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Olli-PekkaSeppälä

Pleural Effusions and Thoracentesis

Essentials

  • Pleural effusion, either unilateral or bilateral, may be caused by many different diseases of the lung, pleura or other organs, or by systemic diseases.
  • Characterization of pleural fluid either as exudate or transsudate helps in diagnostic workout.
    • Exudate is usually caused by a disease of the lung or pleura or by a systemic disease.
    • Transsudate is usually caused by heart failure or by a hepatic or renal disease.

Aetiology

  • Causes of pleural effusion are presented in table T1.

Causes of pleural effusion (E = exudate, T = transsudate)

Common causesLess common causes
Pneumonia PneumoniaEHypoproteinaemia: nephrotic syndromeNephrotic Syndrome, hepatic failureT
Heart failure Acute Heart Failure and Pulmonary OedemaTTuberculosis Diagnosing TuberculosisE
Cancer Lung CancersEAbdominal diseases: pancreatitisAcute Pancreatitis, subphrenic abscessE
Pulmonary embolism Pulmonary EmbolismE/TSystemic connective tissue diseases: rheumatoid arthritis Disease-Specific Signs and Symptoms in Patients with Inflammatory Joint Diseases, SLE Systemic Lupus Erythematosus (Sle), vasculitis VasculitidesE
Postinfarction syndrome or sequela of thoracotomyE
AsbestosAsbestos-Related DiseasesE
Several drugs, most commonly methotrexate, amiodarone and nitrofurantoinE

Symptoms and signs

  • Minor pleural effusion can be asymptomatic.
  • Dyspnoea and dry cough
  • In pleurisy, additionally flank pain and often fever
  • Dull percussion note
  • In pleurisy, friction rub on auscultation (not common). The friction rub will disappear when there is so much fluid in the pleural cavity that the layers of the pleura do not rub against each other anymore.

Investigations

  • In practice there are three stages in investigating the cause of pleural effusion.
    1. The first question to ask is whether the effusion is transudate or exudate by nature. This is defined by determination of the protein concentration of the fluid.
    2. In the case of exudate, it should be determined whether it is due to a malignant or inflammatory condition.
    3. In the case of an inflammatory condition, a search for indications of bacterial pneumonia, tuberculosis and connective tissue disorders will be made.
  • Detailed examination of the patient
    • Since a considerable share of pleural effusion cases is caused by other diseases than those of the pleura or lungs, extensive attention should be paid also to possible signs of disease in other organ groups.
  • Indices of inflammation
    • ESR, plasma CRP, basic blood count
  • Thoracentesis
    • Unless the reason is self-evident
  • Diagnosis of cancer and tuberculosis often require thoracentesis and pleural biopsy, sometimes also thoracoscopy.

Indications for thoracentesis

  • Diagnostic thoracentesis in connection with pleural effusions of uncertain aetiology
  • Therapeutic thoracentesis if a large amount of pleural fluid causes symptoms
  • Thoracentesis is usually unnecessary in cases of right-sided or bilateral pleural effusion in connection with evident heart failure. Such accumulation of pleural fluid is reversed by treatment (pleural effusion that is limited to the left side is not considered to be due to heart failure).
  • There are no actual contraindications for thoracentesis. Careful consideration and caution are required if the patient has bleeding diathesis or medication that affects blood coagulation. With the exception of aspirin, drugs that affect blood coagulation should be paused before the procedure. Platelet level should be over 50 × 109 /l and INR level below 1.5.

Performance of thoracentesis

  • Video Thoracentesis
  • Before the procedure, the presence of excess fluid in the pleural cavity should be confirmed. This can be demonstrated by chest x-ray showing rounding of the lateral and posterior costodiaphragmatic recess (picture ). Rounding of the recess is not always seen with infrapulmonary pleural effusions. Ultrasound examination can be used to confirm the presence of pleural effusion and to locate a suitable puncture site (it is advisable to perform this whenever the apparatus is easily available).
  • The patient should sit leaning slightly forward with forearms on the examination table.
  • The area of dull percussion caused by pleural fluid is located by percussing and comparing the percussion sound with that obtained from the healthy lung. The diaphragmatic margin is marked on the side of the healthy lung. The upper border of dull percussion on the affected side should be at least two intercostal spaces higher.
  • The site of puncture is one or two intercostal spaces below the upper border of percussion dullness along the posterior axillary line (or a site determined by echography).
  • The site is anaesthetized over the upper border of a rib by 1% lidocaine solution. At the end of administration of anaesthetic, aspiration is performed to confirm the presence of pleural fluid.
  • Pleural aspiration is best performed using a disposable needle, syringe, three-way stopcock and tubing connected to a collection bag. It should be kept in mind that there is negative pressure in the pleural cavity, so the equipment should be airtight. If only a small amount of sample is needed (e.g. for protein determination when suspecting transudate), the sample may be aspirated with a thin needle into a syringe.
  • When performing therapeutic thoracentesis, the amount of fluid to be aspirated should be no more than 1 500 ml because of the risk of pulmonary oedema (be even more careful with elderly and debilitated people).
  • With diagnostic thoracentesis, attention is paid to the smell and appearance of the pleural fluid. In empyema, the fluid has a putrid smell. Blood-stained pleural fluid is probably caused by trauma, cancer or pulmonary infarction. Milky pleural effusion (chylothorax) is usually related to a trauma or a mediastinal malignancy.

Samples of pleural fluid

  • Samples are taken in a lithium heparin tube (except for bacterial culture), at least 0.5 ml/test. Approximately 100 ml of pleural fluid is sufficient to obtain comprehensive samples.
  • Protein
  • Differential cell count
  • Bacterial culture is advisable if the fluid is turbid or purulent: 5 ml in a blood culture bottle (aerobic and anaerobic) or with a swab stick into a bacterial sampling and transport tube.
  • Mycobacterial culture in a 10 ml factory-clean plastic tube
  • A cytology sample is shipped to the laboratory for example in a 50 ml plastic bottle. It is mixed with an equal amount of 70% ethanol.
  • If the accumulation of pleural fluid is associated with pneumonia it is advisable to determine the pH of the fluid (lithium heparin tube or heparinized syringe, cold transport) which guides the decisions concerning further treatment (drainage tube, operation or continuation of antimicrobial treatment).
  • Other investigations are performed according to a consultation with a specialist.

Interpretation of the results

  • If the protein concentration is less than 30 g/l, the sample is a transudate.
  • Leucocyte count > 1 000 × 106 /l or granular leucocyte share > 25% suggests bacterial pneumonia.
  • Increased lymphocyte share can be associated with tuberculous pleuritis, viral infection, malignancy or autoimmune disease.
  • The sensitivity of a cytology sample is in the order of 50-60% in cancer.
  • The sensitivity of mycobacterial culture from pleural fluid is usually poor.

    References

    • Bintcliffe OJ, Lee GY, Rahman NM, et al. The management of benign non-infective pleural effusions. Eur Respir Rev 2016;25(141):303-16. [PubMed]
    • Havelock T, Teoh R, Laws D, et al. Pleural procedures and thoracic ultrasound: British Thoracic Society Pleural Disease Guideline 2010. Thorax 2010;65 Suppl 2():ii61-76. [PubMed]
    • Hooper C, Lee YC, Maskell N, et al. Investigation of a unilateral pleural effusion in adults: British Thoracic Society Pleural Disease Guideline 2010. Thorax 2010;65 Suppl 2():ii4-17. [PubMed]