Pocket Medicine: The Massachusetts General Hospital Handbook of Internal Medicine (30 page)

Exudates

•
Lung parenchymal infection
(
25%
)

bacterial (parapneumonic): can evolve along spectrum of
exudative
(but sterile) →
fibropurulent
(infected fluid) →
organization
(fibrosis & formation of rigid pleural peel). Common causes:
Strep pneumo, Staph aureus, Strep milleri, Klebsiella, Pseudomonas, Haemophilus, Bacteroides, Peptostreptococcus
, mixed flora in aspiration pneumonia.

mycobacterial: >50% lymphs 80% of the time, ADA >40, pleural bx ~70% Se

fungal, viral (usually small), parasitic (eg, amebiasis, echinococcosis, paragonimiasis)

•
Malignancy
(
15%
): primary lung cancer most common, metastases (esp. breast, lymphoma, etc.), mesothelioma (✓ serum osteopontin levels;
NEJM
2005;353:15) •
Pulmonary embolism
(
10%
): effusions in ~40% of PEs; exudate (75%) > transudate (25%); hemorrhagic—
must have high suspicion b/c presentation highly variable
•
Collagen vascular disease
: RA (large), SLE (small), Wegener’s, Churg-Strauss •
Gastrointestinal diseases
: pancreatitis, esophageal rupture, abdominal abscess • Hemothorax (Hct
_eff
/Hct
_blood
>50%): trauma, PE, malignancy, coagulopathy, leaking aortic aneurysm, aortic dissection, pulmonary vascular malformation • Chylothorax (triglycerides >110): thoracic duct damage due to trauma, malignancy, LAM

• Other:

post-CABG: left-sided; initially bloody, clears after several wks

Dressler’s syndrome (pericarditis & pleuritis post-MI), uremia, postradiation therapy

Asbestos exposure: benign;
eosinophils

Drug-induced (eg, nitrofurantoin, methysergide, bromocriptine, amiodarone):
eos

Uremia; post-XRT; sarcoidosis

Meigs’ syndrome = benign ovarian tumor → ascites & pleural effusion

Yellow-nail syndrome: yellow nails, lymphedema, pleural effusion, bronchiectasis

Diagnostic studies

•
Thoracentesis
(
NEJM
2006;355:e16)

Indications:
all effusions >1 cm in decubitus view
if suspect due to CHF, can diurese and see if effusions resolve (75% do so in 48 h)
asymmetry, fever
,
chest pain or failure to resolve
→ thoracentesis
parapneumonics should be tapped ASAP
(
cannot
exclude infxn clinically)

Diagnostic studies:
✓ total protein, LDH, glucose, cell count w/ differential, Gram stain & culture, pH; remaining fluid for additional studies as dictated by clinical scenario

Complications:
PTX (5–10%), hemothorax (~1%), re-expansion pulm edema (if >1.5 L removed), spleen/liver lac.; post-tap CXR not routinely needed (
Annals
1996;124:816)

↓ PTX w/ U/S and experienced supervisor (
Chest
2009;135:1315;
Archives
2010;170:332)

•
Transudate vs. exudate
(
Annals
1972;77:507)

Light’s criteria
: exudate = TP
_eff
/TP
_serum
>0.5
or
LDH
_eff
/LDH
_serum
>0.6
or
LDH
_eff
>
²
/
₃
ULN of LDH
_serum
; 98% Se, 83% Sp; best Se of all methods (
Chest
1995;107:1604); however, will misidentify 25% of transudates as exudates; ∴ if clinically suspect transudate but meets criterion for exudate, confirm w/ test w/ higher Sp

exudative criteria w/ better Sp: serum-effusion alb gradient ≤1.2, Se 87%, Sp 92%; serum-effusion TP gradient ≤3.1, Se 84%, Sp 91%; chol
_eff
>45 mg/dL
and
LDH
_eff
>200, 90% Se, 98% Sp (no serum required)

CHF effusions:
TP may
↑
with diuresis or chronicity
→ “pseudoexudate”; alb gradient ≤1.2, chol
_eff
>60 mg/dL (Se 54%, Sp 92%) or clin judgment to distinguish (
Chest
2002;122:1524)

•
Complicated vs. uncomplicated parapneumonic
(
Chest
1995;108:299)

complicated =
Gram stain or culture
or
pH <7.2
or
glucose <60

complicated parapneumonic effusions usually require
drainage
to achieve resolution

empyema = frank pus, also needs drainage to achieve resolution

• Additional pleural fluid studies (
NEJM
2002;346:1971)

NT-proBNP ≥1,500 pg/mL has 91% Se & 93% Sp for CHF (
Am J Med
2004;116:417)

WBC & diff.: exudates tend to have ↑ WBC vs. transudates but nonspecific neutrophils → parapneumonic, PE, pancreatitis lymphocytes (>50%) → cancer, TB, rheumatologic eos (>10%) → blood, air, drug rxn, asbestos, paragonimiasis, Churg-Strauss, PE

RBC: Hct
_eff
1–20% → cancer, PE, trauma; Hct
_eff
/Hct
_blood
>50% → hemothorax

AFB: yield in TB 0–10% w/ stain, 11–50% w/ culture, ~70% w/ pleural bx

adenosine deaminase (ADA): seen w/ granulomas, >70 suggests TB, <40 excludes TB

cytology: ideally ≥150 mL and at least 60 mL should be obtained (
Chest
2010;137:68)

glucose: <60 mg/dL → malignancy, infection, RA

amylase: seen in pancreatic disease and esophageal rupture (salivary amylase)

rheumatoid factor, C
_H
50, ANA:
limited utility
in dx collagen vascular disease

triglycerides: >110 → chylothorax, 50–110 → ✓ lipoprotein analysis for chylomicrons

cholesterol: >60; seen in chronic effusions (eg, CHF, RA, old TB)

creatinine: effusion/serum ratio >1 → urinothorax

fibulin-3: ↑ plasma and/or effusion levels → mesothelioma (
NEJM
2012;367:1417)

• Chest CT; pleural biopsy; VATS

• Undiagnosed persistent pleural effusions (
Clin Chest Med
2006;27:309)

Transudative
: most commonly CHF or hepatic hydrothorax. ✓ s/s CHF or cirrhosis, NT-proBNP
_eff
; consider intraperitoneal injection of technetium-99m sulfur colloid

Exudative
(ensure using Sp test listed above): most commonly malig, empyema, TB, PE. ✓ s/s malig, chest CT (I
⁺
), ADA or IFN-g release assay; consider thoracoscopy.

Treatment

• Symptomatic effusion: therapeutic thoracentesis, treat underlying disease process • Parapneumonic effusion (
Chest
2000;118:1158)

uncomplicated → antibiotics for pneumonia

>
¹
/
₂
hemithorax
or
complicated
or
empyema
→
tube thoracostomy
(otherwise risk of organization and subsequent need for surgical decortication)

loculated→ tube thoracostomy or VATS; intrapleural t-PA + DNase ↓ need for surgical referral (
NEJM
2011;365:518)

• Malignant effusion: serial thoracenteses vs. tube thoracostomy + pleurodesis (success rate ~80–90%) vs. indwelling pleural catheter (
  JAMA
2012;307:2383); choice of pleurodesis agent (talc, bleo, doxy) controversial; systemic steroids & pH <7.2 a/w ↑ pleurodesis failure rate • TB effusions: effusion will often resolve spontaneously; however, treat Pt for active TB

• Hepatic hydrothorax

Rx: Δ pressure gradient (ie, ↓ ascitic fluid volume, NIPPV)

avoid chest tubes; prn thoracenteses, pleurodesis, TIPS or VATS closure of diaphragmatic defects if medical Rx fails; NIPPV for acute short-term management