2010+BTS+胸膜疾病指南：成人单侧胸腔积液的诊治

Investigation of a unilateral pleural effusion in adults: British Thoracic Society pleural disease guideline 2010 Clare Hooper,1 Y C Gary Lee,2 Nick Maskell,3 on behalf of the BTS Pleural Guideline Group INTRODUCTION Pleural effusions are a common medical problem with more than 50 recognised causes including disease local to the pleura or underlying lung, systemic conditions, organ dysfunction and drugs.1 Pleural effusions occur as a result of increased fluid formation and/or reduced fluid resorption. The precise pathophysiology of fluid accumulation varies according to underlying aetiologies. As the differential diagnosis for a unilateral pleural effu- sion is wide, a systematic approach to investigation is necessary. The aim is to establish a diagnosis swiftly while minimising unnecessary invasive investigations and facilitating treatment, avoiding the need for repeated therapeutic aspirations when possible. Since the 2003 guideline, several clinically rele- vant studies have been published, allowing new recommendations regarding image guidance of pleural procedures with clear benefits to patient comfort and safety, optimum pleural fluid sampling and processing and the particular value of thor- acoscopic pleural biopsies. This guideline also includes a review of recent evidence for the use of new biomarkers including N-terminal pro-brain natriuretic peptide (NT-proBNP), mesothelin and surrogate markers of tuberculous pleuritis. CLINICAL ASSESSMENT AND HISTORY < Aspiration should not be performed for bilateral effusions in a clinical setting strongly suggestive of a transudate unless there are atypical features or they fail to respond to therapy. (U) < An accurate drug history should be taken during clinical assessment. (U) The history and physical examination of a patient with a pleural effusion may guide the clinician as to whether the effusion is a transudate or an exudate. This critical distinction narrows the differential diagnosis and directs further investigation. Clinical assessment alone is often capable of identifying transudative effusions. Therefore, in an appropriate clinical setting such as left ventricular failure with a confirmatory chest x-ray, such effusions do not need to be sampled unless there are atypical features or they fail to respond to treatment. Approximately 75% of patients with pulmonary embolism and pleural effusion have a history of pleuritic pain. These effusions tend to occupy less than one-third of the hemithorax and the dyspnoea is often out of proportion to the size of the effu- sion.2 3 As tests on the pleural fluid are unhelpful in diagnosing pulmonary embolism, a high index of suspicion is required to avoid missing the diagnosis. The patient’s drug history is also important. Although uncommon, a number of medications have been reported to cause exudative pleural effusions (box 1). Useful resources for more detailed information include the British National Formulary and the web site http://www.pneumotox.com/. An occupational history including details about known or suspected asbestos exposure and poten- tial secondary exposure via parents or spouses should be documented. An algorithm for the iinvestigation of a unilateral pleural effusion is shown in figure 1. INITIAL DIAGNOSTIC IMAGING Plain radiography < Posteroanterior (PA) chest x-rays should be performed in the assessment of suspected pleural effusion. (U) The plain chest radiographic features of pleural effusion are usually characteristic. The poster- oanterior (PA) chest x-ray is abnormal in the pres- ence of about 200 ml of pleural fluid. However, only 50 ml of pleural fluid can produce detectable posterior costophrenic angle blunting on a lateral chest x-ray.4 In the intensive care setting, most chest x-rays are performed as AP supine examinations, resulting in free pleural fluid lying posteriorly in the depen- dent portion of the chest. Consequently, effusions are seen as an increase in hemithorax opacity with preserved vascular shadows on the supine x-ray. Other signs include the loss of the sharp silhouette of the ipsilateral hemidiaphragm and fluid tracking Box 1 Commonly prescribed drugs known to cause pleural effusions (over 100 cases reported globally) < Methotrexate < Amiodarone < Phenytoin < Nitrofurantoin < b-blockers Source: http://www.pneumotox.com (2009) 1Southmead Hospital, Bristol, UK 2Lung Institute of Western Australia, University Dept Med, Perth, Western Australia, Australia 3Department of Clinical Sciences, Southmead Hospital, University of Bristol, Bristol, UK Correspondence to Nick Maskell, Academic Respiratory Unit, Department of Clinical Sciences, Southmead Hospital, University of Bristol, BS10 5NB; nick.maskell@bristol.ac.uk Received 12 February 2010 Accepted 4 March 2010 ii4 Thorax 2010;65(Suppl 2):ii4eii17. doi:10.1136/thx.2010.136978 BTS guidelines down into the oblique or horizontal fissures resulting in apparent fissural thickening. The volume of pleural fluid is commonly underestimated on a supine chest x-ray and ‘normal’ appearances do not exclude the presence of an effusion.5 Subpulmonic effusions occur when pleural fluid accumulates between the diaphragmatic surface of the lung and the diaphragm. They are often transudates, can be difficult to diagnose on the PA film and may require an ultrasound scan. The PA film will often show a lateral peaking of an apparently raised hemidiaphragm which has a steep lateral slope with a gradual medial slope (see figure 2). The lateral x-ray may have a flat appearance of the posterior aspect of the hemidiaphragm with a steep downward slope at the major fissure.6 Ultrasound < Bedside ultrasound guidance significantly increases the likelihood of successful pleural fluid aspiration and reduces the risk of organ puncture. (B) < Ultrasound detects pleural fluid septations with greater sensitivity than CT. (C) Ultrasound guidance improves the rate of successful pleural aspiration. Several studies have shown that fluid can be successfully obtained using ultrasound in up to 88% of patients after a failed clinical and plain chest x-ray-guided attempt.7e9 Ultrasound guidance reduces the incidence of iatrogenic pneumothorax following thoracentesis and several studies have shown this effect to be independent of the size of the effusion.10 11 This benefit appears to be lost when the ‘X marks the spot’ method is employed, presumably due to differences in patient positioning between the ultrasound and the procedure.12 Clinical judgement with review of the chest x-ray was compared with ultrasonography in planning the diagnostic aspiration site in a prospective study including 255 clinician assessments of 67 patients.4 The sensitivity and specificity of clinical judgement compared with the gold standard of ultra- sound was 76.6% and 60.3%, respectively. Ultrasound increased Figure 1 Diagnostic algorithm for the investigation of a unilateral pleural effusion. History, clinical examination & CXR Does the clinical picture suggest a transudate? e.g. LVF, hypoalbuminaemia, dialysis Has the fluid analysis and clinical features given a diagnosis? Refer to a chest physician Is it a transudate? Resolved? STOP Diagnostic algorithm for the investigation of a unilateral pleural effusion Treat appropriately YES NO NO YES NO YES Cause found? NO Re-consider treatable conditions such as PE, TB, chronic heart failure and lymphoma. Watchful waiting often appropriate. NO Treat the cause YES Treat the cause YES Pleural aspiration (with ultrasound guidance) Send for: cytology, protein, LDH, pH Gram stain, culture and sensitivity. (Additional tests if warranted - see text box) NO Request contrast enhanced CT thorax. Treat appropriately Consider LA thoracoscopy or surgical VATS Consider radiological guided pleural biopsy +/- chest tube drainage if symptomatic Thorax 2010;65(Suppl 2):ii4eii17. doi:10.1136/thx.2010.136978 ii5 BTS guidelines the number of accurate sites by 26%; 15% of clinically deter- mined sites would have resulted in the puncture of liver, spleen or lung and, although there was increasing risk with small or loculated effusions, 60% of potential organ punctures occurred in radiologically large or moderate effusions. Ultrasound is superior to plain radiography in diagnosing and quantifying pleural effusions and distinguishes pleural fluid from thickening with high specificity, particularly when colour Doppler is employed.13e16 It is particularly useful in the diag- nosis of small effusions or in recumbent patients (eg, ventilated and critically ill) due to the low sensitivity of plain radiography in these situations. The diagnostic role of thoracic ultrasound in the early inves- tigation of pleural effusions extends beyond the identification and safe aspiration of fluid. Ultrasound detects septations within pleural fluid with greater sensitivity than CT scanning.17 A septated appearance may be observed in malignant effusions or pleural infection and occurs with similar frequency in the two diagnoses.18 Ultrasound positively identifies exudative effusions when pleural fluid is complex, septated or echogenic, although simple (anechoic) effusions can be exudates or transudates.19 Ultrasound features can distinguish malignant from benign effusions. Qureshi et al demonstrated 95% specificity for a malignant diagnosis, 95% for parietal pleural thickening >1 cm, 100% for visceral pleural thickening, 95% for diaphrag- matic thickening >7 mm and 100% for diaphragmatic nodules as visualised on ultrasound examination.20 Overall sensitivity of ultrasound in the differentiation of malignant from benign effusions was 79% (95% CI 61% to 91%) and specificity of 100% (95% CI 82% to 100%), with specificity comparing favourably with CT scanning (89%). PLEURAL ASPIRATION < A diagnostic pleural fluid sample should be aspirated with a fine-bore (21G) needle and a 50 ml syringe. (U) < Bedside ultrasound guidance improves the success rate and reduces complications (including pneumothorax) and is therefore recommended for diagnostic aspira- tions. (B) < Pleural fluid should always be sent for protein, lactate dehydrogenase, Gram stain, cytology and microbiolog- ical culture. (C) This is the primary means of evaluating pleural fluid and its findings are used to guide further investigation. Pleural ultrasound should be used at the bedside to select a pleural aspiration site with safety. Ultrasound increases the chances of successful aspiration and minimises the need for repeated attempts.21 Direct ultrasound-guided aspiration or ultrasound at the bedside immediately before the procedure is preferable to the ‘X marks the spot’ approach. A lateral site is preferred, provided that adequate fluid is demonstrated here on ultrasound as the risk of intercostal vessel trauma increases with more posterior or medial punctures (see figure 3). Patient consent and further technical details of pleural aspiration are covered in the guideline on pleural procedures. Table 1 shows sample collection guidance for specific pleural fluid tests. A green needle (21G) and 50 ml syringe are adequate for diag- nostic pleural aspirations. If there is diagnostic suspicion of pleural infection and a pleural fluid pH is to be measured, aspi- rated fluid should immediately be drawn into a heparinised blood gas syringe which should then be capped while awaiting analysis to avoid exposure of the fluid to the air. The remaining sample should be divided between sample pots for microbiological (5 ml), biochemical (2e5 ml) and cytological (remaining sample which should be 20e40 ml) analysis. Microscopic examination of Gram- stained pleural fluid sediment is necessary for all pleural fluid samples. If infection is suspected, some of the pleural fluid should be sent in blood culture bottles which increases diagnostic accuracy, particularly for anaerobic organisms.22 Figure 2 Chest x-ray showing a moderate left pleural effusion and subpulmonic effusion on the right (a). Note the lateral peaking of the right hemidiaphragm. Reproduced with permission from Professor David Milne, Auckland University. Figure 3 CT scan (A) before and (B) 2 days later after a pleural aspiration with inappropriate medial approach and intercostal artery puncture with resultant haemothorax requiring surgical intervention. Note the active bleeding indicated by the arrow. ii6 Thorax 2010;65(Suppl 2):ii4eii17. doi:10.1136/thx.2010.136978 BTS guidelines There is conflicting evidence regarding the optimum volume of pleural fluid for diagnosis of malignancy; sensitivity depends on the cellularity of the sample and processing technique as well as volume submitted.23 24 It is sensible to send as large a volume as possible from the 50e60 ml sample obtained following diag- nostic aspiration as other tests only require small volumes. At room temperature the sample for cytology should be sent to the laboratory as quickly as possible but, if a delay is anticipated, the specimen can be refrigerated at 48C for up to 14 days with no deterioration in the diagnostic yield for malignancy (table 1).25 Appearance < The appearance of the pleural fluid and any odour should be recorded. (U) < A pleural fluid haematocrit is helpful in the diagnosis of haemothorax. (U) Table 2 summarises the appearance of pleural effusions due to specific causes. Fluid may appear serous, blood-tinged, frankly bloody or purulent. Centrifuging turbid or milky pleural fluid will distinguish between empyema and lipid effusions. If the supernatant is clear, the turbid fluid was due to cell debris and empyema is likely while, if it is still turbid, chylothorax or pseudochylothorax are likely.26 The unpleasant smell of anaer- obic infection may guide antibiotic choices and the smell of ammonia suggests urinothorax. Grossly bloody pleural fluid is usually due to malignancy, pulmonary embolus with infarction, trauma, benign asbestos pleural effusions or post-cardiac injury syndrome.27 28 A haemothorax can be distinguished from other blood-stained effusions by performing a haematocrit on the pleural fluid. A pleural fluid haematocrit >50% of the patient’s peripheral blood haematocrit is diagnostic of a haemothorax.29 Differentiating between a pleural fluid exudate and transudate < Light’s criteria should be used to distinguish between a pleural fluid exudate and transudate (box 2). (B) < In order to apply Light’s criteria, the total protein and lactate dehydrogenase (LDH) should be measured in both blood and pleural fluid. (B) Categorisation of pleural effusions into transudates and exudates is an important early step in narrowing the differential diagnosis and directing subsequent investigations and manage- ment (see boxes 3 and 4). Classically, pleural fluid protein >30 g/l has indicated an exudate and <30 g/l a transudate. This classification is not accurate when serum protein is abnormal or when the pleural fluid protein is close to 30 g/l and, as this is very common, the application of Light’s criteria is always recommended.30 A considerable number of other biochemical markers have been compared with Light’s criteria but the latter, with a diagnostic Table 1 Pleural fluid tests and sample collection guidance Test Notes Recommended tests for all sampled pleural effusions Biochemistry: LDH and protein 2e5 ml in plain container or serum blood collection tube depending on local policy. Blood should be sent simultaneously to biochemistry for total protein and LDH so that Light’s criteria can be applied Microscopy and culture (MC and S) 5 ml in plain container. If pleural infection is particularly suspected, a further 5 ml in both anaerobic and aerobic blood culture bottles should be sent Cytological examination and differential cell count Maximum volume from remaining available sample in a plain universal container. Refrigerate if delay in processing anticipated (eg, out of hours) Other tests sent only in selected cases as described in the text pH In non-purulent effusions when pleural infection is suspected. 0.5e1 ml drawn up into a heparinised blood gas syringe immediately after aspiration. The syringe should be capped to avoid exposure to air. Processed using a ward arterial blood gas machine Glucose Occasionally useful in diagnosis of rheumatoid effusion. 1e2 ml in fluoride oxalate tube sent to biochemistry Acid-fast bacilli and TB culture When there is clinical suspicion of TB pleuritis. Request with MC and S. 5 ml sample in plain container Triglycerides and cholesterol To distinguish chylothorax from pseudochylothorax in milky effusions. Can usually be requested with routine biochemistry (LDH, protein) using the same sample Amylase Occasionally useful in suspected pancreatitis-related effusion. Can usually be requested with routine biochemistry Haematocrit Diagnosis of haemothorax. 1e2 ml sample in EDTA container sent to haematology LDH, lactate dehydrogenase; PH, pulmonary hypertension; TB, tuberculosis Box 2 Light’s criteria < Pleural fluid is an exudate if one or more of the following criteria are met: < Pleural fluid protein divided by serum protein is >0.5 < Pleural fluid lactate dehydrogenase (LDH) divided by serum LDH is >0.6 < Pleural fluid LDH >2/3 the upper limits of laboratory normal value for serum LDH. Box 3 Causes of pleural transudates Very common causes < Left ventricular failure < Liver cirrhosis Less common causes < Hypoalbuminaemia < Peritoneal dialysis < Hypothyroidism < Nephrotic syndrome < Mitral stenosis Rare causes < Constrictive pericarditis < Urinothorax < Meigs’ syndrome Table 2 Diagnostically useful pleural fluid characteristics Fluid Suspected disease Putrid odour Anaerobic empyema Food particles Oesophageal rupture Bile stained Cholothorax (biliary fistula) Milky Chylothorax/pseudochylothorax ‘Anchovy sauce’ like fluid Ruptured amoebic abscess Thorax 2010;65(Suppl 2):ii4eii17. doi:10.1136/thx.2010.136978 ii7 BTS guidelines accuracy of 93e96%, remains a robust method.31 32 This discrim- inatory accuracy is unlikely to be surpassed as the ‘gold standard’ for comparison in clinical diagnosiswhich itself carries an error rate. In congestive cardiac failure, diuretic therapy increases the concentration of protein, lactate dehydrogenase (LDH) and lipids in pleural fluid and, in this context, Light’s criteria are recognised to misclassify a significant proportion of effusions as exudates.33 34 Although the use of continuous likelihood ratios rather than a dichotomous division of transudates versus exudates has been proposed, particularly to overcome loss of accuracy of Light’s criteria when pleural protein and LDH levels are close to cut-off values, there is probably little value in this cumbersome statis- tical method beyond careful interpretation of test results in the light of clinical judgement.35 N-terminal pro-brain natriuretic peptide (NT-proBNP) NT-proBNP is a sensitive marker of both systolic and diastolic cardiac failure. Levels in blood and pleural fluid correlate closely and measurement of both has been shown in several series to be effective in discriminating transudates associated with conges- tive heart failure from other transudative or exudative causes.36e39 The cut-off value of these studies, however, varied widely from 600 to 4000 pg/ml (with 1500 pg/ml being most commonly used), and most studies excluded patients with more than one possible aetiology for their effusion. NT-proBNP has been shown to correctly diagnose congestive heart failure as a cause of most effusions that have been misclassified as exudates by Light’s criteria. Use of this test may therefore avoid repeated invasive investigations in patients where there is a strong clinical suspicion of cardiac failure.40e42 As results with pleural fluid and blood are comparable, applying the test to blood alone is sufficient (see evidence table A available on the BTS website at www.brit-thoracic.org.uk). Evidence for the use of measuring