Percutaneous biopsy, thoracic

A coagulation defect is a contraindication to the procedure. Other relative contraindications include inability to withstand a pneumothorax, an uncooperative patient, pulmonary arterial hypertension and severe emphysema.

Biopsy is performed using a variety of needles which fall broadly into two categories: aspiration or screw needles which provide material for cytology, and cutting needles which produce a core of material for histological examination. Needles must be narrow (gauge 19-21 for cytology and 18 for histology) but with a relatively large lumen, sharp enough to transfix small lesions and rigid enough that they are not deflected en route through the lung. Cutting needle biopsies are used increasingly when it is considered likely that a histological rather than cytological diagnosis is required. They are most safely deployed when the lesion lies in the outer third of the lung. Prior to the procedure the position of the lesion should be ascertained from frontal and lateral chest radiographs and, if necessary, preliminary CT scans. The patient should be aware of potential complications and give informed consent. The patient is usually placed either supine or prone and made as comfortable as possible to minimize movement. It is important that the patient understands the importance of quiet breathing to reduce movement, especially of small lesions. Biopsy should be performed with the shortest distance between skin and lesion and avoiding fissures whenever possible. Using CT the site for needle insertion is selected using a skin marker and preliminary scans. Local anaesthetic is then introduced down to, but not through, the pleura, care being taken to avoid producing a pneumothorax, following which the patient is rescanned with the anaesthetic needle in place to check position and alignment. The biopsy needle is introduced to a depth previously determined from the CT images and the position of the needle tip checked by imaging with either contiguous thin slices or a short spiral sequences (Fig.1). When the correct position is confirmed samples are taken and processed for cytopathology. Repeated samples are taken until the operator is confident that diagnostic specimens have been obtained following which a single scan is performed to check for a postbiopsy pneumothorax. A further radiograph 4 hours later is recommended to check for a delayed pneumothorax. Some radiologists prefer to use a coaxial technique whereby the biopsy needle is introduced repeatedly through an outer needle positioned with its tip adjacent to the lesion. This technique minimizes the number of times the pleura is transgressed and is particularly useful when biopsying a small or relatively inaccessible lesion. Fluoroscopic biopsy has the advantage of visualizing the needle tip in real time and being quicker. It is often the preferred method for larger and more peripheral lesions.

The most common complications are pneumothorax [CH]  and haemoptysis. A pneumothorax occurs in 10–26% of cases and approximately 5–10% require chest tube drainage. Haemoptysis occurs in approximately 5% of cases and is usually minor and self-limiting. The likelihood and severity of both complications increases in line with the difficulty and length of the procedure, the experience of the operator and the needle gauge. Rarer complications include air embolism, haemothorax [CH] , bronchopleural fistula [CH]  and cardiac tamponade. Radiologists performing percutaneous lung biopsy should be prepared for complications and have appropriate equipment at hand.

Percutaneous biopsy of a pleural lesion is performed to obtain a tissue diagnosis of a pleural mass or pleural thickening, whether focal or diffuse. Unguided pleural biopsy may be performed using an Abrams or Cope needle. For patients with radiological evidence of a focal pleural mass or of focal or diffuse pleural thickening, which may or may not be associated with a pleural effusion, image guided percutaneous biopsy is the preferred diagnostic technique. Focal masses may be accurately targeted using either ultrasound or CT, whereas diffuse pleural thickening is best biopsied using CT guidance (Fig.2). Aspiration of any pleural fluid at the time of biopsy should be performed for cytology as this further increases the success of the procedure.The use of CT and ultrasound enables accurate localization of the area of concern and determines the safest route for biopsy. Core biopsies are obtained for histological analysis as the differentiation of benign and malignant lesions may be difficult. Automated cutting biopsy needles of 18 - 20 Gauge are used.

The technique is similar to that described for percutaneous biopsy of a focal lung lesion. It is important that the needle takes a relatively shallow course, parallel with the chest wall along the plane of the pleura and just above the adjacent rib, care being taken to avoid the neurovascular bundle.

Percutaneous biopsy of a mediastinal lesion is performed as an alternative to surgical biopsy in order to obtain a tissue diagnosis of a mass within the mediastinum. The technique is usually performed using CT guidance; the administration of intravenous contrast medium enables accurate localization of the mass in relation to the great vessels and heart and also displays the internal mammary arteries which may be close to the needle route. Biopsy of anterior mediastinal masses may also be performed under ultrasound guidance. Whenever possible a lung-free approach should be used. Whilst fine needle biopsy, providing a cytological specimen, is satisfactory if a carcinoma is suspected, cutting biopsies, providing histological specimens, are required for accurate diagnosis of other mediastinal masses such as lymphoma, thymoma or mediastinal neurogenic neoplasm. The contraindications and complications are similar to those of percutaneous biopsy of a focal lung lesion.

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