Page 910 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Liver disease 885

VetBooks.ir 5.13 5.14

RISC13

NEEDLE

LIVER

COLON

Fig. 5.13 A liver biopsy being collected using a hand- Fig. 5.14 Ultrasonographic image showing the
operated Tru-Cut needle. biopsy needle within the liver during the biopsy
procedure.

biopsy site on the right or left sides of the horse. If is important to facilitate introduction and operation
evidence of focal or multifocal disease is encoun- of the biopsy needle. The needle is then inserted
tered ultrasonographically, then these areas can be to a predetermined depth and angle based on the
targeted. If no evidence of abnormality is seen then ultrasonographic image. In most cases the needle
a biopsy site (or sites) can be chosen based on the will be introduced to between 4 and 6 cm deep to
size of the hepatic target and absence of perceived the skin surface to ensure penetration of the super-
hazards, such as large blood vessels. It is custom- ficial surface of the liver without emerging from the
ary to biopsy from the right side of the horse due deep surface. Where possible, slight cranial angula-
to generally a larger imageable hepatic mass on tion of the biopsy needle will allow a deeper target
that side, although this is not always the case. Left- of hepatic tissue (Fig. 5.14), but this will frequently
sided biopsies are easily collected with ultrasound cause misfiring of spring-loaded biopsy needles that
guidance but perhaps require more confidence and are best used at an exact perpendicular angle to the
experience, given the close proximity of the left skin surface. The biopsy can be collected under real
ventricle. When the biopsy site(s) has been chosen, time ultrasound guidance or, more simply, based on
clipping and sterile preparation should then be per- measurements of depth and angle taken from the
formed and the horse pre-medicated with a suitable still ultrasound image at the site of biopsy. When the
sedative (generally an alpha-2-antagonist plus butor- biopsy needle is in the desired position, it is activated
phanol). It is this author’s practice to administer a (manually or automatically depending on type) to
single dose of a non-steroidal anti-inflammatory cut the biopsy before withdrawal. Even with perfect
drug (NSAID) to minimise possible post-biopsy placement it is not necessarily always the case that the
discomfort that is commonly reported in people, biopsy specimen completely fills the biopsy cham-
although it is extremely unusual to see clinical signs ber of the device and so multiple biopsies are often
of such in horses. Desensitisation of the skin at the required, and are in fact desirable to increase the
biopsy site(s) with 5 ml local anaesthetic solution likelihood of a representative biopsy. A single 1–2 cm
(e.g. lidocaine or mepivacaine) should be performed, long biopsy specimen collected with a 14-gauge nee-
but deeper infiltration of the intercostal muscle dle is likely to contain between 5 and 10 portal tracts.
and parietal peritoneum is unnecessary. A small A minimum of 10 portal tracts is generally advised in
stab incision in the skin (#11 or #15 scalpel blade) order to gain a reasonably representative impression