Page 909 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

884 CHAPTER 5

VetBooks.ir 5.12 and potentially fatal haemorrhage after puncturing
failing livers in the presence of inadequate clotting
factors. Generations of veterinarians have graduated
with the view that liver biopsy is unjustifiably haz-
ardous and should be reserved for the most serious
and advanced cases, which probably perpetuates the
association of risk with the technique. However, the
hazards of liver biopsy are now widely recognised
to be minimal, especially when performed in the rel-
DUODENUM LIVER
atively early stages of disease (rather than in hepatic
insufficiency cases) and under ultrasound guidance.
As previously mentioned in this chapter, the dis-
tinction between liver disease and hepatic insuffi-
ciency is an important one for many reasons. Cases
COLON of hepatic insufficiency will inevitably have a poorer
prognosis than cases of liver disease without failure.
Therefore, the preferred time to investigate cases of
suspected liver disease is before they develop signs
of insufficiency. At this stage the risks of biopsy are
Fig. 5.12 The so-called ‘starry sky’ pattern of negligible. In this author’s experience of performing
multifocal hepatic echogenicity in a horse with no many hundreds of liver biopsies over two decades,
other evidence of liver disease. not one case of clinically detectable haemorrhage or
any other serious complication has arisen in horses
without evidence of hepatic failure. If presented with
In this author’s view, the primary usefulness of a case of hepatic insufficiency however, then caution
hepatic ultrasonography is to guide liver biopsy should be advised regarding the risks of the biopsy
rather than in providing useful clinical information procedure and consideration should be given to pro-
in itself. A suitable biopsy site is usually chosen based viding additional clotting factors with a fresh plasma
on thickness of imaged hepatic tissue, absence of transfusion pre-biopsy.
large blood vessels and, occasionally, focal presence There are four main different types of instrument
of hepatic tissue with an abnormal ultrasonographic suitable for collection of liver biopsies in horses. In
appearance. most cases a biopsy needle is used of which there
are three main types, comprising: a simple hand-
Liver biopsy operated ‘Tru-Cut’ type needle (Fig. 5.13); a semi-
Liver biopsy has great value in the management automatic spring-loaded needle; and the larger and
of equine liver disease to help establish diagno- more powerful biopsy-gun device into which a
sis, prognosis and to guide selection of appropriate simple needle can be inserted. These needle devices
therapy. Sometimes, but not always, causation can should be 14 gauge and preferably at least 10–15 cm
also be inferred from biopsy findings. Liver biopsy long. A fourth option consists of various laparo-
is a technique that has become far more popular scopic collection devices, but these are very rarely
in equine practice in recent years. The technique employed for this purpose.
was once reserved for cases of end-stage cirrhotic Liver biopsy should always be preceded by a
liver disease seen at specialist institutions. Even thorough ultrasonographic examination of the liver.
at the time of presentation such cases were gener- The widespread availability of diagnostic ultrasound
ally associated with short survival times due to the makes the ongoing use of unguided biopsy tech-
advanced stage of disease. The liver biopsy tech- niques highly questionable practice. Standard land-
nique itself gained a reputation for causing severe marks cannot be used to reliably identify a suitable