Notes on Feline Internal Medicine

Kit Sturgess

• Publisher: Wiley-Blackwell
• Year: 2013
• Print ISBN:
  9780470671177
• eBook ISBN:
  9781118597729
• Edition: 2
• Topic: Medicine
• Subtopic: Veterinary Medicine

feline internal medicine

Helping you get started with a problem-solving approach to a sick cat.

feline internal medicine

kit sturgess

Notes on Feline Internal Medicine, second edition, is part of a popular series specifically designed, through an accessible note-based style, to ensure veterinarians and students have quick and easy access to comprehensive and practical clinical and diagnostic information.

Distinct differences exist between cats and dogs not only in their physiology and metabolism but also in the way disease tends to present. This book is a short 'pocket guide' to feline internal medicine helping you to formulate a diagnostic plan and therapeutic strategy. The focus is on evidence-based medicine where available, otherwise current best-practice is presented.

The book is divided into five sections:

• Section 1 gives an overview of some key areas of feline medicine including paediatric and geriatric medicine.
• Section 2 focuses on the approach to common presenting signs.
• Section 3 covers the differential diagnosis of commonly used haematologic and biochemical parameters.
• Section 4 presents an organ-system based approach.
• Section 5 covers feline infectious diseases.

CHANGES FOR THIS EDITION

• Stronger focus is placed on initial testing for a disease, and what changes might be expected.
• Additional sections have been added on sedation and anaesthesia, health screening, oncology and emergency and critical care.
• More diagrams have been added to aid understanding.
• Care has been taken to avoid repetition and focus on common conditions.

SECTION 1

KEY TOPICS IN FELINE MEDICINE

1.1 Health screening

1.2 Preventative medicine

1.3 Paediatrics

1.4 Gerontology

1.5 Supportive care – fluid therapy and analgesia

1.6 Sedation and anaesthesia

1.7 Emergency and critical care algorithms

1.1 HEALTH SCREENING

1.1.1 Introduction

• Performed to minimise anaesthetic risk and to maximise long-term health.
• Benefit of screening programmes is less clear.
• Clear planning and practice policy relating to which patients to screen, what to screen for and what to do with abnormal results.
• Understood and supported at all levels within the practice.
• Very little is published about health screening in cats and dogs.
• Current consensus opinion – some form of screening in some cats is appropriate so long as
  • The risk–benefit equation for the pet (of undertaking the test) and the owner (anxiety associated with the test and any abnormal parameters found) is taken into account.
  • The test results are available prior to anaesthesia.
  • The tests are selected individually.
  • An action plan is available should abnormal results be found.

Rationale

• Pre-anaesthetic screening determines whether the anaesthetic will be safe and/or whether modifications to the routine anaesthetic regime are required.
• Geriatric screening allows identification of sub-clinical disease and hence earlier management and improved outcome.

1.1.2 Which cats to screen and what screening tests to use

Options are as in Table 1.

Developing a screening plan

• All members of the practice need to be comfortable with the service that is offered.

Table 1 Patient and test selection for screening

Which patients?	Which tests?
*Recommend to all patients over a specific age Only screen patients prior to anaesthesia Only screen at owner's request Actively discourage screening and manage clinically significant disease as it occurs	All patients get the same screening Screening becomes more in-depth as the patient ages *Screening targeted based on historical information
*approach recommended by author

• Clear written guidelines should be available for all staff to follow.
• Clients need to be informed of
  • The existence of the plan.
  • What the plan offers – the pros and cons.
• Clear pricing of the various plans offered.
• Everyone must appreciate that screening can create anxiety for the owner if there are ‘abnormal' results.
• Clear ‘what if' guidelines should be developed:
  • Clients need to have any abnormalities discovered explained to them as to the significance and put into perspective.
  • If you measure a parameter such as blood urea you need to have developed a policy within the practice of an appropriate response if the result is abnormal.
  • Waiting is an acceptable response coupled with further screening at a time in the future; however, if the response is always to wait and rescreen and to do nothing interventional until the patient becomes unwell then what is the point of screening?
  • Changes in anaesthetic protocol should be defined and the costs involved made clear.

What tests to do?

• In the absence of evidence the ‘best' tests to do in an outwardly healthy individual with no significant previous history is unknown:
• Traditional – urea, ALT, TP, glucose (creatinine, ALK-P).
• Less traditional but potentially valuable for pre-anaesthetic screening – USG and dipstick, PCV, electrolytes (with ALT, TP, urea).

Less traditional but potentially valuable for geriatric screening – USG and dipstick, PCV, calcium, cholesterol, BP (with ALT, TP, urea).

1.1.3 Interpreting the test results and developing an action plan

• Tests should be as sensitive and specific (Box 1) as possible to avoid false-positive and false-negative results that could initiate unnecessary, more invasive, risky and expensive further investigation.

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Box 1 Sensitivity and specificity

Sensitivity = proportion of positives which are correctly identified, i.e. 258 abnormal livers of which 231 identified, therefore SENSITIVITY 231/258 = 90%.

Specificity = proportion of negatives which are correctly identified, i.e. 86 normal livers of which 54 identified, therefore SPECIFICITY 54/86 = 63%.

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What to do when …

…the protein is low

Action point

• Total protein is >5 g/l (albumin >3 g/l) below the reference range.

NB – Accurate measurement of albumin on in-house machines is difficult so a low albumin in the face of a normal total protein should be checked at an external laboratory.

• With large falls in proteins, three main causes are likely; urinary loss, GIT loss and failure of liver production.
• Less common causes of hypoalbuminaemia – see Section 3.15
• Elevated albumin levels are due to dehydration.
• Elevated globulin due to dehydration, immune or inflammatory response or neoplasia.

Response

• Pre-anaesthetic – elective procedures should be delayed and investigation undertaken.
• Geriatric screen – monitor or investigate potential cause depending on general health and other abnormalities documented.

…the urea (± creatinine) is high

See Section 3.7.

• Consider whether cause is likely to be pre-, intra- or post-renal in origin.
• Most cases are likely to be pre- or intra-renal.
• Urea/creatinine will not rise until 75% of renal mass is lost.
• All cases should have urinalysis performed.

Response

• Pre-anaesthetic – fluid therapy and maintenance of renal blood flow during anaesthesia are important.
• Geriatric screen – assign to an IRIS stage if intrinsic renal disease with appropriate adjunctive tests.

…the ALT/ALP is high

• Increased liver enzymes are more likely to be pathologic in cats (see Section 3.12).

Response

• Pre-anaesthetic – low–moderate increases are unlikely to affect anaesthetic risk unless there is evidence to support reduced liver function that could affect drug metabolism.

• Geriatric screen:
• Increases >200 iU should be monitored if the cat is healthy.
• Increases >500 iU should be investigated further even if the cat appears healthy.

…the PCV is low

• Mild anaemia is not uncommon especially in older cats; it is often a reflection of systemic disease elsewh...

Table of contents

• Cover
• Notes On
• Title Page
• Copyright
• Abbreviations
• Introduction
• Section 1: Key Topics in Feline Medicine
• Section 2: Clinical Signs
• Section 3: Common Abnormalities of Haematology, Biochemistry and Urinalysis
• Section 4: Organ Systems
• Section 5: Infectious Disease
• Further reading
• Index