is selectively chosen to confirm, not refute, a hypothesis. The clinician only seeks or takes note of information that will confirm his/her diagnosis and does not seek or ignores information that will challenge it.
And finally, the disadvantage of relying entirely on pattern recognition to solve clinical problems means that should the clinician realise subsequently that his/her pattern recognition was incorrect, there is no logical intellectual framework to help reassess the patient. Thus, pattern‐based assessment of clinical cases can result at best in a speedy, correct, ‘good value’ diagnosis but at worst in wasted time and money and, sometimes, it endangers the patient’s life.
I’ll do bloods!
Routine diagnostic tests such as haematology, biochemistry and urinalysis can be enormously useful in progressing the understanding of a patient’s clinical condition. However, relying on blood tests (often called a minimum database) to give us more information about the patient before we form any assessment of possible diagnoses can be useful for disorders of some body systems but totally unhelpful for others.
Serious, even life‐threatening, disorders of the gut, brain, nerves, muscles, pancreas (in cats) and heart, for example, rarely cause significant changes in haematological and biochemical parameters that are measured on routine tests performed in practice. Over‐reliance on blood tests to steer us in the right clinical direction can also be problematical when the results do not clearly confirm a diagnosis. The veterinarian can waste much time and the client’s money searching without much direction for clues as to what is wrong with the patient. And of course, the financial implications of non‐discriminatory blood testing can be considerable, and many clients are unable or unwilling to pay for comprehensive testing. Using blood testing to ‘screen’ for diagnoses can be misleading, as the sensitivity and specificity of any test are very much influenced by the precision of the test and the prevalence of a disorder in the population.
For experienced veterinarians, pattern recognition combined with ‘fishing expeditions’ (i.e. ‘I have no idea what’s going on so I’ll just do bloods and hopefully something will come up!’) can result in a successful diagnostic or therapeutic outcome in many medical cases in first‐opinion practice. However, there are always cases that do not yield their secrets so readily using these approaches, and it is these cases that frustrate veterinarians, prolong animal suffering, impair communication, damage the trust relationship with clients and on the whole make veterinary practice less pleasant than it should be.
You also have to know about and remember lots of diagnoses for this approach to be effective. This is problematical if the veterinarian does not recognise or remember potential diagnoses (e.g. for Brutus) or if, as discussed previously, the pattern of clinical signs doesn’t suggest many feasible differentials (e.g. for Erroll). It is also less useful for inexperienced veterinarians or veterinarians returning to practice after a career break or changing their area of practice.
It is for all of these reasons that we hope this book will enhance your problem‐solving skills as well as build your knowledge base about key pathophysiological principles. We want to assist you to develop a framework for a structured approach to clinical problems that is easy to remember, robust and can be applied in principle to a wide range of clinical problems. The formal term for this is problem‐based inductive clinical reasoning.
Problem‐based inductive clinical reasoning
In problem‐based inductive clinical reasoning, each significant clinicopathological problem is assessed in a structured way before being related to the other problems that the patient may present with. Using this approach, the pathophysiological basis and key questions (see the following sections) for the most specific clinical signs the patient is exhibiting are considered before a pattern is sought. This ensures that one’s mind remains more open to other diagnostic possibilities than what might appear to be initially the most obvious and thus helps prevent pattern‐based tunnel vision.
If there are multiple clinical signs – for example, vomiting, polydipsia and a pulse deficit – each problem is considered separately and then in relation to the other problems to determine if there is a disorder (or disorders) that could explain all of the clinical signs present. In this way, the clinician should be able to easily assess the potential differentials for each problem and then relate them rather than trying to remember every disease process that could cause that pattern of particular signs. It is important that the signalment of the patient is seen as a risk factor, but this should not blind the clinician to potential diagnoses beyond what is common for that age, breed and sex.
Thus, we do look for patterns but not until we have put in place an intellectual framework that helps prevent tunnel vision too early in the diagnostic process.
Figure 2.2 shows the steps in the clinical reasoning flow. As each step is explained you will see the numbered keys to help you understand where you are in the diagnostic process. We use these steps, their colours and numbered keys throughout the book to help ‘anchor’ the process for you through the repetition shown in Figure 2.1. Colour bars or shading are also used to identify introductory concepts (blue), diagnostic approach and steps (brown) and key introductory and summary points (purple).
Figure 2.2 Clinical reasoning step‐by‐step.
Essential components of problem‐based clinical reasoning
The problem list
The initial step in logical clinical problem‐solving is to clarify and articulate the clinical problems the patient has presented with. This is best achieved by constructing a problem list – either in your head or, in more complex cases, on paper or the computer.
For example, for Erroll the problem list in the order the problems are reported would be:
1 Vomiting
2 Anorexia
3 Depression
4 Dysuria and haematuria.
Why is constructing a problem list helpful?
It helps make the clinical signs explicit to our current level of understanding.
It transforms the vague to the more specific.
It helps the clinician determine which are the key clinical problems (‘hard findings’) and which are the ‘background noise’ (‘soft findings’) that may inform the assessment of the key problems but do not require specific assessment.
And most importantly, it helps prevent overlooking less obvious but nevertheless crucial clinical signs.
Prioritising the problems
Having identified the presenting problems, you then need to assign them some sort of priority on the basis of their specific nature.
For example, anorexia, depression and lethargy are all fairly non‐specific clinical problems that do not suggest involvement of any particular body system and can be clinical signs associated with a vast number of disease processes.
However, clinical signs such as vomiting, polydipsia/polyuria,