Harrison's Internal Medicine Chapter 294

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Questions and Answers

What is a pleural effusion?

An excess quantity of fluid in the pleural space. (correct)

Destruction of lung tissue.

A blockage of the airway.

An inflammation of the pleura.

What primarily influences the accumulation of pleural fluid?

Decrease in chest wall elasticity.

Increased formation and reduced absorption of fluid. (correct)

Decreased lung capacity for air intake.

Increased atmospheric pressure on the lungs.

What method has replaced lateral decubitus x-ray for evaluating suspected pleural effusions?

Fluoroscopic imaging.

Computed tomography (CT) scan.

Magnetic resonance imaging (MRI).

Chest ultrasound. (correct)

Through which structure is pleural fluid primarily absorbed under normal conditions?

Lymphatics in the parietal pleura. Signup and view all the answers

What two factors can lead to the development of pleural effusion?

Excess fluid formation and decreased fluid removal. Signup and view all the answers

Which of the following is a characteristic of a transudative pleural effusion?

It occurs due to systemic factors affecting fluid dynamics. Signup and view all the answers

What is the primary role of the thin layer of fluid in the pleural space?

To facilitate lung expansion and contraction. Signup and view all the answers

Where can pleural fluid enter into the pleural space from aside from the capillaries?

The peritoneal cavity. Signup and view all the answers

What is the LDH level in pleural fluid that suggests it is exudative when compared to serum?

More than two-thirds the normal upper limit for serum Signup and view all the answers

What can be ignored if the gradient between serum and pleural fluid protein levels is greater than 31 g/L?

Exudative categorization criteria Signup and view all the answers

When is it likely for transudates to be misidentified as exudates?

When exudative criteria are met Signup and view all the answers

What is the suggested pleural fluid protein/serum protein ratio to indicate an exudative effusion?

<blockquote> 0.5 </blockquote> Signup and view all the answers

If a patient is suspected of having a transudative effusion, what should be done if exudative criteria are met?

Measure the gradient between protein levels Signup and view all the answers

Which criterion is NOT part of the exudative criteria for pleural fluid analysis?

Pleural fluid bilirubin levels Signup and view all the answers

What problem arises if the exudative criteria are applied incorrectly?

Misidentification of transudates as exudates Signup and view all the answers

What is the expected condition of patients with a gradient greater than 31 g/L?

They are likely to have a transudative pleural effusion. Signup and view all the answers

What tests are indicated for a patient with an exudative pleural effusion?

Description of the appearance of the fluid Signup and view all the answers

In heart failure patients, when is a diagnostic thoracentesis required?

If the patient has pleuritic chest pain Signup and view all the answers

What indicates that a pleural effusion is likely due to congestive heart failure?

Pleural fluid NT-proBNP level >1500 pg/mL Signup and view all the answers

What is the most common cause of exudative pleural effusion in the United States?

Parapneumonic effusion Signup and view all the answers

Why does hepatic hydrothorax predominately occur on the right side?

Direct movement of peritoneal fluid through diaphragm openings Signup and view all the answers

What symptoms do patients with aerobic bacterial pneumonia and pleural effusion typically present with?

Chest pain, sputum production, and leukocytosis Signup and view all the answers

What complication may arise if pleural effusions persist despite heart failure therapy?

Development of empyema Signup and view all the answers

What is the predominant mechanism causing pleural effusions in patients with cirrhosis?

Direct movement of peritoneal fluid through diaphragm Signup and view all the answers

What is a leading cause of transudative pleural effusions in the United States?

Cirrhosis Signup and view all the answers

Which of the following conditions is NOT a leading cause of exudative pleural effusions?

Congestive heart failure Signup and view all the answers

What is the primary reason for distinguishing between transudative and exudative pleural effusions?

To decide on additional diagnostic procedures Signup and view all the answers

Which of the following criteria is used to classify exudative pleural effusions?

Pleural fluid protein/serum protein >0.5 Signup and view all the answers

Which condition is typically associated with high protein levels in pleural fluid?

Bacterial pneumonia Signup and view all the answers

What type of pleural effusion would likely require additional diagnostic testing?

Exudative pleural effusion Signup and view all the answers

Which of the following factors is NOT typically altered in transudative pleural effusions?

LDH levels in pleural fluid Signup and view all the answers

What is one of the leading causes of exudative pleural effusions?

Tuberculosis Signup and view all the answers

Study Notes

Pleural Effusion Overview

The pleural space is between the lung and chest wall and contains a thin layer of fluid for lubrication.
An excess of fluid in this space is termed pleural effusion.

Etiology of Pleural Effusion

Accumulation occurs when fluid formation surpasses absorption by lymphatics.
Fluid enters the pleural space via capillaries in the parietal pleura and interstitial lung spaces.
The lymphatics can absorb 20 times more fluid than is normally formed.
Pleural effusions can result from increased fluid formation or decreased fluid removal.

Diagnostic Approach

Chest imaging (preferably ultrasound) is essential for diagnosing pleural effusions.
Classification into transudative or exudative effusions is crucial for further diagnostic steps.

Transudative Pleural Effusions

Caused by systemic factors affecting fluid dynamics.
Leading causes include left ventricular failure and cirrhosis.

Exudative Pleural Effusions

Occur due to local factors altering fluid dynamics.
Major causes include bacterial pneumonia, malignancy, viral infections, and pulmonary embolism.
Requires additional diagnostic procedures to identify underlying local disease.

Differentiation Criteria

Distinguish between transudative and exudative effusions based on:
- Pleural fluid protein/serum protein >0.5
- Pleural fluid LDH/serum LDH >0.6
- Pleural fluid LDH over two-thirds of the serum upper limit.
Misidentification occurs in ~25% of cases using these criteria.
If suspected transudate shows exudative criteria, measure serum-pleural fluid protein gradient:
- A gradient >31 g/L (3.1 g/dL) indicates a transudate.

Further Testing for Exudative Effusions

If exudative fluid is confirmed, analyze:
- Appearance of the fluid
- Glucose level
- Differential cell count
- Microbiologic studies
- Cytology

Common Causes of Pleural Effusions

Heart Failure:
- Most frequent cause; linked to left ventricular failure.
- Effusion often occurs when interstitial lung fluid overwhelms lymphatic removal.
- Thoracentesis is advised if effusions are asymmetric or if the patient shows fever or pleuritic pain.
- NT-proBNP level >1500 pg/mL suggests effusion from heart failure.
Hepatic Hydrothorax:
- Occurs in ~5% of cirrhosis patients with ascites.
- Primarily right-sided, fluid moves through diaphragm openings, potentially causing severe dyspnea.
Parapneumonic Effusion:
- Associated with bacterial pneumonia, lung abscess, or bronchiectasis.
- Most common exudative effusion in the U.S.
- Empyema refers to purulent effusion. Presenting symptoms include fever, chest pain, and increased sputum production.

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Description

Explore the crucial details regarding pleural disorders in Chapter 294 of Harrison's Principles of Internal Medicine. This quiz covers the mechanisms, causes, and implications of pleural effusion, offering insights into the pleural space and its function within respiratory health.