ULTRASOUND GUIDED BIOPSY
Category: Diagnostic Radiology
Abstract : ULTRASOUND-GUIDED BIOPSY: Percutaneous biopsy of organs, masses or focal visceral lesions is an integral part of the diagnostic process for a large number of patients. Although changes on ultrasound may confirm the suspected clinical suspicion, that is, a bright liver may indicate fatty change, a nodular liver may suggest cirrhosis or enlarged kidneys of increased echogenicity may suggest glome
ULTRASOUND-GUIDED BIOPSY:
Percutaneous biopsy of organs, masses or focal visceral lesions is an integral part of the diagnostic process for a large number of patients.
Although changes on ultrasound may confirm the suspected clinical suspicion, that is, a bright liver may indicate fatty change, a nodular liver may suggest cirrhosis or enlarged kidneys of increased echogenicity may suggest glomerulonephritis, imaging alone is not enough and a definitive histological diagnosis is required.
The advantages of using ultrasound to guide such procedures are numerous:
● The needle tip is directed, in real time, along the biopsy path and visualized within the lesion.
● Greater precision is obtained; needle guidance is essential for all small lesions and lesions at depth.
● Fewer needle passes are required to obtain the desired result.
● The best route can be utilized and vital structures, such as blood vessels, avoided.
● Postprocedure complications, such as haematoma, are minimized.
● Confidence in the biopsy result, particularly a negative one, is increased due to direct visualization of the needle tip in the lesion.
● All the advantages of ultrasound over other imaging methods apply (quick, direct vision, no radiation hazard, low cost). The limitations due to bone and air-filled structures also apply.
● The capability to perform bedside procedures for critically ill patients and to use in conjunction with other imaging techniques, for example fluoroscopy, is advantageous.
With ultrasound the biopsy procedure is quick, safe and accurate and is therefore acceptable to the patient. There are several accepted methods of performing a guided biopsy, but certain generic rules are common to the procedure, regardless of the organ under investigation:
● A written request form from a medical practitioner with the results of any previous investigations should be available. The reason for biopsy should be appropriate.
● Assessment of blood clotting status. Normally the prothrombin time should be within 3 s of the control, platelet count > 75 000/ml and international normalized ratio (INR) < 1.3.
● Identification of possible contraindications to biopsy, for example an uncooperative patient, coagulopathy.
● Careful explanation of the procedure to the patient, including risks and benefits.
● Informed, written consent for the procedure.
● Procedure should be performed in a quiet and clean environment. Appropriate measures should be taken to preserve pre-, peri- and postprocedure sterility.
● A prebiopsy scan to identify a suitable biopsy route avoiding vital structures.
● Satisfactory care of the patient both during and after the biopsy procedure with relevant observations of vital signs. A pulse oximeter and appropriate nurse cover are now recommended.
● Appropriate preparation of the specimen.
● Contraindications are relative and include the biopsy pathway, an uncooperative patient and uncorrectable coagulation and should be assessed on an individual basis.
Analgesia
For the vast majority of biopsy procedures local anaesthetic is administered following localization of the biopsy site on ultrasound. Either 1% or 2% lidocaine (lignocaine) is commonly used; the volume will depend upon patient build, depth of lesion and patient anxiety. Normally a short period of time, commonly 4 - 5 min, is allowed to pass so that the anaesthetic can work, after which a small scalpel incision is made in the skin to facilitate the biopsy needles introduction, with little or no discomfort to the patient. In cases of, for example, simple aspiration with a 22-gauge needle or smaller, local anaesthetic is normally unnecessary. Patients who are particularly apprehensive may require preprocedure medication with a sedative such as diazepam or similar anxiolytic agent; however this is not common.
Very occasionally intravenous analgesia and/or sedation may be required during the procedure; it is often a good idea to have an intravenous cannula in situ prior to biopsy. The use of a general anaesthetic for children is common practice, to enable the procedure to be carried out quickly and accurately while the child remains still.
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