Achieving tissue diagnosis

A combination of increased use of diagnostic imaging and advances in therapeutic interventions means that obtaining tissue to aid diagnosis and cellular typing is now more essential than ever. Most diagnostic and interventional radiologists require core skills in biopsy. The vast majority of lesions can be biopsied with minimal risk. Determining a safe access route and accurate targeting requires a clear understanding of the principles of image guidance for intervention ( Ch. 25 ). The shortest, straightest route is usually the best approach but there are important exceptions to this rule, e.g. peripheral liver lesion. Take time to plan an approach that avoids important structures, e.g. bowel, lung, major vessels and the gallbladder.

To minimize complications, the patient should be fasted for abdominal biopsy and coagulopathy should be excluded. Make sure that the patient has given consent and that all parties are aware of the potential risks (and their consequences) of the procedure.

Pre-procedure

The aim of aspiration or biopsy is to obtain a satisfactory tissue specimen for cytology, biochemistry, microbiology or histology. Make sure that you are clear exactly what is required, any specific requirements for handling and where to send it. Ultrasound is used whenever possible as it allows real-time guidance without exposing you or the patient to ionizing radiation.

The patient

Fine-needle aspiration requires minimal preparation and local anaesthetic is rarely necessary. The vast majority of biopsies are performed under local anaesthesia and patient cooperation is essential. Explain what the procedure entails; in particular, stress the importance of breath-holding during the needle pass. If the patient does not understand or cannot cooperate, then stop now! Most biopsies are not painful; emphasize that analgesia is available if needed. Make sure that the patient is aware that regular post-biopsy observations are normal and do not indicate a problem.

Contraindications

Fine-needle aspiration usually does not require any pre-assessment of coagulation. Biopsy, particularly of vascular solid organs, will usually have a pre-intervention coagulation screen.

No additional precautions are necessary when the international normalized ratio (INR) is ≤1.5 and the platelet count ≥50,000.

When the clotting is more deranged, consider transfusion of fresh frozen plasma (FFP) ± platelets.

Alarm

Antiplatelet therapy (e.g. Clopidogrel) will increase the risk of bleeding, seek advice before discontinuing, especially in patients following recent coronary intervention. Always consider the risk–benefit for the individual patient.

Vascular lesion

Some tumours are highly vascular, e.g. renal cell tumour metastases. Switch on the colour Doppler if there is any doubt. If you need to biopsy a vascular lesion, make sure that the patient is adequately prepared. This may require large-bore IV access and cross-matched blood. Try to avoid the main tumoral vessels and be prepared to plug the biopsy tract and embolize the lesion if necessary.

Obstructed system

The target for biopsy is likely to be the point of obstruction, e.g. a pancreatic mass, consequently fistula or intra-abdominal leakage can occur. Consider draining the system before biopsy. Attempting drainage after a complication can be very difficult.

Uncooperative patient

Consider sedation or general anaesthesia.
Remember that a sedated patient will not be able to breath-hold.

Diagnosis irrelevant to management

Do not be persuaded to do the biopsy just because it would ‘be nice to know’.

Which specimen – cytology or histology

There are two sampling techniques: aspiration cytology and cutting needle biopsy. The local pathology service will guide you on the type of specimen they require. Usually only a few cells are needed to diagnose malignancy but a core of tissue is needed to subtype tumours or assess diffuse liver/renal pathology.

Fine-needle aspiration biopsy

Aspiration cytology, sometimes referred to as fine-needle aspiration cytology (FNAC), is performed with a 21G or 22G needle. The specimen contains only a few cells, but for many conditions, this will establish the diagnosis. The risks involved are very small; FNAC is frequently possible even in hazardous areas.

FNAC is frequently used for neck lesions and nearly always using ultrasound guidance. Ask the laboratory for help if you are uncertain how to handle the specimen, e.g. to make a smear on a slide.

Cutting needle biopsy

Cutting needle biopsy obtains a larger specimen, typically a 1-mm core of 20-mm length for histological analysis.

Tip

Remember that with a fully automatic system, the biopsy is taken from the tissue 10–20 mm in front of the needle tip, depending on the size of the specimen notch.

Biopsy – specific sites

Liver

Liver biopsy is one of the most frequently requested interventional procedures, and it is usually one of the simplest to perform. Biopsies are either targeted to a focal lesion or random cores in diffuse liver disease. Non-targeted biopsies are usually taken from the right lobe. When there are multiple lesions, choose the most accessible.

When taking a biopsy of the right lobe of the liver, a lateral approach is usually chosen. The ribs can interfere with access; choose an approach which allows scanning parallel to the line of the ribs. Sometimes the needle has to be angled up or down to accommodate this.

Tip

To minimize the risk of haemorrhage when taking a biopsy of peripheral lesions, always make a tract that passes through 2–3 cm of normal liver before hitting the target ( Fig. 38.1 ).

Fig. 38.1, Direct biopsy of peripheral liver lesions.

Mild shoulder tip pain is not uncommon after liver biopsy and the patient should be warned that this may occur. The risks of biopsy are increased in the presence of biliary obstruction and ascites. Drainage is recommended before biopsy. In the presence of mildly deranged clotting, consider a plugged biopsy.

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