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ABDOMINAL ULTRASOUND
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Figure 11.9 (A) CT-guided biopsy of a pancreatic head mass. The tip of the biopsy needle (arrow) is positioned in the
periphery of the lesion so that when the biopsy is taken a good core of tissue is obtained. Note the artifact from the
needle tip. (B) CT-guided bioposy of a retroperitoneal lymph node mass (arrowheads). The mass lies adjacent to the
aorta (arrow); however this is protected from the needle by the angle of approach and its relationship to the vertebral
body. CT is the preferred biopsy method of choice for deep structures within the retroperitoneum.
performed in the majority of centres under ultrasound
guidance. Contraindications to biopsy
include hydronephrosis, which may be more
appropriately treated with catheterization or
nephrostomy, or small kidneys, that is < 8 cm longitudinal
axis (these appearances being indicative
of chronic renal impairment). Kidneys > 9 cm can
potentially be biopsied; however other factors,
including cortical thickness, age, clinical history
and the requirement for definitive diagnosis will
all have a bearing on whether biopsy is performed
or not. Hydronephrosis and kidney size are easily
assessable with a prebiopsy scan.
In most cases the biopsy is performed with the
patient prone over a small bolster to maximize
access to the kidney. The shortest route, avoiding
adjacent structures, is selected; subcostally, traversing
the cortex of the lower pole and avoiding the
collecting system and major vessels is recommended.
With ultrasound guidance, either kidney
may be chosen and accessibility will vary between
patients. The depth of penetration and angle of
approach are carefully assessed. Biopsy is normally
with a 16G needle.
The patient’s cooperation is required with suspending
respiration at the crucial moment. This
avoids undue damage to the kidney as the needle is
introduced through the capsule. The needle
should be positioned just within the capsule prior
to biopsy so that the maximum amount of cortical
tissue is obtained for analysis, as the throw of the
needle may be up to 2 cm.
Renal transplant biopsy
Biopsy is a valuable tool in the postoperative management
of the transplant patient (Chapter 7),
enabling the cause of graft dysfunction to be identified,
in particular differentiating acute tubular
necrosis from acute rejection. Ultrasound guidance
is essential in order to reduce complications such as
haematoma, vascular damage (which may result in
arteriovenous fistula or pseudoaneurysm formation)
and laceration of the renal collecting system.
A single-pass technique, using the spring-loaded
biopsy gun with a 16-gauge needle, is usually
sufficient for histological purposes; however
two passes are often required so that electron
microscopy and immunofluorescence can also be
perfomed. The procedure is well tolerated by the
patient and the complication rate low, at less
than 5%. 3