Diagnostic Techniques in Equine Medicine. A textbook for students and practitioners describing diagnostic techniques applicable to the adult horse PDF
Preview Diagnostic Techniques in Equine Medicine. A textbook for students and practitioners describing diagnostic techniques applicable to the adult horse
Dedication To my wife Sabine and our children Anna, James and Max, for their forbearance during the preparation of this book. Frank Taylor Commissioning Editor: Robert Edwards Development Editor: Nicola Lally Project Manager: Emma Riley and K Anand Kumar Designer/Design Direction: Charles Gray Illustration Manager: Bruce Hogarth Illustrator: Samantha Elmhurst First edition © WB Saunders Company Ltd 1997 Second edition © 2010, Elsevier Limited. All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permissions may be sought directly from Elsevier’s Rights Department: phone: (+1) 215 239 3804 (US) or (+44) 1865 843830 (UK); fax: (+44) 1865 853333; e-mail: [email protected]. You may also complete your request online via the Elsevier website at http://www.elsevier.com/permissions. ISBN 978-0-7020-2792-5 British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library Library of Congress Cataloging in Publication Data A catalog record for this book is available from the Library of Congress Notice Knowledge and best practice in this field are constantly changing. As new research and experience broaden our knowledge, changes in practice, treatment and drug therapy may become necessary or appropriate. Readers are advised to check the most current information provided (i) on procedures featured or (ii) by the manufacturer of each product to be administered, to verify the recommended dose or formula, the method and duration of administration, and contraindications. It is the responsibility of the practitioner, relying on their own experience and knowledge of the patient, to make diagnoses, to determine dosages and the best treatment for each individual patient, and to take all appropriate safety precautions. To the fullest extent of the law, neither the Publisher nor the Editors assumes any liability for any injury and/or damage to persons or property arising out of or related to any use of the material contained in this book. The Publisher The Working together to grow publisher’s libraries in developing countries policy is to use paper manufactured from sustainable forests www.elsevier.com | www.bookaid.org | www.sabre.org Printed in China CONSULTING AUTHORS Chapter 1: Submission of laboratory samples and Dr Grant S Frazer BVSc MS DipACT interpretation of results Associate Professor of Theriogenology & Reproductive Professor Sidney Ricketts LVO BSc BVSc DESM DipECEIM Medicine, Department of Veterinary Clinical Sciences, FRCPath FRCVS College of Veterinary Medicine, The Ohio State University, Rossdale & Partners, Beaufort Cottage Laboratories, High Columbus, Ohio, USA Street, Newmarket, Suffolk, UK Chapter 8: Blood disorders Chapter 2: Alimentary diseases Professor Michelle Barton DVM PhD DipACVM Professor Anthony T Blikslager DVM PhD DipACVS Department of Large Animal Medicine, University of Equine Surgery & Gastrointestinal Biology, North Carolina Georgia, Athens, Georgia, USA State University, Raleigh, North Carolina, USA Chapter 9: Cardiovascular diseases Chapter 3: Chronic wasting Dr Lesley E Young BVSc PhD DipECEIM DVC MRCVS Kristopher J Hughes BVSc FACVSc DipECEIM MRCVS Specialist Equine Cardiology Services, Ousden, Newmarket, Professor Sandy Love BVMS PhD MRCVS Suffolk, UK Division of Companion Animal Sciences, Faculty of Veterinary Medicine, University of Glasgow, Glasgow, UK Chapter 10: Lymphatic diseases Amanda M House DVM DACVIM Chapter 4: Liver diseases Assistant Professor, Large Animal Clinical Sciences, Mr Andrew Durham BSc BVSc CertEP DEIM DipECEIM MRCVS University of Florida College of Veterinary Medicine, Gainesville, Florida, USA The Liphook Equine Hospital, Forest Mere, Liphook, Hants, UK Chapter 11: Fluid, electrolyte and acid–base balance Chapter 5: Endocrine diseases Dr Louise Southwood Professor Philip J Johnson BVSc MS DipACVIM Assistant Professor, Emergency Medicine & Critical Care, School of Veterinary Medicine, New Bolton Center, DipECEIM MRCVS Philadelphia, Pennsylvania, USA Professor of Equine Internal Medicine, Department of Veterinary Medicine & Surgery, College of Veterinary Medicine, University of Missouri, Columbia, Missouri, USA Chapter 12: Respiratory diseases Dr TS Mair BVSc PhD DipECEIM DEIM DESTS MRCVS Chapter 6: Urinary diseases Bell Equine Veterinary Clinic, Mereworth, Maidstone, Kent, Professor Thomas J Divers DVM DipACVIM DipACVECC UK Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York, USA Chapter 13: Musculoskeletal diseases Professor ARS Barr MA VetMB PhD DVR CertSAO DEO Chapter 7: Genital diseases, fertility and pregnancy DipECVS MRCVS Dr Carlos RF Pinto Med.Vet PhD DipACT Department of Clinical Veterinary Science, University of Bristol, Langford House, Langford, North Somerset, UK Associate Professor of Theriogenology & Reproductive Medicine, Department of Veterinary Clinical Sciences, College of Veterinary Medicine, The Ohio State University, Columbus, Ohio, USA Consulting authors Chapter 14: Neurological diseases Chapter 18: Post-mortem examination Philip AS Ivens MA VetMB Cert EM (Int Med) MRCVS Dr Frank GR Taylor BVSc PhD MRCVS Richard J Piercy VetMB MA DipACVIM MRCVS Head of the School of Clinical Veterinary Science, University Comparative Neuromuscular Diseases Laboratory, The Royal of Bristol, Langford House, Langford, North Somerset, UK Veterinary College, Hawkshead Lane, North Mymms, Hatfield, Herts, UK Chapter 19: Sudden and unexpected death Dr Frank GR Taylor BVSc PhD MRCVS Chapter 15: Ocular diseases Head of the School of Clinical Veterinary Science, University Dennis E Brooks DVM PhD DipACVO of Bristol, Langford House, Langford, North Somerset, UK Professor of Ophthalmology, University of Florida, Dr Tim J Brazil BVSc PhD CertEM (Int Med) DECEIM MRCVS Gainesville, Florida, USA Equine Medicine on the Move, Moreton-in-Marsh, Gloucestershire, UK Chapter 16: Fat diseases Professor Michel Levy DVM DipACVIM Associate Professor, Large Animal Internal Medicine, School of Veterinary Medicine, Purdue University, West Lafayette, Indiana, USA Chapter 17: Skin diseases Hilary Jackson BVM&S DVD DipACVD Dermatology Referral Service, Glasgow, Lanarkshire, UK viii PREFACE Diagnosis is fundamental to the appropriate treat- We have tried to ensure that the instructions are ment and wellbeing of the equine patient. Despite sufficiently detailed to allow completion of a proce- the many excellent clinical texts that are available, dure by following the text. Where appropriate, the few seem to explain in sufficiently precise terms advantages and disadvantages of a technique receive which clinicopathological tests are appropriate or brief comment, together with a guide to the inter- how particular techniques should be performed. pretation of results. For the purpose of practicality The first edition of this book was designed to provide the techniques are again grouped by chapter on an an illustrated practical guide to the various diagnos- organ system basis. In addition, a number of chap- tic techniques employed in equine medicine. This ters have appendices that indicate applications of second edition is an update by international experts the described techniques to a given set of clinical in the field. Once again, it predominantly covers the circumstances such as anaemia, polyuria/polydip- adult horse and is intended for students, recent sia, nasal discharge, etc. The importance of recogniz- graduates and those veterinarians who do not spe- ing clinical signs is paramount and these are given cialize in equine work and may therefore be unfa- when relevant. miliar with some of the diagnostic approaches. We hope that this book will prove useful to prac- Some of the more specialized techniques made pos- titioners, and beneficial to their patients. sible by recent advances, notably ultrasound, are now available to practitioners and figure more Bristol 2009 FGR Taylor prominently in this edition. TJ Brazil MH Hillyer 1 CHAPTER Submission of laboratory samples and interpretation of results Chapter contents I. Submission of laboratory samples 1 Serum enzymes 17 Choice of test 2 Bile acids 19 Suitability of the sample for the Cardiac troponin (cTnI) 19 intended test 2 Blood urea and creatinine 19 Haematology samples 3 Blood glucose 19 Biochemistry samples 4 Serum bilirubin 19 Urine samples 6 Electrolytes 19 Faecal samples 7 Triglycerides 21 Microbiology samples 7 Serum biochemistry profiles 21 Cytopathology samples 8 Interpretation of endocrinological test results 21 Histopathology samples 8 Pregnancy tests 21 Information that should accompany the Cryptorchidism 22 sample 8 Thyroid function 23 Packaging for postal or other delivery 8 Pituitary function 23 Interpretation of urine analysis results 23 II. Interpretation of results 10 Interpretation of parasitological test results 23 Laboratory reference ranges 10 Faecal worm egg counts 23 Interpretation of haematological results 11 Erythrocyte parameters 11 Further reading 24 Leukocyte parameters 12 Plasma fibrinogen concentration 14 APPENDIX 1.1 25 Interpretation of blood biochemical results 14 Haematological and biochemical reference ranges for Serum proteins 14 adult non-Thoroughbred horses I. SUBMISSION OF LABORATORY assist in the systematic deduction of a diagnosis. SAMPLES Laboratory investigations are no substitute for a thorough consideration of the history and clinical Clinical pathology should be used to help narrow a examination; they are complementary in that they differential diagnosis, to confirm a diagnosis or to provide further information. However, laboratory Diagnostic techniques in equine medicine screening may play a part in preventive medicine can be applied to the different organ systems of the and performance assessment programmes. horse. From these guidelines the clinician must Routine clinicopathological investigations select the laboratory tests most likely to confirm or include the following: refute a diagnosis based upon the history and clini- • Haematology cal examination. A batch of ill-chosen tests will • Biochemistry of serum/plasma or other fluids provide little or no information at considerable • Endocrinology expense. If in any doubt, test selection should be discussed with a clinical pathologist by telephone. • Parasitology Communication between clinician and clinical • Microbiology pathologist will only enhance the end result of the • Cytopathology investigation. • Histopathology. Many practices have or are developing their own Suitability of the sample for the laboratory facilities but in many cases it will be intended test necessary to forward samples to a more specialized equine clinical pathology laboratory. One of the An adequate sample volume must be collected into major limitations to test quality is the suitability of an appropriate container and submitted to the labo- the sample that is received by the laboratory. Before ratory as quickly as possible. Commercial laborato- submitting material, several factors should be ries recommend 5 ml anticoagulated samples for considered: haematological analyses and 10 ml clotted blood • The choice of test samples for biochemical analyses. Blood samples • The suitability of the sample for the intended that are haemolysed or lipaemic are unsuitable for test analysis and those taken from dehydrated horses • The information that should accompany the must be interpreted carefully, as haematological and sample serum biochemical parameters may be raised for • The suitability of packaging for postal or other that reason alone. delivery. Table 1.1 shows the samples and containers that are appropriate to particular tests, but the specific requirements of individual laboratories should be Choice of test checked. Some will supply their own preferred con- Tests must be relevant to and provide information tainers, packaging and labels on request. Two blood about the implicated organ system or the clinical collection systems are currently in common veteri- presentation. One of the purposes of this book is to nary use: the Vacutainer (Becton Dickinson) and the indicate the range of clinicopathological tests that Monovette (Sarstedt) systems (Fig. 1.1 (Plate 1)), Table 1.1 The two most commonly used blood sampling systems for equine clinical pathology sampling Test Anticoagulant Monovette (Sarstedt) Vacutainer (BD) Haematology EDTA 4.5 ml (blue) 10 ml (mauve) Serum biochemistry, endocrinology None or clot separation 9 ml (brown) 10 ml (red) beads or gel Clotting function/plasma fibrinogen Sodium citrate 3 ml (green) 4.5 ml (blue) Glucose Fluoride oxalate 5.5 ml (yellow) 4.5 ml (grey) Plasma biochemistry, endocrinology Lithium heparin 9 ml (orange) 10 ml (green) 2 1 Diagnostic techniques in equine medicine Submission of laboratory samples and interpretation of results should be the one submitted for haematological examination, in order to minimize the effect of splenic contraction. If the horse is clearly excited or has recently been exercised, this should be noted on the request form to the laboratory. Blood tubes should be filled to capacity and gently mixed by several inversions. If a needle and syringe are used to collect blood, the following precautions must be observed: • Blood must not be kept in the syringe for more than 90 seconds, otherwise clots form • The needle must be removed from the syringe before transferring blood into the sample tube, Figure 1.1 (Plate 1 in colour plate section) Various tubes suitable for collecting specific blood samples from horses otherwise haemolysis may occur (see Table 1.1). (Left) Becton Dickinson’s Vacutainers. (Right) • The sample tube must be filled to the indicated Sarstedt’s Monovettes. line to maintain the working concentration of EDTA. An increased concentration causes with individual clinicians and laboratories having changes in red cell size and inaccurate results, their own preferences. whereas a decrease predisposes clot formation • The blood must be mixed with the Haematology samples anticoagulant by immediate, gentle inversion. The most suitable anticoagulant for haematological Haematology samples are best processed immedi- investigations is ethylenediamine tetra-acetic acid ately but for short-term storage the tube should be (EDTA). Heparin may cause ‘clumping’ of leuko- kept cool. Refrigeration at 4°C is not recommended cytes and alter their staining properties. Plasma for equine blood samples. An air-dried smear should fibrinogen estimation can be undertaken using an be prepared soon after sampling, because prolonged EDTA sample, but only if the laboratory employs a contact with EDTA can alter cell morphology and heat precipitation technique. The more accurate leukocytes can become difficult to identify. The thrombin coagulation estimation requires blood to smear can be dispatched to the laboratory in the be submitted in sodium citrate anticoagulant. Blood unstained state, together with the parent blood coagulation studies (e.g. prothrombin time; partial sample. Special slide holders can be supplied for this thromboplastin time) require whole blood to be purpose (Fig. 1.2). However, in most cases well- submitted in sodium citrate. It is wise to collect packaged equine blood samples that have been care- blood samples into three tubes for general equine fully collected into EDTA and properly mixed will clinical pathology purposes: travel well for next-day delivery to the laboratory. • EDTA for haematological studies Most problems occur in hot weather and when samples are delayed for more than 24 hours in the • Sodium citrate for plasma fibrinogen estimation post. • Empty or clot separation bead tube for serum biochemical studies. Preparation of a blood smear If blood glucose estimation is required then an addi- tional sample should be collected into fluoride The glass slides used for smear preparation must be oxalate anticoagulant. scrupulously clean. Ideally, they should be stored in Blood samples should be collected at rest from spirit and wiped dry with a tissue before use. The the jugular vein. If possible, the horse should not be sample is well mixed by gentle inversion and a drop excited, but if this seems likely the first sample taken of blood is placed towards the end of a horizontal 3 Diagnostic techniques in equine medicine Figure 1.3 Preparing a blood smear. Biochemistry samples Samples submitted for biochemical and endocrino- logical testing may be of serum, plasma or other fluid. Figure 1.2 Polypropylene slide holders suitable for Serum is preferred by most laboratories for blood transporting blood smears. biochemical and endocrinological testing and is essential for certain tests such as serological tests (anti- body titration), protein electrophoresis and equine slide by pipette. The short edge of a second slide is chorionic gonadotrophin (eCG) testing. Although a used as a spreader and is placed in front of the drop perceived advantage of plasma is that it is easily sepa- of blood at an angle of about 40° (Fig. 1.3). It is rated from whole blood by standing or centrifuging first drawn gently backwards to make contact with prior to dispatch, it is unsuitable for some electrolyte the drop, which is immediately distributed along and enzyme estimations and does not store satisfacto- the spreading edge by capillary action. Once evenly rily. Always send a clotted blood sample if possible. distributed along this edge, the blood is then Where plasma is acceptable, the blood should be col- smeared along the length of the slide by a single, lected into lithium heparin anticoagulant. Common steady, forward movement of the spreader. The pre- container requirements are shown in Table 1.2. pared smear is then dried quickly by waving it Whether clotted or heparinized samples are used, rapidly in air. The slide can be identified by writing the serum or plasma should be separated from the across the frosted end or the centre of the dried clot or red cells as soon as possible to avoid interac- smear with a pencil; this will not interfere with sub- tions between the two. Haemolysis may interfere sequent staining or the differential count. with the measurement of enzymes, electrolytes and The technique of smear preparation is easily minerals. Haemolysis can be minimized by using acquired but requires a little practice. Poor smears clean dry equipment, avoiding perivascular blood are produced by one or more of the following sampling and not traumatizing the sample during mistakes: or after collection. Whole blood samples sent by • Using dirty slides and/or a chipped spreader post during extremes of hot or cold weather are • Using a drop of blood that is too large particularly prone to haemolysis. • Using a spreader angle that is insufficiently acute Serum separation • Using a forward movement that is too fast An optimal serum yield can be obtained by collect- • Using a slow, jerky forward movement. ing blood into a plain Monovette or Vacutainer tube, 4 1 Diagnostic techniques in equine medicine Submission of laboratory samples and interpretation of results Table 1.2 Appropriate samples and containers for clinicopathological tests Test Sample Container/medium Haematology Blood count ± differential Whole blood EDTA Plasma fibrinogen Labs vary: Whole blood (heat precipitation) EDTA or heparin Plasma (thrombin coagulation) Sodium citrate Coagulation tests PT/PTT Whole blood Sodium citrate Blood enzymes Most enzymes Labs vary: Serum usually preferred Plain glass Plasma possible Heparin Glutathione peroxidase Whole blood Heparin LDH Serum Plain glass Blood electrolytes Serum electrolytes Serum preferred Plain glass Plasma electrolytes possible Heparin Other biochemistry Urea Serum (preferred) or plasma Plain glass or heparin Creatinine Serum (preferred) or plasma Plain glass or heparin Total protein Serum Plain glass Albumin (and globulin) Serum Plain glass Protein electrophoresis Serum Plain glass Glucose Plasma Oxalate–fluoride Total bilirubin Serum (preferred) or plasma Plain glass or heparin Total serum bile acids Serum Plain glass Serum triglycerides Serum Plain glass Blood hormones Cortisol Serum (preferred) or plasma Plain glass or heparin Thyroxine Serum (preferred) or plasma Plain glass or heparin Triiodothyronine Serum (preferred) or plasma Plain glass or heparin Progesterone Serum (preferred) or plasma Plain glass or heparin Testosterone Serum (preferred) or plasma Plain glass or heparin Oestradiol Serum (preferred) or plasma Plain glass or heparin Oestrone sulphate Serum (preferred) or plasma Plain glass or heparin eCG Serum Plain glass Continued 5
The list of books you might like
