pulmonary tissue sampling

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BY Dr. Ayman El Deeb Tissue Sampling

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Lung biopsy is a relatively frequently  performed procedure with considerable benefit for patient management but it may on rare occasions result in the death of the patient.

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Types of lung biopsies Lung biopsies may be classified according to the Method of access (percutaneous- bronchoscope- open operation). Reason for biopsy (sampling of diffuse lung disease or obtaining tissue from a mass). According to the tissue obtained (cytological or histological).

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Percutaneous transthoracic lung biopsy (PTLB) It is performed with imaging guidance usually to diagnose a defined mass. Imaging modalities are Fluoroscope- Computed tomography and ultrasound. Bronchoscopic biopsy For proximal endobronchial lesions small bites are obtained under vision. For more peripheral lesions biopsy imaging guidance may be used such as the C arm.

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Open Lung Biopsy. Provide large samples of tissue with improved accuracy, the morbidity and length of stay are greater than the other two methods of biopsy.

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There is probably a tendency to under report patient death. Sinner in 1975 reported no deaths in his series of 5300 biopsies. Berquist et al reported 2 deaths in 430 procedures, a rate of .47% Richardson et al had a morality rate of 0.15%. P.T.L.B

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Causes of death:- It is an early event the causes include:- Massive hemoptysis in 0.25-5% Pulmonary haemarrhage in 5-16.9% Air embolism. Large hemothorax in 1.5%.

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Morbidity: Pneumothorax is the most common complication. It occurs in 0-61% of lung biopsies- 15% of them will require a chest tube. The risk of pneumothorax increases if the lesion is deep and not related to the chest wall.

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Other complications such as tumor seeding along the needle tract, cardiac tamponade, chest infection pneumonia and empyema are all reported. Patients are at risk from drugs taken during the procedure.

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Indications for lung biopsy PTLB is indicated in the following New or enlarging solitary nodule or mass which is unlikely to be accessible by bronchoscopy.

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Multiple nodules in a patient not known to have malignancy

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persistent focal infiltrates single or multiple for which no diagnosis has been made.

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Hilar mass following –ve bronchoscopy

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Contraindications to lung biopsy:- The are relative contraindications and the balance of benefit against risk should be assessed before the procedure. Relative contraindications include platelet count less than 100.000/ml. Activated partial thromboplastin time (APTT) or (PT) ratio less than 1.4.

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Preoperative investigations. Pt, APTT, platelet count and pulmonary functions test. Recent chest radiographs and CT scans CT should preferably be performed before bronchoscopy Repeat the imaging in case of any significant change in the patient’s clinical condition.

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Consent. Written information should be given to all patients Informed consent should be obtained in a written form all patients.

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Expected accuracy of sampling False positive less than 1% Adequacy of sample 90% Sensitivity for malignancy should be in the range of 85-90% in lesions over 2cm.

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The biopsy procedure Sedation:- The cooperation of the patients is very important. Particularly in suspending respiration during sampling, so all biopsies should be performed without sedation. Adequate explanation to the patients and adequate local anesthesia is mandatory. An oral anxiolytic drug may be helpful

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Type of the needle used when deciding to use FNAB or CNB it is important to be aware of the technique as well as its complication. FNAB has an accuracy of up to 95% for malignant lesions but the yield for benign lesions is lower (10-50%). Several recent studies have found the diagnostic yield for malignancy with CNB to be lower than FNA (Charig and Philips) found the diagnostic accuracy of CNB to be similar to FNAB with on site cytopathologist.

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The false negative results for malignancy may be due to a variety of factors including. The patient’s inability to cooperate Overlying bone which may contribute to missing the lesion completely Obtaining only necrotic tissue Sampling pneumonitis distal to the obstructing lesion. False +ve rate of 0.8% have been reported with FNAB but no false +ve cases have been reported with CNB.

Biopsy technique : 

Biopsy technique The pt. is asked to lie prone or supine according to the site of the lesion and its proximity to the operator Pre biopsy imaging to locate the site of the lesion and to determine the best cut for the biopsy. The best cut is determined by the light line and is marked using a marker

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The site of needle entry is chosen by measuring the distance from a bony land mark to the site of the lesion also the safe depth of the needle advancement is measured on the computer of the CT machine. So the best site of the needle entry is marked. The skin entry site should be sterilized and the cutaneous and subcutaneous tissue infiltrated with lignocaine up to a maximum dose of 20ml of a 2% solution

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The pleura should not anaesthetised directly as this increase the risk of pneumothorax before the biopsy. You leave the needle in place and you take an image. Then you proceed taking the biopsy The number of passes of the needle has not been defined. Most operators perform at least two.

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The presence of on site cytologist may reduce the number of passes required. Post biopsy x ray should be done one hour after the procedure.

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Complication:- pneumothorax- pulmonary hemorrhage or hemoptysis and air embolism.

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Management of complications Pneumothorax if it is detected the options include. Observation Aspiration Drain insertion (usually required in 3.3-15% patients Hemorrhage. With or without hemoptysis x ray will help to identify eumothorax or pleural collection.

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Hemoptysis. Is usually self limiting, the pt. is placed in the lateral position with the biopsed side lower down, this is usually adequate but if massive hemoptysis occurs Resuscitation and O2 should be administered. Endobronchial intubation or rigid bronchoscopy is considered to protect the other lung.

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Air embolism. It is usually fatal when gas passes into the coronary or cerebral circulation on removal of the needle. Presentation may be with cardiac on neurological signs and symptoms:- chest pains-circulatory collapse-generalized seizures or focal neurological defects.

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Treatment is to administer 100% O2 anticonvulsants where necessary. To put the patient in the trendlenburg position and on the left lateral decubitus position in cases of residual gas in the left heart Steroids and aspirin are also recommended hyperbaric O2 therapy was successful in a case report. (Shepard JO intervent radiol, 1994)

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Precut lung biopsy can be performed safely High risk patients should not have biopsy Post biopsy x ray one hour after the procedure. Recommendations

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