EQUINE CLINICAL PATHOLOGY - Rossdale & Partners

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T h e B e a u f o r t c o t t a g e l a b o r a t o r i e s biopsy sampling Skin Biopsy These are best obtained by full-thickness wedge incision. While skin punch biopsy techniques may be simpler to obtain, they are seldom as rewarding to examine. Tissues obtained should be fixed immediately in 10% formol saline. Lump biopsy Biopsy is recommended for masses that appear in or under the skin and sometimes for deeper masses that may be palpated or imaged by ultrasound or laparoscopic examination. If a total lesion resection is not possible, as is the case for many skin and subcutaneous masses, representative biopsies are best obtained by full-thickness wedge incision, and fixed immediately in 10% formol saline. Liver Biopsy Liver biopsy is recommended where serum biochemical examinations have suggested hepatic pathology. With the horse restrained standing, ideally in stocks, the liver on the right side of the horse is examined with ultrasound to determine the ideal site for puncture and to detect signs of gross pathology, e.g. choleliths or Echinococcus spp. cysts. Biopsies are best obtained with a 6' 'Trucut' biopsy needle inserted between the 14th and 15th ribs, on the right side of the horse, along a straight line drawn between the point of the hip and the shoulder, or elsewhere, if suggested by ultrasound examination. Specific lesion biopsies are best obtained by ultrasound guidance. The tissue sample should be carefully removed from the needle and fixed in 10% formol saline. The needle channel should then be carefully swabbed for bacterial culture. Lung Biopsy Lung biopsy may be indicated where there is clear ultrasonic evidence of pulmonary pathology. As biopsy of a lung abscess or focus of infection is contraindicated, evidence should suggest neoplasia or focal non-septic pathology before biopsy is attempted. Pulmonary neoplasia is very rare in horses so lung biopsy is seldom indicated. Needles specifically designed for lung biopsy should be used and the specific lesion to be biopsied should be imaged by ultrasound scan examination. The overlying intercostal skin site identified, infiltrated with local anaesthetic and clipped and prepared as for surgical intervention. With the transducer coupled in a sterile surgical glove and sterile coupling gel on its surface, the lung lesion is imaged and a lung biopsy device is introduced through the skin and into the lesion to collect the biopsy. The tissue sample is fixed in 10% formol saline without delay and the needle channel may, if required, be swabbed immediately for bacterial culture. 52
G u i d e t o e q u i n e c l i n i c a l p a t h o l o g y Kidney Biopsy Renal biopsy may be indicated where there is clinicopathological and ultrasonic evidence of kidney pathology. The technique is not without risk of injury to the horse and therefore should only be contemplated if clearly indicated and should only be performed with great care, using an ultrasound-guided technique. The right kidney is more easily accessible. Ultrasound scan examination is used to identify a suitable site, free from large blood vessels, in the posterior poles. The horse should be restrained, sedated in stocks. The skin over the kidney is clipped for imaging to identify the site for penetration, local anaesthesia is induced and the skin is then prepared as for surgical intervention. With the transducer coupled in a sterile surgical glove and sterile coupling gel on its surface, the kidney is imaged to find the ideal site for puncture. The biopsy needle is then introduced through the skin and into the renal parenchyma, sampling specific pathological features if visible. If biopsy of the left kidney is to be attempted, it is helpful for an assistant to palpate the kidney per rectum in order to stabilise it against the body wall, facilitating the ultrasound-guided biopsy technique. The tissue sample is fixed in 10% formol saline without delay and the needle channel may be swabbed immediately for bacterial culture. The horse should be stable-rested for at least 48 hours after biopsy and should be monitored for signs of ill health, particularly associated with renal haemorrhage. Endometrial Biopsy Endometrial biopsies are indicated for the routine investigation of barren mares and for the investigation of specific endometrial pathology. Ideally, they are more easily obtained and interpreted when the mare is in mid-dioestrus, but samples may be safely obtained at any stage of the oestrous cycle from any non-pregnant mare. Biopsies are obtained with special forceps (Kruuse UK or Rocket of London Ltd.), via the vagina and cervix. The mare is restrained as for routine gynaecological examinations with her tail bandaged, rectum evacuated of faeces, tail bandaged and perineum hygienically prepared. The mare is re-confirmed not pregnant. The sterile biopsy forceps are introduced into the mare’s vagina with a gloved hand, the cervix is identified (making sure that the urethral opening has not been accidentally entered) and the index finger is placed through the mare’s cervix into the uterine body. The forceps are then advanced along the index finger, as a guide, through the cervix and into the uterine body. The finger is then ‘hooked’ in the cervix, which may then be retracted caudally. This straightens the cervix and the uterine body, allows the biopsy forceps to fully enter the uterine body in a cranial direction and prevents 53
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EQUINE CLINICAL PATHOLOGY - Rossdale & Partners

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