Pleural Effusion, Approach

Approach to Pleural Effusion:

a. First step is to rule out clinically evident heart failure, if not:

b. Proceed to diagnostic thoracentesis and measure pleural fluid LDH and protein.

c. Occassionally the appearance of the pleural fluid will suggest the diagnosis (empyema, hemothorax, chylothorax), if so pursue additional testing (culture, Hct, TG etc.)

d. If Light’s criteria not met (see below), then you have a transudate (treat CHF, cirrhosis etc.)

e. If 1 or more of Light’s criteria are fulfilled, then it generally can be considered an exudate** and further diagnostic testing should include: glucose, cell count + diff, ADA, cytology, amylase and if infection suspected, pH and culture.  

i. If ADA>40 and lymphocytic predominance, consider treatment for TB pleurisy

ii. If still no diagnosis, pursue CTA to rule out PE

1. if +, PE confirmed

2. if negative, consider image-guided pleural biopsy

3. consider bronchoscopy if hemoptysis or consolidation present

Physical exam findings in pleural effusion:

a) Unlike aortic stenosis, which we discussed two weeks ago, the physical exam is not great for detecting pleural effusions.

b) Classic finding is dullness to precussion, which can indicate either consolidation or effusion.

c) Tactile fremitus can help differentiate between the two (decreased in effusion, increased in consolidation).

d) Asymmetric chest excursion can also be helpful.

Diagnosis of pleural effusion:

a) Any new pleural effusion warrants diagnostic thoracentesis, unless the picture is clearly consistent with CHF.

b) Classic teaching is that CHF can result in isolated R-sided effusion, but studies have shown that effusions in CHF are typically bilateral.

c) Imaging:

      - Lateral CXR can detect 50ml fluid, PA 200ml fluid as meniscus; at 500ml, meniscus obscures hemidiaphragm

      - Effusion >1cm on lateral decubitus film indicates fluid is sufficient for thoracentesis (200ml)

      - CT can detect 2ml fluid

Criteria for exudative vs transudative effusion

a) Modified Light's criteria: PL-protein/S-protein > 0.5, PL-LDH/S-LDH > 0.6, PL-LDH > 2/3 upper limit of normal serum level - any one positive indicates exudate

b) Other criteria include:

      - Abbreviated Light's: PL-protein/S-protein > 0.5 or PL-LDH > 2/3 upper limit of normal serum level

      - Two-test: PL-cholesterol > 45 mg/dL or PL-LDH > 0.45 upper limit of normal serum level

      - Three-test: PL-protein > 2.9 mg/dL, PL-cholesterol > 45 mg/dL or PL-LDH > 0.45 upper limit of normal serum level

c) Advantage of two- and three-test criteria is lack of need for blood sample

d) All criteria perform similarly, and are highly sensitive, but not specific, in order to prevent missing exudative effusion.

e) In CHF, thoracentesis in setting of diuresis can result in false positive - in this setting, the serum-effusion albumin gradient can help (>1.2 suggests transudate).

Ddx of a transudative effusion:

· CHF

· atelectasis

· Hypoalbuminemia, nephrotic syndrome

· Hepatic hydrothorax (almost always with ascites)

· Iatrogenic (ie. CVC into pleural space, etc.)

· Peritoneal dialysis

· Rare: csf leak, urinothorax (caused by ipsilateral obstructive uropathy)

Typically exudative effusions than can uncommonly present as transudates:

· Amyloidosis

· Constrictive pericarditis

· Malignancy (3-10% due to lymphatic obstruction, atelectasis or concomitant disease)

· PE

· Sarcoidosis

· SVC syndrome

· Trapped lung

Management of parapneumonic effusion

a) Uncomplicated: results from inflammatory response, with sterile fluid --> observe

b) Complicated: results from persistent bacterial invasion of pleural space characterized by positive gram stain/culture, pH <7.2, and glucose <60 mg/dL--> therapeutic thoracentesis vs tube thoracostomy

c) Empyema: frank pus in pleural space --> video assisted thoracoscopic surgery

d) Key is to get thoracic surgery involved early if there is concern for complicated parapneumonic effusion or empyema in order to prevent progression of the fibrinopurulent response to frank fibrosis of pleural space.

Malignant pleural effusions (MPEs):

· Defined as malignant cells in the pleural space

· Result from primary malignancies of the pleurae or from underlying intrathoracic or extrathoracic malignancies that reach the pleural space by hematogenous, lymphatic, or contiguous spread

· majority of MPEs caused by lung, breast or ovarian ca or lymphoma

· regardless of etiology, average survival is 4 months from time of diagnosis of MPE

· The detection of an effusion coincident with a newly diagnosed cancer does not establish an MPE because 50% of such effusions are nonmalignant

Pathogenesis: tumor deposits spread along parietal pleural membranes and obstruct intrapleural lymphatics; pleural tumor deposits also stimulate the release of chemokines that increase vascular and pleural membrane permeability

Diagnosis:

o Radiographic findings: On CXR, a massive effusion increases the probability of a malignant etiology; commonly produces a meniscus sign with fluid tracking up the lateral chest wall, a shift of the mediastinum to the contralateral side, pleural thickening, and an inversion of the diaphragm. PET CT has a sensitivity of 93-100% for MPE (but obviously not specific).

o Pleural fluid:

§ most MPEs are exudates, but up to 10% can be classified as transudates

§ more than 50% have lymphocytic predominance (50-75% lymphs)

§ bloody effusions and eosinophilic effusions are also associated with MPE

§ standard pleural fluid cytology confirms an MPE with a diagnostic yield of only ~65%; diagnostic yield can be increased with repeated thoracenteses, but not with the submission of larger volumes

§ combinations of tumor markers can be applied to the pleural fluid analysis to improve diagnosis in certain malignancies

o Thoracoscopy with pleural biopsy has a sensitivity of >90% for diagnosing MPE

(Christopher Woo MD, 7/6/10)

(Victoria Kelly MD, 3/31/11)