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INTERVENTIONAL AND OTHER TECHNIQUES 269
PV
RPV
MPV
c(i)
c(ii)
Figure 11.15 cont’d (C) i, Before contrast injection, portal vein thrombosis is suspected in a patient with alcoholic
liver disease; ii, after injection, the main portal vein is confirmed as thrombosed. Forward flow is seen in the right
portal vein (presumably due to collateral circulation), and increased hepatic arterial flow is clearly demonstrated.
of life and an overall 5-year survival of 20–45%,
and up to 60% in unifocal disease. Without surgery
the 5-year survival in this patient group is effectively
zero. However, not all patients with liver
metastases are deemed suitable for resection, being
poor surgical risks or having lesions which are
either too large or affect too many hepatic segments.
Percutaneous ablation of liver tumours is
now a viable and rapidly developing option for
control of liver metastases, prolonging survival
time after initial diagnosis and, in some cases,
shrinking tumours to enable future curative resection.
Various methods have been investigated,
using ultrasound guidance.
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Alcohol injection has proved highly effective
for hepatocellular carcinoma (HCC), 32,33
shrinking tumours over a period of time and
causing necrosis within them, but has not
proved as effective for metastatic liver disease.
This is thought to reflect the fact that HCC is
a ‘soft’ tumour and so the alcohol can be
instilled effectively into the tumour whereas
metastases are ‘hard’ lesions and often the
alcohol seeps out of the lesion.
Radiofrequency (RF) thermal ablation and laser
ablation are also developing as minimally
invasive percutaneous therapeutic techniques
and are becoming increasingly popular.
Ablation of liver metastases using RF is a
recent method of ultrasound-guided therapy
for liver metastases and HCC in which RF,
applied to monopolar electrodes either
individually or with multiprobe arrays, is
guided into the lesion to be treated. RF tissue
ablation through an 18G needle uses fewer
probes than laser. It is an outpatient procedure:
1–4 sessions has been reported to achieve
complete necrosis of liver metastases in 67% of
lesions. 34 It is a simple, safe and potentially
effective treatment for liver metastases,
associated with a low rate of complications (in
one study only one small area of haemorrhage
was observed in 75 sessions) 35 together with a
significant rate of shrinking or stabilization of
the metastases.
ENDOSCOPIC ULTRASOUND
Some of the limitations of conventional ultrasonography
in biliary and pancreatic imaging can
be overcome by the use of endoscopic probes and
miniprobes. Endoscopic probes are either radial
or linear arrays which are incorporated into the
end of an endoscope. They have a frequency of
7.5–12 MHz and are used to image the pancreas,
biliary tract, portal vein and adjacent structures