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ABDOMINAL ULTRASOUND
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:
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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:
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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.
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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 needle’s 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.