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Case study
A 70-year-old women presents with slowly increasing dyspnoea.
She cannot lie flat without feeling more short of breath. She has a
history of HTN and osteoarthritis, and she has been taking
NSAIDs with increasing frequency over the previous few months.
On physical examination, she appears dyspnoeic at rest, her BP is
140/90 mm Hg, and pulse is 90 bpm. Her jugular venous pressure
is elevated to the angle of the jaw. The left lung field is dull to
percussion with decreased air entry basally. Crackles are heard in
the right lung field and above the line of dullness on the left.
Lower extremities have pitting oedema to the knee.
Pleural fluid
•The pleural cavity is a potential space lined by mesothelium of
the visceral and parietal pleurae.
•The pleural cavity normally contains a small amount of fluid.
•This fluid is a plasma filtrate derived from capillaries of the
parietal pleura.
•It is produced continuously at a rate dependent on capillary
hydrostatic pressure, plasma oncotic pressure, and capillary
permeability
•Pleural fluid is reabsorbed through the lymphatics and venules
of the visceral pleura.
•An accumulation of fluid, called an effusion, results
from an imbalance of fluid production and reabsorption.
•Excessive amounts of such fluid can impair breathing
by limiting the expansion of the lungs during
ventilation .
Types of fluids
Four types of fluids can accumulate in the pleural space:
1. Serous fluid (hydrothorax)
2. Blood (haemothorax(
3. Chyle (chylothorax)
4. Pus (pyothorax or empyema(
Diagnosis
• Pleural effusion is usually diagnosed on the basis of medical
history and physical exam ,and confirmed by chest x-ray .
• Once accumulated fluid is more than 300 ml, there are usually
detectable clinical signs in the patient, such as
1.
Decreased movement of the chest on the affected side,
2.
Stony dullness to percussion over the fluid,
3. Diminished breath sounds on the affected side,
4.
In large effusion there may be tracheal deviation away from
the effusion .
Imaging
A pleural effusion will show up as an area of whiteness
on a standard posteroanterior X-ray .
Chest radiographs acquired in the lateral decubitus
position (with the patient lying on his side) are more
sensitive and can pick up as little as 50 ml of fluid.
At least 300 ml of fluid must be present before upright
chest films can pick up signs of pleural effusion (e.g.,
blunted costophrenic angles)
Massive left sided pleural effusion in a patient presenting with lung
cancer .
CT scan of chest showing loculated pleural effusion in left side. Some
thickening of pleura is also noted .
SPECIMEN COLLECTION
Thoracentesis is indicated for any undiagnosed pleural effusion or for
therapeutic purposes in patients with massive symptomatic effusions;
•
•
A needle is inserted through the back of the chest wall in the sixth, seventh, or
eighth intercostal space on the midaxillary line, into the pleural space.
The fluid may then be evaluated for the following:
1.
Chemical composition including protein ,lactat dehydrogenaseLDH ,
albumin ,amylase ,pH ,and glucose.
2.
Gram stain and culture to identify possible bacterial infections
3.
Cell count and differential
4.
Cytopathology to identify cancer cells, some infective organisms
5.
Other tests as suggested by the clinical situation – lipids ,fungal culture ,viral
culture ,specific immunoglobulins
Contraindications
• An uncooperative patient or a coagulation disorder that can not be
corrected are absolute contraindications
• Relative contraindications include cases in which the site of
insertion has known bullous disease (e.g .emphysema( and use of
mechanical ventilation.
TRANSUDATES AND EXUDATES
Transudates are usually bilateral owing to systemic conditions leading to
increased capillary hydrostatic pressure or decreased plasma oncotic pressure
Exudates are more often unilateral, associated with localized disorders that
increase vascular permeability or interfere with lymphatic resorption
Classical teaching stressed that exudates and transudates can be distinguished
on the basis of total protein concentrations above (exudates) or below
(transudates) 3.0 g/dL
Accordingly, an exudate meets one or more of the following criteria:
(1) Pleural fluid/serumv protein ratio greater than 0.5;
(2) pleural fluid/serum LD ratio greater than 0.6; and
(3) pleural fluid LD level greater than two thirds of the serum upper limit of
normal.
GROSS EXAMINATION
Transudates are typically clear, pale yellow to straw-colored, and odorless, and
do not clot. Approximately 15% of transudates are blood tinged.
A bloody pleural effusion (hematocrit >1%) suggests trauma, malignancy, or
pulmonary infarction. A pleural fluid hematocrit greater than 50% of the blood
hematocrit is good evidence for a hemothorax
Exudates may grossly resemble transudates, but most show variable degrees of
cloudiness or turbidity, and they often clot if not heparinized.
A feculent odor may be detected in anaerobic infections.
Turbid, milky, and/or bloody specimens should be centrifuged and the
supernatant examined. If the supernatant is clear, the turbidity is most likely due
to cellular elements or debris. If the turbidity persists after centrifugation, a
chylous effusion is likely.
MICROSCOPIC EXAMINATION
Cell Counts
Leukocyte counts have limited utility in separating transudates (<1000/μL) from
exudates (>1000/μL).
Although red cell counts above 100,000/μL are highly suggestive of malignancy,
trauma, or pulmonary infarction, they are not specific for these conditions.
Differential Leukocyte Count and Cytology
Cytologic analysis will establish the
diagnosis of metastatic carcinoma
in 70% or more of cases