

• Adult patients aged ≥18 years of either sex
• Clinically and radiologically documented pleural effusion (confirmed by chest X-ray and/or thoracic ultrasound)
• Patients scheduled for diagnostic or therapeutic thoracentesis as part of their standard clinical care
• Ability to provide written informed consent

Exclusion Criteria:

• Patients with a history of prior pleural interventions, including chemical or surgical pleurodesis or previous chest tube insertion on the affected side
• Patients with absolute contraindications to thoracentesis (e.g., uncorrectable coagulopathy, uncooperative patients, or hemodynamic instability)
• Poor transthoracic ultrasound window preventing adequate evaluation of the pleural space (e.g., due to severe obesity, extensive subcutaneous emphysema, or chest wall deformities)
• Patients with traumatic hemothorax.

Study Plan

How is the study designed?

Number of groups / cohorts

1

Cohorts and Interventions

Group / Cohort

Pleural Effusion Cohort; Adult patients (18 years or older) presenting with clinically and radiologically confirmed pleural effusion. All participants in this cohort will undergo a chest ultrasound and a diagnostic thoracentesis within 24 to 48 hours of each other. The pleural fluid obtained via thoracentesis will be analyzed using Light's criteria, which will serve as the reference standard to evaluate the diagnostic accuracy of the ultrasound.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Diagnostic Accuracy of Chest Ultrasound Measured by Area Under the Curve (AUC)	The overall diagnostic accuracy of chest ultrasound in differentiating exudative from transudative pleural effusions will be evaluated by calculating the Area Under the Receiver Operating Characteristic Curve (AUC). Sonographic features (such as echogenicity and septations) will be assessed and validated against the biochemical reference standard (Light's criteria) obtained from pleural fluid analysis via thoracentesis.	Up to 48 hours post-enrollment (Imaging and thoracentesis are performed within 24-48 hours of each other)

Collaborators and Investigators

• Sponsor: Assiut University

Study record dates

Study Major Dates

• Study Start (Estimated): May 1, 2026
• Primary Completion (Estimated): May 1, 2027
• Study Completion (Estimated): June 1, 2027

Study Registration Dates

• First Submitted: March 31, 2026
• First Submitted That Met QC Criteria: March 31, 2026
• First Posted (Actual): April 7, 2026

Study Record Updates

• Last Update Posted (Actual): April 13, 2026
• Last Update Submitted That Met QC Criteria: April 8, 2026
• Last Verified: April 1, 2026

More Information

Terms related to this study

• Keywords: Computed Tomography; Thoracentesis; Exudate; Chest Ultrasound; Transudate; Light's Criteria
• Additional Relevant MeSH Terms: Respiratory Tract Diseases; Pleural Diseases; Pleural Effusion; Hydrothorax
• Other Study ID Numbers: US in Pleural Effusions