Page 411 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

386 CHAPTER 1

VetBooks.ir 1.758 1.759

Fig. 1.758 Ultrasound images from the left and Fig. 1.759 A skeletal muscle biopsy being collected
right hindlimbs of the caudal stifle region muscles. from the semimembranosus muscle by an open
Note the left hindlimb image (left) has an irregular approach.
hyperechoic scar within a generally more hyperechoic
muscle belly compared with the right hindlimb (right).
This is a healed muscle injury in the left hindlimb.
(Photo courtesy Graham Munroe)

scintigraphic examination for the investigation of Muscle biopsy procedure:
gait abnormalities or poor performance. Diffuse
uptake in the gluteal or semimembranosus muscles 1 Horses are usually sedated prior to biopsy collection.
is often seen in horses with exertional rhabdomyoly- 2 The area is clipped and aseptically prepared.
sis that have exercised recently. While this may be 3 5–10 ml of local anaesthetic (mepivicaine) is
significant, other lesions should not be overlooked infiltrated subcutaneously along a vertical line at
as this may be a coincidental finding in a horse with the biopsy site.
another lesion. The findings should therefore be 4 A blade is used to incise through the skin and
interpreted with regard to the clinical history and subcutaneous tissue down to the surface of the
other diagnostic findings. muscle. Retractors can be helpful at this point to
improve visualisation.
Muscle biopsy 5 Two parallel vertical incisions 1 cm apart and
Histopathology of skeletal muscle biopsy samples 2 cm long are made into the underlying muscle.
provides useful information regarding the under- 6 The area under the muscle, between the
lying disease process. This is frequently necessary incisions, is undermined using haemostats.
to make a specific diagnosis in the horse with an 7 The top and bottom of the elevated piece of
underlying myopathy, and may also provide infor- muscle is then sharply incised while holding a
mation regarding the severity of the underlying corner securely with haemostats.
muscle damage and, therefore, the prognosis. Open 8 The muscle specimen should be divided into two
incisional biopsies are usually collected (Fig. 1.759). equal portions, one placed in formal saline and
In the horse with exertional rhabdomyolysis (see the other into an empty sterile pot, and placed
below) biopsies are collected from the semimembra- on ice packs.
nosus or gluteal muscles. In the case of focal clinical 9 The subcutaneous tissue is closed using a
signs, biopsy of the affected muscle would be more continuous suture pattern and dissolvable suture
appropriate. material such as 0 Vicryl.
10 Staples are placed in the overlying skin.