Pleural Biopsy

Many diseases may cause an accumulation of fluid in the pleural space. Pleural effusion is a major diagnostic problem, since the pleural cavity is an inner cavity with no direct access.^[1] Pleural biopsy is carried out where pleural fluid aspiration (thoracocentesis) and other investigations have not revealed the cause of a pleural effusion. It is only necessary where pleural fluid has been shown to be exudate, rather than transudate (pleural total protein/serum total protein ratio >0.5). The procedure was historically used in around 40% of suspected malignant pleural effusions.^[2] Biopsies taken from a random area of pleura have a relatively low diagnostic yield. The yield was increased by taking multiple samples of pleura and/or using CT-guided cutting-needle biopsy to detect specific abnormal areas, particularly for malignancy.^{[3, 4]} Closed blind pleural biopsy is now not recommended because the yield is much better with image-guided pleural biopsy or thoracoscopy.^[5] It appears that a single sample is usually sufficient to diagnose tuberculous disease.^[2]

Indications

Exudative pleural effusion with uncertain diagnosis after thoracocentesis and pleural fluid analysis.

• Suspected pleural malignancy including metastatic lung cancer, mesothelioma, leukaemia, lymphoma. (If mesothelioma is the suspected diagnosis, it may be better to use open or thoracoscopic biopsy.)
• Suspected tuberculous pleural effusion - pleural biopsy is the only reliable method of diagnosing this condition due to low yield of pleural fluid staining/culture.^[6]
• Sarcoidosis - with relevant clinical features and associated biochemistry, the presence of non-caseating granulomata with negative pleural tissue culture can suggest/confirm this diagnosis.
• Systemic lupus erythematosus (SLE) - the use of immunofluorescent staining can diagnose de novo or drug-induced lupus.

Contra-indications

• Dry tap on insertion of needle/low volume pleural effusion.
• Underlying empyema.
• Significant coagulopathy/uncorrected anticoagulation (anticoagulated patients should come off warfarin and receive heparin, discontinued for a few hours either side of biopsy).
• Very anxious/unco-operative subject.

Equipment

The procedure is usually conducted with a special needle that has a hook, aperture and a central closing core that snags a piece of parietal pleura. The two types of needle used are the Abrams' needle or Cope's needle.

The procedure

• Firstly, explain the procedure in full to the patient and obtain written consent, documenting that the major complications of the procedure (see below) have been discussed and understood.
• Check that the coagulation screen and platelet count have been checked recently and are normal. Ensure there is no allergy to local anaesthetic agents.
• Check the position of effusion by percussion and checking CXR.
• Adequate local anaesthesia of the skin, rib periosteum and parietal pleura is essential, as the procedure can be very painful if this is not done correctly. Use up to 8 ml of 2% lidocaine and be sure to infiltrate the relevant structures fully and allow time for the local anaesthetic to act. Use aseptic technique and avoid passing the needle on the underside of the ribs to prevent damaging the neurovascular bundle.
• Sit the patient upright and leaning forwards with arms well supported on a pillow, usually resting on a table or similar structure.
• Make a large enough incision in the skin to admit the biopsy needle easily. Incise subcutaneous tissue. Check again the position of effusion by percussion and checking CXR. Pass the needle (connected to a 50 ml syringe) over the top of the lower rib into the pleural space. Confirm the position by withdrawing a small quantity of pleural fluid.
• On entering the pleural space (as confirmed by 'give' of reduced resistance on entering it), if using Abrams' needle, open side hole by twisting and slightly withdrawing the central cannula. If using a Cope needle then remove the stylet and inner needle together while the patient exhales and makes an 'ooh' sound, to reduce the risk of air entering the pleural space.
• Carefully withdraw the needle, angling it so that the side aperture snags the pleura. The inner cannula is then pushed forward and twisted to obtain a sample. Avoid pointing the aperture upwards as there is a risk of damaging the neurovascular bundle.
• Ask the patient to breathe out (exhale) and say 'ooh' as the needle is withdrawn.
• Remove the sample from the biopsy needle, using a small hypodermic needle to 'snag' it out, and place samples for histology in 10% formalin, and those for culture/immunofluorescence in saline.
• It is not necessary to take more than one sample for suspected tuberculosis (TB). When more are taken this is done by positioning a needle at 3, 6, 7 and 9 o'clock.^[4] Such multiple samples are now not recommended.^[5]
• When the procedure is finished, clean the area and apply a pressure bandage to mop up any leakage and reduce chance of aspiration of air into the pleural cavity.

Post-procedure care

• Give simple analgesia for any pain and examine the chest to ensure there is no evidence of pneumothorax.
• Post-procedure CXR may be used if there is reason to suspect a pneumothorax or other complication. Some recommend routine use of CXR after the procedure.
• Advise the patient to seek medical advice if any severe pain, dyspnoea or bleeding.

Analysis of biopsy

Send for histology, acid-fast bacillus (AFB) and fungal cultures and consider sending a sample for immunofluorescence if there is suspicion of SLE. Electron microscopy may be used if there is a possible diagnosis of mesothelioma.

Possible complications

• Haemorrhage with haemothorax occurs very rarely but poor technique may complicate damage to the neurovascular bundle. Patients with thrombocytopenia or renal failure are particularly at risk of haemorrhage.
• Empyema due to subsequent infection is possible but rare.
• Pneumothorax may happen if the needle is inserted too deeply, puncturing the lung. It is more likely if a small effusion is present. Usually it self-corrects without the need for a chest drain. However, such cases should be carefully monitored. Air can enter the pleural cavity during introduction/withdrawal of a needle, but this is rarely significant. Typically, it may be noticed if the needle is withdrawn during inspiration and the patient notices sudden pain. Small amounts of air often enter during the procedure, causing a 'slurping' or 'sucking' sound. This is not usually problematic and spontaneously resorbs.
• Tumour seeding may occur but doesn't usually affect the outcome (because any lung tumour is already metastatic if it involves pleura). However, it occurs relatively commonly with mesothelioma and can be a distressing and painful complication. Again, if mesothelioma is the suspected diagnosis, it may be better to use open or thoracoscopic biopsy.
• Extravasation of pleural fluid can occur through the incision and cause wetting of the dressing or spilling of fluid. Patients need to know that this may occur and that they may have to change their dressing if it is wet. Occasionally fluid can track through tissue planes, causing skin swelling over the chest, abdominal wall and genitalia (particularly if there is a very large effusion under pressure). Drawing off of effusion fluid after biopsy may be worthwhile for such large effusions, to prevent or ameliorate this complication.