and Spencer W. Beasley2
(1)
Department of Urology, Royal Children’s Hospital, Melbourne, Australia
(2)
Paediatric Surgery Department Otago, University Christchurch Hospital, Christchurch, New Zealand
Abstract
This chapter describes the logical principles behind physical diagnosis. What knowledge is needed and why does a problem-oriented approach work? Are these principles applicable to other branches of medicine? How can students learn these skills? The second half describes the specific steps in clinical examination: introduce yourself, gain rapport, take a history, make a preliminary diagnosis and predict historical clues and physical signs and do a goal-oriented examination.
Clinical diagnosis in any branch of medicine requires more finesse than knowing merely how to elicit physical signs. It is often a great mystery to medical students how an experienced doctor can reach a correct diagnosis with the minimum of history and examination while they may have spent an hour or more with the same patient to no avail. They may despair of ever attaining the same level of expertise. Shrewd students, however, suspect that their senior colleague uses a direct approach to reach the diagnosis, avoiding the lengthy process of aimless and exhaustive history-taking and examination, much of which may be irrelevant to the patient’s needs. It is the aim of this book to teach students of paediatric surgery how to improve their clinical acumen and to enable them to reach the correct diagnosis by the simplest route. This direct approach to clinical diagnosis is problem-oriented, where the diagnosis can be anticipated by the early elimination of alternatives. It is the same method that is used in ‘decision trees’, algorithms and flow charts. Although students may be aware already of this type of decision-making process, its formal description in the following pages underlines the strength of the technique and demonstrates how it can be applied in clinical diagnosis. Consider the following difference in approach to the simple mathematical problem of identifying an unknown number between 1 and 1,000 by asking questions with a ‘yes’ or ‘no’ answer. How many such questions are needed? There are two ways of solving this problem. One is to ask whether every number in sequence is the chosen one, beginning with 1 and continuing for up to 999 questions until the correct number is identified! An alternative approach is based on the realization that a ‘yes/no’ question identifies specifically a number in a two-element set. Therefore, all that is needed is to divide the 1,000 choices into two and ask: ‘Is the number greater than 500?’ The answer will immediately eliminate half the possibilities. With this simple device, the unknown number can always be found in ten questions or fewer. The first technique is analogous to the student who asks every conceivable question and then examines every part of the body from head to toe, before thinking about the possible diagnosis. The latter approach echoes that of the experienced physician who reaches the diagnosis after limited questioning and physical examination.
What Knowledge Is Needed to Make a Diagnosis or Solve a Clinical Problem?
First, an understanding of the scientific foundations is required; in paediatric surgery, this involves knowledge of the embryology, anatomy and physiology of the neonate and infant and of normal growth and development. Secondly, it is essential to be familiar with the common pathological processes (which vary in different times, cultures and localities) to ensure a sensible differential diagnosis.
Why Does a Problem-Oriented Approach Work?
The answer to this question is not obvious immediately, yet it is a fundamental principle of problem-solving by observation. In a clinical context, the clues to the diagnosis are often subtle and will be found only by someone who knows exactly where to look and then knows how to interpret the findings. A physical sign may be detectable if the examiner is working with a hypothesis and specifically looks to see whether the sign is present, but will be missed on ‘routine’ examination. It is rare that important evidence from the history or physical examination is found by accident – the observer must be consciously prepared for it (Fig. 1.1).
Fig. 1.1
Unless clinicians deliberately consider the relevance of the information they obtain they will become mindless fact-collectors, perform a meaningless examination and miss the clues vital to arriving at the correct diagnosis
While it may seem improbable at first, it is a well-recognized characteristic of the brain and senses to ignore apparently irrelevant observations. Pasteur expressed the sentiment when he said: ‘Fortune favours the prepared mind’. Once this limitation of the senses is appreciated, it is evident that the secret of rapid and accurate diagnosis lies in having a prepared mind at the commencement of the interview and examination. Only then can important clues actively be sought from the history and examination.
Does the Problem-Orientated Approach Work for Fields of Medicine Other Than Paediatric Surgery?
The approach is applicable to all branches of medicine, but the lack of degenerative diseases in paediatrics means that multiple disease processes are less likely to account for the presenting complaint; this is an example of the principle known as Ockham’s razor. William of Ockham was an English monk who provided scientific method with its fundamental principle 700 years ago when he suggested we should always favour simple explanations when trying to account for the world’s mysteries. In paediatric surgery, this means that a range of different physical signs are most likely to be caused by a single anomaly.
If Anticipation of the Diagnosis Comes with Experience, How Can the Student Hope to Learn the Technique While Still Inexperienced?
This is the ‘Catch-22’ of medical education. It is our belief that the technique can be learnt after limited clinical experience, subject to certain conditions.
First, the significance of each piece of evidence must be considered from the beginning of the interview, so that a simple list of differential diagnoses can be formulated early. Failure to recognize the significance of information as it is provided will prejudice recognition of those clues which assist in the identification of possible diagnoses. Therefore, when first learning the method, students must ask themselves continuously what the evidence suggests and which relevant questions should be asked. Later, with experience and practice, this process occurs automatically.
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