Diagnostic Tests for Pleural effusion
Pleural effusion: Diagnostic Tests
The list of diagnostic tests
mentioned in various sources as
used in the diagnosis of Pleural effusion
includes:
- Chest examination
- Chest x-rays
- Laboratory tests of pleural fluid - when the fluid is extracted as a treatment.
Pleural effusion Tests: Book Excerpts
Home Diagnostic Testing
These home medical tests may be relevant to Pleural effusion:
- Lung & Respiratory Health Tests:
Pleural effusion Diagnosis: Book Excerpts
Diagnostic Tests for Pleural effusion: Online Medical Books
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Pleural Effusion:
Physical examination (PE)
(The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter)
A. Focused PE. Observe the patient’s appearance and respiratory effort. Is the patient splinting or showing signs of respiratory distress? Vital signs should include respiratory rate. Is there tachycardia present (Chapter 7.12)? Typical findings on pulmonary examination include decreased or absent breath sounds over the affected side, dullness to percussion, decreased tactile fremitus, and possibly splinting of the affected side. Findings can be bilateral (e.g., CHF) or unilateral. The examination can also vary with the severity of the effusion. Findings are usually normal when less than 300 ml of fluid is present. A pleural rub may be noted. With a large effusion ( >1,500 ml), the affected hemithorax is often larger with bulging interspaces (2).
B. Additional physical examination. Think in terms of differential diagnosis to look for signs of underlying causes. Cardiac examination should look for signs of congestive heart failure, including cardiomegaly, displaced point of maximal impulse, and an S3 gallop. Is a heart murmur present? Abdominal examination may reveal hepatomegaly, liver tenderness, a fluid wave, and other signs of ascites. Are there signs of malignancy, including generalized or regional lymphadenopathy (Chapters 15.1 and 15.2)?
Testing
A. Radiographic study. Initial testing focuses on confirming that a pleural effusion is present. A chest x-ray study is the typical starting point. On the upright anteroposterior view, a small effusion may show up as blunting of the costophrenic angle. Larger effusions will show a meniscus sign at the air fluid border. Lateral decubitus views help estimate the size of the effusion.
B. Ultrasound and other modalities. Unfortunately, the chest x-ray study can fail to show small effusions, even with decubitus views. Ultrasound can detect as little as 5 to 50 ml of fluid. It is also helpful in locating pockets of fluid and guiding thoracentesis for small effusions. Computed tomography scan, which is very sensitive, can differentiate pleural fluid from pleural thickening and focal masses.
C. Thoracentesis. Thoracentesis allows evaluation of any undiagnosed pleural effusion. Note that not all effusions require diagnostic thoracentesis. If the cause is apparent from the clinical presentation (e.g., CHF), observation may be appropriate (3). In general, parapneumonic effusions require thoracentesis to confirm diagnosis and assess the need for chest tube placement.
1. Relative contraindications include bleeding diathesis, systemic anticoagulation, small volume of pleural fluid, mechanical ventilation, inability of patient to cooperate, and cutaneous disease at the needle entry site.
2. Transudate or exudate? Based on a revision of the “modified” Light criteria, pleural fluid is an exudate if it meets one or more of the following parameters (5):
a. Pleural fluid serum lactate dehydrogenase (LDH) more than 0.45 the upper limit of normal LDH
b. Pleural:serum LDH more than 0.6
c. Pleural:serum protein more than 0.5
3. Other measures used to test for an exudate include pleural fluid cholesterol, fluid:serum albumin gradient and fluid:serum bilirubin ratio. Cell count, pH, glucose, Gram’s stain and culture help assess for infection.
Diagnostic assessment
In developing a diagnostic assessment for the patient with pleural effusion, it is important to consider that pleural fluid analysis does not establish a specific diagnosis, but supports a clinical impression. Ordering and interpreting tests must be guided by pretest clinical impressions (4). Initially, it may be appropriate to order only pleural fluid LDH and protein levels to determine the presence or absence of an exudate. Additional fluid can be reserved for further testing if an exudate is found.
If the pleural fluid analysis shows a transudate, the most likely diagnosis is CHF. Additional possibilities include cirrhosis with ascites, nephrotic syndrome, hypoalbuminemia, and acute atelectasis. Further diagnostic evaluation of the pleural fluid would not be necessary.
If the pleural fluid is exudative, the most likely diagnostic possibilities are malignancy, infection, or tuberculosis, but the differential diagnosis is quite broad. In one study, malignancy accounted for 25% of all pleural effusions seen in the general hospital setting. Cytology is helpful in looking for malignancy. In 54% to 63% of patients with malignant effusions, pleural fluid cytology will be positive (4). Glucose level, cell count, and pH will help guide management in the setting of parapneumonic effusions and aid in determining the need for chest tube placement. Tuberculous effusions may require pleural biopsy to confirm the diagnosis. Amylase can be elevated in pancreatitis, pancreatic pseudocyst, malignancy, and esophageal rupture. Triglycerides would be elevated in the setting of chylothorax.
Studies on pleural fluid will yield a definitive or presumptive diagnosis in 74% of cases (4). Those that are undiagnosed may require repeat thoracentesis, pleural biopsy, bronchoscopy, or thoracoscopy to ascertain the cause.
References
1. Stagner SW, Campbell GD. Pleural effusion: What can you learn from the results of the a “tap”? Postgrad Med 1992;91:439–454.
2. Jay SJ. Diagnostic procedures for pleural disease. Clin Chest Med 1985;6:33–48.
3. Burgher LW, Jones FL, Patterson JR, Selecky PA. Guidelines for thoracentesis and needle biopsy of the pleura. Am Rev Respir Dis 1989;140:257–258.
4. Bartter T, Santarelli R, Akers S, Pratter M. The evaluation of pleural effusion. Chest 1994;106:1209–1214.
5. Heffner JE, Brown LK, Barbier C. Diagnostic value of tests that discriminate between exudative and transudative pleural effusions. Chest 1997;111:970–980.
» READ BOOK EXCERPT ONLINE »
Source: The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter, 2000
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